Point Rainfall Estimation for a Mountainous Region

Abstract

Several point rainfall estimation techniques including the conventionally used arithmatic average and normal ratio methods, inverse-distance method, modified normal ratio method, and method of using linear programming model are applied to the Sierra-Nevada mountainous region. In the study area, the elevation difference between the rain gages range from 70 ft to 1750 ft (21m to 534m) and the distance from 10 miles to 35 miles (18km to 63km). It is found that the recently advocated inverse-distance method fails to provide a desirable result. A method is proposed which takes into account the effect of topographic elevation variation for the region. Also, the issue about the number of index stations to be used in the estimation procedure is explored and discussed.