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  • 1.
    Bring, Arvid
    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.
    Hydro-climatic changes and their monitoring in the Arctic: Observation-model comparisons and prioritization options for monitoring development2013In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 492, p. 273-280Article in journal (Refereed)
    Abstract [en]

    The Arctic undergoes particularly large and rapid hydro-climatic changes, and information on hydrological responses to these changes is crucial to plan for societal adaptation. We investigate hydro-climatic change severity and monitoring in 14 major hydrological basins across the pan-Arctic, in view of different possible strategies for their monitoring prioritization. Results show that the current distribution of monitoring density in these basins is more relevant for so far observed precipitation changes than for observed temperature changes, or for projected future temperature and precipitation changes. Furthermore, present and projected future hot-spots of greatest hydro-climatic change differ spatially, so that major spatial shifts must occur in the future among the different Arctic basins in order for observations and climate model projections to converge with regard to hydro-climatic change severity. Also temporally, observation-model convergence requires that important change direction shifts occur in major Arctic basins, which have currently decreasing precipitation while model projections imply future increasing precipitation within them. Different prioritization options for rational development of hydro-climatic monitoring can be argued for based on the present results. The divergent prioritization options imply a need for an explicit strategy for achieving certain information goals, which must be selected from a larger set of different possible goals based on societal importance.

  • 2.
    Cornelissen, Gerard
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Okkenhaug, Gudny
    Breedveld, Gijsbert D.
    Sorlie, Jan-Erik
    Transport of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in a landfill: A novel equilibrium passive sampler to determine free and total dissolved concentrations in leachate water2009In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 369, no 04-mar, p. 253-259Article in journal (Refereed)
    Abstract [en]

    Equilibrium passive sampling devices consisting of 17-mu m thick polyoxymethylene (POM) were in situ deployed as a novel technique for landfill groundwater leachate water sampling of freely dissolved poly-cyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). POM was deployed in two groundwater leachate wells (flow around 100 m y(-1)) and an effluent leachate tank. The dissipation of >90% of spiked performance reference compounds and comparison between 60 d and 140 d of equilibration confirmed that POM-water equilibrium was reached for all PAHs and most PCBs within 60 d. Comparison of total and freely dissolved concentrations yielded dissolved organic carbon-water distribution ratios that were on average 0.4 log-unit below amorphous organic carbon-water distribution ratios and in accordance with literature values. Particle-bound fractions ranged from 50% (small PAHs) to 99.9% (large PCBs), and were >95% for most compounds. It was concluded that POM-17 equilibrium passive samplers provide a facile method to measure freely dissolved concentrations of PAH and PCB in groundwater leachate, which will yield valuable information on its ecotoxicological risk for aquatic and benthic organisms. 

  • 3.
    Dahlke, Helen E.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Easton, Zachary M.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Walter, M. Todd
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Steenhuis, Tammo S.
    Dissecting the variable source area concept - Subsurface flow pathways and water mixing processes in a hillslope2012In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 420, p. 125-141Article in journal (Refereed)
    Abstract [en]

    This study uses an instrumented (trenched) 0.5 ha hillslope in the southern tier of New York State, USA, to provide new data and insights on how variable source areas and associated flow pathways form and combine to connect rainfall with downstream water flows across a hillslope. Measurements of water fluxes in the trench, upslope water table dynamics, surface and bedrock topography, and isotopic and geochemical tracers have been combined for a four-dimensional (space-time) characterization of subsurface storm flow responses. During events with dry antecedent conditions infiltrating rainwater was found to percolate through a prevailing fragipan layer to deeper soil layers, with much (33-71%) of the total discharge of the hillslope originating from deeper water flow below the fragipan. During storm events with wet antecedent conditions and large rainfall amounts, shallow lateral flow of event and pre-event water above the fragipan occurred and was one magnitude greater than the deeper water flow contribution. Spatial surface and subsurface water quality observations indicate that water from a distance of up to 56 m contributed runoff from the hillslope during storm events. In addition, mobilization of total dissolved phosphorus (TDP) with subsurface flow played a greater role than with overland or near-surface flow. During all events TDP loads were highest in the total discharge during peak flows (8-11.5 kg ha(-1) d(-1)), except during the largest storm event, when TDP concentrations were highly diluted. These results have implications for strategies to protect streams and other downstream water recipients from waterborne nutrient and pollutant loading.

  • 4.
    Destouni, Georgia
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Verrot, Lucile
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Screening long-term variability and change of soil moisture in a changing climate2014In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 516, p. 131-139Article in journal (Refereed)
    Abstract [en]

    Soil moisture is an essential component of water variability and change in the landscape. This paper develops a conceptual and analytical framework for linking hydro-climatic change at the surface and soil-groundwater conditions in the subsurface, and quantifying long-term development of soil moisture statistics in a changing climate. Soil moisture is evaluated both in the unsaturated zone and over a fixed soil depth that may also include a variable groundwater table. Long-term variability and change of soil moisture are assessed for a hydro-climatic observation record that extends over the whole 20th century in a major Swedish drainage basin. Frequencies of particularly dry and wet soil moisture events are investigated for different 20-year climatic periods. Results show major increase in the frequency of dry events from the beginning to the end of the 20th century. This indicates increased risk for hydrological and agricultural drought even though the risk for meteorological drought, in terms of precipitation, has decreased in the region. The developed quantification framework can also be used to screen future scenarios of soil moisture change under projected climate change.

