Recharge in Arid Regions
Ground Water Hydrology
Published Online: 15 APR 2005
Copyright © 2005 by John Wiley & Sons, Inc.
How to Cite
Leonhart, L. S. 2005. Recharge in Arid Regions. Water Encyclopedia. 5:408–413.
- Published Online: 15 APR 2005
Groundwater recharge in arid regions or deserts is a process that requires a favorable combination of hydrologic factors. Accordingly, recharge, in arid regions occurs more rarely and supplies annual quantities of water to the groundwater table lower than typical of more humid regions. Many of the processes by which recharge occurs, such as surface infiltration, stream channel loss, and seepage from impounded water bodies, however, are common to both regions.
By definition, the aridity of a region is determined by the ratio of mean annual precipitation to mean annual potential evapotranspiration (PET). As shown in Fig. 1, arid regions in both the Northern and Southern Hemispheres are situated mostly between 10° and 35° latitude worldwide. Regions that have average annual precipitation (P) totaling less than 250 mm (10 in) make up an estimated 25% of the worldwide land areas outside of the polar regions. Arid regions are sometimes further classified as hyperarid, arid, or semiarid, according to the ranges in the P/PET ratio.
For several reasons, estimates of mean annual precipitation are difficult to relate directly to recharge in arid regions. Largely, this difficulty arises from characteristically high temporal and spatial variability in both the distribution of precipitation and recharge in arid regions. Longer term recharge to precipitation ratios (R/P) for various arid regions in the United States generally are typically less than 5%.
- soil moisture deficit;
- P/PET ratio;
- ephemeral streams infiltration