An Assessment of Climate Change and Possible Impact on Available Water Resources on the Odzi sub-catchment in Zimbabwe

Abstract

Climate change according to IPCC usage refers to any change in climate over time, whether due to natural variability or as a result of human activity. This study focused on assessing rainfall and runoff data of a micro catchment in the Odzi sub catchment to see if any trends existed and how far the results would explain climate change. The main 2 river in the subcatchment is the Odzi River. Total catchment area is 2 486 km . For runoff, this study dealt with 5 stations. Of the five stations, only station E32 showed a significant change (p=0.04) in runoff over time. The rest of the stations had no significant downward trends at 95% confidence level. A further analysis into the possible causes of this difference was done by looking at land use patterns in the catchment area supplying flows through station E32. This particular station is on the irrigation board of the Odzani river. Thus, this decline is most likely explained by an increase in abstructions by irrigators. For rainfall, this study dealt with 4 stations. Rusape and Odzi Police rail stations showed no significant change in rainfall over the 1959-2006 period. Mukandi showed a negative trend or drop in rainfall over the same period of 1959-2006. However, Nyanga station showed a rising trend in rainfall over the same period. Such a variation within the same catchment is expected under the given conditions of global and local temperature rises or it could merely be because of spatial variation. Therefore, this could be the reason for decline in rainfall over station Mukandi and an upward trend over Nyanga. However, a further study is necessary to establish the main causes of these two contrasting outcomes. The Sub Catchment has an estimated population of 33409. It was calculated that 24206 persons of an estimated total population of 33409 could be sustained with life line water in the sub catchment. Therefore, these results show that the water situation in the sub- catchment is stressed. About 9000 out of about 34000 persons cannot be sustained (life line) by the available surface water. Further on, with the increase in population and the factoring in of water requirements by food grown, this figure could be seen going up.