HR: 11:20h
AN: H12B-05    [Abstracts]
TI: Comparison of Methods to Estimate Ephemeral Channel Recharge, Walnut Gulch, San Pedro River Basin, Arizona
AU: * Goodrich, D C
EM: dgoodrich@tucson.ars.ag.gov
AF: USDA-ARS-SWRC, 2000 E. Allen Rd. , Tucson, AZ 85719 United States
AU: Williams, D G
EM: dgw@uwyo.edu
AF: University of Wyoming , Dept. of Renewable Resources, Laramie, WY 82071 United States
AU: Unkrich, C L
EM: cunkrich@tucson.ars.ag.gov
AF: USDA-ARS-SWRC, 2000 E. Allen Rd. , Tucson, AZ 85719 United States
AU: Hogan, J F
EM: jhogan@hwr.arizona.edu
AF: University of Arizona, Dept. of Hydrology and Water Resources, Tucson, AZ 85721 United States
AU: Scott, R L
EM: rscott@tucson.ars.ag.gov
AF: USDA-ARS-SWRC, 2000 E. Allen Rd. , Tucson, AZ 85719 United States
AU: Hultine, K R
EM: hultine@biology.utah.edu
AF: University of Arizona, School of Renewable Nat. Res., Tucson, AZ 85721 United States
AU: Pool, D R
EM: drpool@usgs.gov
AF: U.S. Geological Survey - WRD, 520 N. Park Ave., Tucson, AZ 85719 United States
AU: Coes, A L
EM: alcoes@usgs.gov
AF: U.S. Geological Survey - WRD, 520 N. Park Ave., Tucson, AZ 85719 United States
AU: Miller, S N
EM: snmiller@uwyo.edu
AF: University of Wyoming , Dept. of Renewable Resources, Laramie, WY 82071 United States
AB: Ephemeral channel transmission loss represents an important groundwater-surface water exchange in arid and semiarid regions and is potentially a significant source of recharge at the basin scale. However, identification of the processes and dynamics that control this exchange is a challenging problem. Specifically, data on the proportion of runoff transmission losses that escape from near-channel transpiration and wetted channel evaporation to become deep groundwater recharge are difficult to obtain. This issue was addressed through coordinated field research and modeling within the USDA-ARS Walnut Gulch Experimental Watershed (WGEW) located in the San Pedro River Basin of southeastern Arizona. Recharge was estimated using several independent methods which included a reach water balance approach, with near-channel ET estimated using sap flux and micrometeorological measurements; geochemical methods such as chloride mass balance; modeling of changes in groundwater level or microgravity measurements; and vadose zone water and temperature transport modeling. It was found that during the relatively wet 1999 and average 2000 monsoon seasons, the range of ephemeral channel recharge estimated from these methods differed by a factor of less than three. A rough scaling to the entire San Pedro Basin indicates that ephemeral channel recharge constitutes between approximately 15 percent and 40 percent of total annual recharge to the regional aquifer as estimated from a calibrated groundwater model. In contrast, during the weak monsoon seasons of 2001 and 2002 limited runoff and stream channel infiltration did occur but no discernable deep aquifer recharge was detected.
DE: 1818 Evapotranspiration
DE: 1821 Floods
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting