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  • 1. Brauer, C. C.
    et al.
    Teuling, A. J.
    Overeem, A.
    van der Velde, Y.
    Hydrology and Quantitative Water Management Group, Wageningen University, Wageningen, The Netherlands.
    Hazenberg, P.
    Warmerdam, P. M. M.
    Uijlenhoet, R.
    Anatomy of extraordinary rainfall and flash flood in a Dutch lowland catchment2011In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 15, p. 1991-2005Article in journal (Refereed)
    Abstract [en]

    On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of rainfall events lasting for more than a day. Over an area of 740 km(2) more than 120 mm of rainfall were observed in 24 h. This extreme event resulted in local flooding of city centres, highways and agricultural fields, and considerable financial loss. In this paper we report on the unprecedented flash flood triggered by this exceptionally heavy rainfall event in the 6.5 km(2) Hupsel Brook catchment, which has been the experimental watershed employed by Wageningen University since the 1960s. This study aims to improve our understanding of the dynamics of such lowland flash floods. We present a detailed hydrometeorological analysis of this extreme event, focusing on its synoptic meteorological characteristics, its space-time rainfall dynamics as observed with rain gauges, weather radar and a microwave link, as well as the measured soil moisture, groundwater and discharge response of the catchment. At the Hupsel Brook catchment 160 mm of rainfall was observed in 24 h, corresponding to an estimated return period of well over 1000 years. As a result, discharge at the catchment outlet increased from 4.4x10(-3) to nearly 5m(3) s(-1). Within 7 h discharge rose from 5x10(-2) to 4.5m(3) s(-1). The catchment response can be divided into four phases: (1) soil moisture reservoir filling, (2) groundwater response, (3) surface depression filling and surface runoff and (4) backwater feedback. The first 35mm of rainfall were stored in the soil without a significant increase in discharge. Relatively dry initial conditions (in comparison to those for past discharge extremes) prevented an even faster and more extreme hydrological response.

  • 2.
    Clason, Caroline C.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Coch, Caroline
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Brugger, K.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dye tracing to determine flow properties of hydrocarbon-polluted Rabots glaciar, Kebnekaise, Sweden2015In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, no 6, p. 2701-2715Article in journal (Refereed)
    Abstract [en]

    Over 11 000 L of kerosene was deposited on the surface of Rabots glaciar on the Kebnekaise Massif, northern Sweden, following the crash of a Royal Norwegian Air Force aircraft in March 2012. An environmental monitoring programme was subsequently commissioned, including a series of dye tracing experiments during the 2013 melt season, conducted to investigate the transport of pollutants through the glacier hydrological system. This experimental set-up provided a basis from which we could gain new insight into the internal hydrological system of Rabots glaciar. Results of dye tracing experiments reveal a degree of homogeneity in the topology of the drainage system throughout July and August, with an increase in efficiency as the season progresses, as reflected by decreasing temporary storage and dispersivity. Early onset of melting likely led to formation of an efficient, discrete drainage system early in the melt season, subject to decreasing sinuosity and braiding as the season progressed. Four distinct meltwater flow regimes are identified to summarize the temporal and spatial evolution of the system. Analysis of turbidity-discharge hysteresis further supports the formation of discrete, efficient drainage, with clockwise diurnal hysteresis suggesting easy mobilization of readily available sediments in channels. Dye injection immediately downstream of the pollution source zone reveals prolonged storage of dye followed by fast, efficient release. Twinned with a low dye recovery, and supported by sporadic detection of hydrocarbons in the proglacial river, we suggest that meltwater, and thus pollutants in solution, may be released periodically through an efficient, and likely pressurized, hydrological system within the upper reaches of the glacier.

  • 3.
    Dahlke, Helen E.
    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.
    Stedinger, J. R.
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Contrasting trends in floods for two sub-arctic catchments in northern Sweden - does glacier presence matter?2012In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 16, no 7, p. 2123-2141Article in journal (Refereed)
    Abstract [en]

    Our understanding is limited to how transient changes in glacier response to climate warming will influence the catchment hydrology in the Arctic and Sub-Arctic. This understanding is particularly incomplete for flooding extremes because understanding the frequency of such unusual events requires long records of observation not often available for the Arctic and Sub-Arctic. This study presents a statistical analysis of trends in the magnitude and timing of flood extremes and the mean summer discharge in two sub-arctic catchments, Tarfala and Abisko, in northern Sweden. The catchments have different glacier covers (30% and 1%, respectively). Statistically significant trends (at the 5% level) were identified for both catchments on an annual and on a seasonal scale (3-months averages) using the Mann-Kendall trend test. Stationarity of flood records was tested by analyzing trends in the flood quantiles, using generalized least squares regression. Hydrologic trends were related to observed changes in the precipitation and air temperature, and were correlated with 3-months averaged climate pattern indices (e.g. North Atlantic oscillation). Both catchments showed a statistically significant increase in the annual mean air temperature over the comparison time period of 1985-2009 (Tarfala and Abisko p < 0.01), but did not show significant trends in the total precipitation (Tarfala p = 0.91, Abisko p = 0.44). Despite the similar climate evolution over the studied period in the two catchments, data showed contrasting trends in the magnitude and timing of flood peaks and the mean summer discharge. Hydrologic trends indicated an amplification of the streamflow and flood response in the highly glacierized catchment and a dampening of the response in the non-glacierized catchment. The glacierized mountain catchment showed a statistically significant increasing trend in the flood magnitudes (p = 0.04) that is clearly correlated to the occurrence of extreme precipitation events. It also showed a significant increase in mean summer discharge (p = 0.0002), which is significantly correlated to the decrease in glacier mass balance and the increase in air temperature (p = 0.08). Conversely, the non-glacierized catchment showed a significant decrease in the mean summer discharge (p = 0.01), the flood magnitudes (p = 0.07) and an insignificant trend towards earlier flood occurrences (p = 0.53). These trends are explained by a reduction of the winter snow pack due to higher temperatures in the winter and spring and an increasing soil water storage capacity or catchment storage due to progressively thawing permafrost.

