Spatial and Temporal Variability of Antecedent Moisture Content On Model-Generated Runoff From a Watershed.

Streams in the arid southwest are typically arid, and stream gages are not commonly available. Consequently, runoff data from storm events is not available, and flood control facility design or other water resource related decisions are based on synthetic hydrographs.  Additionally, soils information used in the calculations for these synthetic hydrographs is generally shown on maps that are developed for a broad range of issues and do not consider spatial or temporal variability in the hydraulic properties.  The antecedent moisture content can vary due to a number of physical conditions that change within a specific soil type, and this variation can have a significant impact on the watershed runoff response.  A physically based hydrologic model has been developed for a meso-scale watershed in the arid Mojave Desert to evaluate the watershed response to design storm frequencies of 2-, 5-, 25-, 50-, and 100 year return periods.  The soil information used in this model is varied through the use of a pedotransfer function that was developed for this study from field measurements of soil hydrologic and hydraulic parameters.  The pedotransfer function will be used to develop the varying antecedent moisture content for storms occurring at 1-, 5-, 10-, and 30 days.