Water budgets and cave recharge on juniper rangelands in the Edwards Plateau

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Title: Water budgets and cave recharge on juniper rangelands in the Edwards Plateau
Author: Gregory, Lucas Frank
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 .
URI: http : / /hdl .handle .net /1969 .1 /3791
Date: 2006-08-16


Water budgets and cave recharge on juniper rangelands in the Edwards Plateau. Available electronically from http : / /hdl .handle .net /1969 .1 /3791 .

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