WATCH (Water and Global Change): Estimation of global groundwater status with the WaterGAP model

Background

Global freshwater resources in general are influenced heavily by global change. As a part of the freshwater resources, groundwater is a key source of water for society, but there is currently no approach for quantitatively including both groundwater resources and use in global assessments. To estimate the influence of global change to groundwater status, it is necessary to evaluate groundwater resources and withdrawals on a global scale.
The Integrated Project WATCH brings together 25 project partners from the hydrological, water resources and climate communities. Together, they analyse, quantify and predict the components of the current and future global water cycles and related water resources states, evaluate their uncertainties and clarify the overall vulnerability of global water resources related to the main societal and economic sectors.

Objective

The University of Frankfurt takes a leading role in the project in developing a representation of groundwater in the WATCH water modelling framework. There are three questions to be answered:

  1. How large is the groundwater resource?
  2. How much of the groundwater resource is used?
  3. Are there further restrictions for the groundwater resource (e.g. depletion by pesticide exposure)?

The objective is to consolidate and improve existing tools in order to estimate groundwater resources and use on the global basis. For this purpose, a concept of groundwater status will be developed considering

  • groundwater recharge
  • groundwater withdrawals
  • aquifer type

and also other groundwater related characteristics.

Methodology

The WaterGAP Global Hydrology Model (Döll et al. 2003) which currently simulates groundwater recharge at a spatial resolution of 0.5° globally, will be further improved based on river discharge measurements (base flow estimates) and independent smaller-scale information on groundwater recharge.
The freshwater withdrawals already calculated by the WaterGAP model for the sectors irrigation, household/manufacturing and thermal power plants are split up in surface water withdrawals and groundwater withdrawals. Further, it is distinguished between groundwater withdrawals from renewable groundwater resources and those from fossil groundwater resources. The estimation of groundwater withdrawals is based on statistical as well as on demographic data, which are downscaled to the 0.5° grid taking into account groundwater resources and hydrogeology.
As a result, the vulnerability of groundwater is estimated on a global scale with the WaterGAP model considering groundwater resources as well as their use. The groundwater datasets developed in WATCH will be integrated into the IGRAC data base on groundwater to become widely available.

Keywords: global hydrological modeling, climate change, groundwater resources, groundwater recharge, groundwater withdrawals

Participants: Felix Portmann, Petra Döll

Cooperating institutions:
Centre for Ecology and Hydrology of the Natural Environment Research Council, UK
UK Met Office/Hadley Centre, UK
Wageningen University & Research Centre, The Netherlands
Centre for Environmental Systems Research at the University of Kassel, Germany
International Groundwater Resources Assessment Centre (IGRAC), The Netherlands

Duration: February 2007 - January 2011

Funding entity: WATCH is an integrated project (IP) supported by the European Commission under the Sixth Framework Programme, theme 1.1.6.3 “Global change and ecosystems”, Contract no: 036946

Contact: hydrology@em.uni-frankfurt.de