  • 4. de Louw, P. G. B.
    et al.
    van der Velde, Y.
    Wageningen University, Environmental Sciences Group, Hydrology and quantitative water management, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
    van der Zee, S. E. A. T. M.
    Quantifying water and salt fluxes in a lowland polder catchment dominated by boil seepage: a probabilistic end-member mixing approach2011In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 15, p. 2101-2117Article in journal (Refereed)
    Abstract [en]

    Upward saline groundwater seepage is leading to surface water salinization of deep lying polders in the Netherlands. Identifying measures to reduce the salt content requires a thorough understanding and quantification of the dominant sources of water and salt on a daily basis. However, as in most balance studies, there are large uncertainties in the contribution from groundwater seepage. Taking these into account, we applied a probabilistic (GLUE) end-member mixing approach to simulate two years of daily to weekly observations of discharge, salt loads and salt concentration of water pumped out of an artificially drained polder catchment area. We were then able to assess the contribution from the different sources to the water and salt balance of the polder and uncertainties in their quantification. Our modelling approach demonstrates the need to distinguish preferential from diffuse seepage. Preferential seepage via boils contributes, on average, 66% to the total salt load and only about 15% to the total water flux into the polder and therefore forms the main salinization pathway. With the model we were able to calculate the effect of future changes on surface water salinity and to assess the uncertainty in our predictions. Furthermore, we analyzed the parameter sensitivity and uncertainty to determine for which parameter the quality of field measurements should be improved to reduce model input and output uncertainty. High frequency measurements of polder water discharge and weighted concentration at the outlet of the catchment area appear to be essential for obtaining reliable simulations of water and salt fluxes and for allotting these to the different sources.

  • 5. Ewen, Tracy
    et al.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. University of Zurich, Germany; Uppsala University, Sweden.
    Learning about water resource sharing through game play2016In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 20, no 10, p. 4079-4091Article in journal (Refereed)
    Abstract [en]

    Games are an optimal way to teach about water resource sharing, as they allow real-world scenarios to be enacted. Both students and professionals learning about water resource management can benefit from playing games, through the process of understanding both the complexity of sharing of resources between different groups and decision outcomes. Here we address how games can be used to teach about water resource sharing, through both playing and developing water games. An evaluation of using the web-based game Irrigania in the classroom setting, supported by feedback from several educators who have used Irrigania to teach about the sustainable use of water resources, and decision making, at university and high school levels, finds Irrigania to be an effective and easy tool to incorporate into a curriculum. The development of two water games in a course for masters students in geography is also presented as a way to teach and communicate about water resource sharing. Through game development, students learned soft skills, including critical thinking, problem solving, team work, and time management, and overall the process was found to be an effective way to learn about water resource decision outcomes. This paper concludes with a discussion of learning outcomes from both playing and developing water games.

  • 6. Exbrayat, J. -F
    et al.
    Viney, N. R.
    Seibert, J.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Wrede, S.
    Frede, H. -G
    Breuer, L.
    Ensemble modelling of nitrogen fluxes: data fusion for a Swedish meso-scale catchment2010In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 14, no 12, p. 2383-2397Article in journal (Refereed)
  • 7.
    Gong, Lebing
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Halldin, S.
    Xu, C-Y
    Large-scale runoff generation - parsimonious parameterisation using high-resolution topography2011In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 15, no 8, p. 2481-2494Article in journal (Refereed)
    Abstract [en]

    World water resources have primarily been analysed by global-scale hydrological models in the last decades. Runoff generation in many of these models are based on process formulations developed at catchments scales. The division between slow runoff (baseflow) and fast runoff is primarily governed by slope and spatial distribution of effective water storage capacity, both acting at very small scales. Many hydrological models, e. g. VIC, account for the spatial storage variability in terms of statistical distributions; such models are generally proven to perform well. The statistical approaches, however, use the same runoff-generation parameters everywhere in a basin. The TOPMODEL concept, on the other hand, links the effective maximum storage capacity with real-world topography. Recent availability of global high-quality, high-resolution topographic data makes TOPMODEL attractive as a basis for a physically-based runoff-generation algorithm at large scales, even if its assumptions are not valid in flat terrain or for deep groundwater systems. We present a new runoff-generation algorithm for large-scale hydrology based on TOPMODEL concepts intended to overcome these problems. The TRG (topography-derived runoff generation) algorithm relaxes the TOPMODEL equilibrium assumption so baseflow generation is not tied to topography. TRG only uses the topographic index to distribute average storage to each topographic index class. The maximum storage capacity is proportional to the range of topographic index and is scaled by one parameter. The distribution of storage capacity within large-scale grid cells is obtained numerically through topographic analysis. The new topography-derived distribution function is then inserted into a runoff-generation framework similar VIC's. Different basin parts are parameterised by different storage capacities, and different shapes of the storage-distribution curves depend on their topographic characteristics. The TRG algorithm is driven by the HydroSHEDS dataset with a resolution of 3 '' (around 90 m at the equator). The TRG algorithm was validated against the VIC algorithm in a common model framework in 3 river basins in different climates. The TRG algorithm performed equally well or marginally better than the VIC algorithm with one less parameter to be calibrated. The TRG algorithm also lacked equifinality problems and offered a realistic spatial pattern for runoff generation and evaporation.

  • 8. Harpold, A. A.
    et al.
    Marshall, J. A.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Barnhart, T. B.
    Fisher, B. A.
    Donovan, M.
    Brubaker, K. M.
    Crosby, C. J.
    Glenn, N. F.
    Glennie, C. L.
    Kirchner, P. B.
    Lam, Norris
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mankoff, K. D.
    McCreight, J. L.
    Molotch, N. P.
    Musselman, K. N.
    Pelletier, J.
    Russo, T.
    Sangireddy, H.
    Sjöberg, Ylva
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Swetnam, T.
    West, N.
    Laser vision: lidar as a transformative tool to advance critical zone science2015In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, no 6, p. 2881-2897Article in journal (Refereed)
    Abstract [en]