  • 5.
    Frampton, Andrew
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Painter, Scott
    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.
    Non-isothermal, three-phase simulations of near-surface flows in a model permafrost system under seasonal variability and climate change2011In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 403, no 3-4, p. 352-359Article in journal (Refereed)
    Abstract [en]

    Permafrost responses to a changing climate can affect hydrological and biogeochemical cycling, ecosystems and climate feedbacks. We have simulated a model permafrost system in the temperature range associated with discontinuous permafrost focusing on interactions between permafrost and hydrology using a non-isothermal, three-phase model of water migration coupled to heat transport in partially frozen porous media. We explore the subsurface hydraulic property controls on the formation and dynamics of permafrost, and how this impacts seasonal variability of subsurface runoff to surface waters. For all subsurface conditions considered, the main common hydrological signal of permafrost degradation in a warming trend is decreasing seasonal variability of water flow. This is due to deeper and longer flow pathways with increasing lag times from infiltration or thawing through subsurface flow to surface water discharge. These results show how physically based numerical modelling can be used to quantitatively and qualitatively improve the understanding of how permafrost thawing relates to, and may be detected in, hydrological data. This is advantageous since hydrological data is considerably easier to obtain, may be available in longer time series, and generally reflects larger-scale conditions than direct permafrost observations.

  • 6. Frech, Michael
    et al.
    Samuelsson, Patrick
    Stockholm University, Faculty of Science, Department of Meteorology .
    Tjernström, Michael
    Stockholm University, Faculty of Science, Department of Meteorology .
    Jochum, Anne
    Regional surface fluxes over the NOPEX area1998In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 212-213, p. 155-171Article in journal (Refereed)
  • 7.
    Grabs, Thomas
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Laudon, Hjalmar
    Bishop, Kevin
    Modeling spatial patterns of saturated areas: A comparison of the topographic wetness index and a dynamic distributed model2009In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 373, no 1-2, p. 15-23Article in journal (Refereed)
    Abstract [en]

    Topography is often one of the major controls on the spatial pattern of saturated areas, which in turn is akey to understanding much of the variability in soils, hydrological processes, and stream water quality.The topographic wetness index (TWI) has become a widely used tool to describe wetness conditions atthe catchment scale. With this index, however, it is assumed that groundwater gradients always equalsurface gradients. To overcome this limitation, we suggest deriving wetness indices based on simulationsof distributed catchment models. We compared these new indices with the TWI and evaluated the differ-ent indices by their capacity to predict spatial patterns of saturated areas. Results showed that the model-derived wetness indices predicted the spatial distribution of wetlands significantly better than the TWI.These results encourage the use of a dynamic distributed hydrological model to derive wetness indexmaps for hydrological landscape analysis in catchments with topographically driven groundwater tables.

  • 8.
    Hoff, Holger
    Stockholm University, Stockholm Resilience Centre, Stockholm Environment Institute.
    Preface: The global water challenge – Modeling green and blue water2010In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 384, no 3/4, p. 175-176Article in journal (Refereed)
  • 9.
    Hoff, Holger
    et al.
    Stockholm University, Stockholm Resilience Centre, Stockholm Environment Institute.
    Falkenmark, Malin
    Stockholm University, Stockholm Resilience Centre.
    Gerten, D.
    Gordon, Line
    Stockholm University, Stockholm Resilience Centre.
    Karlberg, Louise
    Stockholm University, Stockholm Resilience Centre, Stockholm Environment Institute.
    Rockström, Johan
    Stockholm University, Stockholm Resilience Centre, Stockholm Environment Institute.
    Greening the global water system2010In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 384, no 04-mar, p. 177-186Article in journal (Refereed)
    Abstract [en]

    Recent developments of global models and data sets enable a new, spatially explicit and process-based assessment of green and blue water in food production and trade. An initial intercomparison of a range of different (hydrological, vegetation, crop, water resources and economic) models, confirms that green water use in global crop production is about 4-5 times greater than consumptive blue water use. Hence, the full green-to-blue spectrum of agricultural water management options needs to be used when tackling the increasing water gap in food production. The different models calculate considerable potentials for complementing the conventional approach of adding irrigation, with measures to increase water productivity, such as rainwater harvesting, supplementary irrigation, vapour shift and soil and nutrient management. Several models highlight Africa, in particular sub-Saharan Africa, as a key region for improving water productivity in agriculture, by implementing these measures. Virtual water trade, mostly based on green water, helps to close the water gap in a number of countries. It is likely to become even more important in the future, when inequities in water availability are projected to grow, due to climate, population and other drivers of change. Further model developments and a rigorous green-blue water model intercomparison are proposed, to improve simulations at global and regional scale and to enable tradeoff analyses for the different adaptation options.

  • 10.
    Jaramillo, Fernando
    et al.
    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.
    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.
    Multimethod assessment of evapotranspiration shifts due to non-irrigated agricultural development in Sweden2013In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 484, p. 55-62Article in journal (Refereed)
    Abstract [en]

    During the 20th century, Sweden underwent a persistent agricultural development. In this study, we use and combine historical hydroclimatic and agricultural data to investigate how this large scale change of land use, and subsequent intensification of crop production, affected regional hydrology in two adjacent Swedish drainage basins. We find a main increase of evapotranspiration (ET) as cultivated area and/or crop production increased during the period 1901-1940. Thereafter, ET stabilized at a new higher level. Comparison between the data given, water balance constrained ET quantification (ETwb), and a range of different comparative estimates of purely climate driven ET (ETclim) shows that only 31% of the steep 1901-1940 increase of ETwb can be explained by climate change alone. The remaining 69% of this ETwb shift, which occurred in both investigated drainage basins, is instead explainable to large degree by the regional land use conversion from seminatural grasslands to cultivated land and associated enhanced productivity of herbaceous species.

  • 11.
    Johansson, A. Malin
    et al.
    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.
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Spatial and temporal variations in lakes on the Greenland Ice Sheet2013In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 476, p. 314-320Article in journal (Refereed)
    Abstract [en]

    Surface lakes on the Greenland Ice Sheet provide temporary storage for meltwater that influences both the surface and basal water fluxes. Thus, to understand the effects of variations in surface melt on ice sheet dynamics it is necessary to understand the surface hydrology. We have used satellite imagery, acquired at 5-day intervals, to map lake initiation and cessation on two sub-sections on the south west Greenland Ice Sheet over three melt seasons (2007–2009). We observe that lake initiation is closely tied to a threshold energy input of approximately 40 ± 18.5 positive-degree-days. This applies to all studied melt seasons, regardless of evolution and melting index anomalies. Lake longevity averages 24 days with little variation between different melt seasons. Our observed median lake area is larger than previously reported. Approximately 50% of all lakes have a life span of <10 d. Cessation of identified lakes is caused by two processes: drainage during the melt season (88% – 2007, 78% – 2008 and 88% – 2009) and freezeup at the end of the season (12% – 2007, 22% – 2008 and 12% – 2009). Inclusion of the energy needed for lake initiation and number of lakes that freeze up at the end of the season into supra-glacial lake models will add further insight into the hydrological system dynamics.

  • 12.
    Johansson, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Swedish Nuclear Fuel and Waste Management Co, Sweden.
    Gustafsson, Lars-Göran
    Berglund, Sten
    Lindborg, Tobias
    Selroos, Jan-Olof
    Stockholm University, Faculty of Science, Department of Physical Geography. Swedish Nuclear Fuel and Waste Management Co, Sweden.
    Claesson Liljedahl, Lillemor
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Data evaluation and numerical modeling of hydrological interactions between active layer, lake and talik in a permafrost catchment, Western Greenland2015In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 527, p. 688-703Article in journal (Refereed)
    Abstract [en]

    This study investigates annual water balance conditions and their spatiotemporal variability under a wide variety of atmospheric driving conditions in the periglacial permafrost catchment of Two Boat Lake in Western Greenland. The study uses and combines a comprehensive hydrological multi-parameter dataset measured at the site with site conceptualization and numerical model development, application and testing. The model result reproduces measured lake and groundwater levels, as well as observations made by time-lapse cameras. The results highlights the importance of numerical modeling that takes into account and combines evapotranspiration with other surface and subsurface hydrological processes at various depths, in order to quantitatively understand and represent the dynamics and complexity of the interactions between meteorology, active layer hydrology, lakes, and unfrozen groundwater below permafrost in periglacial catchments. Regarding these interactions, the water flow between the studied lake and a through talik within and beneath it is found to be small compared to other water balance components. The modeling results show that recharge and discharge conditions in the talik can shift in time, while the lake and active layer conditions in the studied catchment are independent of catchment-external landscape features, such as the unfrozen groundwater system below the permafrost and the nearby continental-scale ice sheet.

  • 13.
    Jonsson, Christina E.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Leng, Melanie J.
    NERC Isotope Geosciences Laboratory , BGS, UK.
    Rosqvist, Gunhild C.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Arrowsmith, Carol
    NERC Isotope Geosciences Laboratory, BGS, UK.
    Stable oxygen and hydrogen isotopes in sub-Arctic lake wateras from northern Sweden2009In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 376, p. 143-151Article in journal (Refereed)
    Abstract [en]

    Lakes in sub-Arctic regions have the potential of retaining many different aspects of water isotope composition in their sediments which can be used for palaeoclimate reconstruction. It is therefore important to understand the modern isotope hydrology of these lakes. Here we discuss the significance of variations in water isotope composition of a series of lakes located in north-west Swedish Lapland. Climate in this region is forced by changes in the North Atlantic which renders it an interesting area for climate reconstructions. We compare δ18Olake and δ2Hlake collected between 2001 and 2006 and show that the lakes in this sub-Arctic region are currently mainly recharged by shallow groundwater and precipitation which undergoes little subsequent evaporation, and that the d18O and δ2H composition of input to the majority of the lakes varies on a seasonal basis between winter precipitation (and spring thaw) and summer precipitation. Seasonal variations in the isotopic composition of the lake waters are larger in lakes with short residence times (<6 months), which react faster to seasonal changes in the precipitation, compared to lakes with longer residence times (>6 months), which retain an isotopic signal closer to that of annual mean precipitation. Lake waters also show a range of isotope values between sites due to catchment elevation and timing of snow melt. The lake water data collected in this study was supported by isotope data from lake waters, streams and ground waters from1995 to 2000 reported in other studies.

