Bureau of Economic Geology, The University of Texas at Austin (www.beg.utexas.edu).
Bureau Seminar, November 21, 2003
Land Use Controls on Groundwater Recharge
Robert C. Reedy and Dr. Bridget R. Scanlon
Quantification of groundwater recharge is important for assessing aquifer vulnerability to contamination because most contaminant sources occur at or near the land surface and recharge, among other factors, determines the rate that contaminants can be transported to an aquifer. The purpose of this study was to estimate recharge rates for the Southern High Plains Aquifer. Recharge was estimated using field studies including measurement of soil physics (water content, matric potential head) and environmental tracers (chloride) in soil samples from boreholes installed in different land use settings, including natural, dryland farming, and irrigated farming.
Recharge rates based on the
chloride mass balance approach ranged from 0.5 to 26 mm/yr in the Southern
High Plains. The variation in recharge correlated with land use: low recharge
rates in natural settings (0.5 to 0.8 mm/yr) and much higher recharge
rates in dryland farming settings (6 to 26 mm/yr). The variation in recharge
rates is consistent with the soil physics measurements: low matric potential
heads in natural settings (-208 to -270 m) indicate dry conditions and
much higher matric potential heads in dryland and irrigated settings (-2
to -2.8 m) indicate wet conditions. The results of this study have important
implications for assessing aquifer vulnerability to contamination and
indicate that land use is an important factor in controlling recharge
and aquifer susceptibility to contamination.