    Observation and quantification of the Earth's surface is undergoing a revolutionary change due to the increased spatial resolution and extent afforded by light detection and ranging (lidar) technology. As a consequence, lidar-derived information has led to fundamental discoveries within the individual disciplines of geomorphology, hydrology, and ecology. These disciplines form the cornerstones of critical zone (CZ) science, where researchers study how interactions among the geosphere, hydrosphere, and biosphere shape and maintain the 'zone of life', which extends from the top of unweathered bedrock to the top of the vegetation canopy. Fundamental to CZ science is the development of transdisciplinary theories and tools that transcend disciplines and inform other's work, capture new levels of complexity, and create new intellectual outcomes and spaces. Researchers are just beginning to use lidar data sets to answer synergistic, transdisciplinary questions in CZ science, such as how CZ processes co-evolve over long timescales and interact over shorter timescales to create thresholds, shifts in states and fluxes of water, energy, and carbon. The objective of this review is to elucidate the transformative potential of lidar for CZ science to simultaneously allow for quantification of topographic, vegetative, and hydrological processes. A review of 147 peer-reviewed lidar studies highlights a lack of lidar applications for CZ studies as 38 % of the studies were focused in geomorphology, 18 % in hydrology, 32 % in ecology, and the remaining 12 % had an interdisciplinary focus. A handful of exemplar transdisciplinary studies demonstrate lidar data sets that are well-integrated with other observations can lead to fundamental advances in CZ science, such as identification of feedbacks between hydrological and ecological processes over hillslope scales and the synergistic co-evolution of landscape-scale CZ structure due to interactions amongst carbon, energy, and water cycles. We propose that using lidar to its full potential will require numerous advances, including new and more powerful open-source processing tools, exploiting new lidar acquisition technologies, and improved integration with physically based models and complementary in situ and remote-sensing observations. We provide a 5-year vision that advocates for the expanded use of lidar data sets and highlights subsequent potential to advance the state of CZ science.

  • 9.
    Hoff, Holger
    et al.
    Stockholm University, Stockholm Environment Institute. Potsdam Institute for Climate Impact Research.
    Döll, P.
    Fader, M.
    Gerten, D.
    Water footprints of cities - indicators for sustainable consumption and production 2014In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 18, no 1, p. 213-226Article in journal (Refereed)
    Abstract [en]

    Water footprints have been proposed as sustainability indicators, relating the consumption of goods like food to the amount of water necessary for their production and the impacts of that water use in the source regions. We further developed the existing water footprint methodology, by globally resolving virtual water flows from production to consumption regions for major food crops at 5 arcmin spatial resolution. We distinguished domestic and international flows, and assessed local impacts of export production. Applying this method to three exemplary cities, Berlin, Delhi and Lagos, we find major differences in amounts, composition, and origin of green and blue virtual water imports, due to differences in diets, trade integration and crop water productivities in the source regions. While almost all of Delhi's and Lagos' virtual water imports are of domestic origin, Berlin on average imports from more than 4000 km distance, in particular soy (livestock feed), coffee and cocoa. While 42% of Delhi's virtual water imports are blue water based, the fractions for Berlin and Lagos are 2 and 0.5%, respectively, roughly equal to the water volumes abstracted in these two cities for domestic water use. Some of the external source regions of Berlin's virtual water imports appear to be critically water scarce and/or food insecure. However, for deriving recommendations on sustainable consumption and trade, further analysis of context-specific costs and benefits associated with export production will be required.

  • 10.
    Jantze, Elin J.
    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.
    Subsurface release and transport of dissolved carbon in a discontinuous permafrost region2013In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 17, no 10, p. 3827-3839Article in journal (Refereed)
    Abstract [en]

    Subsurface hydrological flow pathways and advection rates through the landscape affect the quantity and timing of hydrological transport of dissolved carbon. This study investigates hydrological carbon transport through the subsurface to streams and how it is affected by the distribution of subsurface hydrological pathways and travel times through the landscape. We develop a consistent mechanistic, pathway- and travel time-based modeling approach for release and transport of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). The model implications are tested against observations in the subarctic Abiskojokken catchment in northernmost Sweden (68 degrees 21'N, 18 degrees 49'E) as a field case example of a discontinuous permafrost region. The results show: (a) For DOC, both concentration and load are essentially flow-independent because their dynamics are instead dominated by the annual renewal and depletion. Specifically, the flow independence is the result of the small characteristic DOC respiration-dissolution time scale, in the range of 1 yr, relative to the average travel time of water through the subsurface to the stream. (b) For DIC, the load is highly flow-dependent due to the large characteristic weathering-dissolution time, much larger than 1 yr, relative to the average subsurface water travel time to the stream. This rate relation keeps the DIC concentration essentially flow-independent, and thereby less fluctuating in time than the DIC load.

  • 11.
    Jaramillo, Fernando
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, Stockholm Resilience Centre. University of Gothenburg, Sweden.
    Cory, Neil
    Arheimer, Berit
    Laudon, Hjalmar
    van der Velde, Ype
    Hasper, Thomas B.
    Teutschbein, Claudia
    Uddling, Johan
    Dominant effect of increasing forest biomass on evapotranspiration: interpretations of movement in Budyko space2018In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 22, no 1, p. 567-580Article in journal (Refereed)
    Abstract [en]

    During the last 6 decades, forest biomass has increased in Sweden mainly due to forest management, with a possible increasing effect on evapotranspiration. However, increasing global CO2 concentrations may also trigger physiological water-saving responses in broadleaf tree species, and to a lesser degree in some needleleaf conifer species, inducing an opposite effect. Additionally, changes in other forest attributes may also affect evapotranspiration. In this study, we aimed to detect the dominating effect(s) of forest change on evapotranspiration by studying changes in the ratio of actual evapotranspiration to precipitation, known as the evaporative ratio, during the period 1961-2012. We first used the Budyko framework of water and energy availability at the basin scale to study the hydroclimatic movements in Budyko space of 65 temperate and boreal basins during this period. We found that movements in Budyko space could not be explained by climatic changes in precipitation and potential evapotranspiration in 60% of these basins, suggesting the existence of other dominant drivers of hydroclimatic change. In both the temperate and boreal basin groups studied, a negative climatic effect on the evaporative ratio was counteracted by a positive residual effect. The positive residual effect occurred along with increasing standing forest biomass in the temperate and boreal basin groups, increasing forest cover in the temperate basin group and no apparent changes in forest species composition in any group. From the three forest attributes, standing forest biomass was the one that could explain most of the variance of the residual effect in both basin groups. These results further suggest that the water-saving response to increasing CO2 in these forests is either negligible or overridden by the opposite effect of the increasing forest biomass. Thus, we conclude that increasing standing forest biomass is the dominant driver of long-term and large-scale evapotranspiration changes in Swedish forests.

