The global freshwater availability and water use model WaterGAP 2.2e – features, evaluation and application within ISIMIP3

The availability of freshwater resources is of essential importance for humans, freshwater biota, and ecosystem functions. In this scope, global hydrological models (GHMs) are developed to improve the understanding of the global freshwater situation in a globalized world, by filling gaps in observational coverage and assessing scenarios of the future under consideration of different socioeconomic developments and climate change. The Water Global Assessment and Prognosis (WaterGAP) model calculates water use and availability and is in development since 25 years. It consists of five water use models (for irrigation, domestic, cooling of thermal power plants, manufacturing, and livestock sectors) and the WaterGAP Global Hydrology Model (WGHM). Recently, the latest model version, WaterGAP 2.2e, was finalized, containing a number of enhancements and revisions such as integrating new reservoirs, improving naturalized simulations and updating the calibration data base. Furthermore, WaterGAP2.2e is applied in the Inter-Sectoral Impact Model Intercomparison Project ISIMIP3.

This presentation provides an overview of the WaterGAP 2.2e scheme and features, assesses streamflow and total water storage anomalies against reference data, shows water balance components, and provides examples of application within ISIMIP3 with a focus on climate forcing uncertainty and selected indicators of climate change hazards.