Development and testing of the WaterGAP 2 global model of water use and availability

Abstract

Growing interest in global environmental issues has led to the need for global and regional assessment of water resources. A global water assessment model called "WaterGAP 2" is described, which consists of two main components-a Global Water Use model and a Global Hydrology model. These components are used to compute water use and availability on the river basin level. The Global Water Use model consists of (a) domestic and industry sectors which take into account the effect of structural and technological changes on water use, and (b) an agriculture sector which accounts especially for the effect of climate on irrigation water requirements. The Global Hydrology model calculates surface runoff and groundwater recharge based on the computation of daily water balances of the soil and canopy. A water balance is also performed for surface waters, and river flow is routed via a global flow routing scheme. The Global Hydrology model provides a testable method for taking into account the effects of climate and land cover on runoff. The components of the model have been calibrated and tested against data on water use and runoff from river basins throughout the world. Although its performance can and needs to be improved, the WaterGAP 2 model already provides a consistent method to fill in many of the existing gaps in water resources data in many parts of the world. It also provides a coherent approach for generating scenarios of changes in water resources. Hence, it is especially useful as a tool for globally comparing the water situation in river basins.

The WULCA consensus characterization model for water scarcity footprints: assessing impacts of water consumption based on available water remaining (AWARE)

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Broad-scale ecosystem services of European wetlands—overview of the current situation and future perspectives under different climate and water management scenarios

“…WaterGAP consists of two main components: a Global Hydrology Model (Alcamo et al 2003, Döll et al 2003 The Global Hydrology Model calculates, for each individual grid cell, daily water balances for land areas and open water bodies. Thereby, spatially distributed physiographic characteristics, such as land cover, soil properties, hydrogeology, elevation and slope, as well as location and extent of wetlands, lakes and reservoirs are taken into account.…”

Modelling historical and current irrigation water demand on the continental scale: Europe

“…Monthly GIR and NIR in 5 resolution are then exported to the global hydrology and water use model Water-GAP, where accumulated anthropogenic water requirements from the different sectors (livestock, electricity production, manufactures and domestic) are considered as abstractions from the naturally available water in each grid cell to give a holistic approach for the calculation of total European water use (Alcamo et al, 2003).…”

“…WaterGAP3 is a global hydrology and water use model (Alcamo et al, 2003), which calculates water fluxes and anthropogenic water abstractions on a 5 grid. River runoff is calibrated and validated against 1600 stations of observed river flow.…”