  • 14.
    Karlsson, Johanna Mård
    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.
    Thermokarst lake, hydrological flow and water balance indicators of permafrost change in Western Siberia2012In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 464, p. 459-466Article in journal (Refereed)
    Abstract [en]

    Permafrost, mainly of discontinuous type, that underlies the tundra and taiga landscapes of the Nadym and Put river basins in northwestern Siberia has been warming during the recent decades. A mosaic of thermokarst lakes and wetlands dominates this area. In this study we tested the hypothesis chain that permafrost thawing changes thermokarst lake area and number, and is then also reflected in and detectable through other associated hydrological changes. Based on indications from previous studies, the other hydrological changes in a basin were expected to be decreasing intra-annual runoff variability (quantified by decreasing maximum and increasing minimum runoff) and systematically decreasing water storage. To test this hypothesis chain, we mapped thermokarst lake changes using remote sensing analysis and analyzed both climate (temperature and precipitation) and water flow and balance changes using available monthly data records. This was done for the whole Nadym and Pur river basins and a smaller sub-basin of the former (denoted 7129) with comparable data availability as the whole river basins. The results for the 7129 sub-basin show all the indicators (thermokarst lake and other hydrological) changing consistently, as could be expected in response to permafrost thawing that alters the connections between surface and subsurface waters, and leads to overall decreases in water (including ground ice) storage within a basin. Over the Nadym and Pur basins, the relative area influenced by similar permafrost thawing and associated lake and hydrological effects appears (yet) too small to be clearly and systematically reflected in the basin-average indicators for these large basins.

  • 15. Konz, M.
    et al.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    On the value of glacier mass balances for hydrological model calibration2010In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 385, no 1-4, p. 238-246Article in journal (Refereed)
    Abstract [en]

    Hydrological modelling of glacierized catchments is challenging because internal inconsistencies might be hidden due to ice melt which represents an additional source of water. This is even more significant if there are no data available to evaluate model simulations, as is often the case in remote areas. On the other hand, these glacierized catchments are important source regions for water, and detailed knowledge of water availability is a prerequisite for good resource management strategies. An important question is how useful a limited amount of data might be for model applications. Therefore, in this study the predictive power of limited discharge measurements, mass balance observations and the combination of both was analyzed by means of Monte Carlo analyses with multi-criteria model performance evaluation. Ensembles of 100 parameter sets were selected by evaluating the simulations based on a limited number of discharge measurements, glacier mass balance, and the combination of discharge and mass balance observations. Then the ensemble simulation of runoff was evaluated for the entire runoff series. The result indicated that a single annual glacier mass balance observation contained useful information to constrain hydrological models. Combining mass balance observations with a few discharge data improved the internal consistency and significantly reduced the uncertainties compared to parameter set selections based on discharge measurements alone. To obtain good ensemble predictions, information on discharge was required for at least 3 days during the melting season. This demonstrated that the timing of runoff measurements is important for the information contained in these data.

  • 16. Koussis, Antonis D.
    et al.
    Mazi, Ekaterini
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. National Observatory of Athens, Greece.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Analytical single-potential, sharp-interface solutions for regional seawater intrusion in sloping unconfined coastal aquifers, with pumping and recharge2012In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 416, p. 1-11Article in journal (Refereed)
    Abstract [en]

    Contamination of groundwater by intruding seawater is a major problem in many parts of the world. This work derives novel analytical solutions for addressing this problem by extending the Girinskii-Strack concept of discharge potential to represent regional, steady-state, sharp-interface seawater intrusion in a sloping unconfined coastal aquifer. The aquifer has hydraulic conductivity K, is recharged uniformly at the rate r, receives an inflow at its land boundary and has a collector trough (or well gallery idealised as line sink) located at the distance I-w from the coastline that penetrates the aquifer and draws groundwater at the rate q(w). The theory rests on the approximation of a linearised gravity-part of the hydraulic potential. Analytical solutions for the discharge potential are derived, through which the hydraulic head, the flow depth and the sharp interface, and particularly the location of the interface toe, l(T), are also determined. These solutions simplify to known results for the horizontal aquifer case. The utility (and robustness to uncertainty regarding the base slope) of the results in applications is demonstrated in the regional example of the Akrotiri Coastal Aquifer, Cyprus. Recasting the problem in non-dimensional form provides a relationship for the dependence of the relative interface toe location l(T)/l(w) on the appropriately normalised difference between the groundwater flow just up-gradient of the collector trough, q(o), and the pumping rate, q(w), given values of the base slope, r/K and H-sea/l(w), where H-sea is the sea-surface elevation above the aquifer base at the coastline. That relationship frames a common groundwater management problem in coastal aquifers subject to a certain exploitation scheme, with l(T) as decision variable. In an exploratory demonstration study, non-dimensional sets of performance curves are calculated for the regional Akrotiri aquifer. In general, the derived analytical solutions can be used for first-order assessments of seawater intrusion vulnerability and management possibilities across a wide range of current regional coastal aquifer conditions and/or projected water demand, groundwater management and climatic change scenarios.

