Application of an integrated catchment-lake model approach for simulating effects of climate change on lake inputs and biogeochemistry.

Climate change is simultaneously affecting lakes and their catchments, resulting in altered runoff patterns in the catchment and modified mixing and biogeochemical dynamics in lakes. The effects of climate change in a catchment will eventually have an impact on the dynamics of a downstream water body as well. An integrated model would allow considering how changes in the watershed affect the lake, but coupled modelling studies are rare.

Assessing the effectiveness of potential best management practices for science-informed decision support at the watershed scale: The case of the Mar Menor coastal lagoon, Spain.

Coastal lagoons are ecosystems of high environmental importance but are quite vulnerable to human activities. The continuous inflow of pollutant loads can trigger negative impacts on the ecological status of these water bodies, which is contrary to the European Green Deal. One example is the Mar Menor coastal lagoon in Spain, which has experienced significant environmental degradation in recent years due to excessive external nutrient input, especially from non-point source (NPS) pollution.

Impacts of land use, climate change and hydrological model structure on nitrate fluxes: Magnitudes and uncertainties.

Nitrate pollution and eutrophication are of increasing concern in agriculturally dominated regions, and with projected future climate changes, these issues are expected to worsen for both surface and groundwater. Changes in land use and management have the potential to mitigate some of these concerns. However, to what extent these changes will interact is unknown, and are associated with significant uncertainty.

Identifying key drivers of harmful algal blooms in a tributary of the Three Gorges Reservoir between different seasons: Causality based on data-driven methods.

Intense harmful algal blooms (HABs) can occur in the backwaters of tributaries supplying large-scale reservoirs. Due to the characteristics of process-based models and difficulties in modelling complex nonlinear processes, traditional models have difficulties disentangling the driving factors of HABs. In this study, we used data-driven methods (i.

Subsurface hydrological processes and groundwater residence time in a coastal alluvium aquifer: Evidence from environmental tracers (δO, δH, CFCs, H) combined with hydrochemistry.

As an important part of the water cycle, the hydrologic process and chemical compositions of groundwater have changed significantly due to the joint influence of climate change and human activities. Groundwater salinization becomes a serious threat to water security in coastal areas. In order to assess the relationships between surface water, groundwater and seawater in the coastal plain, we performed a synthesis study based on hydrochemical-isotopic data, hydro-dynamical records and environmental tracers.

Quantifying the effects of climate change on hydrological regime and stream biota in a groundwater-dominated catchment: A modelling approach combining SWAT-MODFLOW with flow-biota empirical models.

Climate change may affect stream ecosystems through flow regime alterations, which can be particularly complex in streams with a significant groundwater contribution. To quantify the impacts of climate change on hydrological regime and subsequently the stream biota, we linked SWAT-MODFLOW (A model coupling the Soil and Water Assessment Tool and the Modular Finite-difference Flow Model) with flow-biota empirical models that included indices for three key biological taxonomic identities (fish, macroinvertebrates and macrophytes) and applied the model-complex to a groundwater-dominated catchment in Denmark. Effects of predicted climate change towards the end of this century relative to the reference period (1996-2005) were tested with two contrasting climate change scenarios of different greenhouse gas emissions (Representative Concentration Pathway 2.

Predicting ecosystem state changes in shallow lakes using an aquatic ecosystem model: Lake Hinge, Denmark, an example.

In recent years, considerable efforts have been made to restore turbid, phytoplankton-dominated shallow lakes to a clear-water state with high coverage of submerged macrophytes. Various dynamic lake models with simplified physical representations of vertical gradients, such as PCLake, have been used to predict external nutrient load thresholds for such nonlinear regime shifts. However, recent observational studies have questioned the concept of regime shifts by emphasizing that gradual changes are more common than sudden shifts.

Assessing the impacts of groundwater abstractions on flow regime and stream biota: Combining SWAT-MODFLOW with flow-biota empirical models.

Assessing the impacts of groundwater abstractions on stream ecosystems is crucial for developing water planning and regulations in lowland areas that are highly dependent on groundwater, such as Denmark. To assess the effects of groundwater abstractions on flow regime and stream biota in a lowland groundwater-dominant catchment, we combined the SWAT-MODFLOW model with flow-biota empirical models including indices for three key biological taxonomic identities (fish, macroinvertebrates, and macrophytes). We assessed the effects of the current level of abstractions and also ran a scenario for assessing the effect of extreme groundwater abstractions (pumping rates of the drinking water wells were increased by 20 times in one subbasin of the catchment).