  • 12.
    Jarsjö, Jerker
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Asokan, Shilpa M.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Prieto, Carmen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Bring, Arvid
    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.
    Hydrological responses to climate change conditioned by historic alterations of land use and water use2012In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 16, no 5, p. 1335-1347Article in journal (Refereed)
    Abstract [en]

    This paper quantifies and conditions expected hydrological responses in the Aral Sea Drainage Basin (ASDB; occupying 1.3% of the earth's land surface), Central Asia, to multi-model projections of climate change in the region from 20 general circulation models (GCMs). The aim is to investigate how uncertainties of future climate change interact with the effects of historic human re-distributions of water for land irrigation to influence future water fluxes and water resources. So far, historic irrigation changes have greatly amplified water losses by evapotranspiration (ET) in the ASDB, whereas 20th century climate change has not much affected the regional net water loss to the atmosphere. Results show that errors in temperature (T) and precipitation (P) from single GCMs have large influence on projected change trends (for the period 2010-2039) of river runoff (R), even though the ASDB is spatially well resolved by current GCMs. By contrast, observed biases in GCM ensemble mean results have relatively small influence on projected R change trends. Ensemble mean results show that projected future climate change will considerably increase the net water loss to the atmosphere. Furthermore, the ET response strength to any future T change will be further increased by maintained (or increased) irrigation practices, which shows how climate change and water use change can interact in modifying ET (and R). With maintained irrigation practices, R is likely to decrease to near-total depletion, with risk for cascading ecological regime shifts in aquatic ecosystems downstream of irrigated land areas. Without irrigation, the agricultural areas of the principal Syr Darya river basin could sustain a 50% higher T increase (of 2.3 A degrees C instead of the projected 1.5 A degrees C until 2010-2039) before yielding the same consumptive ET increase and associated R decrease as with the present irrigation practices.

  • 13. Jonker, L.
    et al.
    van der Zaag, P.
    Gumbo, B.
    Rockström, Johan
    Stockholm University, Stockholm Resilience Centre.
    Love, D.
    Savenije, H. H. G.
    A regional and multi-faceted approach to postgraduate water education - the WaterNet experience in Southern Africa2012In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 16, no 11, p. 4225-4232Article in journal (Refereed)
    Abstract [en]

    This paper reports the experience of a regional network of academic departments involved in water education that started as a project and evolved, over a period of 12 yr, into an independent network organisation. The paper pursues three objectives. First, it argues that it makes good sense to organise postgraduate education and research on water resources on a regional scale and presents the WaterNet experience as an example that a regional approach can work. Second, it presents preliminary findings and conclusions that the regional approach presented by WaterNet did make a contribution to the capacity needs of the region both in terms of management and research capacity. Third, it draws two generalised lessons from the WaterNet experience. Lesson one pertains to the importance of legitimate ownership and an accountability structure for network effectiveness. Lesson two is related to the financial and intellectual resources required to jointly developing educational programmes through shared experience.

  • 14.
    Keys, Patrick W.
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Colorado State University, USA.
    Barnes, E. A.
    van der Ent, R. J.
    Gordon, Line J.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Variability of moisture recycling using a precipitationshed framework2014In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 18, no 10, p. 3937-3950Article in journal (Refereed)
    Abstract [en]

    Recent research has revealed that upwind land-use changes can significantly influence downwind precipitation. The precipitationshed (the upwind ocean and land surface that contributes evaporation to a specific location's precipitation) may provide a boundary for coordination and governance of these upwind-downwind water linkages. We aim to quantify the variability of the precipitationshed boundary to determine whether there are persistent and significant sources of evaporation for a given region's precipitation. We identify the precipitationsheds for three regions (i.e., western Sahel, northern China, and La Plata) by tracking atmospheric moisture with a numerical water transport model (Water Accounting Model-2layers, or WAM-2layers) using gridded fields from both the ERA-Interim (European Reanalysis Interim) and MERRA (Modern-Era Retrospective Analysis for Research and Applications) reanalyses. Precipitationshed variability is examined first by diagnosing the persistence of the evaporation contribution and second with an analysis of the spatial variability of the evaporation contribution. The analysis leads to three key conclusions: (1) a core precipitationshed exists; (2) most of the variance in the precipitationshed is explained by a pulsing of more or less evaporation from the core precipitationshed; and (3) the reanalysis data sets agree reasonably well, although the degree of agreement is regionally dependent. Given that much of the growing-season evaporation arises from within a core precipitationshed that is largely persistent in time, we conclude that the precipitationshed can potentially provide a useful boundary for governing land-use change on downwind precipitation.

  • 15. Lin, H.
    et al.
    Vogel, H. J.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    'Towards holistic studies of the Earth's Critical Zone: hydropedology perspectives' Preface2010In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 14, no 3, p. 479-480Article in journal (Refereed)
  • 16.
    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.

  • 17.
    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.

  • 18.
    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.

  • 19.
    Mazi, Aikaterini
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. National Observatory of Athens, Greece.
    Koussis, Antonis D.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Intensively exploited Mediterranean aquifers: resilience to seawater intrusion and proximity to critical thresholds2014In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 18, no 5, p. 1663-1677Article in journal (Refereed)
    Abstract [en]

    We investigate seawater intrusion in three prominent Mediterranean aquifers that are subject to intensive exploitation and modified hydrologic regimes by human activities: the Nile Delta, Israel Coastal and Cyprus Akrotiri aquifers. Using a generalized analytical sharp interface model, we review the salinization history and current status of these aquifers, and quantify their resilience/vulnerability to current and future seawater intrusion forcings. We identify two different critical limits of seawater intrusion under groundwater exploitation and/or climatic stress: a limit of well intrusion, at which intruded seawater reaches key locations of groundwater pumping, and a tipping point of complete seawater intrusion upto the prevailing groundwater divide of a coastal aquifer. Either limit can be reached, and ultimately crossed, under intensive aquifer exploitation and/or climate-driven change. We show that seawater intrusion vulnerability for different aquifer cases can be directly compared in terms of normalized intrusion performance curves. The site-specific assessments show that: a) the intruding seawater currently seriously threatens the Nile Delta Aquifer, b) in the Israel Coastal Aquifer the sharp interface toe approaches the well location and c) the Cyprus Akrotiri Aquifer is currently somewhat less threatened by increased seawater intrusion.

  • 20. Pastor, A.V.
    et al.
    Ludwig, F.
    Biemans, H.
    Hoff, Holger
    Stockholm University, Stockholm Environment Institute. Potsdam Institute for Climate Impact Research.
    Kabat, P.
    Accounting for environmental flow requirements in global water assessments2014In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 18, no 12, p. 5041-5059Article in journal (Refereed)
    Abstract [en]

    As the water requirement for food production and other human needs grows, quantification of  environmental flow requirements (EFRs) is necessary to assess the amount of water needed to sustain freshwater ecosystems. EFRs are the result of the quantification of water necessary to sustain the riverine ecosystem, which is calculated from the mean of an environmental flow (EF) method. In this study, five EF methods for calculating EFRs were compared with 11 case studies of locally assessed EFRs. We used three existing methods (Smakhtin, Tennant, and Tessmann) and two newly developed methods (the variable monthly flow method (VMF) and the Q90_Q50 method). All methods were compared globally and validated at local scales while mimicking the natural flow regime. The VMF and the Tessmann methods use algorithms to classify the flow regime into high, intermediate, and low-flow months and they take into account intra-annual variability by allocating EFRs with a percentage of mean monthly flow (MMF). The Q90_Q50 method allocates annual flow quantiles (Q90 and Q50) depending on the flow season. The results showed that, on average, 37% of annual discharge was required to sustain environmental flow requirement. More water is needed for environmental flows during low-flow periods (46–71% of average low-flows) compared to high-flow periods (17–45% of average high-flows). Environmental flow requirements estimates from the Tennant, Q90_Q50, and Smakhtin methods were higher than the locally calculated EFRs for river systems with relatively stable flows and were lower than the locally calculated EFRs for rivers with variable flows. The VMF and Tessmann methods showed the highest correlation with the locally calculated EFRs (R2=0.91). The main difference between the Tessmann and VMF methods is that the Tessmann method allocates all water to EFRs in low-flow periods while the VMF method allocates 60% of the flow in low-flow periods. Thus, other water sectors such as irrigation can withdraw up to 40% of the flow during the low-flow season and freshwater ecosystems can still be kept in reasonable ecological condition. The global applicability of the five methods was tested using the global vegetation and the Lund-Potsdam-Jena managed land (LPJmL) hydrological model. The calculated global annual EFRs for fair ecological conditions represent between 25 and 46% of mean annual flow (MAF). Variable flow regimes, such as the Nile, have lower EFRs (ranging from 12 to 48% of MAF) than stable tropical regimes such as the Amazon (which has EFRs ranging from 30 to 67% of MAF).

  • 21.
    Persson, Klas
    et al.
    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.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Diffuse hydrological mass transport through catchments: scenario analysis of coupled physical and biogeochemical uncertainty effects2011In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 15, no 10, p. 3195-3206Article in journal (Refereed)
    Abstract [en]

    This paper quantifies and maps the effects of coupled physical and biogeochemical variability on diffuse hydrological mass transport through and from catchments. It further develops a scenario analysis approach and investigates its applicability for handling uncertainties about both physical and biogeochemical variability and their different possible cross-correlation. The approach enables identification of conservative assumptions, uncertainty ranges, as well as pollutant/nutrient release locations and situations for which further investigations are most needed in order to reduce the most important uncertainty effects. The present scenario results provide different statistical and geographic distributions of advective travel times for diffuse hydrological mass transport. The geographic mapping can be used to identify potential hotspot areas with large mass loading to downstream surface and coastal waters, as well as their opposite, potential lowest-impact areas within the catchment. Results for alternative travel time distributions show that neglect or underestimation of the physical advection variability, and in particular of those transport pathways with much shorter than average advective solute travel times, can lead to substantial underestimation of pollutant and nutrient loads to downstream surface and coastal waters. This is particularly true for relatively high catchment-characteristic product of average attenuation rate and average advective travel time, for which mass delivery would be near zero under assumed transport homogeneity but can be orders of magnitude higher for variable transport conditions. A scenario of high advection variability, with a significant fraction of relatively short travel times, combined with a relevant average biogeochemical mass attenuation rate, emerges consistently from the present results as a generally reasonable, conservative assumption for estimating maximum diffuse mass loading, when the prevailing physical and biogeochemical variability and cross-correlation are uncertain.

  • 22. Pool, Sandra
    et al.
    Vis, Marc J. P.
    Knight, Rodney R.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography. Uppsala University, Sweden; University of Zurich, Switzerland.
    Streamflow characteristics from modeled runoff time series importance of calibration criteria selection2017In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 21, no 11, p. 5443-5457Article in journal (Refereed)
    Abstract [en]

    Ecologically relevant streamflow characteristics (SFCs) of ungauged catchments are often estimated from simulated runoff of hydrologic models that were originally calibrated on gauged catchments. However, SFC estimates of the gauged donor catchments and subsequently the ungauged catchments can be substantially uncertain when models are calibrated using traditional approaches based on optimization of statistical performance metrics (e.g., Nash-Sutcliffe model efficiency). An improved calibration strategy for gauged catchments is therefore crucial to help reduce the uncertainties of estimated SFCs for ungauged catchments. The aim of this study was to improve SFC estimates from modeled runoff time series in gauged catchments by explicitly including one or several SFCs in the calibration process. Different types of objective functions were defined consisting of the Nash-Sutcliffe model efficiency, single SFCs, or combinations thereof. We calibrated a bucket-type runoff model (HBV-Hydrologiska Byrans Vattenavdelning-model) for 25 catchments in the Tennessee River basin and evaluated the proposed calibration approach on 13 ecologically relevant SFCs representing major flow regime components and different flow conditions. While the model generally tended to underestimate the tested SFCs related to mean and high-flow conditions, SFCs related to low flow were generally overestimated. The highest estimation accuracies were achieved by a SFC-specific model calibration. Estimates of SFCs not included in the calibration process were of similar quality when comparing a multi-SFC calibration approach to a traditional model efficiency calibration. For practical applications, this implies that SFCs should preferably be estimated from targeted runoff model calibration, and modeled estimates need to be carefully interpreted.

  • 23.
    Retsö, Dag
    Stockholm University, Faculty of Social Sciences, Department of Economic History.
    Documentary Evidence of Historical Floods and Extreme Rainfall Events in Sweden 1400-18002014In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 11, p. 10085-10116Article in journal (Refereed)
    Abstract [en]

    This article explores documentary evidence of floods and extreme rainfall events in Sweden in the pre-instrumental period (1400–1800). The survey shows that two subperiods can be considered as flood-rich, 1590–1670 and the early 18th century. The result is related 5 to a low degree of human impact on hydrology during the period, and suggest that climatic factors, such as lower temperatures and increased precipitation connected to the so called Little Ice Age, should be considered as the main driver behind flood frequency and magnitude.

  • 24.
    Seibert, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Uhlenbrook, S.
    Wagener, T.
    Hydrology education in a changing world Preface2013In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 17, no 4, p. 1393-1399Article in journal (Other academic)
  • 25.
    Seibert, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Vis, M. J. P.
    Irrigania - a web based game about sharing water resources2012In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 16, no 8, p. 2523-2530Article in journal (Refereed)
    Abstract [en]

    For teaching about collaboration and conflicts with regard to shared water resources, various types of games offer valuable opportunities. Single-player computer games often give much power to the player and ignore the fact that the best for some group might be difficult to achieve in reality if the individuals have their own interests. Here we present a new game called Irrigania, which aims at representing water conflicts among several actors in a simplified way. While simple in its rules, this game illustrates several game-theoretical situations typical for water-related conflicts. The game has been implemented as a web-based computer game, which allows easy application in classes. First classroom applications of the game indicated that, despite the simple rules, interesting patterns can evolve when playing the game in a class. These patterns can be used to discuss game theoretical considerations related to water resource sharing.

  • 26. Smedberg, E.
    et al.
    Humborg, C.
    Stockholm University, Stockholm Resilience Centre.
    Jacobsson, M.
    Mörth, C-M.
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Landscape elements and river chemistry as affected by river regulation – a 3-D perspective.2009In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 13, p. 1597-1606Article in journal (Refereed)
  • 27.
    Smedberg, Erik
    et al.
    Stockholm University, Stockholm Resilience Centre.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Landscape elements and river chemistry as affected by river regulation: a 3-D perspective2009In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 13, no 9, p. 1597-1606Article in journal (Refereed)
    Abstract [en]

    We tested the hypothesis whether individual land classes within a river catchment contribute equally to river loading with dissolved constituents or whether some land classes act as “hot spots” to river loading and if so, are these land classes especially affected by hydrological 5 alterations. The amount of land covered by forests and wetlands and the average soil depth of a river catchment explain 58–93% of the variability in total organic carbon (TOC) and dissolved silicate (DSi) concentrations for 22 river catchments in Northern Sweden. Whereas only 3% of the headwater areas of the Luleälven have been inundated by the creation of reservoirs, some 10% of the soils and aggregated 10 forest and wetland areas have been lost due to damming and further hydrological alteration such as bypassing entire sub-catchments by headrace tunnels. However, looking at individual forest classes, our estimates indicate that some 37% of the deciduous forests have been inundated by the four major reservoirs built in the Luleälven headwaters.These deciduous forest and wetlands formerly growing on top of alluvial deposits 15 along the river corridors forming the riparian zone play a vital role in loading river water with dissolved constituents, especially DSi. A digital elevation model draped with land classes and soil depths which highlights that topography of various land classes acting as hot spots is critical in determining water residence time in soils and biogeochemical fluxes. Thus, headwater areas of the Luleälven appear to be most sensitive 20 to hydrological alterations due to the thin soil cover (on average 2.7–4.5m) and only patchy appearance of forest and wetlands that were significantly perturbed. Moreover, since these headwater areas are characterized often by high specific discharge, this relatively minor change in the landscape when compared to the entire river catchment may indeed explain the significant lower fluxes at the river mouth.

    We tested the hypothesis whether individual land classes within a river catchment contribute equally to river loading with dissolved constituents or whether some land classes act as “hot spots” to river loading and if so, are these land classes especially affected by hydrological 5 alterations. The amount of land covered by forests and wetlands and the average soil depth of a river catchment explain 58–93% of the variability in total organic carbon (TOC) and dissolved silicate (DSi) concentrations for 22 river catchments in Northern Sweden. Whereas only 3% of the headwater areas of the Luleälven have been inundated by the creation of reservoirs, some 10% of the soils and aggregated10 forest and wetland areas have been lost due to damming and further hydrological alteration such as bypassing entire sub-catchments by headrace tunnels. However, looking at individual forest classes, our estimates indicate that some 37% of the deciduous forests have been inundated by the four major reservoirs built in the Luleälven headwaters.These deciduous forest and wetlands formerly growing on top of alluvial deposits 15 along the river corridors forming the riparian zone play a vital role in loading river water with dissolved constituents, especially DSi. A digital elevation model draped with land classes and soil depths which highlights that topography of various land classes acting as hot spots is critical in determining water residence time in soils and biogeochemicalfluxes. Thus, headwater areas of the Luleälven appear to be most sensitive 20 to hydrological alterations due to the thin soil cover (on average 2.7–4.5m) and only patchy appearance of forest and wetlands that were significantly perturbed. Moreover, since these headwater areas are characterized often by high specific discharge, this relatively minor change in the landscape when compared to the entire river catchment may indeed explain the significant lower fluxes at the river mouth.

  • 28. Stalnacke, P.
    et al.
    Pengerud, A.
    Vassiljev, A.
    Smedberg, Erik
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Hägg, H. E.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Humborg, Christop
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Andersen, H. E.
    Nitrogen surface water retention in the Baltic Sea drainage basin2015In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, no 2, p. 981-996Article in journal (Refereed)
    Abstract [en]

    In this paper, we estimate the surface water retention of nitrogen (N) in all the 117 drainage basins to the Baltic Sea with the use of a statistical model (MESAW) for source apportionment of riverine loads of pollutants. Our results show that the MESAW model was able to estimate the N load at the river mouth of 88 Baltic Sea rivers, for which we had observed data, with a sufficient degree of precision and accuracy. The estimated retention parameters were also statistically significant. Our results show that around 380 000 t of N are annually retained in surface waters draining to the Baltic Sea. The total annual riverine load from the 117 basins to the Baltic Sea was estimated at 570 000 t of N, giving a total surface water N retention of around 40 %. In terms of absolute retention values, three major river basins account for 50% of the total retention in the 117 basins; i.e. around 104 000 t of N are retained in Neva, 55 000 t in Vistula and 32 000 t in Oder. The largest retention was found in river basins with a high percentage of lakes as indicated by a strong relationship between N retention (%) and share of lake area in the river drainage areas. For example in Gota alv, we estimated a total N retention of 72 %, whereof 67% of the retention occurred in the lakes of that drainage area (Lake Vanern primarily). The obtained results will hopefully enable the Helsinki Commission (HELCOM) to refine the nutrient load targets in the Baltic Sea Action Plan (BSAP), as well as to better identify cost-efficient measures to reduce nutrient loadings to the Baltic Sea.

