Document: SCO-3-65-44

Landscape patterns of overland flow in a semi-arid biome transition zone.

MARTENS, S.N.*

University of New Mexico, Albuquerque, NM 87131 USA ¹

Abstract:
I investigated the patterns and importance of overland flow in semi-arid landscapes, using the ecohydrological model SPLASH (Simulator for Processes of Landscapes: Surface/Subsurface Hydrology) and the extensive data sets of the Sevilleta LTER. The Sevilleta National Wildlife Refuge covers about 100,000 ha in central New Mexico and encompasses the transition zone of four biomes: Chihuahuan Desert, Great Plains grassland, Great Basin shrubland, and Rocky Mountain conifer. SPLASH simulates precipitation interception, snowmelt by energy balance calculations, Penman-Monteith evaporation of intercepted water, free water, soil water and transpiration, vadose zone infiltration using the Green-Ampt equation, groundwater recharge, lateral Darcian groundwater flow, and lateral overland flow using Manning's equation and the zero inertia assumption. SPLASH includes simulation of soil evaporation appropriate for arid lands. Meteorological variables measured at seven stations were spatially distributed over the landscape using inverse distance weighting and elevation lapse functions. Vegetation was parameterized using Landsat TM and extensive field measurements. Terrain was described by USGS digital elevation model at 30 m horizontal resolution. Most soil physical parameters were derived from the NRCS soil survey. However, surface roughness (Manning's n) was difficult to parameterize from existing data. I used an inverse, iterative technique to determine Manning's n for a small watershed (76 ha) runoff event by matching SPLASH simulations to the measured exit hydrograph. Subsequent applications of this spatially-averaged Manning's n parameterization to other events and watersheds gave mixed results. Because of non-linear interactions among watershed elements, improved results might be achieved by methods that can yield higher spatial resolution parameterizations.

Keywords: semiarid hydrology runoff simulation

This abstract is being presented at: 8:30 AM in session:
Oral Session #58: Landscape Ecology.