| dc.description.abstract | 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. | en |