  • 29. Stiller-Reeve, Mathew A.
    et al.
    Heuze, Céline
    Ball, William T.
    White, Rachel H.
    Messori, Gabriele
    Stockholm University, Faculty of Science, Department of Meteorology .
    van der Wiel, Karin
    Medhaug, Iselin
    Eckes, Annemarie H.
    O'Callaghan, Amee
    Newland, Mike J.
    Williams, Sian R.
    Kasoar, Matthew
    Wittmeier, Hella Elisa
    Kumer, Valerie
    Improving together: better science writing through peer learning2016In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 20, no 7, p. 2965-2973Article in journal (Refereed)
    Abstract [en]

    Science, in our case the climate and geosciences, is increasingly interdisciplinary. Scientists must therefore communicate across disciplinary boundaries. For this communication to be successful, scientists must write clearly and concisely, yet the historically poor standard of scientific writing does not seem to be improving. Scientific writing must improve, and the key to long-term improvement lies with the early-career scientist (ECS). Many interventions exist for an ECS to improve their writing, like style guides and courses. However, momentum is often difficult to maintain after these interventions are completed. Continuity is key to improving writing. This paper introduces the ClimateSnack project, which aims to motivate ECSs to develop and continue to improve their writing and communication skills. The project adopts a peer-learning framework where ECSs voluntarily form writing groups at different institutes around the world. The group members learn, discuss, and improve their writing skills together. Several ClimateSnack writing groups have formed. This paper examines why some of the groups have flourished and others have dissolved. We identify the challenges involved in making a writing group successful and effective, notably the leadership of self-organized groups, and both individual and institutional time management. Within some of the groups, peer learning clearly offers a powerful tool to improve writing as well as bringing other benefits, including improved general communication skills and increased confidence.

  • 30.
    Teutschbein, Claudia
    et al.
    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.
    Is bias correction of regional climate model (RCM) simulations possible for non-stationary conditions?2013In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 17, no 12, p. 5061-5077Article in journal (Refereed)
    Abstract [en]

    In hydrological climate-change impact studies, regional climate models (RCMs) are commonly used to transfer large-scale global climate model (GCM) data to smaller scales and to provide more detailed regional information. Due to systematic and random model errors, however, RCM simulations often show considerable deviations from observations. This has led to the development of a number of correction approaches that rely on the assumption that RCM errors do not change over time. It is in principle not possible to test whether this underlying assumption of error stationarity is actually fulfilled for future climate conditions. In this study, however, we demonstrate that it is possible to evaluate how well correction methods perform for conditions different from those used for calibration with the relatively simple differential split-sample test.

  • 31.
    van der Velde, Y.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    de Rooij, G. H.
    Torfs, P. J. J. F.
    Catchment-scale non-linear groundwater-surface water interactions in densely drained lowland catchments2009In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 13, p. 1867-1885Article in journal (Refereed)
    Abstract [en]

    Freely discharging lowland catchments are characterized by a strongly seasonal contracting and expanding system of discharging streams and ditches. Due to this rapidly changing active channel network, discharge and solute transport cannot be modeled by a single characteristic travel path, travel time distribution, unit hydrograph, or linear reservoir. We propose a systematic spatial averaging approach to derive catchment-scale storage and discharge from point-scale water balances. The effects of spatial heterogeneity in soil properties, vegetation, and drainage network are lumped and described by a relation between groundwater storage and the spatial probability distribution of groundwater depths with measurable parameters. The model describes how, in lowland catchments, the catchment-scale flux from groundwater to surface water via various flow routes is affected by a changing active channel network, the unsaturated zone and surface ponding. We used observations of groundwater levels and catchment discharge of a 6.6 km(2) Dutch watershed in combination with a high-resolution spatially distributed hydrological model to test the model approach. Good results were obtained when modeling hourly discharges for a period of eight years. The validity of the underlying assumptions still needs to be tested under different conditions and for catchments of various sizes. Nevertheless, at this stage the model can already improve monitoring efficiency of groundwater-surface water interactions.

  • 32.
    van der Velde, Y.
    et al.
    Soil Physics, Ecohydrology and Groundwater management Group, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
    Rozemeijer, J. C.
    de Rooij, G. H.
    van Geer, F. C.
    Torfs, P. J. J. F.
    de Louw, P. G. B.
    Improving catchment discharge predictions by inferring flow route contributions from a nested-scale monitoring and model setup2011In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 15, p. 913-930Article in journal (Refereed)
    Abstract [en]

    Identifying effective measures to reduce nutrient loads of headwaters in lowland catchments requires a thorough understanding of flow routes of water and nutrients. In this paper we assess the value of nested-scale discharge and groundwater level measurements for the estimation of flow route volumes and for predictions of catchment discharge. In order to relate field-site measurements to the catchment-scale an upscaling approach is introduced that assumes that scale differences in flow route fluxes originate from differences in the relationship between groundwater storage and the spatial structure of the groundwater table. This relationship is characterized by the Groundwater Depth Distribution (GDD) curve that relates spatial variation in groundwater depths to the average groundwater depth. The GDD-curve was measured for a single field site (0.009 km(2)) and simple process descriptions were applied to relate groundwater levels to flow route discharges. This parsimonious model could accurately describe observed storage, tube drain discharge, overland flow and groundwater flow simultaneously with Nash-Sutcliff coefficients exceeding 0.8. A probabilistic Monte Carlo approach was applied to upscale field-site measurements to catchment scales by inferring scale-specific GDD-curves from the hydrographs of two nested catchments (0.4 and 6.5 km(2)). The estimated contribution of tube drain effluent (a dominant source for nitrates) decreased with increasing scale from 76-79% at the field-site to 34-61% and 25-50% for both catchment scales. These results were validated by demonstrating that a model conditioned on nested-scale measurements improves simulations of nitrate loads and predictions of extreme discharges during validation periods compared to a model that was conditioned on catchment discharge only.

  • 33.
    Wang-Erlandsson, Lan
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Delft University of Technology, The Netherlands.
    Bastiaanssen, W. G. M.
    Gao, H.
    Jägermeyr, J.
    Senay, G. B.
    van Dijk, A. I. J. M.
    Guerschman, J. P.
    Keys, Patrick W.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Colorado State University, USA.
    Gordon, Line J.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Savenije, H. H. G.
    Global root zone storage capacity from satellite-based evaporation2016In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 20, no 4, p. 1459-1481Article in journal (Refereed)
    Abstract [en]

    This study presents an "Earth observation-based" method for estimating root zone storage capacity – a critical, yet uncertain parameter in hydrological and land surface modelling. By assuming that vegetation optimises its root zone storage capacity to bridge critical dry periods, we were able to use state-of-the-art satellite-based evaporation data computed with independent energy balance equations to derive gridded root zone storage capacity at global scale. This approach does not require soil or vegetation information, is model independent, and is in principle scale independent. In contrast to a traditional look-up table approach, our method captures the variability in root zone storage capacity within land cover types, including in rainforests where direct measurements of root depths otherwise are scarce. Implementing the estimated root zone storage capacity in the global hydrological model STEAM (Simple Terrestrial Evaporation to Atmosphere Model) improved evaporation simulation overall, and in particular during the least evaporating months in sub-humid to humid regions with moderate to high seasonality. Our results suggest that several forest types are able to create a large storage to buffer for severe droughts (with a very long return period), in contrast to, for example, savannahs and woody savannahs (medium length return period), as well as grasslands, shrublands, and croplands (very short return period). The presented method to estimate root zone storage capacity eliminates the need for poor resolution soil and rooting depth data that form a limitation for achieving progress in the global land surface modelling community.

  • 34.
    Wang-Erlandsson, Lan
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Delft University of Technology, The Netherlands; Research Institute for Humanity and Nature (RIHN), Japan.
    Fetzer, Ingo
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Keys, Patrick W.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Colorado State University, USA.
    van der Ent, Ruud J.
    Savenije, Hubert H. G.
    Gordon, Line J.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Remote land use impacts on river flows through atmospheric teleconnections2018In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 22, no 8, p. 4311-4328Article in journal (Refereed)
    Abstract [en]

    The effects of land-use change on river flows have usually been explained by changes within a river basin. However, land-atmosphere feedback such as moisture recycling can link local land-use change to modifications of remote precipitation, with further knock-on effects on distant river flows. Here, we look at river flow changes caused by both land-use change and water use within the basin, as well as modifications of imported and exported atmospheric moisture. We show that in some of the world's largest basins, precipitation was influenced more strongly by land-use change occurring outside than inside the basin. Moreover, river flows in several non-transboundary basins were considerably regulated by land-use changes in foreign countries. We conclude that regional patterns of land-use change and moisture recycling are important to consider in explaining runoff change, integrating land and water management, and informing water governance.

  • 35. Westerberg, I. K.
    et al.
    Guerrero, J. -L
    Younger, P. M.
    Beven, K. J.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Halldin, S.
    Freer, J. E.
    Xu, C. -Y
    Calibration of hydrological models using flow-duration curves2011In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 15, no 7, p. 2205-s were tested - based on equal intervals of discharge and of volume of = ter. The method was tested and compared to a calibration using the = aditional model efficiency for the daily four-parameter WAS-MOD model = the Paso La Ceiba catchment in Honduras and for Dynamic TOPMODEL = aluated at an hourly time scale for the Brue catchment in Great = itain. The volume method of selecting EPs gave the best results in = th catchments with better calibrated slow flow, recession and = aporation than the other criteria. Observed and simulated time series = uncertain discharges agreed better for this method both in = libration and prediction in both catchments. An advantage with the = thod is that the rejection criterion is based on an estimation of the = certainty in discharge data and that the EPs of the FDC can be chosen = reflect the aims of the modelling application, e. g. using more/less =Article in journal (Refereed)
    Abstract [en]

    The degree of belief we have in predictions from hydrologic models will normally depend on how well they can reproduce observations. Calibrations with traditional performance measures, such as the Nash-Sutcliffe model efficiency, are challenged by problems including: (1) uncertain discharge data, (2) variable sensitivity of different performance measures to different flow magnitudes, (3) influence of unknown input/output errors and (4) inability to evaluate model performance when observation time periods for discharge and model input data do not overlap. This paper explores a calibration method using flow-duration curves (FDCs) to address these problems. The method focuses on reproducing the observed discharge frequency distribution rather than the exact hydrograph. It consists of applying limits of acceptability for selected evaluation points (EPs) on the observed uncertain FDC in the extended GLUE approach. Two ways of selecting the EPs were tested - based on equal intervals of discharge and of volume of water. The method was tested and compared to a calibration using the traditional model efficiency for the daily four-parameter WAS-MOD model in the Paso La Ceiba catchment in Honduras and for Dynamic TOPMODEL evaluated at an hourly time scale for the Brue catchment in Great Britain. The volume method of selecting EPs gave the best results in both catchments with better calibrated slow flow, recession and evaporation than the other criteria. Observed and simulated time series of uncertain discharges agreed better for this method both in calibration and prediction in both catchments. An advantage with the method is that the rejection criterion is based on an estimation of the uncertainty in discharge data and that the EPs of the FDC can be chosen to reflect the aims of the modelling application, e. g. using more/less EPs at high/low flows. While the method appears less sensitive to epistemic input/output errors than previous use of limits of acceptability applied directly to the time series of discharge, it still requires a reasonable representation of the distribution of inputs. Additional constraints might therefore be required in catchments subject to snow and where peak-flow timing at sub-daily time scales is of high importance. The results suggest that the calibration method can be useful when observation time periods for discharge and model input data do not overlap. The method could also be suitable for calibration to regional FDCs while taking uncertainties in the hydrological model and data into account.

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