I urval från Stockholms universitets publikationsdatabas

• Robust Assessment of Uncertain Freshwater Changes

  2018. Georgia Destouni, Carmen Prieto. Water 10 (11)

  Artikel

  We develop a data-driven approach to robustly assess freshwater changes due to climate change and/or human irrigation developments by use of the overarching constraints of catchment water balance. This is applied to and tested in the high-uncertainty case of Greece for five nested catchments of different scales across the country and for freshwater changes from an early period (1930-1949) with small human influences on climate and irrigation to a recent period (1990-2009) with expected greater such influences. The results show more or less equal contributions from climatic decrease in precipitation and from human irrigation development to a considerable total decrease in runoff (R) over Greece. This is on average -75 +/- 10 mm/year and is greatest for the Ionian catchment in the west (-119 +/- 18 mm/year) and the Peloponnese catchment in the south (-91 +/- 16 mm/year). For evapotranspiration (ET), a climate-driven decrease component and an irrigation-driven increase component have led to a net total increase of ET over Greece. This is on average 26 +/- 7 mm/year and is greatest for the Mainland catchment (29 +/- 7 mm/year) and the Aegean catchment in the east (28 +/- 6 mm/year). Overall, the resulting uncertainties in the water-balance constrained estimates of R and ET changes are smaller than the input data uncertainties.

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• Water quality and ecosystem management

  2017. Georgia Destouni, Ida Fischer, Carmen Prieto. Water resources research 53 (8), 6395-6406

  Artikel

  This study investigates nutrient-related water quality conditions and change trends in the first management periods of the EU Water Framework Directive (WFD; since 2009) and Baltic Sea Action Plan (BASP; since 2007). With mitigation of nutrients in inland waters and their discharges to the Baltic Sea being a common WFD and BSAP target, we use Sweden as a case study of observable effects, by compiling and analyzing all openly available water and nutrient monitoring data across Sweden since 2003. The data compilation reveals that nutrient monitoring covers only around 1% (down to 0.2% for nutrient loads) of the total number of WFD-classified stream and lake water bodies in Sweden. The data analysis further shows that the hydro-climatically driven water discharge dominates the determination of waterborne loads of both total phosphorus and total nitrogen across Sweden. Both water discharge and the related nutrient loads are in turn well correlated with the ecosystem status classification of Swedish water bodies. Nutrient concentrations do not exhibit such correlation and their changes over the study period are on average small, but concentration increases are found for moderate-to-bad status waters, for which both the WFD and the BSAP have instead targeted concentration decreases. In general, these results indicate insufficient distinction and mitigation of human-driven nutrient components in inland waters and their discharges to the sea by the internationally harmonized applications of the WFD and the BSAP. The results call for further comparative investigations of observable large-scale effects of such regulatory/management frameworks in different parts of the world.

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• Wetlands as large-scale nature-based solutions

  2017. Josefin Thorslund (et al.). Ecological Engineering 108 (Part B), 489-497

  Artikel

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

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• Climate-Driven Phenological Change

  2015. Carmen Prieto, Georgia Destouni. PLoS ONE 10 (11)

  Artikel

  Our possibility to appropriately detect, interpret and respond to climate-driven phenological changes depends on our ability to model and predict the changes. This ability may be hampered by non-linearity in climate-phenological relations, and by spatiotemporal variability and scale mismatches of climate and phenological data. A modeling methodology capable of handling such complexities can be a powerful tool for phenological change projection. Here we develop such a methodology using citizen scientists' observations of first flight dates for orange tip butterflies (Anthocharis cardamines) in three areas extending along a steep climate gradient. The developed methodology links point data of first flight observations to calculated cumulative degree-days until first flight based on gridded temperature data. Using this methodology we identify and quantify a first flight model that is consistent across different regions, data support scales and assumptions of subgrid variability and observation bias. Model application to observed warming over the past 60 years demonstrates the model usefulness for assessment of climate-driven first flight change. The cross-regional consistency of the model implies predictive capability for future changes, and calls for further application and testing of analogous modeling approaches to other species, phenological variables and parts of the world.

