The Value of Irrigation Water Reservoirs for Tomato Production in the Upper East Region of Ghana
Improving crop water productivity is one among the strategies for addressing water scarcity in Sub-Saharan African countries. However, existing studies on water productivity rarely consider other factors of production such a labour and non-water inputs resulting to over estimation of the productivity of water. This study was conducted to assess the value of irrigation water for tomato production at Tono and Dorongo schemes. A residual imputation method was used to determine the value of irrigation water for tomato production. Semi-structured questionnaire was administered to 60 irrigator’s households from each of the study sites to collect data on farm inputs (capital, labour and non-water inputs), crop yield and market price for dry season irrigated tomato. The agricultural asset price index (API) of five years (2000-2005) was constructed and used to estimate farmer’s capital using the 2000 as base year. Labour and cost of labour was estimated using reported work hours and hired labour charge in the study area. Quantities and unit cost of inputs reported by farmers were used to estimate costs of farming inputs. The total revenue was estimated using farm gate prices and the quantity of tomato harvested. The return to management was assumed 5% of the total revenue. The estimates of irrigation water use from previous studies in the two sites were adopted and used to determine the value of water. The economic return to water represented 58% and 64% of the total revenue for tomato production at Tono and Dorongo schemes respectively. The high economic return underscored the importance of water for dry season irrigation in the two study sites respectively. Considering the different water use components, the value of water ranged from 0.20US$/m3 to 0.38US$/m3 at Tono and 0.31US$/m3 to 0.48US$/m3at Dorongo respectively. The water use under the actual evapotranspiration represented good indicator of the value of water at Tono because of potential reuse of surface and groundwater losses downstream of the scheme while the irrigation water use was a good indicator of the value of water at Dorongo. The value of water for tomato production in this study was far higher than the values of high water consumptive crops such as rice in the region. There is a potential to improve the value of water especially at Tono scheme through reduction of surface and ground water losses.