Water resource use in the Great Ruaha Basin of Tanzania

The historic and new data on water availability, use and demands were collected and subjected to rigorous analysis. The key finding indicates that water abstracted from rivers for irrigation is 56% of wet season flow, 93% of dry season flow, and 64% overall. However, there are significant differences between irrigation water requirements and current abstraction rates; some, but not all, of these differences are accounted for by return flows. The indications are that more water is being abstracted than required for crop production. There is little evidence of significant changes in rainfall or in river flows into Usangu plain. However, there is clear evidence that water entering Usangu plain is being diverted in large amounts into irrigation schemes. The effect of irrigation is, however, complicated and varies both seasonally and annually.