In many countries, the groundwater reservoirs contribute a large part of the total water supply. It is especially true for Denmark, where 99% of the water supply depends on groundwater. This is why Scientists at the University of Copenhagen and the Geological Survey of Denmark and Greenland (GEUS) investigated the effects of future climate change on groundwater recharge, storage, and discharge to streams for two geologically and climatologically different regions in Denmark in a study funded by the Danish Environmental Protection Agency. These results are also published in the special section of Vadose Zone Journal.
The climate data used in this study was gathered from regional climate simulations for two scenarios of the Intergovernmental Panel on Climate Change for the period of 2071-2100. Average annual precipitation, temperature, and loss of water in the soil increased, but clear seasonal variations occurred. A model was used to simulate the altered water system that resulted from changes in weather conditions. As most groundwater systems react slowly to changes that occur on the earth's surface, the main focus of this study was the average monthly values for a 15-year period.
The magnitude of the water response to the simulated climate change was highly dependant on the geological setting. In the study area characterized by sandy top soils and large, interconnected aquifers, the groundwater levels rose significantly. For the other study, with low-permeable top soils and thick clay layers, the groundwater levels only showed minor changes. The primary effect in this area was the change in river discharge with up to 50% increase in winter and 50% decrease in summer. Research is ongoing at the University of Copenhagen and GEUS to investigate other combined impacts of changes in climate, land use, irrigation demand, and sea-level on water resources.
According to the guest editors, resource management and government policies will need to be assessed based on both surface and underground climate impacts altered by human activity. According to Timothy Green, one of the guest editors, the simulations in these studies help to explain the complex interactions between climate on plants and soils. For full adaptation as part of the Earth's water security discussions, he recommends that underground climate change needs to surface as a full-fledged part of the global system.
Results of this research are published in the August 2007 Vadose Zone Journal in a special section titled, "Groundwater Resources Assessment under the Pressures of Humanity and Climate Change." The eight-articles in this special section are available as open-access for a limited time. This special section was edited by Timothy Green (USDA-ARS), Makoto Taniguchi (Research Institute for Humanity and Nature, Japan), and Henk Kooi (Vrije University, The Netherlands) includes studies of several locations around the world, including regions of Africa, Asia, Australia, Micronesia, North America, and Europe
