Ghana: Water Resources Assessment
The global objective of the “Productive Investments” programme to which this specific contract was contributing was to enable access to productive environment-friendly infrastructure to contribute to enhanced household incomes and increased trade of commodities (in a sustainable environment). This Programme provided a better access to market, eased the use of water for agricultural production and allowed for the generation of energy for different productive uses in the supported value chains (rice, sorghum, groundnut, soya, vegetables, mango and cashew).
Within this Programme, the Ministry of Food & Agriculture (MoFA) and AFD were preparing a new project called “Agricultural Water Management in Upper West” (AWaMUW) to implement the water management component. The intervention area covered the eleven districts of Upper West Region (UWR) and three districts (bordering UWR) from the Northern Region. The AWaMUW project aimed at improving agriculture water management and providing the zone with irrigation facilities in order to create employment opportunities in agriculture and reduce seasonal migrations. This project thus increased the mobilisation and use of water resources (WR) within, and beyond, the Black Volta river basin. The infrastructure it built relied on the surface and groundwater water resources availability on the long term, taking into account the effect of the climate change. For the preparation and design of the project, accurate information on the condition and trend of the water resources – surface water and groundwater, quantity and quality – within the Black Volta river basin and the project’s area of influence was required, particularly to:
- Ensure that the long term WR availability will enable a proper operation of the infrastructure and water dependent activities, particularly irrigation;
- Assess the potential cumulative impact of the project on the long term WR status, to ensure that the other needs can still be met.
Therefore, the specific objectives of this assignment were to:
- Assess the availability of water resources in the AWaMUW project’s intervention area;
- Provide a full understanding of all the water flows and storages in the Ghanaian part of the Black Volta river basin
- Estimate the sustainable flows available for the project and draw recommendations on the sustainability of the proposed investments
The main results of this assignment were:
- R1: The necessary data was collected and a model developed
- R2: Based on the model developed, the impact of the project’s intervention (AWaMUW) was assessed and recommendations were made
- Assessed the contribution of regional and local climate events to the precipitation, evapotranspiration, streamflow and groundwater recharge in the BVRB
- Digital Elevation Model (DEM) was used to delineate the boundaries of the watersheds from which water flows to reservoirs, and all the sub-watersheds within them
- Prepared two sets of land use maps for the watersheds
- Selected a model to predict seasonal and annual surface water and groundwater recharge in watersheds
- Quantified the recharge rate using climate data and geological spatial data
- Assessed temporal changes in groundwater and surface water level
- Studied the impact on surface water resources of the development of the newly proposed projects in the basin
- Estimated future trends of surface and groundwater regimes
- Recommended a combination of expanding dam-based irrigation schemes and developing groundwater irrigation schemes
- Identified requirements for additional measuring, sampling and monitoring installations and/or programs.