Water budgets and cave recharge on juniper rangelands in the Edwards Plateau
MetadataShow full item record
Increasing demand for water supplies in semi-arid regions, such as San Antonio, has sparked an interest in potential recharge management through brush control. Two shallow caves under woody plant cover in northern Bexar County, Texas were chosen as study sites where a detailed water budget would be developed. The Headquarters Cave site measures natural rainfall and cave recharge while the Bunny Hole site is instrumented to measure throughfall, stemflow, surface runoff, and cave recharge. Large scale rainfall simulation was used at Bunny Hole to apply water directly above the cave footprint allowing us to determine how recharge differs between natural and simulated rainfall events. Under natural conditions, Headquarters Cave recharged 15.05% of the annual rainfall while Bunny Hole received 4.28%. Natural canopy throughfall measured 59.96% of the water budget; stemflow accounted for 0.48% and canopy interception was 39.56%; no surface runoff was measured. Rainfall simulations conducted at Bunny Hole resulted in an average of 74.5% throughfall, 5.3% stemflow, 20.2% canopy interception, 2.8% surface runoff, and 6.9% cave recharge; simulation intensities were typically higher than natural event intensities. General water budgets across the Edwards Plateau have concluded that evapotranspiration represents 65% of total annual rainfall while percolation and storage accounts for 30% and the remaining 5% is runoff. These studies have been focused on broad water budget parameters while this study looks at more detailed components. No other study to date has been able to combine throughfall, stemflow, surface runoff, and vertical recharge monitoring to quantify the water budget in the Edwards Plateau; these parameters are instrumental in determining a detailed water budget in juniper rangelands. Results from this study illustrate the significance of all aspects of the water budget and are the first to yield a firm measurement of actual upland recharge.
Gregory, Lucas Frank (2005). Water budgets and cave recharge on juniper rangelands in the Edwards Plateau. Master's thesis, Texas A&M University. Texas A&M University. Available electronically from