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Tree mortality triggered by bark beetle infestation can significantly affect terrestrial carbon and water balances. However, how to improve the parameterization of the stomatal conductance to express the dynamics of ecosystem disturbance remains unclear. A subalpine forest located in the Rocky Mountains experienced a severe bark beetle outbreak in 2008, which provided a unique opportunity to investigate carbon and water flux changes covering the periods of pre-infestation (2005-2007), infestation (2008-2009), and post-infestation (2010-2014). Affected by bark beetle infestation, the stomatal conductance during the summer season (July and August) significantly reduced from 0.0018 m/s in the pre-infestation period to 0.0011 m/s in the infestation period. The decrease in stomatal conductance was not solely caused by the decrease of LAI, but also related to variation in parameter g1 in three commonly-used models of Ball-Barry, Leuning, and Medlyn. The parameter g1 was related to water use efficiency (WUE), and WUE values increased in the infestation period and decreased in the post-infestation period providing evidence that the physiological behavior was significantly changed due to bark beetle infestation. As for the simulation of transpiration, the fitted parameter significantly improved the accuracy in comparison with recommended parameterization. With the inclusion of temporally varied stomatal conductance, estimated transpiration during the infestation period and post-infestation period was improved by 4.3%~13.6% in comparison with the unvaried parameterization fitted in the pre-infestation period. Accounting for the temporally varied stomatal conductance parameters in response to disturbed environments may improve the description of stomatal conductance leading to better model performance in estimated water and carbon balances.

Wetlands are increasingly considered as nature based solution as they provide valuable services and functions to the society and environment, such as water quality improvement and biodiversity support. However, while land use and climate change have been affecting the functions and service of these ecosystems, it has become important to study the large-scale behaviour of wetlands in the landscape. Consequently, previous studies have suggested studying wetlands within wetlandscapes, defined as catchments containing networks of several wetlands, in order to understand large-scale functions of wetlands and their response to land-use and climate changes. This emphasizes the ecohydrological interactions of wetlands rather than having focus of individual wetlands. As the concept of wetlandscape is new, we have been working on systematically quantifying its governing properties in two different studies.In the first study, we systematically quantified ecohydrological properties of individual wetlands (e.g. wetland area, wetland catchment area and wetland type) in multiple wetlandscapes that may impact biodiversity and modulate nutrient flows as well as characteristics of the whole wetlandscape in terms of their large-scale processes and functions. Results from this work showed that large wetlandscapes generally contained features to support different ecosystem services compare to smaller wetlandscapes. More specifically, results indicated that small wetlandscapes have a poor ability to route water through their wetlands which was in contrast to large wetlandscapes. This implies that large wetlandscapes have a higher potential for large-scale retention of nutrients and contaminants.The second study consisted of investigating spatial and temporal wetland storage dynamics for multiple wetlands in the landscape in order to address considerable knowledge gaps regarding hydrological functions of wetlands and wetlandscapes. More specifically, we use high-resolution monitoring of wetland water levels to assess storage patterns and inundation conditions. A key finding of this work is that the position of wetlands is important for storage dynamics and flood buffering. Notably we find that wetlands located in headwater regions showed larger water level variability during the growing season (spring, summer and autumn) and hence were more active in temporal water storage than wetlands located downstream in the wetlandscape. This variability in water level for headwater wetlands was also associated with complex and patchy inundation conditions, while downstream wetlands essentially showed dry-state conditions during the entire summer.Results from both studies show that ecohydrological properties of wetlandscapes can have implications for ecosystem service delivery (e.g., biodiversity support and water quality) at regional level as well as for using wetlands as nature-based solution. Present results also support the importance of wetlandscape studies and the priority of a wetlandscape focus in future management programs to various regional environmental challenges.

Increasing incidences of eutrophication and groundwater quality impairment from agricultural nitrogen pollution are threatening humans and ecosystem health. Minimal improvements in water quality have been achieved despite billions of dollars invested in conservation measures worldwide. Such apparent failures can be attributed in part to legacy nitrogen that has accumulated over decades of agricultural intensification and that can lead to time lags in water quality improvement. Here, we identify the key knowledge gaps related to landscape nitrogen legacies and propose approaches to manage and improve water quality, given the presence of these legacies.

Study region: Selenga River Delta (SRD), Russia. Study focus: How is water occurrence changing in the SRD, and what are the hydroclimatic drivers behind these changes? The presence of water on the surface in river deltas is governed by land use, geomorphology, and the flux of water to and from the Delta. We trained an accurate image classification of the Landsat satellite imagery during the last 33 years to quantify surface water occurrence and its changes in the SRD. After comparing our estimations with global-scale datasets, we determined the hydrological drivers of these changes. New hydrological insights for the region: We find mild decreases in water occurrence in 51% of the SRD's surface area from 1987–2002 to 2003–2020. Water occurrence in the most affected areas decreased by 20% and in the most water-gaining areas increased by 10%. We find a significant relationship between water occurrence and runoff (R2 =0.56) that does not exist between water occurrence and suspended sediment concentration (SSC), Lake Baikal's water level, and potential evapotranspiration. The time series of water occurrence follows the peaks in the runoff but not its long-term trend. However, the extremes in SSC do not influence surface water occurrence (R2

Assessments of ecosystem service and function losses of wetlandscapes (i.e., wetlands and their hydrological catchments) suffer from knowledge gaps regarding impacts of ongoing hydro-climatic change. This study investigates hydro-climatic changes during 1976–2015 in 25 wetlandscapes distributed across the world’s tropical, arid, temperate and cold climate zones. Results show that the wetlandscapes were subject to precipitation (P) and temperature (T) changes consistent with mean changes over the world’s land area. However, arid and cold wetlandscapes experienced higher T increases than their respective climate zone. Also, average P decreased in arid and cold wetlandscapes, contrarily to P of arid and cold climate zones, suggesting that these wetlandscapes are located in regions of elevated climate pressures. For most wetlandscapes with available runoff (R) data, the decreases were larger in R than in P, which was attributed to aggravation of climate change impacts by enhanced evapotranspiration losses, e.g. caused by land-use changes.

Water bodies provide essential ecosystem services linked to morphometric features that might differ between natural lakes and reservoirs. We use the HydroLAKES global dataset to quantitatively compare large (area1 km

Laboratory experiments and point observations, for instance in wetlands, have shown evidence that microbial sulfate reduction (MSR) can lower sulfate and toxic metal concentrations in acid mine drainage (AMD). We here hypothesize that MSR can impact the fate of AMD in entire catchments. To test this, we developed a sulfur isotope fractionation and mass-balance method, and applied it at multiple locations in the catchment of an abandoned copper mine (Nautanen, northern Sweden). Results showed that MSR caused considerable, catchment-scale immobilization of sulfur corresponding to a retention of 27 ± 15% under unfrozen conditions in the summer season, with local values ranging between 13 ± 10% and 53 ± 18%. Present evidence of extensive MSR in Nautanen, together with previous evidence of local MSR occurring under many different conditions, suggest that field-scale MSR is most likely important also at other AMD sites, where retention of AMD may be enhanced through nature-based solutions. More generally, the developed isotope fractionation analysis scheme provides a relatively simple tool for quantification of spatio-temporal trends in MSR, answering to the emerging need of pollution control from cumulative anthropogenic pressures in the landscape, where strategies taking advantage of MSR can provide viable options.

Acid mine drainage (AMD) threaten ecosystems world-wide and research on biological remediation techniques are increasing. One of them is bacterial sulfate reduction (BSR) that immobilizes the aqueous sulfate and through coprecipitation removes dissolved metals from the more bioavailable phase. Although BSR has previously only been investigated at the local wastewater treatment scale (e.g. for constructed wetlands), it is unknown to which extent they contribute to contaminant attenuation at larger scales (e.g. a hydrological basin). We developed a new method to trace the activity of BSR within an AMD-impacted catchment using sulfur isotopes (δ34S) and found that they naturally reduce 30% of the riverine sulfate and metal concentrations, with a spread from 10 to 50% reduction within the catchment. These results are based on surface water field measurements from our test site in northern Sweden combined in a mass-balance mixing model where we explicitly addressed the isotopic fractionation from bacterial activity. This innovative mapping of catchment-scale biogeochemical natural attenuation provides important clues to strategically target remediation measures, e.g. potential in-situ enhancement of the BSR activity. In combination with stable water isotopes we hope to refine this method to further identify BSR hot spots within the catchment and to extend its application to other sites, e.g. the Khibiny mining region, Russia.

Water resources are deteriorating across the world, which is of particular concern in water-scarce arid and semi-arid regions. Saline lakes often lack outflow, and are vulnerable to environmental change. When they start to shrink, salinity levels increase, due to evapoconcentration of salts in the reduced water volumes. This may harm the aquatic environment and limit the usability for humans. The associated exposure of their dry lakebeds may also bring severe regional problems of wind-blown saline dust and soil degradation. Although some of the world’s major cases of lake drying have been well studied, like the case of the Aral Sea desiccation, there is a lack of coherent assessments made at the global scale. Such assessments are critical for identifying vulnerable regions and main drivers of change, which may contribute to the prevention of future catastrophes. We here synthesise information on and analyse the desiccation status of 28 major saline lakes, each one of them having a surface area of ≥ 100 km2 and salinity of ≥ 10 g·L-1. They are geographically distributed over the world’s all continents, except Europe and Antarctica. In total, our results show that more than half of the world’s major saline lakes have dried up considerably in the last couple of decades. Out of these, 36 % are already, or are close to being completely desiccated. Preliminary analyses show correlations between original lake depth, lake bathymetry and resulting lakebed exposure from drying, suggesting that a lake’s general resilience to drying may be predictable. Our estimates further show that the world’s major saline lakes together contain 1177 billion tonnes of salt, of which 79 billion tonnes are currently in drying or already dried up lakes. If all of these lakes would desiccate, around 1 billion people are currently living within reach of saline dust storms that could spread from dry lakebeds.

Farm ponds, which are sometimes numerous and widely distributed in agricultural regions, have faced widespread degradation in recent decades. Although relevant conservation strategies have gradually increased, detailed assessments on their roles in regional biogeochemistry and ecology are lacking. We concluded that farm ponds provided hydrologic, biogeochemical, and socioeconomic benefits to southern China for thousands of years, but they are facing contemporary threats and management challenges, including (1) inadequate planning in terms of construction and conservation regulations; (2) rural nonpoint source and mini-point source pollution; (3) climate change-induced abnormalities in the hydroperiod and disturbance to wildlife; (4) invasive species; and (5) inadequate social and political capacity to consider ecological conservation. As farm ponds function as wetland complexes that are embedded within or integral to larger ecosystems, we recommend multi-disciplinary efforts over scales ranging from within-pond to regional for their assessment and conservation.Excessive nitrogen (N) discharge from agriculture is a major factor of widespread problems in aquatic ecosystems. Knowledge of spatiotemporal patterns and source attribution of N pollution in these small, scattered ponds is a critical first step for nutrient management and ecosystem health in low-order agricultural watersheds. We applied the process-based HSPF model for ponds, ditches, and downstream waters in a 4.8 km2 test watershed in southern China. The results exhibited distinctive spatial-seasonal variations with an overall seriousness rank for the three indicators: total nitrogen (TN) > nitrate/nitrite nitrogen (NOx--N) > ammonia nitrogen (NH3-N). TN pollution was severe for the entire watershed, while NOx--N pollution was significant for ponds and ditches far from the village, and the NH3-N concentrations were acceptable except for the ponds near the village in summer. Although food and cash crop production accounted for the largest source of N loads, we discovered that mini-point pollution sources, including animal feeding operations, rural residential sewage, and waste, together contributed as high as 47% of the TN and NH3-N loads in ponds and ditches.Our synthetic analysis and process-based modeling studies focused on farm ponds in an agriculturally dominated developing country (China), but similar small, scattered wetlands and their degradation trends are observed worldwide (e.g., vernal pools and prairie potholes in North American, farm ponds in Western and Central Europe, and chain of natural pond system in Australia). Nature-based solutions are becoming increasingly recognized as important for addressing the complex challenges in hydrology, ecology, and biodiversity under anthropogenic and climatic pressures. Apart from proposed conservation policies, including public awareness building, top-down regulations and bottom-up engagement, and sustainable management and utilization, we are also trying techniques that involve interconnected smart sensors and integrated modeling methods to better understand pond hydrological processes. We believe that such solutions can provide a basis for the numerical assessments on their ecosystem services and associated conservation cost analyses.

Surface water occurrence in river deltas is governed by precipitation, evaporation, and the influx and outflux of water to and from the delta. Although studies of changes in water occurrence have b...

Lake Baikal is the largest freshwater body on Earth, once famous for its pristine conditions. However, the lake and its drainage basin with their unique ecosystems have in recent decades been subject to both climate warming above the world average and severe anthropogenic pressures from mining and agriculture. Although previous studies have targeted various hydroclimatic, geochemical, and biological conditions of the Lake Baikal basin, the heterogeneous nature and large size of the basin leave considerable knowledge gaps regarding ongoing metal contamination of the basin&rsquo, s suspended sediments and waters. To address these knowledge gaps, the main objectives of this study are to (i) determine regional background values for water and suspended sediment quality with respect to multiple metals (representing undisturbed conditions) and (ii) further evaluate spatio-temporal concentration patterns of these metals, including regions with heavy anthropogenic impacts. We synthesize data from extensive field measurements within the Selenga River basin performed between 2011 and 2016, covering over 100 sampling locations. Results show that although the background metal concentrations (of both dissolved and suspended metal forms) in the alkaline Selenga River waters were close to the world averages, metal concentrations of up to two orders of magnitude above the background values were seen for Zn, As, Cd, Cu, Mo, and Pb in regions subject to anthropogenic impacts (cities and the mining industry). Specifically, dissolved As levels within the Selenga River basin were 2&ndash, 5 times higher than the world average and well above the global guideline value in several regions. Notable hotspots for anthropogenic impacts of Cd were particularly found in Zakamensk and Ulaanbaatar. Our results highlight clear anthropogenic impacts and large-scale spreading of several pollutants of concern, with risks even to downstream parts including the Selenga delta and Lake Baikal. We expect that these results will aid in increasing the understanding of large-scale metal transport processes, as well as for designing relevant measures to mitigate further spreading of metals to Lake Baikal.

Injection of free-phase supercritical CO2 into deep geological reservoirs is associated with risk of considerable return flows towards the land surface due to the buoyancy of CO2, which is lighter than the resident brine in the reservoir. Such upward movements can be avoided if CO2 is injected in the dissolved phase (CO2aq). In this work, injection of CO2-saturated brine in a subsurface carbonate reservoir was modelled. Physical and geochemical interactions of injected low-pH CO2-saturated brine with the carbonate minerals (calcite, dolomite and siderite) were investigated in the reactive transport modelling. CO2-saturated brine, being low in pH, showed high reactivity with the reservoir minerals, resulting in a significant mineral dissolution and CO2 conversion in reactions. Over the injection period of 10 yr, up to 16% of the injected CO2 was found consumed in geochemical reactions. Sorption included in the transport analysis resulted in additional quantities of CO2 mass stored. However, for the considered carbonate minerals, the consumption of injected CO2aq was found mainly in the form of ionic trapping.

Wetlands are increasingly considered as nature based solution as they provide valuable services and functions to the society and environment, such as water quality improvement and biodiversity support. However, while land use and climate change have been affecting the functions and service of these ecosystems, it has become important to study the large-scale behaviour of wetlands in the landscape. Consequently, previous studies have suggested to study wetlands within wetlandscapes, defined as catchments containing networks of several wetlands, in order to understand large-scale functions of wetlands and their response to land-use and climate changes. This emphasizes the ecohydrological interactions of wetlands rather than having focus of individual wetlands. However, as the concept of wetlandscape is new, its governing properties have not yet been systematically quantified.In this paper, we quantify ecohydrological properties of individual wetlands in multiple wetlandscapes, typical for northern Europe, that may impact biodiversity and modulate nutrient flows (e.g. wetland area, wetland catchment area and wetland type) as well as characteristics of the whole wetlandscape in terms of their large-scale processes and functions. We also investigate possible systematic differences between wetlandscapes of different size. Results show that large wetlandscapes generally contained features to support different ecosystem services compare to smaller wetlandscapes. More specifically, results indicated that small wetlandscapes have a poor ability to route water through their wetlands (i.e. catch flow from the entire wetlandscape) which was in contrast to large wetlandscapes. This implies that large wetlandscapes have a higher potential for large-scale retention of nutrients and contaminants. Present result support the importance of wetlandscape studies and the priority of a wetlandscape focus in future management programs for instance targeting regions with large-scale pollution issues.

Lake Baikal, located in eastern Russia, is the oldest (25 million years) and the deepest (~1800 meters) lake in the world. There are many rivers flowing into the Lake Baikal (~ 365 rivers), of which the Selenga River is the most important one being responsible for almost 55% of the runoff water into the system and also 60% of the transported sediments. As the hydrological changes of the river and its delta enormously alter the neighbouring area, it is of utmost importance to explore the dynamics of change in terms of flow magnitude, paths and fluvial geomorphology, and the related tipping points defining different states. The questions this study aims to answer are: What are the fluvial geomorphological and hydrological changes? What fluvial geomorphological tipping points can be identified during the last 34 years and what are the discharge and climatic conditions that induce them? In this study, we use the Global Surface Water Dataset (GSWD) to analyze the changes in the river’s stream network. With these products, we assess changes in several fluvial geomorphological proxies (e.g., sinuosity, fractal dimension, meandering characteristics, planform information) and identify possible tipping points. We relate these changes to different hydrological and climatic conditions such as precipitation, river discharge and Lake Baikal water level. We find evident changes in the meandering behaviour and flow path of the Selenga River tributaries in the Delta. The number of oxbow lakes based and corresponding size distribution has varied in time, and evident flow path changes occur that seem to be related to flooding periods, and there appears to be a consistent relationship between meandering and the river discharge variability. These results enable policymakers to understand different contributing factors altering the Selenga River Delta and ultimately leading to better decisions to manage the effects of these changes in the area.

The distribution of organic substrates and microorganisms in soils is spatially heterogeneous at the microscale. Most soil carbon cycling models do not account for this microscale heterogeneity, which may affect predictions of carbon (C) fluxes and stocks. In this study, we hypothesize that the mean respiration rate R‾ at the soil core scale (i) is affected by the microscale spatial heterogeneity of substrate and microorganisms and (ii) depends upon the degree of this heterogeneity. To theoretically assess the effect of spatial heterogeneities on R‾, we contrast heterogeneous conditions with isolated patches of substrate and microorganisms versus spatially homogeneous conditions equivalent to those assumed in most soil C models. Moreover, we distinguish between biophysical heterogeneity, defined as the nonuniform spatial distribution of substrate and microorganisms, and full heterogeneity, defined as the nonuniform spatial distribution of substrate quality (or accessibility) in addition to biophysical heterogeneity. Four common formulations for decomposition kinetics (linear, multiplicative, Michaelis–Menten, and inverse Michaelis–Menten) are considered in a coupled substrate–microbial biomass model valid at the microscale. We start with a 2-D domain characterized by a heterogeneous substrate distribution and numerically simulate organic matter dynamics in each cell in the domain. To interpret the mean behavior of this spatially explicit system, we propose an analytical scale transition approach in which microscale heterogeneities affect R‾ through the second-order spatial moments (spatial variances and covariances). The model assuming homogeneous conditions was not able to capture the mean behavior of the heterogeneous system because the second-order moments cause R‾ to be higher or lower than in the homogeneous system, depending on the sign of these moments. This effect of spatial heterogeneities appears in the upscaled nonlinear decomposition formulations, whereas the upscaled linear decomposition model deviates from homogeneous conditions only when substrate quality is heterogeneous. Thus, this study highlights the inadequacy of applying at the macroscale the same decomposition formulations valid at the microscale and proposes a scale transition approach as a way forward to capture microscale dynamics in core-scale models.

Lakes have significant hydraulic connections with their surrounding groundwater, thus the coupled simulation of lake and groundwater interactions is an important component of the numerical modelling of groundwater flow. This paper proposes a new approach for simulating lake-groundwater interactions (Sloping Lakebed Method, short for SLM) based on the block-centered finite difference method. In this approach, a discretization of the lakebed elevation in the vertical direction is conducted independently of the spatial discretization of the aquifer system, greatly simplifying the subdivision of the aquifer system. The lakebed is generalized by a slope across each lake cell, and the lake grid cells are classified as fully submerged, partially submerged, and unsubmerged to simulate the interactions between the lake and the aquifer according to the relative elevations of the lake surface and lake bed. Transitions between different states ensure the continuity of the boundary conditions, improving the convergence of the calculation process. The proposed method accounts for all source and sink terms for the lake, establishing a governing equation for lake water balance. The lake stage can then be obtained by solving this equation. A series of tests were run verifying the rationality and superiority of the SLM, suggesting that it provides similar results to those of the well-established MODFLOW LAK3 Package developed by the United States Geological Survey. However, the SLM has significant advantages over LAK3 in its ease of use and calculation stability.

Pollution from small abandoned mines is usually overseen compared to larger historical mining sites. Especially in the Arctic more research is needed on long-term water quality degradation from mine waste (e.g. metal leakage). We have studied changes in water quality from a historical copper (Cu) mining area, Nautanen, northern Sweden, that was shortly in operation for six years before abandonment in 1908 (~110 years ago). Water quality data from previous studies of the site (1993-2014) was compared to results from our own field campaigns in 2017, which provided us with a rare Arctic case study of 25 years of data. The results showed Cu, Zn and Cd concentrations at the mining zone being orders of magnitude larger than local background levels. This was surprising considering Nautanen’s short time of operation, the small scale of the mining site, and the long time since closure. We found no declining trend of metal concentrations over the surveyed 25-year period (1993-2017) and during the past 110 years (1907-2017) a mass flow of 43 tons of Cu was estimated to have been released to the local surface water system from the mining zone and 7 tons of Cu at 4 km downstream. Nautanen stands out with its high metal leakage relative to its small volume of mine waste compared to mass flows of other larger historical mining sites in e.g. Sweden and Canada. Small abandoned sites, which are numerous, could add disproportionately large amounts of metals to surface water systems. This information is crucial in upscaling local low-priority sites to regional assessments of total pollution pressures in sensitive Arctic environments. We are currently further investigating pollution transport pathways through oxygen and sulfur isotopes to trace water originating from the mine and other sources (e.g. atmospheric deposition, bacterial sulfate reduction). This method could give valuable information in data scares sites where e.g. groundwater data is inaccessible.

Reservoir construction has led to the development of numerous wetlands, and these wetlands play an important role in global environmental change. In this paper, we investigate the relationship between reservoir wetlands and hydroclimatic variables. We used the MODIS land cover product to extract the wetland area of the Sanmenxia Reservoir, China. Then, various indices of reservoir wetland landscape patterns were calculated. Principal component analysis was performed to build the Sanmenxia Reservoir wetland comprehensive landscape pattern index (CLPI) to depict the changes in Sanmenxia Reservoir wetlands from 2001 to 2013. Pearson correlation analysis was used to assess their relationship. The following results were obtained. Firstly, the Sanmenxia Reservoir wetland area considerably declined and the landscape heterogeneity decreased from 2001 to 2013, especially in 2004. Secondly, the CLPI is significantly negatively correlated with annual runoff and significantly positively correlated with annual sediment discharge, annual average water level and annual shallow groundwater table in Sanmenxia Reservoir regions. Additionally, due to the decline in the reservoir wetland area, the values of Shannon’s diversity index and Simpson’s diversity index decreased in the study area. Therefore, the study suggests that maintaining a stable and healthy reservoir wetland area should be the focus of ecological reservoir management.

Pollution from small historical mining sites is usually overlooked, in contrast to larger ones. Especially in the Arctic, knowledge gaps remain regarding the long-term mine waste impacts, such as metal leakage, on water quality. We study the small copper (Cu) mines of Nautanen, northern Sweden, which had been in operation for only six years when abandoned approximately 110 years ago in 1908. Measurements from field campaigns in 2017 are compared to synthesized historical measurement data from 1993 to 2014, and our results show that concentrations of Cu, Zn, and Cd on-site as well as downstream from the mining site are order(s) of magnitude higher than the local background values. This is despite the small scale of the Nautanen mining site, the short duration of operation, and the long time since closure. Considering the small amount of waste produced at Nautanen, the metal loads from Nautanen are still surprisingly high compared to the metal loads from larger mines. We argue that disproportionately large amounts of metals may be added to surface water systems from the numerous small abandoned mining sites. Such pollution loads need to be accounted for in sustainable assessments of total pollutant pressures in the relatively vulnerable Arctic environment.

Catchments are complex social-ecological systems involving multiple, and often competing, interests. Water governance and management regimes are increasingly embracing pluralistic, participatory, and holistic norms as a means to engage with issues of complexity, uncertainty, and value-conflicts. Integrated, participatory approaches are theoretically linked to improved learning amongst stakeholders across sectors and decision-making that is grounded in shared knowledge, experiences and scientific evidence. However, few studies have empirically examined the impacts of an integrated approach to learning and knowledge practices related to water resources. Here, a Swedish sub-catchment that has adopted such an approach in association with implementation of the European Water Framework Directive (WFD) is examined. Interview-based analyses show that WFD implementation has both helped and hindered learning and knowledge practices surrounding both water planning and spatial planning. Whilst communities of practice have developed in the study area, a number of important challenges remain. These include the rigid goal-orientation of the WFD, the fragmentation of knowledge caused by an over-reliance on external consultants, as well as a lack of resources to synthesise information from multiple sources. Present results raise questions regarding the efficacy of the WFD to sufficiently enable the development of learning and knowledge practices capable of handling the complexity, uncertainties and value-conflicts facing catchments in Sweden and elsewhere.

