The global water resources and use model WaterGAP v2.2e: description and evaluation of modifications and new features

Water – Global Assessment and Prognosis (WaterGAP) is a modelling approach for quantifying water resources and water use for all land areas of the Earth that has served science and society since 1996. In this paper, the refinements, new algorithms and new data of the most recent model version v2.2e are described, together with a thorough evaluation of simulated water use, streamflow and total water storage anomaly against observation data. WaterGAP v2.2e improves the handling of inland sinks and now excludes not only large but also small man-made reservoirs when simulating naturalized conditions. The reservoir and non-irrigation water use data were updated. In addition, the model was calibrated against an updated and extended dataset of streamflow observations at 1509 gauging stations. The model can now be started using pre-scribed water storages and other conditions, which facilitates data assimilation as well as near real-time monitoring and forecast simulations. For specific applications, the model can consider the output of a glacier model, approximate the effect of rising CO2 concentrations on evapotranspiration or calculate the water temperature in rivers. In the paper, the publicly available standard model output is described and caveats of the model version are provided alongside the description of the model setup in the ISIMIP3 framework

Water demand scenarios for electricity generation at the global and regional levels

Electricity generation requires water. With the global demand for electricity expected to increase significantly in the coming decades, the water demand in the power sector is also expected to rise. However, due to the ongoing global energy transition, the future structure of the power supply - and hence future water demand for power generation - is subject to high levels of uncertainty, because the volume of water required for electricity generation varies significantly depending on both the generation technology and the cooling system. This study shows the implications of ambitious decarbonization strategies for the direct water demand for electricity generation. To this end, water demand scenarios for the electricity sector are developed based on selected global energy scenario studies to systematically analyze the impact up to 2040. The results show that different decarbonization strategies for the electricity sector can lead to a huge variation in water needs. Reducing greenhouse gas emissions (GHG) does not necessarily lead to a reduction in water demand. These findings emphasize the need to take into account not only GHG emission reductions, but also such aspects as water requirements of future energy systems, both at the regional and global levels, in order to achieve a sustainable energy transition

Effect of changing anthropogenic and climate conditions on BOD loading and in-stream water quality in Europe

Catchment scale modelling of water and solute transport and transformations is a widely used technique to study pollution pathways and effects of natural changes, policies and mitigation measures. There are, however, only a few examples of global water quality modelling. This paper provides a description of the new continental-scale water quality model WorldQual and the analysis of model simulations under changed climate and anthropogenic conditions with respect to changes in diffuse and point loading as well as surface water quality. Biological Oxygen Demand (BOD) is used as an indicator of the level of organic pollution and its oxygen-depleting potential, and for the overall health of aquatic ecosystems. The first application of WorldQual is to river systems of Europe. The model itself is being developed as part of the EU-funded SCENES Project which has the principal goal of developing new scenarios of the future of freshwater resources in Europe. Using WorldQual the influence of climate and anthropogenic changes on European water resources can be compared. The results indicate that changes in loading and in-stream concentrations following socio-economic changes and seem to override the effect of climate change

Reference concentrations of biochemical oxygen demand (BOD), faecal coliform bacteria (FC), and total dissolved solids (TDS) from published literature sources used for model validation

The attached table contains source information and measured concentrations of faecal coliform bacteria (FC), biochemical oxygen demand (BOD), and total dissolved solids (TDS). These measurements come from published literature and constitute supplementary information for the manuscript mentioned in the reference (in this context, the data was used for model validation and testing). This dataset was used for the project “The world's water quality: A pre-study for a worldwide assessment” for which funding was provided by the United Nations Environmental Programme (UNEP) and UN-Water

WaterGAP v2.2e

<p>This version of the source code from the WaterGAP Global Hydrological Model (WGHM) is used in version v2.2e.</p&gt