Determination of electrical energy loss from reservoirs through evaporation case study of Nyumba ya Mungu reservoir.

This study was conducted at Nyumba Ya Mungu (NYM) hydropower plant reservoir in order to determine the amount of electrical energy loss as a result of water loss through evaporation. The study started by measuring the evaporation parameters using weather station WXT520 instrument and fabricating a Class A evaporation pan, for direct evaporation measurements. Indirect evaporation estimation was done by using model equations utilizing evaporation parameter values. The study indicated the average air temperature of 26.910C, wind speed of 4.54m/s, relative humidity of 62.389 % with air pressure of 929.72 Hpa and solar radiation of 230.467W/m2 for five (5) months on water surface at NYM hydropower reservoir. Also the correlation linear model equation was developed between evaporation values collected on water surface with evaporation values collected off shore surrounding the reservoir as a dependant variable. It was indicated a coefficient of correlation (r) of 0.79. The values of evaporation rate estimated was ranged from 170.8 mm/month being the lowest to 255.6mm/month as the highest, with the average of 218.6 mm/month. The results indicated the electrical energy loss from NYM hydropower plant reservoir to be11,551.4 MWh with an average monthly water loss of 46,555,850.3mm/month. Therefore, the researcher recommends regular measurement of evaporation parameters, calibration and validation of the correlation model developed at NYM hydropower plant.