HR: 1330h
AN: H32A-0525    [PDF]
TI: Field Measured Infiltration Fluxes at the Onset of Ephemeral Streamflow
AU: * Blasch, K W
EM: kblasch@usgs.gov
AF: U.S. Geological Survey, 520 N. Park Ave, Suite 221, Tucson, AZ 85719 United States
AU: * Blasch, K W
EM: kblasch@usgs.gov
AF: University of Arizona, P.O. Box 210011, Tucson, AZ 85721 United States
AU: Ferre, T P
EM: ty@hwr.arizona.edu
AF: University of Arizona, P.O. Box 210011, Tucson, AZ 85721 United States
AU: Hoffmann, J P
EM: jphoffma@usgs.gov
AF: U.S. Geological Survey, 520 N. Park Ave, Suite 221, Tucson, AZ 85719 United States
AU: Cordova, J T
EM: jcordova@usgs.gov
AF: U.S. Geological Survey, 520 N. Park Ave, Suite 221, Tucson, AZ 85719 United States
AU: Cordova, J T
EM: jcordova@usgs.gov
AF: University of Arizona, P.O. Box 210011, Tucson, AZ 85721 United States
AB: A variety of physical and chemical methods have been used to measure transmission losses and infiltration fluxes within large ephemeral streams in southern Arizona, USA. Often these methods are used to estimate a single infiltration flux for a streamflow event, typically measured during steady-state conditions. For long duration events this single estimate can be reasonable, but for short duration events ($<$24 hrs) typical of those in southern Arizona, infiltration fluxes at the onset of flow can differ substantially in magnitude from those throughout the duration of an event. Use of steady-state infiltration fluxes for short duration events can underestimate the true volume of infiltrated water if the magnitude of the fluxes at flow onset are larger than steady-state values and the duration of the initial transient period is long. For detailed water-budget analyses and hydrologic models dependent on accurate transmission-loss and infiltration-flux estimates, a more comprehensive event record that estimates these values throughout the duration of events is required. A two-dimensional array of water-content and temperature sensors was installed in Rillito Creek in Tucson, Arizona, for the purpose of measuring infiltration fluxes in situ during streamflow events. Infiltration fluxes measured at the onset of 25 streamflow events over a 3-year period ranged from 0.02 to 0.2 m/s in comparison to steady-state fluxes that ranged from 6x10$^{-7}$ to 2x10$^{-6}$ m/s. Fluctuations in antecedent soil-water content and fluid/sediment temperatures were examined as possible factors contributing to the observed range of onset fluxes. The average antecedent moisture content of the profiles for the 25 events varied from 0.16 to 0.33 m3/m3. Lower antecedent moisture contents were associated with higher onset infiltration fluxes. Average antecedent temperatures for the profiles ranged from 10$^{o}$C to 30$^{o}$C and were directly proportional to onset infiltration rates.
DE: 1860 Runoff and streamflow
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting