In order to cope with a severe reduction of the rain gauge network in the Great Ruaha River Basin over the past 30 years, an interpolation scheme using spatial patterns from satellite images as covariate has been evaluated. The regression based interpolation attempts to combine the advantages of accurate rainfall amounts from rain gauge records with the unique spatial pattern information obtained from satellite based rainfall estimates. A spatial pattern analysis reveals that the simple interpolation of the sparse current rain gauge network compares very poorly to the pattern originating from the much denser historic network. In contrast, the rainfall data sets that include patterns from satellite data show good correlation with the historic pattern. The evaluation based on hydrological modeling, showed similar and good performance for all rainfall products including rain gauge records, whereas the purely satellite based product performed poorly.