  • 17. Koussis, Antonis D.
    et al.
    Mazi, Katerina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Riou, Fabien
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    A correction for Dupuit-Forchheimer interface flow models of seawater intrusion in unconfined coastal aquifers2015In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 525, p. 277-285Article in journal (Refereed)
    Abstract [en]

    Interface flow models that use the Dupuit-Forchheimer (DF) approximation for assessing the freshwater lens and the seawater intrusion in coastal aquifers lack representation of the gap through which fresh groundwater discharges to the sea. In these models, the interface outcrops unrealistically at the same point as the free surface, is too shallow and intersects the aquifer base too far inland, thus overestimating an intruding seawater front. To correct this shortcoming of DF-type interface solutions for unconfined aquifers, we here adapt the outflow gap estimate of an analytical 2-D interface solution for infinitely thick aquifers to fit the 50%-salinity contour of variable-density solutions for finite-depth aquifers. We further improve the accuracy of the interface toe location predicted with depth-integrated DF interface solutions by similar to 20% (relative to the 50%-salinity contour of variable-density solutions) by combining the outflow-gap adjusted aquifer depth at the sea with a transverse-dispersion adjusted density ratio (Pool and Carrera, 2011), appropriately modified for unconfined flow. The effectiveness of the combined correction is exemplified for two regional Mediterranean aquifers, the Israel Coastal and Nile Delta aquifers.

  • 18. Köhler, S. J.
    et al.
    Buffam, I.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Bishop, K. H.
    Laudon, H.
    Dynamics of stream water TOC concentrations in a boreal headwater catchment: Controlling factors and implications for climate scenarios2009In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 373, no 1-2, p. 44-56Article in journal (Refereed)
    Abstract [en]

    Two different but complementary modelling approaches for reproducing the observed dynamics of total organic carbon (TOC) in a boreal stream are presented. One is based on a regression analysis, while the other is based on riparian soil conditions using a convolution of flow and concentration. Both approaches are relatively simple to establish and help to identify gaps in the process understanding of the TOC transport from soils to catchments runoff. The largest part of the temporal variation of stream TOC concentrations (4-46 mg L-1) in a forested headwater stream in the boreal zone in northern Sweden may be described using a four-parameter regression equation that has runoff and transformed air temperature as sole input variables. Runoff is assumed to be a proxy for soil wetness conditions and changing flow pathways which in turn caused most of the stream TOC variation. Temperature explained a significant part of the observed inter-annual variability. Long-term riparian hydrochemistry in soil solutions within 4 m of the stream also captures a surprisingly large part of the observed variation of stream TOC and highlights the importance of riparian soils. The riparian zone was used to reproduce stream TOC with the help of a convolution model based on flow and average riparian chemistry as input variables. There is a significant effect of wetting of the riparian soil that translates into a memory effect for subsequent episodes and thus contributes to controlling stream TOC concentrations. Situations with high flow introduce a large amount of variability into stream water TOC that may be related to memory effects, rapid groundwater fluctuations and other processes not identified so far. Two different climate scenarios for the region based on the IPCC scenarios were applied to the regression equation to test what effect the expected increase in precipitation and temperature and resulting changes in runoff would have on stream TOC concentrations assuming that the soil conditions remain unchanged. Both scenarios resulted in a mean increase of stream TOC concentrations of between 1.5 and 2.5 mg L-1 during the snow free season, which amounts to approximately 15% more TOC export compared to present conditions. Wetter and warmer conditions in the late autumn led to a difference of monthly average TOC of up to 5 mg L-1, suggesting that stream TOC may be particularly susceptible to climate variability during this season.

  • 19.
    Matti, Bettina
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Coventry University, UK.
    Dahlke, Helen E.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    On the variability of cold region flooding2016In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 534, p. 669-679Article in journal (Refereed)
    Abstract [en]

    Cold region hydrological systems exhibit complex interactions with both climate and the cryosphere. Improving knowledge on that complexity is essential to determine drivers of extreme events and to predict changes under altered climate conditions. This is particularly true for cold region flooding where independent shifts in both precipitation and temperature can have significant influence on high flows. This study explores changes in the magnitude and the timing of streamflow in 18 Swedish Sub-Arctic catchments over their full record periods available and a common period (1990–2013). The Mann–Kendall trend test was used to estimate changes in several hydrological signatures (e.g. annual maximum daily flow, mean summer flow, snowmelt onset). Further, trends in the flood frequency were determined by fitting an extreme value type I (Gumbel) distribution to test selected flood percentiles for stationarity using a generalized least squares regression approach.

    Results highlight shifts from snowmelt-dominated to rainfall-dominated flow regimes with all significant trends (at the 5% significance level) pointing toward (1) lower magnitudes in the spring flood; (2) earlier flood occurrence; (3) earlier snowmelt onset; and (4) decreasing mean summer flows. Decreasing trends in flood magnitude and mean summer flows suggest widespread permafrost thawing and are supported by increasing trends in annual minimum daily flows. Trends in selected flood percentiles showed an increase in extreme events over the full periods of record (significant for only four catchments), while trends were variable over the common period of data among the catchments. An uncertainty analysis emphasizes that the observed trends are highly sensitive to the period of record considered. As such, no clear overall regional hydrological response pattern could be determined suggesting that catchment response to regionally consistent changes in climatic drivers is strongly influenced by their physical characteristics.

