干旱区生态环境知识资源中心

Although playas are specifically mentioned as protected in Federal regulations regarding the Clean Water Act, there is a lack of supporting evidence describing basic concepts relevant to vegetation, soils, and hydrology for the purposes of establishing a scientifically sound method of playa delineation. To date no hydrological studies have attempted to describe the frequency and duration associated with ponded water on desert playa systems. This study analyzed the duration and frequency of inundation on hard playas in the western Mojave Desert on Edwards Air Force Base, CA during the wet season (Oct.-Mar.) using satellite imagery over the last 19 years and precipitation records over the last 59 years. Our results indicate that ponding on these playas, lasting at least 16 days, occurs with a frequency of 0.51 or every other year. Average precipitation needed to initiate ponding is 8.29 cm. Years in which ponding was verified for 16 days between October and March could also be verified for ponding for at least 16 days during the growing season (Mar.-Nov.). Total duration of ponding through the wet season was found to range between I and 32 weeks with a second order non-linear relationship between length of inundation and total rainfall during the wet season.