Investigation of Relationships among Climate, Stream Flow and Water Supply

ABSTRACT

The detection and attribution of past trends, changes and variability of climatic variables is essential for the understanding of potential future changes resulting from anthropogenic activities. Analyses of trends and responses in stream flow are very important, since stream flow represents the integrated basin responses to the variations of several important climatic variables such as precipitation and temperature. Increasing significant trends in annual mean precipitation were detected in three of the four watersheds considered for the study in West Shewa. Increasing significant trends in annual mean stream flow were detected in two of the four watersheds. All watersheds exhibited significant trends in seasonal shift of precipitation and stream flows. Significant responses of stream flows to precipitation were also detected. Regional regression models of annual stream flow relating the basin area, mean annual precipitation, mean annual temperature, and basin relief were developed for Belo, Bite, Indris and Guder watersheds. The storage-reliability-resilience and yield relationships were investigated in those watersheds. The resilience indices of those watersheds were computed. Those indices showed that year-to-year (carryover) storage is required in all of the four watersheds. The values of the mean annual inflows and the standard deviations were close to each other implying that the stream flow fluctuations have followed similar trends in all of the watershed. The calculated N-year non-failure reliability gave very small values even for only two years.

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