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• Implications of freshwater flux data from the CMIP5 multimodel output across a set of Northern Hemisphere drainage basins

  2015. Arvid Bring (et al.). Earths Future 3 (6), 206-217

  Artikel

  The multimodel ensemble of the Coupled Model Intercomparison Project, Phase 5 (CMIP5) synthesizes the latest research in global climate modeling. The freshwater system on land, particularly runoff, has so far been of relatively low priority in global climate models, despite the societal and ecosystem importance of freshwater changes, and the science and policy needs for such model output on drainage basin scales. Here we investigate the implications of CMIP5 multimodel ensemble output data for the freshwater system across a set of drainage basins in the Northern Hemisphere. Results of individual models vary widely, with even ensemble mean results differing greatly from observations and implying unrealistic long-term systematic changes in water storage and level within entire basins. The CMIP5 projections of basin-scale freshwater fluxes differ considerably more from observations and among models for the warm temperate study basins than for the Arctic and cold temperate study basins. In general, the results call for concerted research efforts and model developments for improving the understanding and modeling of the freshwater system and its change drivers. Specifically, more attention to basin-scale water flux analyses should be a priority for climate model development, and an important focus for relevant model-based advice for adaptation to climate change.

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• Interacting effects of change in climate, human population, land use, and water use on biodiversity and ecosystem services

  2015. Bodil Elmhagen (et al.). Ecology & society 20 (1)

  Artikel

  Human population growth and resource use, mediated by changes in climate, land use, and water use, increasingly impact biodiversity and ecosystem services provision. However, impacts of these drivers on biodiversity and ecosystem services are rarely analyzed simultaneously and remain largely unknown. An emerging question is how science can improve the understanding of change in biodiversity and ecosystem service delivery and of potential feedback mechanisms of adaptive governance. We analyzed past and future change in drivers in south-central Sweden. We used the analysis to identify main research challenges and outline important research tasks. Since the 19th century, our study area has experienced substantial and interlinked changes; a 1.6 degrees C temperature increase, rapid population growth, urbanization, and massive changes in land use and water use. Considerable future changes are also projected until the mid-21st century. However, little is known about the impacts on biodiversity and ecosystem services so far, and this in turn hampers future projections of such effects. Therefore, we urge scientists to explore interdisciplinary approaches designed to investigate change in multiple drivers, underlying mechanisms, and interactions over time, including assessment and analysis of matching-scale data from several disciplines. Such a perspective is needed for science to contribute to adaptive governance by constantly improving the understanding of linked change complexities and their impacts.

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• Hydroclimatic shifts driven by human water use for food and energy production

  2013. Georgia Destouni, Fernando Jaramillo, Carmen Prieto. Nature Climate Change 3 (3), 213-217

  Artikel

  Hydrological change is a central part of global change(1-3). Its drivers in the past need to be understood and quantified for accurate projection of disruptive future changes(4). Here we analyse past hydro-climatic, agricultural and hydropower changes from twentieth century data for nine major Swedish drainage basins, and synthesize and compare these results with other regional(5-7) and global(2) assessments of hydrological change by irrigation and deforestation. Cross-regional comparison shows similar increases of evapotranspiration by non-irrigated agriculture and hydropower as for irrigated agriculture. In the Swedish basins, non-irrigated agriculture has also increased, whereas hydropower has decreased temporal runoff variability. A global indication of the regional results is a net total increase of evapotranspiration that is larger than a proposed associated planetary boundary(8). This emphasizes the need for climate and Earth system models to account for different human uses of water as anthropogenic drivers of hydro-climatic change. The present study shows how these drivers and their effects can be distinguished and quantified for hydrological basins on different scales and in different world regions. This should encourage further exploration of greater basin variety for better understanding of anthropogenic hydro-climatic change.

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• Multimethod assessment of evapotranspiration shifts due to non-irrigated agricultural development in Sweden

  2013. Fernando Jaramillo (et al.). Journal of Hydrology 484, 55-62

  Artikel

  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.

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• Hydrological responses to climate change conditioned by historic alterations of land use and water use

  2012. Jerker Jarsjö (et al.). Hydrology and Earth System Sciences 16 (5), 1335-1347

  Artikel

  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.

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• Is submarine groundwater discharge predictable?

  2011. Carmen Prieto, Georgia Destouni. Geophysical Research Letters 38, L01402

  Artikel

  The contribution of submarine groundwater discharge (SGD) to the total hydrological discharges to the sea may be large but has been difficult to quantify. We have tested the applicability and generality of a suggested linear relationship between annual average total SGD and its fresh groundwater component against various SGD simulation results and field data. This relationship is found to constitute a general attractor for hydrologically simulated and directly measured SGD values across a wide range of conditions and world regions. But these consistent SGD quantifications differ systematically and largely from indirect SGD interpretations of tracers in seawater. This is an essential gap between inland- and sea-based methods of SGD estimation that needs to be bridged.

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• Cost-efficient management of coastal aquifers via recharge with treated wastewater and desalination of brackish groundwater: Application to the Akrotiri Basin and Aquifer, Cyprus

  2010. A. D. Koussis (et al.). Hydrological Sciences Journal 55 (7), 1234-1245

  Artikel

  We investigate the general methodology for an intensive development of coastal aquifers, described in a companion paper, through its application to the management of the Akrotiri aquifer, Cyprus. The Zakaki area of that aquifer, adjacent to Lemessos City, is managed such that it permits a fixed annual agricultural water demand to be met, as well as and a fraction of the water demand of Lemessos, which varies according to available surface water. Effluents of the Lemessos wastewater treatment plant are injected into the aquifer to counteract the seawater intrusion resulting from the increased pumping. The locations of pumping and injection wells are optimized based on least-cost, subject to meeting the demand. This strategy controls sea intrusion so effectively that desalting of only small volumes of slightly brackish groundwater is required over short times, while ∼2.3 m³ of groundwater is produced for each 1 m³ of injected treated wastewater. The cost over the 20-year period 2000-2020 of operation is ∼40 M€ and the unit production cost of potable water is under 0.2 €/m³. The comparison between the deterministic and stochastic analyses of the groundwater dynamics indicates the former as conservative, i.e. yielding higher groundwater salinity at the well. The Akrotiri case study shows that the proposed aquifer management scheme yields solutions that are preferable to the widely promoted seawater desalination, also considering the revenues from using the treated wastewater for irrigation.

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• Cost-efficient management of coastal aquifers via recharge with treated wastewater and desalination of brackish groundwater: General framework

  2010. A. D. Koussis (et al.). Hydrological Sciences Journal 55 (7), 1217-1233

  Artikel

  Semi-arid coastal zones often suffer water-stress, as water demand is high and markedly seasonal, due to agriculture and tourism. Driven by scarcity of surface water, the communities in semi-arid coastal regions turn to aquifers as prime water source; but intensive exploitation of coastal aquifers causes seawater intrusion, which degrades the quality of groundwater. The cost-efficient and sustainable development of coastal aquifers can be achieved through a holistic management scheme which combines two non-traditional water sources: (a) saltwater, to be treated to the desired quality, and (b) wastewater, to be re-claimed to augment aquifer recharge for control of seawater intrusion, and also to meet certain demands. This management scheme is based on the idea that it is cost-advantageous to: (i) desalt brackish groundwater, instead of seawater, as the former requires far less energy, and (ii) to re-use wastewater at only the differential cost to any treatment already practiced. In this paper, we present the general framework of the proposed management scheme, and a decision aid tool (DAT) which has been developed to assist decision makers to explore the scheme's decision space. The DAT uses cost as optimization criterion to screen various management scenarios, via modelling of the dynamic natural-engineered system behaviour, and identifies those cost-efficient ones that meet the water demand and achieve aquifer protection.

