Determination of Reservoir Capacity from Catchment Area of the Proposed Dam in the Federal University of Agriculture Makurdi, Nigeria

Abstract

A proposed dam is to be built at a North Core watershed of the Federal University of Agriculture Makurdi. Reservoir capacity based on the mean inflow from the catchment yield into the proposed dam was assessed. The hydrological soil group of the area was studied. Mean annual rainfall for a period of 31 years (1987 to2017) was used to determine the runoff from catchment areas. Reservoir capacity was estimated using an analytical, mass curve, and residual mass curve methods. The area of the catchment was 8.82km². The mean annual runoff from catchment areas was 1222.59mm. The mean annual catchment yield (inflow) was 10,783,243.8m³. Cumulative inflow was used to prepare mass curve inflow into the reservoir at drafts 60% and 80% on the cumulative draft line, superimposed on the cumulative mass curve. At draft 60%, reservoir capacity of 9,513,000m³ resulted; at draft 80%, 10,549,000m^{3. The residual} mass curve of the inflow from the catchment area at a draft of 60%, gave a reservoir capacity of 3,632,000m³, while 80%, gave 4,426,000m3. An annual sediment discharge of 1302.02 tons was expected. A reservoir capacity of 11,000,000m³ was recommended for the proposed dam. Installment of an upstream sedimentation basin, soil conservation systems, vegetative screenings are recommended to reduce sediment load into the reservoir.