Global modelling of water resources, water use and water quality
Since 1996, the global water resources and water use model WaterGAP (Water - Global Analysis and Prognosis) has been developed at the Center for Environmental Systems Research at the University of Kassel. Since 2003, further model development is done both in Kassel and at theUniversity of Frankfurt. Based on WaterGAP, the global model of terrestrial nitrogen WaterGAP-N is now being developed at the University ofFrankfurt.
For the whole land area of the world (except Antarctica), WaterGAP computes both the terrestrial components of water flow and storage (surface runoff, groundwater recharge, river discharge, water storage in soil, groundwater and surface water bodies) and water use (for irrigation, livestock, households, thermal power plant and manufacturing) at a spatial resolution of 0.5 degree (55 x 55 km at the equator). The postersWaterGAP 2: Global Hydrology Model (16 MB) and WaterGAP 2: Global Water Use Model (12 MB) provide an overview of the model.
WaterGAP is a tool for assessing the current water resources situation and for estimating the impact of global change on freshwater issues, in particular on the problem of water scarcity. It is designed to simulate the characteristic macro-scale behaviour of the terrestrial water cycle, including the human impact, and to take advantage of all pertinent information that is globally available. WaterGAP simulates the impact of demographic, socioeconomic and technological change on water use as well as the impact of climate change and variability on water availability and irrigation water use. In the course of developing WaterGAP, three global data sets were generated: a global map of irrigated areas, a global drainage direction map and a global lakes and wetlands data set. The current model version WaterGAP 2.1 is unique in that:
- It includes the only comprehensive global water use model which computes sectoral water uses in grid cells.
- It includes a global hydrological model that is tuned against measured discharge for 50% of the global land area.
- It is based on the best global data sets available.
- The hydrological model computes both natural and actual discharge (by taking into account streamflow reduction by water use).
- The impact of climate variability on water availability and irrigation water use is taken into account.
- The important driving forces of global change are included such that relevant global change scenarios can be generated.
The computations of present-day and future water availability, water use and water stress that have been generated based on WaterGAP have contributed to various global and continental freshwater resources assessments such as:
- the 1997 Report of the German Advisory Council on Global Change (Wissenschaftlicher Beirat Globale Umweltveränderungen): World in Transition: Ways Towards Sustainable Management of Freshwater Resources
- the World Water Vision global scenarios of the year 2025 (Vision Report, Chapter 3)
- Eurowasser - a project financed by BMBF (Federal Ministry of Education and Research) to assess the impact of climate change on water resources, droughts, floods and hydropower in Europe (Kassel World Water Series Report 5)
- World Water Development Report 2003 of UNESCO (global maps of current water situation) (UNESCO webpage of Report)
- Third World Water Development Forum, Kyoto 2003
- Millenium Ecosystem Assessment (2005)
