Investigation of stream flow characteristics of the Wami-Ruvu basin.

Regionalization was introduced into hydrology in the near past. Heterogeneity among sites in the region, use of historical data and correlation between sites in a region are the limitations of this concept. This study tries to minimize their effects and assesses the significance of some of the limitations. The Wami-Ruvu basin was delineated into homogeneous regions for hydrological in studies. In order to achieve this objective physiographic; climatic and drainage characteristics were used to preliminarily identify homogeneous regions. Using statistics obtained from available annual maximum series and 10-day annual minimum series, these regions were tested for homogeneity. The tests were mainly based on regional weighted average L-moments. Based on this study 4 regions were obtained for Flood Frequency Analysis and 3 regions were obtained for Low Flow Frequency Analysis. Before starting the analysis, the data were checked for temporal and spatial independence. A procedure based on descriptive and predictive ability tests, adopted for selecting a suitable flood frequency model with the corresponding method of parameter estimation described. Storage required to augment low flows were also computed for varying demands expressed as a percentage of the mean flow at different probabilities of failure.