Effects of changes in land use and climate on aquatic ecosystems: Coupling of models and decomposition of uncertainties.

To analyse the potential future ecological state of estuaries located in the temperate climate (here exemplified with the Odense Fjord estuary, Denmark), we combined end-of-the-century climate change projections from four different climate models, four contrasting land use scenarios ("Agriculture for nature", "Extensive agriculture", "High-tech agriculture" and "Market driven agriculture") and two different eco-hydrological models. By decomposing the variance of the model-simulated output from all scenario and model combinations, we identified the key sources of uncertainties of these future projections. There was generally a decline in the ecological state of the estuary in scenarios with a warmer climate.

Modelling the fate and transport of Cryptosporidium, a zoonotic and waterborne pathogen, in the Daning River watershed of the Three Gorges Reservoir Region, China.

Oospores of Cryptosporidium, a waterborne pathogen of great concern, are widely distributed in surface waters in China and pose a threat to human health. This study seeks to explore the spatio-temporal patterns of Cryptosporidium concentrations. We focus on the Daning River watershed (4166 km) of the Three Gorges Reservoir Region (TGR) during the period 2008 to 2013 and use the SWAT (Soil and Water Assessment Tool) model to test two mitigation scenarios.

Modeling the effects of climatic and land use changes on phytoplankton and water quality of the largest Turkish freshwater lake: Lake Beyşehir.

Climate change and intense land use practices are the main threats to ecosystem structure and services of Mediterranean lakes. Therefore, it is essential to predict the future changes and develop mitigation measures to combat such pressures. In this study, Lake Beyşehir, the largest freshwater lake in the Mediterranean basin, was selected to study the impacts of climate change and various land use scenarios on the ecosystem dynamics of Mediterranean freshwater ecosystems and the services that they provide.

Quantifying the combined effects of land use and climate changes on stream flow and nutrient loads: A modelling approach in the Odense Fjord catchment (Denmark).

Water pollution and water scarcity are among the main environmental challenges faced by the European Union, and multiple stressors compromise the integrity of water resources and ecosystems. Particularly in lowland areas of northern Europe, high population density, flood protection and, especially, intensive agriculture, are important drivers of water quality degradation. In addition, future climate and land use changes may interact, with uncertain consequences for water resources.

Future water availability in the largest freshwater Mediterranean lake is at great risk as evidenced from simulations with the SWAT model.

Inter- and intra-annual water level fluctuations and changes in water flow regime are intrinsic characteristics of Mediterranean lakes. Additionally, considering climate change projections for the water-limited Mediterranean region, increased air temperatures and decreased precipitation are anticipated, leading to dramatic declines in lake water levels as well as severe water scarcity problems. The study site, Lake Beyşehir, the largest freshwater lake in the Mediterranean basin, is - like other Mediterranean lakes - threatened by climatic changes and over-abstraction of water for irrigated crop farming.

Application of a three-dimensional water quality model as a decision support tool for the management of land-use changes in the catchment of an oligotrophic lake.

While expansion of agricultural land area and intensification of agricultural practices through irrigation and fertilizer use can bring many benefits to communities, intensifying land use also causes more contaminants, such as nutrients and pesticides, to enter rivers, lakes, and groundwater. For lakes such as Benmore in the Waitaki catchment, South Island, New Zealand, an area which is currently undergoing agricultural intensification, this could potentially lead to marked degradation of water clarity as well as effects on ecological, recreational, commercial, and tourism values. We undertook a modeling study to demonstrate science-based options for consideration of agricultural intensification in the catchment of Lake Benmore.

Effects of climate and nutrient load on the water quality of shallow lakes assessed through ensemble runs by PCLake.

Complex ecological models are used to predict the consequences of anticipated future changes in climate and nutrient loading for lake water quality. These models may, however, suffer from nonuniqueness in that various sets of model parameter values may yield equally satisfactory representations of the system being modeled, but when applied in future scenarios these sets of values may divert considerably in their simulated outcomes. Compilation of an ensemble of model runs allows us to account for simulation variability arising from model parameter estimates.

Watershed land use effects on lake water quality in Denmark.

Mitigating nutrient losses from anthropogenic nonpoint sources is today of particular importance for improving the water quality of numerous freshwater lakes worldwide. Several empirical relationships between land use and in-lake water quality variables have been developed, but they are often weak, which can in part be attributed to lack of detailed information about land use activities or point sources. We examined a comprehensive data set comprising land use data, point-source information, and in-lake water quality for 414 Danish lakes.