HR: 0800h
AN: H41D-0439    [Abstracts]
TI: Monitoring Cave Recharge in the Edwards Aquifer Recharge Zone for Natural and Simulated Rainfall Events
AU: * Gregory, L
EM: lucasgregory@tamu.edu
AF: Water Management and Hydrological Science, 2126 TAMU, College Station, TX 77843-2126 United States
AU: Veni, G
EM: gveni@satx.rr.com
AF: George Veni and Associates, 11304 Candle Park, San Antonio, TX 78249-4421 United States
AU: Shade, B
EM: bev@purificacion.org
AF: Private Contractor, 4811 Duval St., Austin, TX 78751 United States
AU: Wilcox, B P
EM: bwilcox@tamu.edu
AF: Dept. of Rangeland Ecology and Management, 2126 TAMU, College Station, TX 77843-2126 United States
AU: Munster, C L
EM: c-munster@tamu.edu
AF: Dept. of Biological and Agricultural Engineering, 2117 TAMU, College Station, TX 77843-2117 United States
AU: Owens, M K
EM: m-owens@tamu.edu
AF: Texas Agricultural Experiment Station, 1618 Garner Field Rd. , Uvalde, TX 77801-6205 United States
AB: Across semi-arid regions of the world, woody plant encroachment is widespread with potential implications for groundwater recharge and streamflow. In an effort to better understand the interactions between woody plants and recharge, we are monitoring drip rates in shallow caves in the Edwards Aquifer recharge zone of Central Texas. The surface is covered by a dense stand of ashe juniper (Juniperus ashei). In addition to stemflow, throughfall, and surface runoff was monitored for both natural precipitation events as well as simulated rainfall. Interception and throughfall are measured using a grid of rain gauges and throughfall collectors. Surface runoff measurements were quantified with a 15.24 centimeter H- flume instrumented with an ultrasonic water level sensor. Drip collectors constructed inside the cave collect recharge entering the cave from the ceiling. Large scale rainfall simulation equipment onsite allows us to "re-create" these naturally occurring rainfall events and compare the resulting data with that from the original event. Performing these types of tests allows us to learn important information about the cave footprint's ability to transmit recharge waters into the cave. During a simulation, water is applied directly to the cave footprint and not to the entire hillslope as in a natural rain event. We found that recharge for the natural and simulated events were similar. In each case, recharge makes up less than 5% of the water budget, in spite of the fact that there was little, if any, surface runoff. The working hypothesis is that most of the rainfall is routed off the hillslope as lateral subsurface flow.
DE: 1804 Catchment
DE: 1876 Water budgets
DE: 1879 Watershed
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: Fall Meeting 2005