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  • 51.
    Livsey, John
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Katterer, Thomas
    Vico, Giulia
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography. The Nature Conservancy, USA..
    Lindborg, Regina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Scaini, Anna
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Da, Chau Thi
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Do alternative irrigation strategies for rice cultivation decrease water footprints at the cost of long-term soil health?2019In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 14, no 7, article id 074011Article in journal (Refereed)
    Abstract [en]

    The availability of water is a growing concern for flooded rice production. As such, several water-saving irrigation practices have been developed to reduce water requirements. Alternate wetting and drying and mid-season drainage have been shown to potentially reduce water requirements while maintaining rice yields when compared to continuous flooding. With the removal of permanently anaerobic conditions during the growing season, water-saving irrigation can also reduce CO2 equivalent (CO2eq) emissions, helping reduce the impact of greenhouse gas (GHG) emissions. However, the long-term impact of water-saving irrigation on soil organic carbon (SOC)-used here as an indicator of soil health and fertility-has not been explored. We therefore conducted a meta-analysis to assess the effects of common water-saving irrigation practices (alternate wetting and drying and mid-season drainage) on (i) SOC, and (ii) GHG emissions. Despite an extensive literature search, only 12 studies were found containing data to constrain the soil C balance in both continuous flooding and water-saving irrigation plots, highlighting the still limited understanding of long-term impacts of water-saving irrigation on soil health and GHG emissions. Water-saving irrigation was found to reduce emissions of CH4 by 52.3% and increased those of CO2 by 44.8%. CO2eq emissions were thereby reduced by 18.6% but the soil-to-atmosphere carbon (C) flux increased by 25% when compared to continuous flooding. Water-saving irrigation was also found to have a negative effect on both SOC-reducing concentrations by 5.2%-and soil organic nitrogen-potentially depleting stocks by more than 100 kgN/ha per year. While negative effects of water-saving irrigation on rice yield may not be visible in short-term experiments, care should be taken when assessing the long-term sustainability of these irrigation practices because they can decrease soil fertility. Strategies need to be developed for assessing the more long-term effects of these irrigation practices by considering trade-offs between water savings and other ecosystem services.

  • 52.
    Lyon, S. W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Laudon, H.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Morth, M.
    Tetzlaff, D.
    Bishop, K. H.
    Controls on snowmelt water mean transit times in northern boreal catchments2010In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 24, no 12, p. 1672-1684Article in journal (Refereed)
    Abstract [en]

    Catchment-scale transit times for water are increasingly being recognized as an important control on geochemical processes. In this study, snowmelt water mean transit times (MTTs) were estimated for the 15 Krycklan research catchments in northern boreal Sweden. The snowmelt water MTTs were assumed to be representative of the catchment-scale hydrologic response during the spring thaw period and, as such, may be considered to be a component of the catchment's overall MTT. These snowmelt water MTTs were empirically related to catchment characteristics and landscape structure represented by using different indices of soil cover, topography and catchment similarity. Mire wetlands were shown to be significantly correlated to snowmelt MTTs for the studied catchments. In these wetlands, shallow ice layers form that have been shown to serve as impervious boundaries to vertical infiltration during snowmelt periods and, thus, alter the flow pathways of water in the landscape. Using a simple thought experiment, we could estimate the potential effect of thawing of ice layers on snowmelt hydrologic response using the empirical relationship between landscape structure (represented using a catchment-scale Pe number) and hydrologic response. The result of this thought experiment was that there could be a potential increase of 20-45% in catchment snowmelt water MTTs for the Krycklan experimental catchments. It is therefore possible that climatic changes present competing influences on the hydrologic response of northern boreal catchments that need to be considered. For example, MTTs may tend to decrease during some times of the year due to an acceleration in the hydrologic cycle, while they tend to increase MTTs during other times of the year due to shifts in hydrologic flow pathways. The balance between the competing influences on a catchment's MTT has consequences on climatic feedbacks as it could influence hydrological and biogeochemical cycles at the catchment scale for northern latitude boreal catchments. Copyright (C) 2010 John Wiley & Sons, Ltd.

  • 53.
    Lyon, Steve
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Desilets, S
    Troch, P
    A tale of two isotopes: differences in hydrograph separation fora runoff event when using δD versus δ18O2009In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 23, no 14, p. 2095-2101Article in journal (Refereed)
    Abstract [en]

    It is often assumed that stable water isotopes (dD and d18O) provide redundant information for a given sample of water. In this note we illustrate  that the choice of isotope used may influence the resultant hydrograph separation. This is especially true in light of the spatial and temporal variability in the isotopic composition of rainfall water at the catchment scale. We present several possible hydrograph separations based on both dD and d18O observed in rainfall for a single runoff event occurring in the southwest USA. This study demonstrates the potential of using both stable water isotopes by showing that dD and d18O may provide unique information for catchment hydrologists. We also report on the utility of new technology capable of simultaneous measurements of both dD and d18O using off-axis integrated cavity output spectroscopy (OA-ICOS) methods. This may be of interest to catchment hydrologists seeking to incorporate this type of equipment into their laboratory.

  • 54.
    Lyon, Steve
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Desilets, Sharon
    Troch, Peter
    Characterizing the response of a catchment to an extreme rainfall event using hydrometric and isotopic data2008In: Water Resources Research, Vol. 44, p. W06413-Article in journal (Refereed)
    Abstract [en]

    In this study we investigate an event-scale transit time distribution (TTD) for a catchment located in the Santa Catalina Mountains northeast of downtown Tucson, AZ USA during a series of extreme rainfall events. Traditionally, TTD studies look at the long-time response of a catchment to an input variation in tracer concentration. Few studies have determined the TTD at the scale of an event. Isotopic and hydrometric data collected during the event considered in this study provides the unique opportunity to characterize the response of the catchment under extreme conditions using both TTD modeling and hydrograph separation. This revealed similarity in the shapes of the event TTD and event water recession hydrograph. Also, the first moment of the event water recession hydrograph and the mean transit time of the TTD were similar. Due to the extreme nature of this event, it is likely that the catchment reaches and relaxes from the maximum possible storage making its response a time-invariant characteristic of the catchment based on hydraulic theory. The similarity between the event water recession and event TTD during this characteristic response of the catchment may, thus, allow for the derivation of a time-invariant event TTD. This result is especially valuable as it lays a basis for catchment similarity analysis linking a catchment’s hydrological response and geomorphic properties.

  • 55.
    Lyon, Steve
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, G.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Giesler, R.
    Humborg, C.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Mörth, M.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    The relationship between subsurface hydrology and dissolved carbon fluxes for a sub-arctic catchment2010In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 14, p. 941-950Article in journal (Refereed)
    Abstract [en]

     In recent years, there has been increased interest in carbon cycling in natural systems due to its role in a changing climate. Northern latitude systems are especially important as they may serve as a potentially large source or sink of terrestrial carbon. There are, however, a limited number of investigations reporting on actual flux rates of carbon moving from the subsurface landscape to surface water systems in northern latitudes. In this study, we determined dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) fluxes from the subsurface landscape for a sub-arctic catchment located in northern Sweden. These are based on observed annual flux-averaged concentrations of DOC and DIC for the 566 km2 Abiskojokken catchment. We demonstrate the importance to correctly represent the spatial distribution of the advective solute travel times along the various flow and transport pathways. The fluxes of DOC and DIC from the subsurface landscape to the surface water system were comparable in magnitude. This balance could shift under future climatic changes that influence the hydrological and biogeochemical system.

  • 56.
    Lyon, Steve
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Changes in catchment-scale recession flow properties in response to permafrost thawing in the Yukon River Basin2010In: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 30, no 14, p. 2138-2145Article in journal (Refereed)
    Abstract [en]

    Permafrost influences the hydrologic response of a catchment. In this study, we test the ability of recession flow analysis to reflect thawing of permafrost at the catchment scale for the well-studied Yukon river basin (YRB), covering large portions of Alaska, USA and parts of Canada. The changes in the recession flow properties detected in the YRB agree well with observations of permafrost thawing across central Alaska. In addition, there is good agreement between the relative increases in recession flow intercept (a proxy for effective depth to permafrost) and the relative annual increases in groundwater flow (independently assessed as a permafrost thawing effect) in the YRB catchments that have exhibited such groundwater flow increases. This study demonstrates the utility of recession flow analysis to reflect catchment-scale changes in permafrost across a variety of permafrost conditions. The strength of this method is that it requires only daily observations of streamflow to reflect permafrost thawing on much larger measurement support scales than the local scales of direct permafrost observations.

  • 57.
    Lyon, Steve
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Dominguez, Francina
    Gochis, David
    Coupling terrestrial and atmospheric water dynamics to improve prediction in a changing environment2008In: Bulletin of the American Meteorological Society, Vol. 89, no 9, p. 1275-1279Article in journal (Refereed)
    Abstract [en]

    Humans have profoundly influenced their environment. It has been estimated that nearly one-third of the global land cover has been modified while approximately 40% of the photosynthesis has been appropriated. As the interface between the subsurface and the atmosphere is altered, it is imperative that we understand the influence this alteration has in terms of changing regional and global climates. Land surface heterogeneity is sometimes a principal modulator of local and regional climates and, as such, there are potential aggregation and teleconnection effects ranging in scales from soil pores to the general atmospheric circulation when the land surface is altered across a range of scales. The human fingerprint on land surface processes is critical and must also be accounted for in the discourse on land-atmosphere coupling as it pertains to climate and global change as well as local processes such as evapotranspiration and streamflow. It is at this pivotal interface where hydrologists, atmospheric scientists and ecologists must understand how their disciplines interact and influence each other.