Hydrological connectivity describes the water-mediated transfer of mass, energy, and organisms between landscape elements and is the foundation for understanding how individual elements such as wet ...

The Selenga River delta (Russia) is a large (>600km(2)) fluvially dominated fresh water system that transfers water and sediment from an undammed drainage basin into Lake Baikal, a United Nation ...

The Selenga River has historically provided 50% of the total freshwater water input to the Lake Baikal, transporting substances and pollutants that can considerably impact the unique lake ecosystem. In the context of on-going regional to global change, we here aim at identifying and understanding mechanisms behind spatial and temporal variability and trends in the flow of the Selenga River and its tributaries, based on hydrological and meteorological station data (since the 1930s), remote sensing, and statistical analyses. Results show that the flow of the Selenga River exhibits cycles with phases of high flows lasting 12 to 17 years and phases of low flows that historically lasted for about 7 years. However, despite an asynchronous behavior between right-bank tributaries and left-bank tributaries, the flow of the Selenga River near its delta at Lake Baikal has now been low (30% below the 1934–1975 average) for as long as 20 years, due to reduced input from precipitation, particularly during the summer season. Observed decreases in annual maximum hourly flows and decreases in annual minimum 30-day flows are consistent with increasing activation of the groundwater system due to thawing permafrost, and higher winter temperatures that support increased winter flows by preventing rivers to freeze from top to bottom. These recent and relatively large changes have implications for regional water planning and management, including the planned large-scale hydropower expansion in the upper part of the Selenga River Basin.

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.

Mining has become one of the main causes of increased heavy metal loading of river systems throughout the world. There is however an evident gap between assessments of soil contamination and metal release at the mined sites and estimates of river pollution. The present work focuses on Zaamar Goldfield, which is one of the largest placer gold mines in the world, located along the Tuul River, Mongolia, which ultimately drains into Lake Baikal, Russia. It combines field observations in the river basin with soil erosion modelling and aims at quantifying the contribution from natural erosion of metal-rich soil to observed increases in mass flows of metals along the Tuul River. Results show that the sediment delivery from the mining area to the Tuul River is considerably higher than the possible contribution from natural soil erosion. This is primarily due to excessive mining-related water use creating turbid wastewaters, disturbed filtering functions of deposition areas (natural sediment traps) close to the river and disturbances from infrastructures such as roads. Furthermore, relative to background levels, soils within Zaamar Goldfield contained elevated concentrations of As, Sr, Mn,V, Ni, Cu and Cr. The enhanced soil loss caused by mining-related activities can also explain observed, considerable increases in mass flows of metals in the Tuul River. The present example from Tuul River may provide useful new insights regarding the erosion and geomorphic evolution of mined areas, as well as the associated delivery of metals into stream networks.

Due to specific environmental conditions, headwater catchments located on volcanic slopes and valleys are characterized by distinctive hydrology and sediment transport patterns. However, lack of sufficient monitoring causes that the governing processes and patterns in these areas are rarely well understood. In this study, spatiotemporal water discharge and sediment transport from upstream sources was investigated in one of the numerous headwater catchments located in the lahar valleys of the Kamchatka Peninsula Sukhaya Elizovskaya River near Avachinskii and Koryakskii volcanoes. Three different subcatchments and corresponding channel types (wandering rivers within lahar valleys, mountain rivers within volcanic slopes and rivers within submountain terrains) were identified in the studied area. Our measurements from different periods of observations between years 2012–2014 showed that the studied catchment was characterized by extreme diurnal fluctuation of water discharges and sediment loads that were influenced by snowmelt patterns and high infiltration rates of the easily erodible lahar deposits. The highest recorded sediment loads were up to 9∙104 mg/L which was related to an increase of two orders of magnitude within a one day of observations. Additionally, to get a quantitative estimate of the spatial distribution of the eroded material in the volcanic substrates we applied an empirical soil erosion and sediment yield model–modified universal soil loss equation (MUSLE). The modeling results showed that even if the applications of the universal erosion model to different non-agricultural areas (e.g., volcanic catchments) can lead to irrelevant results, the MUSLE model delivered might be acceptable for non-lahar areas of the studied volcanic catchment. Overall the results of our study increase our understanding of the hydrology and associated sediment transport for prediction of risk management within headwater volcanic catchments.

Heavy metal and metalloid contamination of topsoils from atmospheric deposition and release from landfills, agriculture, and industries is a widespread problem that is estimated to affect50% of the EU's land surface. Influx of contaminants from soil to groundwater and their further downstream spread and impact on drinking water quality constitute a main exposure risk to humans. There is increasing concern that the present contaminant loading of groundwater and surface water systems may be altered, and potentially aggravated, by ongoing climate change, through large-scale impacts on recharge and groundwater levels. We investigated this issue by performing hydrogeological-geochemical model projections of changes in metal(loid) (As and Pb) mobilization in response to possible (climate-driven) future shifts in groundwater level and fluctuation amplitudes. We used observed initial conditions and boundary conditions for contaminated soils in the temperate climate zone. The results showed that relatively modest increases (0.2 m) in average levels of shallow groundwater systems, which may occur in Northern Europe within the coming two decades, can increase mass flows of metals through groundwater by a factor of 2-10. There is a similar risk of increased metal mobilization in regions subject to increased (seasonal or event-scale) amplitude of groundwater levels fluctuations. Neglecting groundwater level dynamics in predictive models can thus lead to considerable and systematic underestimation of metal mobilization and future changes. More generally, our results suggest that the key to quantifying impacts of climate change on metal mobilization is to understand how the contact between groundwater and the highly water-conducting and geochemically heterogeneous topsoil layers will change in the future.

Wetlands are interconnected with the larger surrounding landscape through the hydrological cycling of water and waterborne substances. Therefore, the borders of individual wetlands may not be appropriate landscape system boundaries for understanding large-scale functions and ecosystem services of wetlandscapes (wetland network - landscape systems), and how these can be impacted by climate and land-use changes. Recognizing that such large-scale behaviours may not be easily predicted by simple extrapolation of individual wetland behaviours, we here investigate properties of 15 Swedish wetlandscapes in the extensive (22 650 km

Many natural and man-made urban lakes have been developed under urbanization. A unique feature of these lakes is the lack of an outlet; thus, they are defined as urban closed lakes (UCLs). UCLs are facing unexpected eutrophication under climate change and human activities. Our study assessed the trophic state, assimilative capacity (AC) and pollutant reduction of UCLs under different precipitation frequencies in Wuhan, China based on Carlson’s Trophic State Index, assimilative capacity modelling, field investigations and observed data. The UCLs in Wuhan are nearly eutrophic in summer. Three primary nutrient sources are atmospheric deposition, pollutants carried in rainfall and nutrients released by sediments. TN and TP in the UCL water column are primarily contributed by surface runoff. The ACs of TN and TP in 2015 for Lingjiao Lake, Yue Lake, and Houxianghe Lake were 3472.07 kg, 13,800.99 kg, and 2805.58 kg, respectively, and 641.66 kg, 8386.79 kg, and 800.14 kg, respectively. The ACs of TN and TP were much higher at a 25% precipitation frequency (wet year) compared with a 50% frequency, and the lowest AC was observed at a 75% precipitation frequency (dry year). A comparison of the pollution load and AC showed that TN and TP reduction was highest in the dry and wet years, respectively. We found that specific meteorological conditions in the early stage led to the algal bloom. These results can facilitate governmental decision making in the future.

Wetlands are often vital physical and social components of a country’s natural capital, as well as providers of ecosystem services to local and national communities. We performed a network analysis to prioritize Sustainable Development Goal (SDG) targets for sustainable development in iconic wetlands and wetlandscapes around the world. The analysis was based on the information and perceptions on 45 wetlandscapes worldwide by 49 wetland researchers of the Global Wetland Ecohydrological Network (GWEN). We identified three 2030 Agenda targets of high priority across the wetlandscapes needed to achieve sustainable development: Target 6.3—“Improve water quality”, 2.4—“Sustainable food production”, and 12.2—“Sustainable management of resources”. Moreover, we found specific feedback mechanisms and synergies between SDG targets in the context of wetlands. The most consistent reinforcing interactions were the influence of Target 12.2 on 8.4—“Efficient resource consumption”, and that of Target 6.3 on 12.2. The wetlandscapes could be differentiated in four bundles of distinctive priority SDG-targets: “Basic human needs”, “Sustainable tourism”, “Environmental impact in urban wetlands”, and “Improving and conserving environment”. In general, we find that the SDG groups, targets, and interactions stress that maintaining good water quality and a “wise use” of wetlandscapes are vital to attaining sustainable development within these sensitive ecosystems.

This study investigates metal contamination patterns and exposure to Sb, As, Ba, Cd and Pb via intake of drinking water in a region in southeastern Sweden where the production of artistic glass has resulted in a large number of contaminated sites. Despite high total concentrations of metals in soil and groundwater at the glassworks sites properties, all drinking water samples from households with private wells, located at a 30-640m distance from a glassworks site, were below drinking water criteria from the WHO for Sb, As, Ba and Cd. A few drinking water samples showed concentrations of Pb above the WHO guideline, but As was the only element found in concentrations that could result in human exposure near toxicological reference values. An efficient retention of metals in the natural soil close to the source areas, which results in a moderate impact on local drinking water, is implied. Firstly, by the lack of significant difference in metal concentrations when comparing households located upstream and downstream of the main waste deposits, and secondly, by the lack of correlation between the metal concentration in drinking water and distance to the nearest glassworks site. However, elevated Pb and Cd concentrations in drinking water around glassworks sites when compared to regional groundwater indicate that diffuse contamination of the soils found outside the glassworks properties, and not only the glass waste landfills, may have a significant impact on groundwater quality. We further demonstrate that different mobilization patterns apply to different metals. Regarding the need to use reliable data to assess drinking water contamination and human exposure, we finally show that the conservative modelling approaches that are frequently used in routine risk assessments may result in exposure estimates many times higher than those based on measured concentrations in the drinking water that is actually being used for consumption.

The repository concept for geological disposal of spent nuclear fuel in Sweden and Finland is planned to be constructed in sparsely fractured crystalline bedrock and with an engineered bentonite buffer to embed the waste canisters. An important stage in such a deep repository is the postclosure phase following the deposition and the backfilling operations when the initially unsaturated buffer material gets hydrated by the groundwater delivered by the natural bedrock. We use numerical simulations to interpret observations on buffer wetting gathered during an in situ campaign, the Bentonite Rock Interaction Experiment, in which unsaturated bentonite columns were introduced into deposition holes in the floor of a 417 m deep tunnel at the Aspo Hard Rock Laboratory in Sweden. Our objectives are to assess the performance of state-of-the-art flow models in reproducing the buffer wetting process and to investigate to which extent dependable predictions of buffer wetting times and saturation patterns can be made based on information collected prior to buffer insertion. This would be important for preventing insertion into unsuitable bedrock environments. Field data and modeling results indicate the development of a de-saturated zone in the rock and show that in most cases, the presence or absence of fractures and flow heterogeneity are more important factors for correct wetting predictions than the total inflow. For instance, for an equal open-hole inflow value, homogeneous inflow yields much more rapid buffer wetting than cases where fractures are represented explicitly thus creating heterogeneous inflow distributions.

Future sea level rise as a consequence of global warming will affect the world's coastal regions. Even though the pace of sea level rise is not clear, the consequences will be severe and global. Commonly the effects of future sea level rise are investigated for relatively vulnerable development countries; however, a whole range of varying regions need to be considered in order to improve the understanding of global consequences. In this paper we investigate consequences of future sea level rise along the coast of the Baltic Sea island of Gotland, Sweden, with the aim to fill knowledge gaps regarding comparatively well-suited areas in non-development countries. We study both the quantity of loss of infrastructure, cultural and natural values for the case of a two metre sea level rise of the Baltic Sea, and the effects of climate change on seawater intrusion in coastal aquifers, causing the indirect effect of salt water intrusion in wells. We conduct a multi-criteria risk analysis by using Lidar data on land elevation and GIS-vulnerability mapping, which gives formerly unimaginable precision in the application of distance and elevation parameters. We find that in case of a 2 m sea level rise, 3 % of the land area of Gotland, corresponding to 99 km2, will be inundated. The features most strongly affected are items of touristic or nature values, including camping places, shore meadows, sea stack areas, and endangered plants and species habitats. In total, 231 out of 7354 wells will be directly inundated, and the number of wells in the high-risk zone for saltwater intrusion in wells will increase considerably. Some values will be irreversibly lost due to e.g. inundation of sea stacks and the passing of tipping points for sea water intrusion into coastal aquifers; others might simply be moved further inland, but this requires considerable economic means and prioritization. With nature tourism being one of the main income sources of Gotland, monitoring and planning is required to meet the changes. Seeing Gotland in a global perspective, this island shows that holistic multi-feature studies of future consequences of sea level rise are required, to identify overall consequences for individual regions.

The partitioning of metals and metalloids between their dissolved and suspended forms in river systems largely governs their mobility and bioavailability. However, most of the existing knowledge about catchment-scale metal partitioning in river systems is based on a limited number of observation points, which is not sufficient to characterize the complexity of large river systems. Here we present an extensive field-based dataset, composed of multi-year data from over 100 monitoring locations distributed over the large, transboundary Selenga River basin (of Russia and Mongolia), sampled during different hydrological seasons. The aim is to investigate on the basin scale, the influence of different hydroclimatic conditions on metal partitioning and transport. Our results showed that the investigated metals exhibited a wide range of different behaviors. Some metals were mostly found in the dissolved form (84&ndash, 96% of Mo, U, B, and Sb on an average), whereas many others predominantly existed in suspension (66&ndash, 87% of Al, Fe, Mn, Pb, Co, and Bi). Nevertheless, our results also showed a consistently increasing share of metals in dissolved form as the metals were transported to the downstream parts of the basin, closer to the Lake Baikal. Under high discharge conditions (including floods), metal transport by suspended particulate matter was significantly greater (about 2&ndash, 6 times). However, since high and low water conditions could prevail simultaneously at a given point of time within the large river basin, e.g., as a result of on-going flood propagation, snap-shot observations of metal partitioning demonstrated contrasting patterns with domination of both particulate and dissolved phases in different parts of the basin. Such heterogeneity of metal partitioning is likely to be found in many large river systems. These results point out the importance of looking into different hydroclimatic conditions across space and time, both for management purposes and contaminant modeling efforts at the basin scale.

Soil pollution constitutes one of the major threats to public health, where spreading to groundwater is one of several critical aspects. In most internationally adopted frameworks for routine risk assessments of contaminated land, generic models and soil guideline values are cornerstones. In order to protect the groundwater at contaminated sites, a common practice worldwide today is to depart from health risk-based limit concentrations for groundwater, and use generic soil-to-groundwater spreading models to back-calculate corresponding equilibrium levels (concentration limits) in soil, which must not be exceeded at the site. This study presents an extensive survey of how actual soil and groundwater concentrations, compiled for all high-priority contaminated sites in Sweden, relate to the national model for risk management of contaminated sites, with focus on As, Cu, Pb and Zn. Results show that soil metal concentrations, as well as total amounts, constitute a poor basis for assessing groundwater contamination status. The evaluated model was essentially incapable of predicting groundwater contamination (i.e. concentrations above limit values) based on soil data, and erred on the “unsafe side” in a significant number of cases, with modelled correlations not being conservative enough. Further, the risk of groundwater contamination was almost entirely independent of industry type. In essence, since neither soil contaminant loads nor industry type is conclusive, there is a need for a supportive framework for assessing metal spreading to groundwater accounting for site-specific, geochemical conditions.