Hydrological analysis for ungauged potential hydropower river: the case of Dodwe River in Muheza Tanga, Tanzania

Hydrological analysis deals with the measurement or estimation of stream flow. It is difficult to estimate the stream flow when the river is ungauged. It needs more than five years to gauge it or otherwise one has to use other stream flow estimation methods. Three methods have been used in the estimation of stream flow which include ratio of area, regression analysis and run off methods. The estimated mean flows of Dodwe River using these methods are 0.327 m³/sec, 1.32 m³/sec and 0.245 m³/sec, respectively. The hydrograph and the flow duration curve of the Dodwe River have been drawn in this project. From the flow duration curve, the power of 109.2kW, 61.6kW, 39.2kW and 22kW at 20%, 40%, 60%, and 80% respectively were obtained. And from the design flow, the power of 91.56kW was obtained, but this amount of power can only be generated at 28% of the time. The uncertainty of using the above methods were calculated and they were reported as follows, maximum error for the ratio of area, regression analysis and run off method are ±1.4 m³/sec, ±1.8 m³/sec and ±0.45 m³/sec, standard deviation for these methods are 0.5, 0.7, 0.2, Standard error are ±0.04 m³/sec, ±0.06 m³/sec and ±0.02 m³/sec and average deviation are 0.1 m³/sec, 0.6 m³/sec and 0.02 m³/sec respectively.