    Fluxes across the land-surface directly influence predictions of ecological processes, atmospheric dynamics, and terrestrial hydrology. However, many simplifications are made in numerical models when considering terrestrial hydrology from the view point of the atmosphere and visa-versa. While this may be a necessity in the current generation of operational models used for forecasting, it can create obstacles to the advancement of process understanding. These simplifications can limit the numerical prediction capabilities on how water partitions itself throughout all phases of the water cycle. The feedbacks between terrestrial and atmospheric water dynamics are not well understood or represented by the current generation of operational land-surface and atmospheric models. This can lead to erroneous spatial patterns and anomalous temporal persistence in land-atmosphere exchanges and atmospheric water cycle predictions. Cross-disciplinary efforts are needed not only to identify but also to quantify feedbacks between terrestrial and atmospheric water at appropriate spatiotemporal scales. This is especially true as today’s young scientists set their sights on improving process understanding and prediction skill from both research and operational models used to describe such linked systems.

    In recognition of these challenges, a junior faculty and early career scientist forum was recently held at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado with the intent of identifying and characterizing feedback interactions, and their attendant spatial and temporal scales, important for coupling terrestrial and atmospheric water dynamics. The primary focus of this forum is on improved process understanding, rather than operational products, as the possibility of incorporating more realistic physics into operational models is computationally prohibitive. We approached the subject of improved predictability through better process understanding by focusing on the following three framework questions described and discussed below.

  • 58.
    Lyon, Steve
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Grabs, Thomas
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Laudon, Hjalmar
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Bishop, Kevin
    Variability of groundwater levels and total organic carbon (TOC) in the riparian zone of a boreal2011In: Journal of Geophysical Research - Biogeosciences, Vol. 116, no G01020Article in journal (Refereed)
    Abstract [en]

    The riparian zone is a narrow corridor where hillslopes (and their associated hydrobiogeochemical processes) interface with the river system. As such, the riparian zone serves as the last piece of landscape with which water interacts as it transitions from being water flowing primarily through the landscape (i.e., shallow groundwater) to water flowing primarily on the landscape (i.e., stream water). This study investigates the spatiotemporal variability in riparian-zone soil water total organic carbon (TOC) and its relation to the shallow groundwater table using observations from the recently instrumented riparian observatory in the Krycklan catchment study area located in boreal northern Sweden. In general, there is a decrease in TOC concentration with depth down through the soil profile. The rate of this decrease was variable among the six monthly samplings used in this study. The spatial variability of soil water TOC in the riparian zone was connected to the spatial variability of the shallow groundwater levels. This demonstrated the importance of the temporal variation of flow pathways and the mixing of waters from different sources of TOC moving into and through the riparian zone. The coupled variation of the hydrologic and biogeochemical systems raised questions about the ability of simple lumped approaches to accurately predict how in-stream TOC concentrations will change with climate and/or land use. The integrated sampling approach in the riparian observatory covers both hydrologic and biogeochemical aspects of soil water TOC and provides a basis for development and testing of distributed, physically based transport models.

  • 59.
    Lyon, Steve
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Seibert, Jan
    Lembo, Arthur
    Steenhuis, Tammo
    Walter, Todd
    Incorporating landscape characteristics in a distance metric for interpolating between observations of stream water chemistry2008In: Hydrology and Earth System Sciences, Vol. 12, p. 1229-1239Article in journal (Refereed)
    Abstract [en]

    Spatial patterns of water chemistry along stream networks can be quantified using synoptic or ‘snapshot’ sampling. The basic idea is to sample stream water at many points over a relatively short period of time. Even for intense sampling campaigns, the number of sample points is limited and interpolation methods, like kriging, are commonly used to produce continuous maps of water chemistry based on the point observations from the synoptic sampling. Interpolated concentrations are influenced heavily by how distance between points along the stream network is defined. In this study, we investigate different ways to define distance and test these based on data from a snapshot sampling campaign in a 37-km2 watershed in the Catskill Mountains region (New York State). Three distance definitions (or metrics) were compared: Euclidean or straight-line distance, in-stream distance, and in-stream distance adjusted according characteristics of the local contributing area, i.e., an adjusted in-stream distance. Using the adjusted distance metric resulted in a lower cross-validation error of the interpolated concentrations, i.e., a better agreement of kriging results with measurements, than the other distance definitions. The adjusted distance metric can also be used in an exploratory manner to test which landscape characteristics are most influential for the spatial patterns of stream water chemistry and, thus, to target future investigations to gain process-based understanding of in-stream chemistry dynamics.

  • 60.
    Lyon, Steve
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Sorensen, R
    Stendahl, J
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Using landscaep charactersitics to define an adjusted distance metric for improving kriging interpolations2010In: International Journal of Geographical Information Science, ISSN 1365-8816, E-ISSN 1365-8824, Vol. 24, no 5, p. 723-740Article in journal (Refereed)
    Abstract [en]

    Interpolation of point measurements using geostatistical techniques such as kriging can be used to estimate values at non-sampled locations in space. Traditional geostatistics are based on the spatial autocorrelation concept that nearby things are more related than distant things. In this study, additional information was used to modify the traditional Euclidean concept of distance into an adjusted distance metric that incorporates similarity in terms of quantifiable landscape characteristics such as topography or land use. This new approach was tested by interpolating soil moisture content, pH and carbon-tonitrogen (C:N) ratio measured in both the mineral and the organic soil layers at a field site in central Sweden. Semivariograms were created using both the traditional distance metrics and the proposed adjusted distance metrics to carry out ordinary kriging (OK) interpolations between sampling points. In addition, kriging with external drift (KED) was used to interpolate soil properties to evaluate the ability of the adjusted distance metric to incorporate secondary data into interpolations. The new adjusted distance metric typically lowered the nugget associated with the semivariogram, thereby better representing small-scale variability in the measured data compared to semivariograms based on the traditional distance metric. The pattern of the resulting kriging interpolations using KED and OK based on the adjusted distance metric were similar because they represented secondary data and, thus, enhanced small-scale variability compared to traditional distance OK. This created interpolations that agreed better with what is expected for the real-world spatial variation of the measured properties. Based on cross-validation error, OK interpolations using the adjusted distance metric better fit observed data than either OK interpolations using traditional distance or KED.

  • 61.
    Lyon, Steve
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Troch, P
    Development and application of a catchment similarity index for subsurface flow2010In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 46, no 3Article in journal (Refereed)
    Abstract [en]

    In this study, we develop a similarity parameter to describe shallow subsurface hydrological response of small catchments on the basis of the hillslope-Péclet number. This new similarity parameter, named the catchment-Péclet (caPe) number, provides a theoretical framework to compare the relative hydrologic response derived from shallow subsurface flow of small catchments on the basis of geomorphic properties. Using 400,000 synthetically derived catchments to model catchment-scale characteristic response functions (CRFs), we see good agreement between the synthetic and theoretical relationships relating the caPe number to the first two dimensionless moments of the CRF of small catchments. Working with real-world data, however, requires the estimation of hydrologic parameters and delineation of hillslopes to apply the caPe number. Allowing for uncertainty in the estimation of hydrologic parameters and in the definition of the extent of the channel network, the caPe number is able to recreate the observed moments of an approximate catchment-scale CRF for four small catchments ranging in size from 0.025 to 880 ha in two distinct climatic and geologic settings. By using physics to underpin the link between landscape and hydrological response, the caPe number creates a functional relationship between hydraulic theory and a catchment's pedogeomorphological structure. While this study is limited to small headwater catchments, it lays the groundwork for a catchment-scale similarity parameter that could be expanded to larger scales where channel network structure and storage become more important.

  • 62.
    Lyon, Steve
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Troch, Peter
    Broxton, Patrick
    Molotch, Noah
    Brooks, Paul
    Monitoring the timing of snow melt and the initiation of streamflow using a distributed network of temperature/light sensors2008In: Ecohydrology, Vol. 1, no 3, p. 215-224Article in journal (Refereed)
    Abstract [en]

    The loss of snow cover and the initiation of streamflow are key triggers for both terrestrial and aquatic biota. Landscape-scale snowmelt and streamflow dynamics are difficult to estimate however because they integrate large spatial extents and can vary rapidly in time. Remotely sensed observations are often temporally discontinuous and point observations lack sufficient spatial density (e.g., point measures from data-logging piezometers). In this study, we employ inexpensive temperature/light sensors to monitor the distribution of snowmelt and headwater stream discharge as a proxy for hydrological state of the landscape with high spatial and temporal resolution. This study was conducted at Redondo Peak, a large (local relief over 1,100 m) resurgent dome within the caldera complex of the Valles Caldera National Preserve 30 km west of Los Alamos, New Mexico, USA. The first-order streams that drain Redondo Peak encompass the full spectrum of terrain aspects, resulting in significant variability in wind exposure, turbulent and radiative fluxes, snow cover duration, and vegetation structure. Complex interactions between these variables impact groundwater recharge through variations in sublimation, evaporation, and transpiration. To monitor the role this variation plays with respect to spatio-temporal dynamics of snowmelt and headwater stream discharge, we have installed 128 temperature/light sensors in eight different streambeds draining through unique aspects of the peak. The variation of daily temperature/light levels relative to seasonal change in mean temperature/light levels provides a metric of the spatial distribution of surface waters and snow cover. This metric correctly identified flowing lengths of headwater streams with 80% accuracy during an early summer period (10 May 2007) and 79% of the time in late summer period (2 October 2007). Between these two observation periods, the percentage length of headwater streams flowing decreased by 12% indicating a general drying of the landscape. Based on a conceptual model of a groundwater “mound” within the peak that roughly follows the shape of the land surface, such a metric relates directly to the amount of water in the landscape providing insight to the complex ecohydrological interactions between snowmelt, rainfall, and vegetative uptake. This serves as a precursory to developing a broader ecohydrological perspective of the interrelationships between ecology and hydrological processes.

  • 63.
    Lyon, Steve
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Volkmann, T.H.M.
    Hazenberg, P
    Yatheendradas, S.
    Schaffner, M.
    Pytlak, E.
    Unkrich, C.L.
    Goodrich, D.C.
    Troch, P.A.
    Combining radar and rain gauges to capture the space-time variability of monsoon rainfall during an extreme flood event2008In: EGU General Assembly: Vol. 10, EGU2008-A-04734, 2008, 2008Conference paper (Refereed)
    Abstract [en]

    Monsoon rainfall events are typified by high spatial and temporal variability in both rainfall amount and intensity. Monsoon rainfall events occurring in Tucson, AZ, USA over seven consecutive days in July, 2006 lead to the highest ever recorded stream flows in Sabino Canyon Creek and resulted in flash flooding that caused large-scale property damage. Concurrent to these monsoon events, a network of 40 tipping bucket rain gauges were in place throughout the Sabino Canyon Creek watershed. In addition to this rain gauge network, radar data (NEXRAD) was collected during this monsoon period and used to derive rainfall accumulation maps with at 15-minute temporal resolution and 1 km2 spatial resolution. An event based, kinematic-wave overland flow runoff model (KINEROS) was used to model stream flow in Sabino Canyon Creek for the largest of the flooding events using rainfall data from both rain gauge observations and radar estimation. While the modeling results based solely on rain gauge observations agreed well with observed flow, the results were highly reliant on the extent of the spatial coverage of the rain gauge network. To overcome the reliance, geostatistics (kriging with external drift) were used to combine the rain gauge data with the radar data. By combining these two datasets, we could compensate for restricted spatial coverage in the rain gauge network. This allowed for high quality modeling of the flood event even with a great reduction in the spatial extent of the observational rain gauge network. Techniques to combine data from rain gauge networks and radar estimates are quite valuable as the development of real-time rain gauge network with good spatial extent and high spatial density is difficult and costly.

  • 64.
    Lyon, Steve W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Ohio State University, USA.
    Goethals, Peter
    Schneider, Petra
    Dominguez-Granda, Luis
    Hampel, Henrietta
    Lam, Norris
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Nolivos, Indira
    Reinstorf, Frido
    Tejeda, Raymundo C. Rodriguez
    Vázquez, Raúl F.
    Ho, Long
    Improving Water Management Education across the Latin America and Caribbean Region2019In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 11, no 11, article id 2318Article, review/survey (Refereed)
    Abstract [en]

    Education can help secure inclusive and resilient development around water resources. However, it is difficult to provide the latest science to those managing water resources (both now and in the future). Collectively, we hypothesize that dissemination and promotion of scientific knowledge using students as central agents to transfer theoretical knowledge into practice is an efficient way to address this difficulty. In this study, we test this hypothesis in the Latin America and Caribbean (LAC) region as a representative case study region. First, we use a literature review to map a potential gap in research on education around water resources across the LAC region. We then review potential best practices to address this gap and to better translate water resources education techniques into the LAC region. Integral to these efforts is adopting students as agents for information transfer to help bridge the gap between the global state-of-the science and local water resources management. Our results highlight the need to establish a new standard of higher educational promoting exchange between countries as local populations are vulnerable to future shifts in climate at global scales and changes in land usage at regional scales. The new standard should include peer-to-peer mentoring achieved by jointly exchanging and training students and practitioners in water management techniques, increasing access to water data and pedagogic information across the region, and lowering administration roadblocks that prevent student exchange.

  • 65.
    Lyon, Steve W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Jantze, Elin J.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dahlke, Helen E.
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Winterdahl, Mattias
    Stockholm University, Faculty of Science, Department of Physical Geography.
    WHY MONITOR CARBON IN HIGH-ALPINE STREAMS?2016In: Geografiska Annaler. Series A, Physical Geography, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 98, no 3, p. 237-245Article in journal (Refereed)
    Abstract [en]

    In this short communication, we report on dissolved organic and inorganic carbon concentrations from a summer stream monitoring campaign at the main hydrological catchment of the Tarfala Research Station in northern Sweden. Further, we place these unique high-alpine observations in the context of a relevant subset of Sweden's national monitoring programme. Our analysis shows that while the monitoring programme (at least for total organic carbon) may have relatively good representativeness across a range of forest coverages, alpine/tundra environments are potentially underrepresented. As for dissolved inorganic carbon, there is currently no national monitoring in Sweden. Since the selection of stream water monitoring locations and monitored constituents at the national scale can be motivated by any number of goals (or limitations), monitoring at the Tarfala Research Station along with other research catchment sites across Fennoscandia becomes increasingly important and can offer potential complementary data necessary for improving process understanding. Research catchment sites (typically not included in national monitoring programmes) can help cover small-scale landscape features and thus complement national monitoring thereby improving the ability to capture hot spots and hot moments of biogeochemical export. This provides a valuable baseline of current conditions in high-alpine environments against which to gauge future changes in response to potential climatic and land cover shifts.

  • 66.
    Lyon, Steve W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Uppsala University, Sweden; The Nature Conservancy, USA.
    King, Katie
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Polpanich, Orn-uma
    Lacombe, Guillaume
    Assessing hydrologic changes across the Lower Mekong Basin2017In: journal of hydrology regional studies, ISSN 2214-5818, Vol. 12, p. 303-314Article in journal (Refereed)
    Abstract [en]

    Study region: In this study, 33 catchments across the Lower Mekong Basin in Southeast Asia are examined to detect historical changes in their hydrological response via a model-based methodology. Study focus: Intensive development over the past half century across Southeast Asia's Lower Mekong Basin has inevitably affected natural resources. Large areas have been converted from forests for subsistence and commercial agriculture, and urban development. We implement an innovative approach to screen hydrologic data for detecting impacts of such large-scale changes on hydrological response. In a first step, temporal changes in the rainfall-runoff relationship were assessed using the parsimonious, two-parameter GR2M hydrological model. In a second step, a distribution-free statistical test was applied to detect whether significant changes have occurred in the wet season (high flow) and dry season (low flow) conditions. New hydrological insights for the region: Our results indicate that the majority of catchments (64% of those considered) with sufficiently long data records exhibited no discernable trends in hydrological response. Those catchments that did exhibit significant trends in hydrological response were fairly evenly split between increasing trends (between 21% and 24%) and decreasing trends (between 15% and 12%) with time. There was a lack of evidence that these changes where brought about by shifts in precipitation or potential evapotranspiration; however, catchments exhibiting significant increasing trends in hydrological behavior were found to have different land cover compositions (lower percentage of forest coverage and subsequently higher paddy rice coverage) than those exhibiting significant decreasing trends. The approach presented here provides a potentially valuable screening method to highlight regions for further investigation of improved mechanistic understanding. Without this connection, we might be blind to future hydrological shifts that can have significant impact on development.

  • 67.
    Lyon, Steve W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Koutsouris, Alexander
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Scheibler, Friedemann
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Mbanguka, Rene
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Tumbo, Madaka
    Robert, Keven K.
    Sharma, Asha N.
    van der Velde, Ype
    Interpreting characteristic drainage timescale variability across Kilombero Valley, Tanzania2015In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 29, no 8, p. 1912-1924Article in journal (Refereed)
    Abstract [en]

    We explore seasonal variability and spatiotemporal patterns in characteristic drainage timescale (K) estimated from river discharge records across the Kilombero Valley in central Tanzania. K values were determined using streamflow recession analysis with a Brutsaert-Nieber solution to the linearized Boussinesq equation. Estimated K values were variable, comparing between wet and dry seasons for the relatively small catchments draining upland positions. For the larger catchments draining through valley bottoms, K values were typically longer and more consistent across seasons. Variations in K were compared with long-term averaged, Moderate-resolution Imaging Spectroradiometer-derived monthly evapotranspiration. Although the variations in K were potentially related to evapotranspiration, the influence of data quality and analysis procedure could not be discounted. As such, even though recession analysis offers a potential approach to explore aquifer release timescales and thereby gain insight to a region's hydrology to inform water resources management, care must be taken when interpreting spatiotemporal shifts in K in connection with process representation in regions like the Kilombero Valley.

  • 68.
    Lyon, Steve W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Meidani, Roya
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    van der Velde, Ype
    Dahlke, Helen E.
    Swaney, Dennis P.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. Stockholm University, Faculty of Science, Department of Geological Sciences.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Seasonal and Regional Patterns in Performance for a Baltic Sea Drainage Basin Hydrologic Model2015In: Journal of the American Water Resources Association, ISSN 1093-474X, E-ISSN 1752-1688, Vol. 51, no 2, p. 550-566Article in journal (Refereed)
    Abstract [en]

    This study evaluates the ability of the Catchment SIMulation (CSIM) hydrologic model to describe seasonal and regional variations in river discharge over the entire Baltic Sea drainage basin (BSDB) based on 31years of monthly simulation from 1970 through 2000. To date, the model has been successfully applied to simulate annual fluxes of water from the catchments draining into the Baltic Sea. Here, we consider spatiotemporal bias in the distribution of monthly modeling errors across the BSDB since it could potentially reduce the fidelity of predictions and negatively affect the design and implementation of land-management strategies. Within the period considered, the CSIM model accurately reproduced the annual flows across the BSDB; however, it tended to underpredict the proportion of discharge during high-flow periods (i.e., spring months) and overpredict during the summer low flow periods. While the general overpredictions during summer periods are spread across all the subbasins of the BSDB, the underprediction during spring periods is seen largely in the northern regions. By implementing a genetic algorithm calibration procedure and/or seasonal parameterization of subsurface water flows for a subset of the catchments modeled, we demonstrate that it is possible to improve the model performance albeit at the cost of increased parameterization and potential loss of parsimony.

  • 69.
    Lyon, Steve W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Nathanson, Marcus
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lam, Norris
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dahlke, Helen E.
    Rutzinger, Martin
    Kean, Jason W.
    Laudon, Hjalmar
    Can Low-Resolution Airborne Laser Scanning Data Be Used to Model Stream Rating Curves?2015In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 7, no 4, p. 1324-1339Article in journal (Refereed)
    Abstract [en]

    This pilot study explores the potential of using low-resolution (0.2 points/m(2)) airborne laser scanning (ALS)-derived elevation data to model stream rating curves. Rating curves, which allow the functional translation of stream water depth into discharge, making them integral to water resource monitoring efforts, were modeled using a physics-based approach that captures basic geometric measurements to establish flow resistance due to implicit channel roughness. We tested synthetically thinned high-resolution (more than 2 points/m(2)) ALS data as a proxy for low-resolution data at a point density equivalent to that obtained within most national-scale ALS strategies. Our results show that the errors incurred due to the effect of low-resolution versus high-resolution ALS data were less than those due to flow measurement and empirical rating curve fitting uncertainties. As such, although there likely are scale and technical limitations to consider, it is theoretically possible to generate rating curves in a river network from ALS data of the resolution anticipated within national-scale ALS schemes (at least for rivers with relatively simple geometries). This is promising, since generating rating curves from ALS scans would greatly enhance our ability to monitor streamflow by simplifying the overall effort required.

  • 70.
    Lyon, Steve W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Nathanson, Marcus
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Spans, Andre
    Grabs, Thomas
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Laudon, Hjalmar
    Temnerud, Johan
    Bishop, Kevin H.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Specific discharge variability in a boreal landscape2012In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, p. W08506-Article in journal (Refereed)
    Abstract [en]

    Specific discharge variations within a mesoscale catchment were studied on the basis of three synoptic sampling campaigns. These were conducted during stable flow conditions within the Krycklan catchment study area in northern Sweden. During each campaign, about 80 individual locations were measured for discharge draining from catchment areas ranging between 0.12 and 67 km(2). These discharge samplings allowed for the comparison between years within a given season (September 2005 versus September 2008) and between seasons within a given year (May 2008 versus September 2008) of specific discharge across this boreal landscape. There was considerable variability in specific discharge across this landscape. The ratio of the interquartile range (IQR) defined as the difference between the 75th and 25th percentiles of the specific discharges to the median of the specific discharges ranged from 37% to 43%. Factor analysis was used to explore potential relations between landscape characteristics and the specific discharge observed for 55 of the individual locations that were measured in all three synoptic sampling campaigns. Percentage wet area (i.e., wetlands, mires, and lakes) and elevation were found to be directly related to the specific discharge during the drier September 2008 sampling while potential annual evaporation was found to be inversely related. There was less of a relationship determined during the wetter post spring flood May 2008 sampling and the late summer rewetted September 2005 sampling. These results indicate the ability of forests to dry out parts of the catchment over the summer months while wetlands keep wet other parts. To demonstrate the biogeochemical implications of such spatiotemporal variations in specific discharge, we estimate dissolved organic carbon (DOC) exports with available data for the May 2008 and September 2008 samplings using both the spatially variable observed specific discharges and the spatially constant catchment average values. The average absolute difference in DOC export for the various subcatchments between using a variable and using a constant specific discharge was 28% for the May 2008 sampling and 20% for the September 2008 sampling.

  • 71.
    Lyon, Steve W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. The Nature Conservancy, USA.
    Ploum, Stefan W.
    van der Velde, Ype
    Rocher-Ros, Gerard
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Giesler, Reiner
    Lessons learned from monitoring the stable water isotopic variability in precipitation and streamflow across a snow-dominated subarctic catchment2018In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 50, no 1, article id e1454778Article in journal (Refereed)
    Abstract [en]

    This empirical study explores shifts in stable water isotopic composition for a subarctic catchment located in northern Sweden as it transitions from spring freshet to summer low flows. Relative changes in the isotopic composition of streamflow across the main catchment and fifteen nested subcatchments are characterized in relation to the isotopic composition of precipitation. With our sampling campaign, we explore the variability in stream-water isotopic composition that originates from precipitation as the input shifts from snow to rain and as landscape flow pathways change across scales. The isotopic similarity of high-elevation snowpack water and early season rainfall water seen through our sampling scheme made it difficult to truly isolate the impact of seasonal precipitation phase change on stream-water isotopic response. This highlights the need to explicitly consider the complexity of arctic and alpine landscapes when designing sampling strategies to characterize hydrological variability via stable water isotopes. Results show a potential influence of evaporation and source water mixing both spatially (variations with elevation) and temporally (variations from post-freshet to summer flows) on the composition of stream water across Miellajokka. As such, the data collected in this empirical study allow for initial conceptualization of the relative importance of, for example, hydrological connectivity within this mountainous, subarctic landscape.

  • 72.
    Lyon, Steve W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Teutschbein, Claudia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Stockholm Universitet, Sverige.
    Problem-based learning and assessment in hydrology courses: Can non-traditional assessment better reflect intended learning outcomes?2011In: Natural Sciences Education, ISSN 2168-8281, Vol. 40, no 1, p. 199-205Article in journal (Refereed)
    Abstract [en]

    Hydrology has at its core a focus on real-world applications and problems stemming from the importance of water for society and natural systems. While hydrology is firmly founded in traditional “hard” sciences like physics and mathematics, much of the innovation and excitement in current and future research-oriented hydrology comes through intersection with other disciplines. This leads to combinations of intended learning outcomes (ILOs) in hydrology courses that may not be easily or completely achieved using traditional lecture-based learning environments or using basic problem-solving techniques. Problem based learning (PBL) may work well in hydrology courses due to the focus on real-world applications and cross-discipline natureof modern hydrology. Since PBL differs from traditional teacher-centered approaches, student learning must be supported and assessed differently. This article focuses on identifying several non-traditional assessment forms to help facilitate the use of PBL approaches in hydrology courses. We present an example hydrology modeling course employing one such non-traditional PBLspecific form of assessment. Further, we seek to test the hypothesis that  non-traditional assessment associated with PBL better reflects the ability of the students to achieve the ILOs in such courses. Results from the example course considered indicate that students not only preferred but also performed better in a PBL environment with its non-traditional form of assessment. This makes a strong case for incorporating both PBL and associated non-traditional forms of assessment into our teaching in hydrology and other applied science courses.

  • 73.
    Lyon, Steve W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Walter, M. T.
    Jantze, Elin J.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Archibald, J. A.
    Training hydrologists to be ecohydrologists: a "how-you-can-do-it" example leveraging an active learning environment for studying plant-water interaction2013In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 17, no 1, p. 269-279Article in journal (Refereed)
    Abstract [en]

    Structuring an education strategy capable of addressing the various spheres of ecohydrology is difficult due to the inter-disciplinary and cross-disciplinary nature and general breadth of this emergent field. Clearly, there is a need for such strategies to accommodate more progressive educational concepts while highlighting a skills-based education. To demonstrate a possible way to develop courses that include such concepts, we offer a case-study or a potential how-you-can-do-it example from a recent course set in an ecohydrological context co-taught by teachers from Stockholm University and Cornell University at Stockholm University's Navarino Environmental Observatory (NEO) in Costa Navarino, Greece. This course focused on introducing hydrology Master's students to some of the central concepts of ecohydrology, while at the same time supplying process-based understanding relevant for characterizing evapotranspiration. As such, the main goal of the course was to explore some of the central theories in ecohydrology and their connection to plant-water interactions and the water cycle in a semiarid environment. While this course is still in its infancy with regards to addressing some of the more in-depth aspects of ecohydrology, it does provide a relevant basis with an initial emphasis on the more physical concepts of ecohydrology from which to build towards the more physiological concepts (e.g., unique plant adaptations to water availability or differences in water use between native plants and irrigated vegetation). In addition to presenting this roadmap for ecohydrology course development, we explore the utility and effectiveness of adopting active teaching and learning strategies drawing from the suite of learn-by-doing, hands-on, and inquiry-based techniques in such a course. We test a potential gradient of activeness across a sequence of three teaching and learning activities. Our results indicate that there was a clear advantage for utilizing active learning with a preference among the students towards the more active techniques. This demonstrates the added value of incorporating even the simplest active learning approaches in our ecohydrology (or general) teaching.

  • 74.
    Lyon, S.W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Destouni, G.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Giesler, R.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Seibert, J.
    Karlsson, J.
    Troch, P.A.
    Estimation of permafrost thawing rates in a sub-arctic catchment using recession flow analysis2009In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 13, p. 595-604Article in journal (Refereed)
    Abstract [en]

    Permafrost thawing is likely to change the flow pathways taken by water as it moves through arctic and sub-arctic landscapes. The location and distribution of these pathways directly influence the carbon and other biogeochemical cycling in northern latitude catchments. While permafrost thawing due to climate change has been observed in the arctic and sub-arctic, direct observations of permafrost depth are difficult to perform at scales larger than a local scale. Using recession flow analysis, it may be possible to detect and estimate the rate of permafrost thawing based on a long-term streamflow record. We demonstrate the application of this approach to the sub-arctic Abiskojokken catchment in northern Sweden. Based on recession flow analysis, we estimate that permafrost in this catchment may be thawing at an average rate of about 0.9 cm/yr during the past 90 years. This estimated thawing rate is consistent with direct observations of permafrost thawing rates, ranging from 0.7 to 1.3 cm/yr over the past 30 years in the region.

  • 75.
    Lyon, S.W.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Sjöberg, Y.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jantze, E.J.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, G.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Estimating permafrost changes via storage-discharge dynamics2011In: Abstract: C53G-01, 2011Conference paper (Refereed)
  • 76.
    Mansanarez, Valentin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Westerberg, Ida K.
    Lam, Norris
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography. The Nature Conservancy, USA; Ohio State University–OARDC, USA.
    Rapid Stage-Discharge Rating Curve Assessment Using Hydraulic Modeling in an Uncertainty Framework2019In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 55, no 11, p. 9765-9787Article in journal (Refereed)
    Abstract [en]

    Establishing reliable streamflow time series is essential for hydrological studies and water-related decisions, but it can be both time-consuming and costly since streamflow is typically calculated from water level using rating curves based on numerous calibration measurements (gaugings). It can take many years of gauging data collection to estimate reliable rating curves, and even then extreme-flow estimates often still depend on rating curve extrapolation. Hydraulically modeled rating curves are a promising alternative to traditional methods as they can be rapidly derived with few concurrent stage-discharge gaugings. We introduce a novel framework for Rating curve Uncertainty estimation using Hydraulic Modelling (RUHM), based on Bayesian inference and physically based hydraulic modeling for estimating stage-discharge rating curves and their associated uncertainty. The framework incorporates information from the river shape, hydraulic configuration, and the control gaugings as well as uncertainties in the gaugings and model parameters. We explored the interaction of uncertainty sources within RUHM by (1) assessing its performance at two Swedish stations, (2) investigating the sensitivity of the results to the number and magnitude of the calibration gaugings, and (3) evaluating the importance of prior information on the model parameters. We found that rating curves with constrained uncertainty could be estimated using only three gaugings for either low or low and medium flows that have a high probability of occurrence, thereby enabling rapid rating curve estimation. Prior information about the water-surface slope-stage relation, obtainable from site surveys, was needed to adequately constrain uncertainty estimates. Plain Language Summary Reliable streamflow time series are essential for water-related decisions. However, it can take several years and numerous measurements to establish a reliable streamflow time series, and these may still be associated with large uncertainty. To address these issues, we developed a novel framework that couples uncertainty assessment with hydraulic modeling of the relation between water level and streamflow at a hydrological monitoring station using information about the physical characteristics of the channel. This relation between water level and streamflow, known as the rating curve, is the basis for calculating streamflow time series from the water level time series measured at hydrological monitoring stations. We explored the interaction of different uncertainty sources on rating curve estimation at two Swedish stations and found that rating curves could be modeled with high confidence (i.e., low uncertainty) using only three observations for either low flows or low and medium flows. Since such flow conditions occur often and are easy to measure (at least relative to the rare and hard-to-measure high flows) our framework has an advantage over traditional approaches by potentially allowing for more rapid rating curve estimation.

  • 77. Matti, Bettina
    et al.
    Dahlke, Helen E.
    Dieppois, Bastien
    Lawler, Damian M.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography. The Nature Conservancy, USA.
    Flood seasonality across Scandinavia—Evidence of a shifting hydrograph?2017In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 31, no 24, p. 4354-4370Article in journal (Refereed)
    Abstract [en]

    Fluvial flood events have substantial impacts on humans, both socially and economically, as well as on ecosystems (e.g., hydroecology and pollutant transport). Concurrent with climate change, the seasonality of flooding in cold environments is expected to shift from a snowmelt-dominated to a rainfall-dominated flow regime. This would have profound impacts on water management strategies, that is, flood risk mitigation, drinking water supply, and hydro power. In addition, cold climate hydrological systems exhibit complex interactions with catchment properties and large-scale climate fluctuations making the manifestation of changes difficult to detect and predict. Understanding a possible change in flood seasonality and defining related key drivers therefore is essential to mitigate risk and to keep management strategies viable under a changing climate. This study explores changes in flood seasonality across near-natural catchments in Scandinavia using circular statistics and trend tests. Results indicate strong seasonality in flooding for snowmelt-dominated catchments with a single peak occurring in spring and early summer (March through June), whereas flood peaks are more equally distributed throughout the year for catchments located close to the Atlantic coast and in the south of the study area. Flood seasonality has changed over the past century seen as decreasing trends in summer maximum daily flows and increasing winter and spring maximum daily flows with 5-35% of the catchments showing significant changes at the 5% significance level. Seasonal mean daily flows corroborate those findings with higher percentages (5-60%) of the catchments showing statistically significant changes. Alterations in annual flood occurrence also point towards a shift in flow regime from snowmelt-dominated to rainfall-dominated with consistent changes towards earlier timing of the flood peak (significant for 25% of the catchments). Regionally consistent patterns suggest a first-order climate control as well as a local second-order catchment control, which causes inter-seasonal variability in the streamflow response.

  • 78.
    Mbanguka, René P.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Holmgren, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography. Swedish University of Agricultural Sciences, Sweden.
    Lopez, Marc Girons
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Water Balance and Level Change of Lake Babati, Tanzania: Sensitivity to Hydroclimatic Forcings2016In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 8, no 12, article id 572Article in journal (Refereed)
    Abstract [en]

    We develop and present a novel integrated water balance model that accounts for lake watergroundwater interactions, and apply it to the semi-closed freshwater Lake Babati system, Northern Tanzania, East Africa. The model was calibrated and used to evaluate the lake level sensitivity to changes in key hydro-climatic variables such as temperature, precipitation, humidity and cloudiness. The lake response to the Coupled Model Intercomparison Project, Phase 5 (CMIP5) output on possible future climate outcomes was evaluated, an essential basis in understanding future water security and flooding risk in the region. Results show high lake level sensitivity to cloudiness. Increased focus on cloud fraction measurement and interpretation could likely improve projections of lake levels and surface water availability. Modelled divergent results on the future (21st century) development of Lake Babati can be explained by the precipitation output variability of CMIP5 models being comparable to the precipitation change needed to drive the water balance model from lake dry-out to overflow; this condition is likely shared with many other East African lake systems. The developed methodology could be useful in investigations on change-driving processes in complex climatedrainage basinlake systems, which are needed to support sustainable water resource planning in data scarce tropical Africa.

  • 79. McDonnell, J. J.
    et al.
    McGuire, K.
    Aggarwal, P.
    Beven, K. J.
    Biondi, D.
    Destouni, G.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Dunn, S.
    James, A.
    Kirchner, J.
    Kraft, P.
    Lyon, S.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Maloszewski, P.
    Newman, B.
    Pfister, L.
    Rinaldo, A.
    Rodhe, A.
    Sayama, T.
    Seibert, J.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Solomon, K.
    Soulsby, C.
    Stewart, M.
    Tetzlaff, D.
    Tobin, C.
    Troch, P.
    Weiler, M.
    Western, A.
    Worman, A.
    Wrede, S.
    How old is streamwater? Open questions in catchment transit time conceptualization, modelling and analysis2010In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 24, no 12, p. 1745-1754Article in journal (Refereed)
  • 80. Michielsen, Astrid
    et al.
    Kalantari, Zahra
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Liljegren, Eva
    Predicting and communicating flood risk of transport infrastructure based on watershed characteristics2016In: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, Vol. 182, p. 505-518Article in journal (Refereed)
    Abstract [en]

    This research aims to identify and communicate water-related vulnerabilities in transport infrastructure, specifically flood risk of road/rail-stream intersections, based on watershed characteristics. This was done using flooding in Varmland and Vastra Gotaland, Sweden in August 2014 as case studies on which risk models are built. Three different statistical modelling approaches were considered: a partial least square regression, a binomial logistic regression, and artificial neural networks. Using the results of the different modelling approaches together in an ensemble makes it possible to cross-validate their results. To help visualize this and provide a tool for communication with stakeholders (e.g., the Swedish Transport Administration - Trafikverket), a flood 'thermometer' indicating the level of flooding risk at a given point was developed. This tool improved stakeholder interaction and helped highlight the need for better data collection in order to increase the accuracy and generalizability of modelling approaches.

  • 81.
    Nathanson, Marcus
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kean, Jason
    Grabs, Thomas
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Uppsala University, Sweden.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Uppsala University, Sweden; University of Zurich, Switzerland.
    Laudon, Hjalmar
    Lyon, Steve
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Modelling rating curves using remotely sensed LiDAR data2012In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 26, no 9, p. 1427-1434Article in journal (Refereed)
    Abstract [en]

    Accurate stream discharge measurements are important for many hydrological studies. In remote locations, however, it is often difficult to obtain stream flow information because of the difficulty in making the discharge measurements necessary to define stage-discharge relationships (rating curves). This study investigates the feasibility of defining rating curves by using a fluid mechanics-based model constrained with topographic data from an airborne LiDAR scanning. The study was carried out for an 8m-wide channel in the boreal landscape of northern Sweden. LiDAR data were used to define channel geometry above a low flow water surface along the 90-m surveyed reach. The channel topography below the water surface was estimated using the simple assumption of a flat streambed. The roughness for the modelled reach was back calculated from a single measurment of discharge. The topographic and roughness information was then used to model a rating curve. To isolate the potential influence of the flat bed assumption, a ‘hybrid model’ rating curve was developed on the basis of data combined from the LiDAR scan and a detailed ground survey. Whereas this hybrid model rating curve was in agreement with the direct measurements of discharge, the LiDAR model rating curve was equally in agreement with the medium and high flow measurements based on confidence intervals calculated from the direct measurements. The discrepancy between the LiDAR model rating curve and the low flow measurements was likely due to reduced roughness associated with unresolved submerged bed topography. Scanning during periods of low flow can help minimize this deficiency. These results suggest that combined ground surveys and LiDAR scans or multifrequency LiDAR scans that see ‘below’ the water surface (bathymetric LiDAR) could be useful in generating data needed to run such a fluid mechanics-based model. This opens a realm of possibility to remotely sense and monitor stream flows in channels in remote locations.

  • 82.
    Nathanson, Marcus
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kean, Jason W.
    Laudon, Hjalmar
    Seibert, Jan
    Grabs, Thomas
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Using LiDAR data to define stream flow rating curves2012Conference paper (Refereed)
    Abstract [en]

    In remote locations, it is difficult to obtain stream flow information because of the difficulty making sufficient dis- charge measurements. In this study we investigate the feasibility to constrain a fluid mechanics-based flow model for defining stream flow rating curves with remotely sensed topographic data from airborne LiDAR scanning. A near infrared (NIR) LiDAR scan was carried out for an 8-m wide channel in northern Sweden. The topographic information from this NIR LiDAR scan along the 90-m surveyed reach was used to define channel geometry above the water surface. To fill in the channel bed topography below the water surface we used a detailed ground survey to create a hybrid model for comparison to a simple assumption of a flat bottom channel. Based on the boundaries of confidence intervals calculated from the direct measurements, we show that for the channel considered the sim- ple flat bottom assumption performs just as well as the hybrid model with regards to estimating direct discharge measurements. The mismatch between the two models was greatest at low flows and may be associated with unre- solved submerged bed topography. This deficiency, while rather small, could potentially be remedied by scanning during periods of low flow, or use other techniques such as multi-frequency bathymetric LiDAR or passive optical remote sensing that offer alternative ways for generating the necessary topographic information.

  • 83. Nickman, Alireza
    et al.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jansson, Per-Erik
    Olofsson, Bo
    Simulating the impact of roads on hydrological responses: examples from Swedish terrain2016In: Hydrology research, ISSN 1998-9563, Vol. 47, no 4, p. 767-781Article in journal (Refereed)
    Abstract [en]

    In this study, the potential impacts of road topography on hydrologic responses at the watershed scale were simulated. The method considered used a geographic information system to identify road embankment locations and subsequently remove them from the baseline elevation data. Starting from both the 'with' and 'without' road elevation model, the surface and near-surface hydrological responses for 20 watersheds in Sweden were modeled in HEC-HMS under three different storm intensities. Flow duration curves (FDCs) were used to compare hydrologic responses for the different modeling scenarios under the various storm intensities. Specifically, L-moment ratios of the FDCs were calculated and their variation compared. Results showed an increase in peak flow amounts and reduction in time to peak with increased storm intensity. In addition, variations of the L-moment ratios were larger in larger watersheds. However, the impact of the roads on the modeled hydrologic responses was much smaller than anticipated and only identifiable through detailed examination of the L-moment statistical descriptors. Our findings not only highlight the potential impacts of road topography on watershed-scale hydrology (especially concerning high intensity storms) but also provide a methodology for detecting the even rather small changes that could manifest, for example, under coupled road network and climatic changes.

  • 84. Ploum, Stefan W.
    et al.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Teuling, Adriaan J.
    Laudon, Hjalmar
    van der Velde, Ype
    Soil frost effects on streamflow recessions in a subarctic catchment2019In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 33, no 9, p. 1304-1316Article in journal (Refereed)
    Abstract [en]

    The Arctic is warming rapidly. Changing seasonal freezing and thawing cycles of the soil are expected to affect river run-off substantially, but how soil frost influences river run-off at catchment scales is still largely unknown. We hypothesize that soil frost alters flow paths and therefore affects storage-discharge relations in subarctic catchments. To test this hypothesis, we used an approach that combines meteorological records and recession analysis. We studied streamflow data (1986-2015) of Abiskojokka, a river that drains a mountainous catchment (560 km(2)) in the north of Sweden (68 degrees latitude). Recessions were separated into frost periods (spring) and nofrost periods (summer) and then compared. We observed a significant difference between recessions of the two periods: During spring, discharge was linearly related to storage, whereas storage-discharge relationships in summer were less linear. An analysis of explanatory factors showed that after winters with cold soil temperatures and low snowpack, storage-discharge relations approached linearity. On the other hand, relatively warm winter soil conditions resulted in storage-discharge relationships that were less linear. Even in summer, relatively cold antecedent winter soils and low snowpack levels had a propagating effect on streamflow. This could be an indication that soil frost controls recharge of deep groundwater flow paths, which affects storage-discharge relationships in summer. We interpret these findings as evidence for soil frost to have an important control over river run-off dynamics. To our knowledge, this is the first study showing significant catchment-integrated effects of soil frost on this spatiotemporal scale.

  • 85. Polpanich, Orn-Uma
    et al.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography. Uppsala University, Sweden.
    Krittasudthacheewa, Chayanis
    Bush, Angela L.
    Kemp-Benedict, Eric
    Modelling impacts of development on water resources in the Huai Sai Bat sub-basin in north-eastern Thailand with a participatory approach2017In: International Journal of Water Resources Development, ISSN 0790-0627, E-ISSN 1360-0648, Vol. 33, no 6, p. 1020-1040Article in journal (Refereed)
    Abstract [en]

    Little is done to connect hydrological modelling with stakeholder participation. This study incorporates agricultural development and climatic changes within the Water Evaluation and Planning hydrological model. This is done with a participatory approach involving four scenario workshops, 400 household surveys and two focus group discussions in the period of 2010-2012 for the ungauged Huai Sai Bat sub-basin as a case study in the Mekong region. The modelling results indicate future increased streamflow during the wet (monsoon) season in response to shifts in the regional climate. Modelled land-use and management changes brought about large unmet water demands, primarily in the dry season.

  • 86. Rafiee, Mojtaba
    et al.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Zahraie, Banafsheh
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jaafarzadeh, Nemat
    Optimal Wastewater Loading under Conflicting Goals and Technology Limitations in a Riverine System2017In: Water environment research, ISSN 1061-4303, E-ISSN 1554-7531, Vol. 89, no 3, p. 211-220Article in journal (Refereed)
    Abstract [en]

    This paper investigates a novel simulationoptimization (S-O) framework for identifying optimal treatment levels and treatment processes for multiple wastewater dischargers to rivers. A commonly used water quality simulation model, Qual2K, was linked to a Genetic Algorithm optimization model for exploration of relevant fuzzy objective-function formulations for addressing imprecision and conflicting goals of pollution control agencies and various dischargers. Results showed a dynamic flow dependence of optimal wastewater loading with good convergence to near global optimum. Explicit considerations of real-world technological limitations, which were developed here in a new S-O framework, led to better compromise solutions between conflicting goals than those identified within traditional S-O frameworks. The newly developed framework, in addition to being more technologically realistic, is also less complicated and converges on solutions more rapidly than traditional frameworks. This technique marks a significant step forward for development of holistic, riverscape-based approaches that balance the conflicting needs of the stakeholders.

  • 87.
    Senkondo, William
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Dar es Salaam, Tanzania; Water Institute, Dar es Salaam, Tanzania.
    Munishi, Subira E.
    Tumbo, Madaka
    Nobert, Joel
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography. The Nature Conservancy, USA.
    Comparing Remotely-Sensed Surface Energy Balance Evapotranspiration Estimates in Heterogeneous and Data-Limited Regions: A Case Study of Tanzania's Kilombero Valley2019In: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 11, no 11, article id 1289Article in journal (Refereed)
    Abstract [en]

    Evapotranspiration (ET) plays a crucial role in integrated water resources planning, development and management, especially in tropical and arid regions. Determining ET is not straightforward due to the heterogeneity and complexity found in real-world hydrological basins. This situation is often compounded in regions with limited hydro-meteorological data that are facing rapid development of irrigated agriculture. Remote sensing (RS) techniques have proven useful in this regard. In this study, we compared the daily actual ET estimates derived from 3 remotely-sensed surface energy balance (SEB) models, namely, the Surface Energy Balance Algorithm for Land (SEBAL) model, the Operational Simplified Surface Energy Balance (SSEBop) model, and the Simplified Surface Balance Index (S-SEBI) model. These products were generated using the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery for a total of 44 satellite overpasses in 2005, 2010, and 2015 in the heterogeneous, highly-utilized, rapidly-developing and data-limited Kilombero Valley (KV) river basin in Tanzania, eastern Africa. Our results revealed that the SEBAL model had a relatively high ET compared to other models and the SSEBop model had relatively low ET compared to the other models. In addition, we found that the S-SEBI model had a statistically similar ET as the ensemble mean of all models. Further comparison of SEB models' ET estimates across different land cover classes and different spatial scales revealed that almost all models' ET estimates were statistically comparable (based on the Wilcoxon's test and the Levene's test at a 95% confidence level), which implies fidelity between and reliability of the ET estimates. Moreover, all SEB models managed to capture the two spatially-distinct ET regimes in KV: the stable/permanent ET regime on the mountainous parts of the KV and the seasonally varied ET over the floodplain which contains a Ramsar site (Kilombero Valley Floodplain). Our results have the potential to be used in hydrological modelling to explore and develop integrated water resources management in the valley. We believe that our approach can be applied elsewhere in the world especially where observed meteorological variables are limited.

  • 88.
    Senkondo, William
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Tumbo, Madaka
    Lyon W., Steve
    Stockholm University, Faculty of Science, Department of Physical Geography.
    On the evolution of hydrological modelling for water resources in Eastern Africa2018In: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, ISSN 1749-8848, E-ISSN 1749-8848, Vol. 13, p. 1-26, article id 028Article, review/survey (Refereed)
    Abstract [en]

    This review provides an assessment of the evolution of hydrological modelling for Eastern Africa. We outline the historical development and perspectives considered as this region, like many regions around the world, sees increasing attention on how water resources can be sustainably developed. We emphasize the spatial scales and modelling approaches that typify the region and how these have changed with time. The review is done in two complementary approaches. The first approach is to explore a practical, real-world example providing context for the Eastern Africa region and the water resource development issues presently faced. We use Tanzania's 34 000 km2 Kilombero Valley (KV) river basin to explore implications of significant gaps in data and modelling scales. We hypothesize that these gaps limit the application of the current state-of-the-science to inform water management policy and practice under current and estimated future conditions. In our second approach, we investigate possible solutions to bridge these gaps through a review of case studies from other Eastern Africa's basins across a range of sizes. Our result highlight that some applications of the models considered under this review anticipated more recent international developments as indicated in Predictions in Ungauged Basins and Panta Rhei initiatives. Through this review, it is clear that there is a possibility to improve understanding of the hydrological processes relevant at scales such as the KV river basin through the use of (1) global precipitation datasets (e.g. satellite and/or homogenized observed data) as input data; (2) remote sensing datasets as model evaluation variable; (3) regionalization around the transferability of model parameters; (4) modification of model codes/structures to suit local conditions; and (5) understanding and application of uncertainty principles in hydrological modelling. Given that many regions of the world face similar water resource management challenges as Eastern Africa; it is likely that the findings of this review could help guide how we develop the next generation of modelling approaches to leverage information from various scales.

  • 89.
    Senkondo, William
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Dar es Salaam, Tanzania; Water Institute, Tanzania.
    Tuwa, Jamila
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Koutsouris, Alexander
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Tumbo, Madaka
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography. The Nature Conservancy, USA.
    Estimating Aquifer Transmissivity Using the Recession-Curve-Displacement Method in Tanzania's Kilombero Valley2017In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 9, no 12, article id 948Article in journal (Refereed)
    Abstract [en]

    Information on aquifer processes and characteristics across scales has long been a cornerstone for understanding water resources. However, point measurements are often limited in extent and representativeness. Techniques that increase the support scale (footprint) of measurements or leverage existing observations in novel ways can thus be useful. In this study, we used a recession-curve-displacement method to estimate regional-scale aquifer transmissivity (T) from streamflow records across the Kilombero Valley of Tanzania. We compare these estimates to local-scale estimates made from pumping tests across the Kilombero Valley. The median T from the pumping tests was 0.18 m(2)/min. This was quite similar to the median T estimated from the recession-curve-displacement method applied during the wet season for the entire basin (0.14 m(2)/min) and for one of the two sub-basins tested (0.16 m(2)/min). On the basis of our findings, there appears to be reasonable potential to inform water resource management and hydrologic model development through streamflow-derived transmissivity estimates, which is promising for data-limited environments facing rapid development, such as the Kilombero Valley.

  • 90.
    Sjöberg, Ylva
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Coon, Ethan
    Sannel, A. Britta K.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Pannetier, Romain
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Harp, Dylan
    Frampton, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Painter, Scott L.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Thermal effects of groundwater flow through subarctic fens - a case study based on field observations and numerical modelingManuscript (preprint) (Other academic)
  • 91.
    Sjöberg, Ylva
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Coon, Ethan
    Sannel, A. Britta K.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Pannetier, Romain
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Harp, Dylan
    Frampton, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Painter, Scott L.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Thermal effects of groundwater flow through subarctic fens: A case study based on field observations and numerical modeling2016In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 52, no 3, p. 1591-1606Article in journal (Refereed)
    Abstract [en]

    Modeling and observation of ground temperature dynamics are the main tools for understanding current permafrost thermal regimes and projecting future thaw. Until recently, most studies on permafrost have focused on vertical ground heat fluxes. Groundwater can transport heat in both lateral and vertical directions but its influence on ground temperatures at local scales in permafrost environments is not well understood. In this study we combine field observations from a subarctic fen in the sporadic permafrost zone with numerical simulations of coupled water and thermal fluxes. At the Tavvavuoma study site in northern Sweden, ground temperature profiles and groundwater levels were observed in boreholes. These observations were used to set up one- and two-dimensional simulations down to 2 m depth across a gradient of permafrost conditions within and surrounding the fen. Two-dimensional scenarios representing the fen under various hydraulic gradients were developed to quantify the influence of groundwater flow on ground temperature. Our observations suggest that lateral groundwater flow significantly affects ground temperatures. This is corroborated by modeling results that show seasonal ground ice melts 1 month earlier when a lateral groundwater flux is present. Further, although the thermal regime may be dominated by vertically conducted heat fluxes during most of the year, isolated high groundwater flow rate events such as the spring freshet are potentially important for ground temperatures. As sporadic permafrost environments often contain substantial portions of unfrozen ground with active groundwater flow paths, knowledge of this heat transport mechanism is important for understanding permafrost dynamics in these environments.

  • 92.
    Sjöberg, Ylva
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Frampton, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Using streamflow characteristics to explore permafrost thawing in northern Swedish catchments2012In: Hydrogeology Journal, ISSN 1431-2174, E-ISSN 1435-0157, Vol. 21, no 1, p. 121-131Article in journal (Refereed)
    Abstract [en]

    The recent and rapid warming of the Arcticleads to thawing of permafrost, which influences andchanges subsurface water-flow systems in such landscapes.This study explores the utility of catchments as“sentinels of change” by considering long-term dischargedata from 17 stations on unregulated rivers in northernSweden and analyzing trends in annual minimum dischargeand recession flow characteristics. For the catchmentsconsidered, the annual minimum discharge hasincreased significantly (based on the Mann Kendall test ata 95% confidence level) in nine of the catchments anddecreased significantly in one catchment. Consideringchanges in recession-flow characteristics, seven catchmentsshowed significant trends consistent with permafrostthawing while two catchments showed significanttrends in the opposite direction. These results aremechanistically consistent with generic physically basedmodeling studies and the geological setting, as thecatchments considered span the spatial limit of permafrostextent. This study illuminates the potential for usinghydrologic observations to monitor changes in catchmentscalepermafrost. Further, this opens the door for researchto isolate the mechanisms behind the different trendsobserved and to gauge their ability to reflect actualpermafrost conditions at the catchment scale.

  • 93.
    Sjöberg, Ylva
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Marklund, Per
    Pettersson, Rickard
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Geophysical mapping of palsa peatland permafrost2015In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 9, p. 465-478Article in journal (Refereed)
    Abstract [en]

    Permafrost peatlands are hydrological and biogeochemicalhotspots in the discontinuous permafrost zone.Non-intrusive geophysical methods offer a possibility tomap current permafrost spatial distributions in these environments.In this study, we estimate the depths to the permafrosttable and base across a peatland in northern Sweden,using ground penetrating radar and electrical resistivitytomography. Seasonal thaw frost tables (at 0.5m depth),taliks (2.1–6.7m deep), and the permafrost base (at 16mdepth) could be detected. Higher occurrences of taliks werediscovered at locations with a lower relative height of permafrostlandforms, which is indicative of lower ground icecontent at these locations. These results highlight the addedvalue of combining geophysical techniques for assessing spatialdistributions of permafrost within the rapidly changingsporadic permafrost zone. For example, based on a back-ofthe-envelope calculation for the site considered here, we estimatedthat the permafrost could thaw completely within thenext 3 centuries. Thus there is a clear need to benchmark currentpermafrost distributions and characteristics, particularlyin under studied regions of the pan-Arctic.

  • 94. Steenhuis, T.
    et al.
    Dahlke, H.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Easton, Z.
    Lyon, S.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, G.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Brown, L.
    Walte, T.
    Dissecting the variable source area – Four dimensional characterization of flow pathways and water mixing processes in VSAs2011In: Geophysical Research Abstracts, Vol. 13, EGU2011-11184, 2011Conference paper (Refereed)
  • 95.
    Steve, Lyon
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Braun, Hendrik
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Temnerud, Johan
    SLU-Ultuna.
    Accounting for instream lakes when interpolating stream water chemistry observations2012In: Journal of Spatial Hydrology, ISSN 1530-4736, E-ISSN 1530-4736, Vol. 11, no 2, p. 1-20Article in journal (Refereed)
    Abstract [en]

    Direct monitoring of stream water chemistry is an increasingly important tool for securing stream water quality and assessing stream ecological functioning as it relates to overall ecosystem health. Such monitoring is often discontinuous in spatial extent and, thus, needs to be interpolated at unsampled locations if the desired end product is a continuous map of stream water chemistry. Recently there have been major advances in the use and development of geostatistical methods (such as kriging) for interpolating between observations of stream water chemistry within stream networks. This study investigated the influence of distance definition on interpolation of synoptically collected stream water chemistry samples. In particular, we developed a new methodology for adjusting instream distances between stream water chemistry observations such that instream lakes (which are ubiquitous in northern, boreal landscapes) are explicitly accounted for in geostatistical interpolations. The methodology developed was tested using stream chemistry data for five different constituents coming from synoptic sampling campaigns conducted across four boreal Swedish catchments during two distinct seasons. The ability of this new, lake adjusted instream distance (LAID) to produce interpolated maps of stream water chemistry was compared to that of traditional Euclidean distance (ED) and instream distance (ID). The results indicated that using LAIDs in this boreal landscape tended to improve interpolation compared to the other distance definitions considered. The grade of improvement, however, tended to vary between the constituent, watershed and season considered suggesting that the influence of instream lakes on water chemistry is quite variable in this landscape throughout the year.

