HR: 1340h
AN: H43C-0510    [Abstracts]
TI: Using Surficial Geomorphic Information to Describe Spatial and Temporal Variation of Infiltration on Alluvial Fans in Semi-Arid Environments
AU: * Blainey, J
EM: jblainey@arizona.edu
AF: University of Arizona, P.O. Box 210011, Tucson, AZ 85721 United States
AU: Pelletier, J
EM: jon@geo.arizona.edu
AF: University of Arizona, 1040 E 4th St., 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
AB: The increasing demand for water resources in semi-arid regions necessitates more accurate and dynamic quantification of basin-scale water budgets to evaluate the sustainability of water resources. Recharge is often a poorly quantified component of water budgets due to high variability in both space and time. This research addresses water flow on alluvial fans in semi-arid areas. Specifically, we examine the roles of topography and surficial hydraulic properties on the division of precipitation into fan runoff and on-fan infiltration. The goal is to develop techniques to use surficial geomorphic maps and limited hydraulic-property measurements to define potential recharge units on fans. A numerical model was developed that routes surface flow and simulates vertical infiltration on synthetic alluvial fans. The model evaluates the interplay of topography and surface hydraulic properties on infiltration responses for precipitation events of varying duration and frequency. Synthetic topography, with stochastically distributed channels, is generated for a specified fan radius, relief, and width of feeder channel at the apex of the alluvial fan. Surface flows are based on steady-flow routing using the Manning's equation and the continuity equation. Bifurcation routing is used to route flow to multiple downslope directions weighted by slope. Altitudinal differences in the synthetic topography of the alluvial fans define several different surfaces which represent surfaces of varying geomorphic age. The age of geomorphic surfaces can be correlated to the degree of surface armoring, soil texture, and bulk density which are all key components influencing surficial hydraulic properties. Consequently, surface age is used to define hydrologic properties. To account for infiltration, a loss term is added for steady-state vertical infiltration under ponded conditions. The relationship between total infiltration and spatial distribution of infiltration (proximal vs. distal fan) is characterized as a function of fan geometry (slope, active channel geometries) and storm distribution.
DE: 1825 Geomorphology: fluvial (1625)
DE: 1838 Infiltration
DE: 1869 Stochastic hydrology
SC: Hydrology [H]
MN: Fall Meeting 2005