HR: 0800h
AN: H21A-1317    [Abstracts]
TI: Estimating Bedrock Infiltration in the Upper Dry Creek Experimental Watershed, Boise, Idaho Using the Chloride Mass Balance Method
AU: * Aishlin, P S
EM: pamellas@cableone.net
AF: Boise State University, 1910 University Drive, Boise, ID 83725 United States
AU: McNamara, J
EM: jmcnamar@boisestate.edu
AF: Boise State University, 1910 University Drive, Boise, ID 83725 United States
AB: Recharge estimation in mountainous environments is complicated by shallow, variable-depth soils, high variability in slope, aspect and vegetation, complex ground-water flow paths and elevation-dependent precipitation input. Under arid or semi-arid conditions, recharge estimation is further complicated by high rates of evapotranspiration relative to precipitation. This disparity, along with physical variability, renders traditional methods utilizing modeling of evapotranspiration subject to wide margins of error. The chloride mass-balance approach, which quantifies the mass of chloride delivered from precipitation to groundwater, offers an improvement. This approach was initially developed in systems where groundwater underlies a deep vadose zone. In applying this method to mountainous terrain, bedrock infiltration is the resultant estimate. The premise for estimation of bedrock infiltration is that change in concentration of chloride in the system is due to evapotranspiration. Chloride in the system is measured in precipitation, stream water and ground water as parameters to calculate the portion of annual precipitation contributing to bedrock infiltration. Precipitation input is measured at established sites across the watershed, while groundwater samples are taken from springs and wells within the watershed. Stream discharge is determined from continuous discharge measurements taken at the watershed outlet. Preliminary results suggest that bedrock infiltration comprises 5 percent of precipitation received in this 27.2 square km granitic catchment.
DE: 1816 Estimation and forecasting
DE: 1818 Evapotranspiration
DE: 1838 Infiltration
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1876 Water budgets
SC: Hydrology [H]
MN: Fall Meeting 2005