  • 96. Tessema, Selome M.
    et al.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Setegn, Shimelis G.
    Mörtberg, Ulla
    Effects of Different Retention Parameter Estimation Methods on the Prediction of Surface Runoff Using the SCS Curve Number Method2014In: Water resources management, ISSN 0920-4741, E-ISSN 1573-1650, Vol. 28, no 10, p. 3241-3254Article in journal (Refereed)
    Abstract [en]

    Quantifying different hydrological components is an initial step for sustainable water resources planning and management. One rising concern is the conflict between the environment, hydropower and agriculture mainly in lowland areas where a large share of the base flows need to be abstracted. The Soil and Water Assessment Tool (SWAT) model was used to understand the hydrological processes of the Upper Awash River Basin with the emphasis on analyzing the different options for surface runoff generation using the Soil Conservation Service (SCS) Curve Number (CN) method. In this study, SWAT was applied incorporating two methods for estimating the retention parameter (S) for the SCS-CN method. The first allowed S to vary with soil profile moisture content (SM method) and the second allowed S to vary with accumulated plant evapotranspiration (PT method). Hydrograph comparison indicated that the PT method was better in simulating peak flows while the SM method was better in simulating the low flows. While the predicted stream flow hydrographs showed an agreement between the two methods, the simulated annual water balance indicated a disagreement in quantifying the different hydrological components. After evapotranspiration, base flow was the dominant component simulated in the SM method whereas surface runoff was the foremost in the PT method simulation. The analysis indicated that care must be taken when selecting an appropriate tool for quantifying hydrologic system to be used for decision making especially for un-gauged catchments where validation of model results is not possible.

  • 97.
    Thorslund, Josefin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Jawitz, James W.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Basu, Nandita B.
    Chalov, Sergey R.
    Cohen, Matthew J.
    Creed, Irena F.
    Goldenberg, Romain
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hylin, Anna
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kalantari, Zahra
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Koussis, Antonis D.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mazi, Katerina
    Mård, Johanna
    Persson, Klas
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Pietroń, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Prieto, Carmen
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Quin, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography.
    van Meter, Kimberly
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Wetlands as large-scale nature-based solutions: Status and challenges for research, engineering and management2017In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, Vol. 108, p. 489-497Article in journal (Refereed)
    Abstract [en]

    Wetlands are often considered as nature-based solutions that can provide a multitude of services of great social, economic and environmental value to humankind. Changes in land-use, water-use and climate can all impact wetland functions and services. These changes occur at scales extending well beyond the local scale of an individual wetland. However, in practical applications, engineering and management decisions usually focus on individual wetland projects and local site conditions. Here, we systematically investigate if and to what extent research has addressed the large-scale dynamics of landscape systems with multiple wetlands, hereafter referred to as wetlandscapes, which are likely to be relevant for understanding impacts of regional to global change. Although knowledge in many cases is still limited, evidence suggests that the aggregated effects of multiple wetlands in the landscape can differ considerably from the functions observed at individual wetland scales. This applies to provisioning of ecosystem services such as coastal protection, biodiversity support, groundwater level and soil moisture regulation, flood regulation and contaminant retention. We show that parallel and circular flow-paths, through which wetlands are interconnected in the landscape, may largely control such scale-function differences. We suggest ways forward for addressing the mismatch between the scales at which changes take place and the scale at which observations and implementation are currently made. These suggestions can help bridge gaps between researchers and engineers, which is critical for improving wetland function-effect predictability and management.

  • 98. Troch, Peter A.
    et al.
    Berne, Alexis
    Bogaart, Patrick
    Harman, Ciaran
    Hilberts, Arno G. J.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Paniconi, Claudio
    Pauwels, Valentijn R. N.
    Rupp, David E.
    Selker, John S.
    Teuling, Adriaan J.
    Uijlenhoet, Remko
    Verhoest, Niko E. C.
    The importance of hydraulic groundwater theory in catchment hydrology: The legacy of Wilfried Brutsaert and Jean-Yves Parlange2013In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 49, no 9, p. 5099-5116Article, review/survey (Refereed)
    Abstract [en]

    Based on a literature overview, this paper summarizes the impact and legacy of the contributions of Wilfried Brutsaert and Jean-Yves Parlange (Cornell University) with respect to the current state-of-the-art understanding in hydraulic groundwater theory. Forming the basis of many applications in catchment hydrology, ranging from drought flow analysis to surface water-groundwater interactions, hydraulic groundwater theory simplifies the description of water flow in unconfined riparian and perched aquifers through assumptions attributed to Dupuit and Forchheimer. Boussinesq (1877) derived a general equation to study flow dynamics of unconfined aquifers in uniformly sloping hillslopes, resulting in a remarkably accurate and applicable family of results, though often challenging to solve due to its nonlinear form. Under certain conditions, the Boussinesq equation can be solved analytically allowing compact representation of soil and geomorphological controls on unconfined aquifer storage and release dynamics. The Boussinesq equation has been extended to account for flow divergence/convergence as well as for nonuniform bedrock slope (concave/convex). The extended Boussinesq equation has been favorably compared to numerical solutions of the three-dimensional Richards equation, confirming its validity under certain geometric conditions. Analytical solutions of the linearized original and extended Boussinesq equations led to the formulation of similarity indices for baseflow recession analysis, including scaling rules, to predict the moments of baseflow response. Validation of theoretical recession parameters on real-world streamflow data is complicated due to limited measurement accuracy, changing boundary conditions, and the strong coupling between the saturated aquifer with the overlying unsaturated zone. However, recent advances are shown to have mitigated several of these issues. The extended Boussinesq equation has been successfully applied to represent baseflow dynamics in catchment-scale hydrological models, and it is currently considered to represent lateral redistribution of groundwater in land surface schemes applied in global circulation models. From the review, it is clear that Wilfried Brutsaert and Jean-Yves Parlange stimulated a body of research that has led to several fundamental discoveries and practical applications with important contributions in hydrological modeling.

  • 99. van der Velde, Ype
    et al.
    Heidbuechel, Ingo
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Nyberg, Lars
    Rodhe, Allan
    Bishop, Kevin
    Troch, Peter A.
    Consequences of mixing assumptions for time-variable travel time distributions2015In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 29, no 16, p. 3460-3474Article in journal (Refereed)
    Abstract [en]

    The current generation of catchment travel time distribution (TTD) research, integrating nearly three decades of work since publication of Water's Journey from Rain to Stream, seeks to represent the full distribution in catchment travel times and its temporal variability. Here, we compare conceptualizations of increasing complexity with regards to mixing of water storages and evaluate how these assumptions influence time-variable TTD estimates for two catchments with contrasting climates: the Gardsjon catchment in Sweden and the Marshall Gulch catchment in Arizona, USA. Our results highlight that, as long as catchment TTDs cannot be measured directly but need to be inferred from input-output signals of catchments, the inferred catchment TTDs depend strongly on the underlying assumptions of mixing within a catchment. Furthermore, we found that the conceptualization of the evapotranspiration flux strongly influences the inferred travel times of stream discharge. For the wet and forested Gardsjon catchment in Sweden, we inferred that evapotranspiration most likely resembles a completely mixed sample of the water stored in the catchment; however, for the drier Marshall Gulch catchment in Arizona, evapotranspiration predominantly contained the younger water stored in the catchment. For the Marshall Gulch catchment, this higher probability for young water in evapotranspiration resulted in older water in the stream compared to travel times inferred with assumptions of complete mixing. New observations that focus on the TTD of the evapotranspiration flux and the actual travel time of water through a catchment are necessary to improve identification of mixing and consequently travel times of stream water.

  • 100.
    van der Velde, Ype
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Data-driven regionalization of river discharges and emergent land cover-evapotranspiration relationships across Sweden2013In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 118, no 6, p. 2576-2587Article in journal (Refereed)
    Abstract [en]

    Changes in river discharge and river water quality, due to climate change and other drivers such as land cover change, pose both societal and ecosystem threats. Analyses of measured terrestrial river fluxes are key for identifying the drivers and quantifying the magnitudes of such riverine changes. In this paper, we develop and apply a data-driven regionalization approach using the dense network of discharge measurements in Sweden. The developed regionalization approach facilitates detailed mapping of discharges (Q) and change trends in Q across Sweden. Combining these with estimates of precipitation (P) and change trends in P, we estimated actual evapotranspiration (AET) and change trends in AET via catchment-scale water balance constraints. We identified characteristic land cover-evapotranspiration relationships by plotting water use efficiency (AET/P) against energy use efficiency (AET/potential ET) for areas with unique land cover across Sweden. Our results show that wetlands have clearly lower water and energy use efficiencies compared to open waters, forests, and agriculture, and that agriculture has water and energy use efficiencies closest to those of open waters. We further compared the data-driven regionalization estimates of different water balance components with estimates of regional climate models (RCMs). The RCMs do not describe well the observed change trends in Sweden. In particular, for evapotranspiration, the observed change trends are not reproduced by any of the investigated 24 RCMs. Citation: van der Velde, Y., S. W. Lyon, and G. Destouni (2013), Data-driven regionalization of river discharges and emergent land cover-evapotranspiration relationships across Sweden.

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