Climate Change and Ground Water

Abstract

This article summarizes the theory of climate change and the relationship of climate-change forcing to hydrologic and aquifer processes. It focuses on regional aquifer systems and on the methods to link large-scale climate-change processes to ground-water recharge and to simulate ground-water flow and solute transport in a warmer, 2xCO₂ climate. The article reviews methods currently available to generate climate-change forcing and to simulate regional aquifer systems under ensuing hydrologic conditions. In addition, it outlines the development of a methodology to quantify the effects of climate change and of changes in ground-water use by population growth on hydrologic response. An example illustrates a specific procedure and our current capabilities and limitations to assess the potential impacts of a warming climate and population growth on regional-scale aquifer systems. The results indicate that aquifer exploitation strategies must take into account climatic variability and climate-change patterns. During protracted drought, the competition between human and ecological water uses is sharply accentuated. Changes in ground-water use may affect aquifer response more profoundly than climate change associated with modern global warming.

Key Words:

• climate change
• ground water
• population

Acknowledgments

This work was supported in part by the U.S. Environmental Protection Agency and by the U.S. National Science Foundation. The methods, findings, and conclusions cited or made in this article are the responsibility of the author and do not imply endorsement by the funding agencies.

Notes

^aHistorical recharge during 1978—1989, the mean of which=0.949×10⁹ m³ yr⁻¹.

^bThis is the historical recharge scaled to 2xCO₂ conditions according to equation (7).

^cThe average ground-water use between 1978 and 1989=0.567×10⁹ m³ yr⁻¹.

^dThe ground-water use forecast for 2050=0.784×10⁹ m³ yr⁻¹.

Note: Spring flow is in 10⁶ m³ month⁻¹.

^aThe scenarios are the same ones defined in Table 1.

^bThe numbers within parentheses represent the percentage increase (+) or decrease (−) caused by a scenario relative to the base condition (I).

1. A summary of climate-change science may be found in the 2001 report by the Intergovernmental Panel for Climate Change (IPCC) on its Web site.

2. See Loáiciga, Maidment, and Valdes (2000) for a list of GCMs used in hydrologic studies. See http://www. mmm.ucar.edu/mm5/mm5-home.html for a description of the RCM MM5 (Mesoscale Model 5) of the National Center for Atmospheric Research, US.

3. GCM-RCMs yield runoff-scaling ratios rather than stream-flow ratios, but when averaged over relatively large areas, these two ratios converge to the same value. Runoff in GCM-RCMs is equal to the land-based water flux from model cells, while stream-flow is defined in hydrology as the sum of overland flow, interflow, and baseflow concentrated in the stream channel.