The requirement addressed by this study is that of estimating the rainfall over a given area within a given accuracy. Decision criteria are given explicitly, historical data sets are used to obtain the necessary statistics, an optimal interpolation objective analysis (x,y,t) is used to estimate the rainfall, and specific gage density and accumulation times are deduced. Some of the hazards associated with the modeling are discussed. Abstract The requirement addressed by this study is that of estimating the rainfall over a given area within a given accuracy. Decision criteria are given explicitly, historical data sets are used to obtain the necessary statistics, an optimal interpolation objective analysis (x,y,t) is used to estimate the rainfall, and specific gage density and accumulation times are deduced. Some of the hazards associated with the modeling are discussed.