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1 January 2012 Does Shrub Removal Increase Groundwater Recharge in Southwestern Texas Semiarid Rangelands?
Georgianne W. Moore, David A. Barre, M. Keith Owens
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Evapotranspiration (ET) is a key component limiting groundwater recharge past the root zone in semiarid regions. Vegetation management may alter groundwater recharge if ET is altered due to changes in vegetation type or cover. This study quantifies changes in groundwater recharge following vegetation cover change from native woodland to pasture in a semiarid region of southwest Texas. The Carrizo–Wilcox aquifer is a valuable groundwater resource in this area, where overuse by dependent farming practices has lowered aquifer levels significantly in the last 85 yr. Combining data from short-term (30 mo) monitoring of the changes in soil moisture and long-term (5–30 yr) changes in total soil chloride indicated deep drainage increased slightly where land had been cleared of vegetation. Annual recharge rates below rooting depths (standardized to 155 cm) averaged only 0.72 ± 0.2 mm · yr−1 (mean ± SE) in areas not cleared of woody vegetation, as estimated by chloride mass balance. Upon clearing, 72% of the total chloride naturally occurring in the soil profile was flushed away within 30 yr, leading to an estimated 2.59 ± 1.7 mm · yr−1 additional recharge. Deep soil moisture in recently cleared land increased by up to 17% during the growing season of wet years (double the average rainfall) but did not increase in dry or normal precipitation years, providing supporting evidence that more water penetrated below the roots under certain environmental conditions. These results demonstrate that brush management can increase recharge by modest, but measurable, amounts depending on site-specific soil characteristics and degree of reduction in vegetation.

Society for Range Management
Georgianne W. Moore, David A. Barre, and M. Keith Owens "Does Shrub Removal Increase Groundwater Recharge in Southwestern Texas Semiarid Rangelands?," Rangeland Ecology and Management 65(1), 1-10, (1 January 2012).
Received: 22 March 2011; Accepted: 1 August 2011; Published: 1 January 2012

Brush management
Carrizo–Wilcox aquifer
chloride mass balance
deep drainage
natural tracer
soil water balance
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