VARIATIONS IN WATER-BALANCE AND RECHARGE POTENTIAL AT 3 WESTERN DESERT SITES

Radioactive and hazardous waste landfills exist at numerous desert loc ations in the USA. At these locations, annual precipitation is low and soils are generally dry, yet little is known about recharge of water and transport of contaminants to the water table. Recent water balance measurements made at three desert locations, Las Cruces, NM, Beatty, NV, and the U.S. Department of Energy's Hanford Site in the state of W ashington, provide information on recharge potential under three disti nctly different climate and soil conditions. All three sites show wate r storage increases with time when soils are coarse textured and plant s are removed from the surface, the rate of increase being influenced by climatic variables such as precipitation, radiation, temperature, a nd wind. Lysimeter data from Hanford and Las Cruces indicate that deep drainage (recharge) from bare, sandy soils can range from 10 to > 50% of the annual precipitation. At Hanford, when desert plants are prese nt on sandy or gravelly surface soils, deep drainage is reduced but no t eliminated. When surface soils are silt loams, deep drainage is elim inated whether plants are present '' not. At Las Cruces and Beatty, th e presence of plants eliminated deep drainage at the measurement sites . Differences in water balance between sites are attributed to precipi tation quantity and distribution and to soil and vegetation types. The implication for waste management at desert locations is that surface soil properties and plant characteristics must be considered in waste site design in order to minimize recharge potential.