  • 20.
    Mård Karlsson, Johanna
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hydro-climatic and lake change patterns in Arctic permafrost and non-permafrost areas2015In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 529, p. 134-145Article in journal (Refereed)
    Abstract [en]

    This paper investigates patterns of lake-area and hydro-climatic change in Arctic river basins, and possible influence of permafrost change reflected in such patterns. A salient change pattern, emerging across all investigated basins in both permafrost and non-permafrost areas, is an opposite change direction in runoff (R) from that in precipitation (P). To explain this change contrast, an increase (decrease) in relative water-balance constrained evapotranspiration ETwb/P is required where R decreases (increases). Increasing temporal variability of daily river discharge (sdQ) is found in all basins with spatially extensive lake decrease, which also exhibit decrease in ELwb/P. Clear indication of basin-wide permafrost thaw is found in only one basin, and is possible in two more, but unlikely in the largest of the total four investigated permafrost basins.

  • 21.
    Olli, Gull
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Darracq, Amelie
    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.
    Field study of phosphorous transport and retention in drainage reaches2009In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 365, no 1-2, p. 46-55Article in journal (Refereed)
    Abstract [en]

    Phosphorous (P) transport and retention is investigated here based on data from a 3-year field study of five drainage ditch reaches at Färingsö, west of Stockholm, Sweden. Results show that P retention rate in the drainage reaches greatly depends on and decreases with increasing water flow and watercourse depth. This supports previous simulation indications and implies that changing drainage reach depth and flow conditions may considerably change P loading to downstream waters. In deeper drainage reaches with tile-drained fields in their catchment areas, which are common in Nordic lowlands, particulate P amounted to about 80% of total P, with about half of this fraction being bio-available. As much as 70% of that particulate P was retained in a reach section that was flow- and depth-restricted by heavy vegetation. Retained P in sediments was found to be mostly bound to Fe and/or Al. Some of that PAl–Fe fraction may after dissolution become more permanently retained by re-binding to Ca.

  • 22.
    Persson, Klas
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Propagation of water pollution uncertainty and risk from the subsurface to the surface water system of a catchment: 2009In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 377, no 3-4, p. 434-444Article in journal (Refereed)
    Abstract [en]

    This paper investigates the propagation of quantifiable probability and quantification uncertainty of water pollution from local pollutant sources at and below the land surface, through the groundwater system, to downstream surface water recipients. Methodologically, the study shows how the risk and uncertainty of surface water pollution within a catchment may be assessed by a combined methodology of a Lagrangian stochastic advective-reactive modelling approach, which accounts for the quantifiable pollutant transport randomness, and a scenario analysis approach, which accounts for different quantification uncertainties. The results show that, in general, unambiguous risk assessment requires at least a reliable order-of-magnitude quantification of the prevailing relation between the average rate of physical pollutant transport from source to recipient and the average rate of pollutant attenuation. If this average relation can be reliably estimated to fall within two identified, relatively wide open value ranges, the assessment of pollution risk to surface waters from localised sources at or below the soil surface may be unambiguous even under otherwise large quantification uncertainty. For a relatively narrow, closed value range of this average rate relation, however, risk assessment must either rely on conservative assumptions, or else be based on a more detailed and resource demanding quantification of pollutant transport.

  • 23.
    Pietroń, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Romanchenko, Anna O.
    Chalov, Sergey R.
    Model analyses of the contribution of in-channel processes to sediment concentration hysteresis loops2015In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 527, p. 576-589Article in journal (Refereed)
    Abstract [en]

    Sediment concentration (SC)-water discharge (Q) relations in rivers are typically governed by multiple and relatively complex processes. Due to hysteresis effects, sediment discharges can differ for similar or equivalent water discharges, which causes scatter in empirical datasets and may decrease the predictive power of SC rating curves. Such hysteresis effects must therefore be understood and accounted for to make dependable predictions for river system management. The overall objectives of this study are to develop modelling approaches suitable for reproducing and predicting hysteresis effects at larger scales and to investigate the possible contribution of in-channel processes (erosion and deposition) to sediment concentration hysteresis loops. To investigate relevant field-scale conditions, we develop a one-dimensional dynamic sediment transport model of the downstream Tuul River (northern Mongolia), investigating in-channel processes along a 141 km stretch during a hydrological year. The results show that the present modelling approach can reproduce both anti-clockwise and clockwise hysteresis effects. Importantly, in-channel processes alone can cause considerable anti-clockwise hysteresis effects without being reinforced by catchment processes such as hillslope erosion. Such specific contributions from in-channel processes introduced data scatter into the sediment rating curves, decreasing their R-2-values from unity to approximately 0.5 to 0.6. More generally, possible changes in the number or magnitude of high-flow events, caused by climatic or other anthropogenic factors, could influence total sediment deposition, which was primarily found to occur during relatively short high-flow events. Such potential changes also have important implications for the possible spreading of polluted sediments.

  • 24. Reynolds, J. E.
    et al.
    Halldin, S.
    Xu, C. Y.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography. Uppsala University, Sweden; University of Zurich, Switzerland.
    Kauffeldt, A.
    Sub-daily runoff predictions using parameters calibrated on the basis of data with a daily temporal resolution2017In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 550, p. 399-411Article in journal (Refereed)
    Abstract [en]

