• Energy Research

River networks are among Earth’s most threatened hot-spots of biodiversity and provide key ecosystem services (e.g., supply drinking water and food, climate regulation) essential to sustaining human well-being. Climate change and increased human water use are causing more rivers and streams to dry, with devastating impacts on biodiversity and ecosystem services. Currently, more than a half of the global river networks consist of drying channels, and these are expanding dramatically. However, drying river networks (DRNs) have received little attention from scientists and policy makers, and the public is unaware of their importance. Consequently, there is no effective integrated biodiversity conservation or ecosystem management strategy of DRNs. A multidisciplinary team of 25 experts from 11 countries in Europe, South America, China and the USA will build on EU efforts to assess the cascading effects of climate change on biodiversity, ecosystem functions and ecosystem services of DRNs through changes in flow regimes and water use. DRYvER (DRYing riVER networks) will gather and upscale empirical and modelling data from nine focal DRNs (case studies) in Europe (EU) and Community of Latin American and Caribbean States (CELAC) to develop a meta-system framework applicable to Europe and worldwide. It will also generate crucial knowledge-based strategies, tools and guidelines for economically-efficient adaptive management of DRNs. Working closely with stakeholders and end-users, DRYvER will co-develop strategies to mitigate and adapt to climate change impacts in DRNs, integrating hydrological, ecological (including nature-based solutions), socio-economic and policy perspectives. The end results of DRYvER will contribute to reaching the objectives of the Paris Agreement and placing Europe at the forefront of research on climate change.

Statistical monthly and yearly flow intermittence indicators calculated from the simulated daily state of flow in the Albarine DRN (France). Indicators are provided for 3 SSP scenarios and 5 climate models on the projection periods (1985-2014 and 2015-2100).

Hydrological model outputs at daily time step for the projection simulations (1985-2100) in the Bükkösdi DRN (Hungary). Simulated discharge, baseflow an state of flow (flowing/dry) is spatially distributed at the reach scale. Other hydroclimatic variables (temperature, precipitation, rainfall, snowfall, potential evapotranspiration, actual evapotranspiration, vegetation interception, snow water equivalent, saturation of the soil layer, saturation of the grounwater layer) are spatially aggregated at the catchment scale. Hydrological projections were produced for 3 SSP scenarios and 5 climate models.

Statistical monthly and yearly flow intermittence indicators calculated from the simulated daily state of flow in the Butiznica DRN (Croatia). Indicators are provided for 3 SSP scenarios and 5 climate models on the projection periods (1985-2014 and 2015-2100).

Hydrological models outputs for the projection period (1985-2100) for the 6 European catchments studied in the DRYvER project.

Intermittent rivers and ephemeral streams (IRES) account for more than half of the world's rivers.However, few studies have investigated the evolution of IRES under climate change. Aiming toovercome this problem, DRYvER proposed to provide daily hydrological projections, daily flowconditions and flow intermittence indicators in 6 European Drying River Networks (DRNs).The current work aims to produce reach-scale daily hydrological projections available for the period1985-2100 for each DRN. To this end, coarse spatial resolution daily projections from Global ClimateModels (GCMs) are downscaled to obtain high resolution projections over the period 1971-2100.Secondly, the high-resolution projections are used as input to the JAMS/J2000 model to obtain dailycatchment-scale hydrological projections. Several GCMs are used as well as 3 shared socio-economicpathways (SSPs) to capture the uncertainty due to climate modelling and greenhouse gas emissionscenarios.The results show that the methodology is able to reproduce the historical hydrological behaviour ofthe DRNs in terms of seasonality, with some difficulties in Morava and Vantaanjoki regarding summerdischarge. Regarding the future periods, the responses of the six catchments were clearly different,showing an impact of climate change closely related to their location. Spring, summer and autumndischarges show a decrease for all catchments and all SSPs considered. For winter discharge, two of thecatchments show a slight increase, but the other four also show a decrease of varying intensity.

AbstractApproaches available for estimating the ecological impacts of climate change on aquatic communities in river networks range from detailed mechanistic models applicable locally to correlative approaches applicable globally. Among them, hydraulic habitat models (HABMs) link hydraulic models of streams with biological models that reflect how organisms select microhabitat hydraulics. Coarser but more general species distribution models (SDMs) predict changes in geographic distributions; they generally involve coarse predictors such as air temperature or distance to source but neglect proximate habitat descriptors such as microhabitat hydraulics. We propose an original application of HABM for predicting the ecological impacts of climate change at large scales, a comparison of their predictions with those of SDM and a linkage of the two modelling approaches. We showcase our approach in a large catchment (Rhône River) where an available distributed hydrological model estimates present and future unregulated daily flows over the whole river network. Despite large local uncertainties, simulations showed that climate change may strongly reduce low flow percentiles (e.g., a median reduction of 38.6% for a pessimistic climate scenario), inducing important alteration of fish hydraulic habitat suitability (e.g., a median loss of 3.9%–18.7% for three modelled fish species with contrasting habitat use: brown trout, barbel and sculpin). The HABM and SDM individually predicted consistent or opposite fish responses to climate change, depending on the species and their habitat requirements. Our results illustrate that accounting for ecological responses to proximate habitat variables such as hydraulics can strongly modify projections related to climate change.