New Mexico Geological Society Annual Spring Meeting — Abstracts

Soil properties such as texture, bulk density and porosity have a major influence on the partitioning of rainfall into infiltration and runoff. Thus they determine the water available for aquifer recharge, stream flow and ecosystem processes. Quantifying soil hydraulic properties is difficult and time consuming and most researchers use empirically derived relationships between soil physical attributes and soil hydraulic properties when modeling water movement in vadose zones. These relationships termed pedotransfer functions are the basis of well-known vadose zone models such as those developed by Van Genuchten (1980), Brooks and Corey (1964).

In the semi arid southwestern United States, where quantifying rainfall partitioning is of great importance, the soils are characterized by the accumulation of soluble salts, principally calcium carbonate into calcic horizons. Studies have shown that the accumulation of calcium carbonate in soils can influence soil hydraulic properties, including moisture retention and saturated and unsaturated hydraulic conductivity (Baumhardt and Lascano, 1993; Gile 1961; Aronovici et al., 1972, Dong, et al., 2003). However, this data shows no consistent pattern of soil hydraulic properties with varying amounts of calcium carbonate.

Studies have shown that the calcium carbonate content of arid soils increases with increasing age of the soil producing systematic morphological changes in calcic horizons (Gile et al., 1962, Bachman and Machette 1973). They recognized six stages of calcic horizon development recording the gradual accumulation of calcium carbonate cementing the matrix of soils until eventually producing an impermeable layer within the soil profile. I believe that the reported variation in hydraulic properties of calcic horizons reflects the unrecognized variation in calcic horizon development used in the studies of hydraulic properties.

I propose to measure the hydraulic properties of a chronosequence of sandy aridisols, which show a systematic increase in calcium carbonate content, and morphology with increasing age. We will produce a systematic data set relating K_sat, K_unsat, and moisture retention curves to calcium carbonate content and stage of calcic horizon development. Ksat will be determined in the lab from soil blocks, Kunsat in part by disc infiltrometer and by water potential meter, and moisture retention curves by moisture loss from lab samples. Soil properties such as particle size, calcium carbonate content, and bulk density will be measured for each sample characterized hydrologically.