Untitled DocumentEcohydrological controls on desert vadose-zone dynamics
Macro Theme Area:
Basin Scale Water Balance [Project ID: B05]
PI:
Fred Phillips
CO-PI(s):
N/A
Basin focus:
Rio Grande
Specific area in
basin /
field sites:
Transect extending from the Rio Grande on the Sevilleta National Wildlife Refuge to the Bear Mountains bounding the Rio Grande rift on the west.
Summary/Goals: The objective of this project is to test the interrelationship between deep vadose zone fluxes and vegetation community. Previous SAHRA investigations have shown that desert lowland settings (desert shrub and desert grassland communities) are characterized by small upward fluxes toward the base of the root zone, and hence no groundwater recharge. However, sparse data collected under more mesic communities suggest that downward fluxes are significant there. We have drilled a transect of 10-m deep boreholes beneath desert shrub and grassland, juniper, and ponderosa pine communities, located along an elevation/precipitation transect to examine whether we see abrupt changes in vadose-zone flux at ecotones, or gradual changes controlled by increasing precipitation.
Activities and outcomes during past year:
We have obtained GIS datasets of all relevant parameters in order to help select sample sites. Based on this preliminary data we have performed field examinations to find sites characterized by flat topography, deep, relatively fine alluvial soils, and uniform vegetation. Soil characteristics have been examined at each site by electromagnetic induction surveys. Sites have been examined by an archeologist in order to obtain antiquities clearance. Drilling permits have been obtained from the Sevilleta National Wildlife Refuge and Cibola National Forest. Eleven ~10 m-deep core holes were drilled in March 2004. These have been analyzed for water potential, chloride, bromide, particle size, bulk density, root distribution, soil description, water content, and other parameters. The sites have been compared using chloride mass balance analysis and a range of other data synthesis. Methods and results have been written up.
Plans for the upcoming year:
Soil-water dynamics modeling is in progress, using the HYDRUS-1D code. Synthesis and writing of results is planned to be complete by the end of December. A paper for Water Resources Research is in progress and should be complete by early spring.
