DAMS AND RESERVOIRS
Although the North of Ghana is well endowed with water resources, the first step in planning the building of a dam and reservoir for flood mitigation and irrigation purpose is to identify the best location. Because many factors in the Sisili-Kulpawn basin affect the location choice, a hydrologic assessment was carried out (HKV consultants 2013) to analyse the effects related to hydrological and hydraulic processes, based on which reservoir locations were weighted for both the Sisili and Kulpawn sub – basins.
Taking into account the assessment above it was concluded that the Kulpawn river is more favourable compared to the Sisili River for the construction of a reservoir. The defined capacity of 500 Mm3 is available from reservoir locations North of the Mole reserve border and upward. More downstream locations are not efficient and require large impoundment constructions. On the other hand more upstream locations lead to longer water transport lines to the potential irrigation areas.
A cascade construction seems to be a promising solution as its combined capacity can be used, flood mitigation can be optimised and the transport length is limited because the reservoir surface is stretched along the river. To transport the water to the irrigation areas a transport canal can be constructed directly from the reservoir, or the water can be transported through the river to a distribution weir downstream of the cascade.
Mini hydropower potential ranging between 50 – 700 kW is present in both rivers, but higher in the Kulpawn because of a higher average discharge. The more upstream a reservoir is located, the higher the head difference and the higher the hydropower potential.
In the end, the judgment of various stakeholders from Government to grass root level need to balance the trade offs of such a major intervention in terms of the social, economical, environmental and agricultural impacts. These issues will still need to be analysed in the near future in more detail, partially based on the outcomes of this dam – reservoir assessment.