Assessing the impacts of rainfall variability on hydropower sector in Tanzania

Abstract

Industrial production is gradually playing a strategic role in the socio-economic development of the country. This sector is heavily dependent on electrical power generated to a large extent from hydro-electric-power it has been observed that the amount of water in the storage reservoirs fluctuates considerably between different years. There have been drought situations as well as flood in some part of Tanzania which had a negative impact on the electricity generation to operate efficiently. Load shedding might continue to be a problem in the future due to the climatic change, not only due to drought, but also flood that might increase demands for hydropower plants. This research therefore tries to identify the possibility of capturing or exploiting seasonal rainfall as predicted and put into use onto a decision making process for hydropower production based on the interpretation of such available forecasts. While floods or droughts cannot be prevented, but timely availability of scientifically early indication of the most probable rainfall may contribute a lot toward forecasting dam levels well in advance and thus planning to address shortfalls that may be anticipated due to predicted rainfall. The United Republic of Tanzania is located on the East coast of Africa between parallels loS and l20S and meridians 300E and 40uE.electricity supply is primarily from hydroelectric power (60%), with thermal (gas and diesel) and imports from neighboring countries (Uganda and Zambia) making up the remaining supply (40%). Mtera reservoir is the biggest in Tanzania, with 660 km2 at full capacity. Depending on rainfall and the amount of water fed to the power plants the level of Nyurnba ya Mungu Dam vary with /more than 10m and as a result of this the s~ace area is between 50km2 and 160km 2. The overall objective of this study is to assess the impacts of rainfall variability on hydropower generation in Tanzania. Examine, the years of rainfall variability in Tanzania as well as Impact of rainfall variability on discharge and dam levels. Data was collected from rain gauge station within the catchments area of the rivers that flow to generate the hydropower stations in Tanzania .. The data used consist of more than 30 years of monthly rainfall from TMA and 25 years of dam level and Discharge from TANESCO. Rainfall data used in this study derived from 10 rain gauges with the best series for at least 30 years in the period 1978 to 2008. Mass curve was used to check the quality of the data of the area which shows positively and the annual circles was employed to check the homogeneity of the area which also shows positively, Results from correlation analysis between two rain season that is MAM and OND with dam levels and discharge shows some significance correlation where by this help to formulate the relationship with those month of high significance to forecasting the dam level as well as discharge.