New Mexico Geological Society Annual Spring Meeting — Abstracts

Sand sheets are a common feature on the piedmonts of the arid southwest. I am studying sand sheets within the Socorro, New Mexico area to determine if their hydrologic characteristics in the vadose zone are different from adjacent alluvial fan soils. Sand sheets are gently undulating but predominantly flat eolian landforms which may affect recharge and storage in the vadose zone. The sand sheets are usually identified by changes in vegetation as compared to soils developed in alluvial fan deposits. Sand sheets support the only Pinon Juniper trees in the area. The Pinon Juniper forest is usually found in more moist environments rather than the semi-arid environment near Socorro suggesting that the sand sheets are behaving in a different manner hydrologically than the fan surfaces. Increased recharge from poorly sealed surfaces and faster recharge rates may be allowing more water to enter the vadose zone. I am using permeability measurements, infiltration capacities, and soil analysis to characterize the vadose hydrology of the sand sheets and adjacent soils. Sand generally has reduced evaporation because of limited capillary rise. Relatively higher infiltration capacities in the sand sheets may cause water to quickly reach a depth less affected by evaporation in highly permeable soils. Soil analysis confiITIls that carbonate has been leached from the upper soil horizons which would suggest that infiltration is greater and faster in the sand sheet. The goal of this study is to evaluate the role of depth of sand and sand sheets in general to changing hydrological conditions.