    Concentration times in small and medium-sized basins (similar to 10-1000 km(2)) are commonly less than 24 h. Flood-forecasting models are thus required to provide simulations at high temporal resolutions (1 h-6 h), although time-series of input and runoff data with sufficient lengths are often only available at the daily temporal resolution, especially in developing countries. This has led to study the relationships of estimated parameter values at the temporal resolutions where they are needed from the temporal resolutions where they are available. This study presents a methodology to treat empirically model parameter dependencies on the temporal resolution of data in two small basins using a bucket-type hydrological model, HBV-light, and the generalised likelihood uncertainty estimation approach for selecting its parameters. To avoid artefacts due to the numerical resolution or numerical method of the differential equations within the model, the model was consistently run using modelling time steps of one-hour regardless of the temporal resolution of the rainfall-runoff data. The distribution of the parameters calibrated at several temporal resolutions in the two basins did not show model parameter dependencies on the temporal resolution of data and the direct transferability of calibrated parameter sets (e.g., daily) for runoff simulations at other temporal resolutions for which they were not calibrated (e.g., 3 h or 6 h) resulted in a moderate (if any) decrease in model performance, in terms of Nash-Sutcliffe and volume-error efficiencies. The results of this study indicate that if sub-daily forcing data can be secured, flood forecasting in basins with sub-daily concentration times may be possible with model-parameter values calibrated from long time series of daily data. Further studies using more models and basins are required to test the generality of these results.

  • 25. Sterte, Elin Jutebring
    et al.
    Johansson, Emma
    Sjöberg, Ylva
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Karlsen, Reinert Huseby
    Laudon, Hjalmar
    Groundwater-surface water interactions across scales in a boreal landscape investigated using a numerical modelling approach2018In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 560, p. 184-201Article in journal (Refereed)
    Abstract [en]

    Groundwater and surface-water interactions are regulated by catchment characteristics and complex inter- and intra-annual variations in climatic conditions that are not yet fully understood. Our objective was to investigate the influence of catchment characteristics and freeze-thaw processes on surface and groundwater interactions in a boreal landscape, the Krycklan catchment in Sweden. We used a numerical modelling approach and sub-catchment evaluation method to identify and evaluate fundamental catchment characteristics and processes. The model reproduced observed stream discharge patterns of the 14 sub-catchments and the dynamics of the 15 groundwater wells with an average accumulated discharge error of 1% (15% standard deviation) and an average groundwater-level mean error of 0.1 m (0.23 m standard deviation). We show how peatland characteristics dampen the effect of intense rain, and how soil freeze-thaw processes regulate surface and groundwater partitioning during snowmelt. With these results, we demonstrate the importance of defining, understanding and quantifying the role of landscape heterogeneity and sub-catchment characteristics for accurately representing catchment hydrological functioning.

  • 26. Su, Ye
    et al.
    Langhammer, Jakub
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Geochemical responses of forested catchments to bark beetle infestation: Evidence from high frequency in-stream electrical conductivity monitoring2017In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 550, p. 635-649Article in journal (Refereed)
    Abstract [en]

    Under the present conditions of climate warming, there has been an increased frequency of bark beetle induced tree mortality in Asia, Europe, and North America. This study analyzed seven years of high frequency monitoring of in-stream electrical conductivity (EC), hydro-climatic conditions, and vegetation dynamics in four experimental catchments located in headwaters of the Sumava Mountains, Central Europe. The aim was to determine the effects of insect-induced forest disturbance on in-stream EC at multiple timescales, including annual and seasonal average conditions, daily variability, and responses to individual rainfall events. Results showed increased annual average in-stream EC values in the bark beetle-infected catchments, with particularly elevated EC values during baseflow conditions. This is likely caused by the cumulative loading of soil water and groundwater that discharge excess amounts of substances such as nitrogen and carbon, which are released via the decomposition of the needles, branches, and trunks of dead trees, into streams. Furthermore, we concluded that infestation-induced changes in event-scale dynamics may be largely responsible for the observed shifts in annual average conditions. For example, systematic EC differences between baseflow conditions and event flow conditions in relatively undisturbed catchments were essentially eliminated in catchments that were highly disturbed by bark beetles. These changes developed relatively rapidly after infestation and have long-lasting (decadal-scale) effects, implying that cumulative impacts of increasingly frequent bark beetle outbreaks may contribute to alterations of the hydrogeochemical conditions in more vulnerable mountain regions.

  • 27.
    Sundqvist, Hanna S.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Holmgren, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Understanding conditions behind speleothem formation in Korallgrottan, northwestern Sweden2007In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 347, no 1-2, p. 13-22Article in journal (Refereed)
    Abstract [en]

    In this study we investigate and characterise the environmental factors that control active speleothem growth in Korallgrottan, northwestern Sweden, in order to get a better understanding of seepage processes in karst areas and to determine whether the fossil speleothems from this site are suitable as palaeoclimatic archives. The drip rates from fast-dripping stalactites (>100 ml/day) vary substantially with the season and the snow regime. Comparisons with measurements of river discharge and simulated ground water recharge show that the drip rate from fast-dripping stalactites can be used as an estimation of the weekly to monthly ground water recharge. Slow-dripping stalactites however, have a steadier drip rate, with almost no seasonal variations. The δ18O composition of the drip water from both fast- and slow-dripping stalactites show some seasonal variation (±1.2‰), but is fairly stable compared to outside precipitation (±11.1‰). The δ18O signal from fast-dripping stalactites is biased towards summer conditions, while the signal is dampened at slow-dripping sites and an annual or even longer signal is evident. This holds true even though calcite precipitation may not occur continuously throughout the year. Similarly, the trace elemental composition of drip water is more stable in the slow-dripping stalactites, reflecting mean annual values or longer. Generally the drip water reaches the highest saturation level during the summer and autumn when biological activity in the soil zone is most intense, and the partial pressure of carbon dioxide, which controls limestone dissolution, is high.

  • 28.
    Tesi, Tomaso
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Miserocchi, S.
    Acri, F.
    Langone, L.
    Boldrin, A.
    Hatten, J. A.
    Albertazzi, S.
    Flood-driven transport of sediment, particulate organic matter, and nutrients from the Po River watershed to the Mediterranean Sea2013In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 498, p. 144-152Article in journal (Refereed)
    Abstract [en]

    The Po River (Northern Italy) discharge represents a considerable input of the land-derived material entering the Mediterranean Sea. Most of its particulate and dissolved constituents are supplied to the sea in response to short-lived climate events. Although these floods exert first-order control on the transport of organic and inorganic elements, both composition and magnitude of the river material are poorly constrained during high discharge periods. In order to fill this knowledge gap, in this study we carried out an event response sampling in the Po River in November 2011. Beginning in early November, intense rainfall occurred in the Po watershed that resulted in a flood of similar to 6000 m(3) s(-1) year return period). Water samples were collected from the river before and during the flood. Dissolved nitrate, nitrite, ammonia, and silicate were measured and the particulate material was analyzed for total suspended sediment, elemental composition, delta C-13, delta N-15, grain-size, and Cs-137 activity. Our results showed a temporal decoupling between solid and water discharge implying that predicted sediment loads simply derived from sediment rating curves could potentially give rise to large errors, especially when calculations are used to understand the sediment export in response short-lived events. The suspended organic material during high flow was dominated by soil organic matter while high delta N-15 indicated the influence of an additional N-15-enriched source (e.g., manure, sewage, and algal biomass) during low discharge. Because the concentrations of nitrite and ammonia were positively correlated with the content of particulate material in suspension, we inferred that nitrite and ammonia concentrations were driven by either bacteria activity (ammonification-nitrification) or ionic exchange whose rates were proportional to concentration of the suspended material. In addition, due to the dilution with nitrate-poor rainfall, the concentration of nitrate decreased with increasing water discharge. High concentrations of nitrate were instead attributable to the influx of nitrate-rich water from groundwater that is chronically contaminated and constitutes most of the baseflow during low flow. Our results indicate that the event-dominated transport in the Po drainage basin is particularly important for the organic matter supply as flood events account for at least one-third of the particulate annual export (organic carbon and nitrogen). Finally, this study has demonstrated the utility of event-response sampling for understanding the importance of event-dominated transport in rivers.

  • 29.
    Teutschbein, Claudia
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Uppsala Universitet, Sverige.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Uppsala Universitet, Sverige.
    Bias correction of regional climate model simulations for hydrological climate change impact studies: review and evaluation of different methods2012In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 456-457, p. 12-29Article, review/survey (Refereed)
    Abstract [en]

    Despite the increasing use of regional climate model (RCM) simulations in hydrological climate-change impact studies, their application is challenging due to the risk of considerable biases. To deal with these biases, several bias correction methods have been developed recently, ranging from simple scaling to rather sophisticated approaches. This paper provides a review of available bias correction methods and demonstrates how they can be used to correct for deviations in an ensemble of 11 different RCM-simulated temperature and precipitation series. The performance of all methods was assessed in several ways: At first, differently corrected RCM data was compared to observed climate data. The second evaluation was based on the combined influence of corrected RCM-simulated temperature and precipitation on hydrological simulations of monthly mean streamflow as well as spring and autumn flood peaks for five catchments in Sweden under current (1961-1990) climate conditions. Finally, the impact on hydrological simulations based on projected future (2021-2050) climate conditions was compared for the different bias correction methods. Improvement of uncorrected RCM climate variables was achieved with all bias correction approaches. While all methods were able to correct the mean values, there were clear differences in their ability to correct other statistical properties such as standard deviation or percentiles. Simulated streamflow characteristics were sensitive to the quality of driving input data: Simulations driven with bias-corrected RCM variables fitted observed values better than simulations forced with uncorrected RCM climate variables and had more narrow variability bounds.

  • 30.
    Törnqvist, Rebecka
    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.
    Pietroń, Jan
    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.
    Rogberg, Peter
    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.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Evolution of the hydro-climate system in the Lake Baikal basin2014In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 519, p. 1953-1962Article in journal (Refereed)
    Abstract [en]

    Climatic changes can profoundly alter hydrological conditions in river basins. Lake Baikal is the deepest and largest freshwater reservoir on Earth, and has a unique ecosystem with numerous endemic animal and plant species. We here identify long-term historical (1938-2009) and projected future hydro-climatic trends in the Selenga River Basin, which is the largest sub-basin (>60% inflow) of Lake Baikal. Our analysis is based on long-term river monitoring and historical hydro-climatic observation data, as well as ensemble mean and 22 individual model results of the Coupled Model Intercomparison Project, Phase 5 (CMIP5). Study of the latter considers a historical period (from 1961) and projections for 2010-2039 and 2070-2099. Observations show almost twice as fast warming as the global average during the period 1938-2009. Decreased intra-annual variability of river discharge over this period indicates basin-scale permafrost degradation. CMIP5 ensemble projections show further future warming, implying continued permafrost thaw. Modelling of runoff change, however, is highly uncertain, with many models (64%) and their ensemble mean failing to reproduce historical behaviour, and with indicated future increase being small relative to the large differences among individual model results.

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