• Energy Research

Understanding the impacts of climate change requires the development of hydrological modelling tools. However, data scarcity hinders model application, performance, process simulation and uncertainty, especially for Sub-Saharan Africa. In this study, a multi-catchment approach was used to assess hydrological process variability in the Western Cape (WC) of South Africa using the JAMS/J2000 rainfall–runoff model and a Monte Carlo analysis (MCA). Due to much steeper slopes and lower evapotranspiration, the models suggest that WC is dominated by surface runoff from mountainous regions and regional groundwater flow. The results highlight the impact of the catchment size, availability and position of hydroclimatic and anthropogenic factors and the frequency of the signal-to-noise ratio (water balance). For large catchments (>5000 km2), the calibration was able to achieve a Nash–Sutcliffe efficiency (NSE) of 0.61 to 0.88. For small catchments (<2000 km2), NSE was between 0.23 to 0.39. The large catchments had an overall surface runoff, interflow and baseflow contribution of 44, 19 and 37%, respectively, and lower overall uncertainty. The simulated flow components for the small catchments were variable and these results are less certain. The use of a multi-catchment approach allows for identifying the specific factors impacting parameter sensitivities and in turn provides a means to improve hydrological process simulation.

Headwater catchments store valuable resources of quality water, but their hydraulic response is difficult to assess (model) because they are usually deprived of monitoring stations, namely hydrometric stations. This issue becomes even more pertinent because headwater catchments are ideal for the practice of conjunctive water resources management involving the supply of towns with groundwater and surface water, a solution that can be used to mitigate overexploitation of groundwater resources in densely urbanized and populated areas. In this study, a stepwise approach is presented whereby, in a first stage, a gauged basin was modeled for stream flow using the JAMS J2000 framework, with the purpose to obtain calibrated hydraulic parameters and ecological simulated stream flow records. Having validated the model through a comparison of simulated and measured flows, the simulated record was adjusted to the scale of an ungauged sub-basin, based on a new run of JAMS J2000 using the same hydraulic parameters. At this stage, a second validation of modeled data was accomplished through comparison of the downscaled flow rates with discharge rates assessed by field measurements of flow velocity and water column height. The modeled basin was a portion of Jequitiba River basin, while the enclosed sub-basin was the Marinheiro catchment (state of Minas Gerais, Brazil). The latter is a peri-urban watershed located in the vicinity of Sete Lagoas town, a densely urbanized and populated area. This town uses 15.5 hm3 year−1 of karst groundwater for public water supply, but the renewable resources were estimated to be 6.3 hm3 year−1. The impairment between abstraction and renewable resources lasts for decades, and for that reason the town experiences systemic water table declines and sinkhole development. The present study claims that the storage of quality water in the Marinheiro catchment, in a dam reservoir, would help alleviate the depletion of groundwater resources in the karst aquifer because this catchment could deliver 4.73 hm3 year−1 of quality surface water to the municipality without endangering ecologic flows. The construction of a small dam at the outlet of Marinheiro catchment could also improve aquifer recharge. Presently, the annual recharge in this catchment approaches 1.47 hm3 but could be much larger if the small dam was installed in the water course and the captured stream water managed properly.

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.

Key messages from the modelling results of flow intermittence projections under climate change scenarios in the six European river networks studied as part of the H2020 DRYvER project (https://www.dryver.eu/). The dataset contains one global summary fact sheet as well as one fact sheet per studied river network : Albarine (France), Bükkösdi (Hungary), Butiznica (Croatia), Genal (Spain), Lepsämänjoki (Finland), and Velicka (Czechia).