State Water Resources Research Institute Program

Project Id: 2010NV160B
Title: Partition of Evapotranspiration and Scale Issues in Arid Landscape
Project Type: Research
Start Date: 3/01/2010
End Date: 2/28/2011
Congressional District: NV01
Focus Categories: Hydrology, Water Use, Ecology
Keywords: Evapotranspiration, Landscape, Water budget
Principal Investigator: Zhu, Jianting Julian (Desert Research Institute)
Federal Funds: $ 15,257
Non-Federal Matching Funds: $ 31,444
Abstract: In arid regions of the southwestern United States, water is a major determinant affecting vegetation cover and desert landscape. Vegetation cover and biomass affect various hydrologic phenomena, including infiltration, runoff, and interception. Any controls on water movement can exert a major influence on plant community composition, function, and structure. Surface soil structure and texture affect the depth of water penetration, and hence root distributions of perennial plants, and the diversity and vigor of native vegetation. The presence of nonlinear relationships between evapotranspiration (ET) partitioning and various hydrologic and ecological processes suggests that grid scale ET partitioning modeling can not be accurately modeled without subgrid-scale process information. At field scale, spatial variability of soil properties and plant cover patterns could be significant, differentially impacting plant-water relations within the site.

This project is designed to investigate scale effects of numerical predictions on water budget, specifically on ET partitioning, in arid environments. The objectives are to investigate: (1) the effects of plant cover spatial patterns on the field scale water budget of desert landscape, (2) the implications of distinct hydraulic properties of under-canopy and interspace on the large field scale water budget, and (3) the scale effects of numerical models on the water budget predictions at various scales. The study will be built on previous field campaign conducted at the Mojave Global Change Facility (MGCF), located approximately 90 km northwest of Las Vegas, Nevada on the Nevada Test Site.

At the microsite scale (canopy or interspace), field investigations can yield point-scale information on particle size distribution and soil hydraulic properties, but relatively few studies have examine spatial patterns of plant patterns and effects on field scale water budget in the desert environments. The most important contribution from this research project will be to determine how canopy patterns affect large-scale partitioning of ET into evaporation and transpiration in a desert environment. Spatial variability in soils hydraulic properties and spatial patterns of plant cover manifests into a complex problem of soil hydrology and root interactions that further influence partitioning of precipitation into components of soil evaporation and plant transpiration. The problems will be investigated using different ranges of averages and correlation lengths of canopy cover that can be used to estimate landscape patterns (i.e., patchiness of mosaics). The average percent cover will be typical of arid environment from less than 10% to about 30%. The correlation lengths range from a small fraction to significant portion of the landscape scale to about 50% of field domain length.

Progress/Completion Report, 2010, PDF

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