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• General quantification of catchment-scale nutrient and pollutant transport through the subsurface to surface and coastal waters

  2010. G. Destouni (et al.). Environmental Science and Technology 44 (6), 2048-2055

  Artikel

  This study develops a general quantification framework for consistent intermodel and intercatchment comparison of the nutrient and pollutant mass loading from multiple sources in a catchment area to downstream surface and coastal waters. The framework accounts for the wide spectrum of different transport pathways and travel times through the subsurface (soil, groundwater, sediment) and the linked surface (streams, lakes, wetlands) water systems of a catchment. The account is based on key flow partitioning and mass delivery fractions, which can be quantified differently by different flow and transport and reaction models. The framework application is exemplified for two Swedish catchment cases with regard to the transport of phosphorus and of a generic attenuating solute. The results show essential differences in model quantifications of transport pathways and temporal spreading, with important implications for our understanding of cause and effect in the catchment-scale nutrient and pollutant loading to downstream waters.

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• Quantification of advective solute travel times and mass transport through hydrological catchments

  2010. Amelie Darracq (et al.). Environmental Fluid Mechanics 10 (1-2), 103-120

  Artikel

  This study has investigated and outlined the possible quantification and mapping of the distributions of advective solute travel times through hydrological catchments. These distributions are essential for understanding how local water flow and solute transport and attenuation processes affect the catchment-scale transport of solute, for instance with regard to biogeochemical cycling, contamination persistence and water quality. The spatial and statistical distributions of advective travel times have been quantified based on reported hydrological flow and mass-transport modeling results for two coastal Swedish catchments. The results show that the combined travel time distributions for the groundwater-stream network continuum in these catchments depend largely on the groundwater system and model representation, in particular regarding the spatial variability of groundwater hydraulic parameters (conductivity, porosity and gradient), and the possible contributions of slower/deeper groundwater flow components. Model assumptions about the spatial variability of groundwater hydraulic properties can thus greatly affect model results of catchment-scale solute spreading. The importance of advective travel time variability for the total mass delivery of naturally attenuated solute (tracer, nutrient, pollutant) from a catchment to its downstream water recipient depends on the product of catchment-average physical travel time and attenuation rate.

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• Scale and model resolution effects on the distributions of advective solute travel times in catchments

  2010. Amelie Darracq (et al.). Hydrological Processes 24 (12), 1697-1710

  Artikel

  Advective solute travel times and their distributions in hydrological catchments are useful descriptors of the dynamics and variation of the physical mass transport among and along the different source-to-recipient pathways of solute transport through the catchments. This article investigates the scale dependence and the effects of model and data resolution on the quantification of advective travel times and their distributions in the Swedish catchment areas of Norrström and Forsmark. In the surface water networks of the investigated (sub)catchments, the mean advective travel time increases with (sub)catchment scale, whereas the relative travel time variability around the mean value (coefficient of variation, CV) is scale-invariant and insensitive to model resolution. In the groundwater and for the whole (sub)catchments, both the mean value and the CV of travel times are scale-invariant, but sensitive to model resolution and accuracy. Such quantifications and results of advective travel times constitute important steps in the development of improved understanding and modelling of nutrient, pollutant and tracer transport through catchments.

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• Small unmonitored near-coastal catchment areas yielding large mass loading to the sea

  2008. Georgia Destouni (et al.). Global Biogeochemical Cycles 22 (GB4003)

  Artikel

  Continental freshwater transports and loads excess nutrients and pollutants from various land surface sources into downstream inland and coastal water environments. This study shows that even small, hydrologically unmonitored near-coastal catchment areas may generate large nutrient and pollutant mass loading to the sea of a magnitude similar to or greater than monitored river loads. Systematic near-coastal gaps in the monitoring of freshwater discharges to the sea may therefore mislead the quantification of coastal mass loading significantly. A methodology is presented for quantifying the mass load contributions of all the different unmonitored pathways of hydrological mass transport to the coast, including unmonitored river parts, whole unmonitored streams, and submarine groundwater discharge. This can be used for guiding future efforts to improve monitoring so that it includes the essential hydrological pathways of nutrient and pollutant loading to the sea.

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