Abstract:
Small reservoirs provide vital ecosystem services in the semi-arid part of Ghana. Their main
role is the provisioning of water for irrigation in this water-scare part of the country. They
also serve as source of water for fishing, recreation, drinking, and other domestic uses and
play crucial roles in evaporation, water productivity, water scarcity mitigation and climate
modulation in this area. As such, their accessibility by the populace is vital to their wellbeing. Also, their locations, surface area and capacity (volume) are required for water
resources assessments and hydrological modelling. This work was done to map the
distribution of the small reservoirs in the White Volta sub-basin in Ghana. The work assessed
the accessibility of artificially built small reservoirs in the relevant communities using
satellite images and ground information. The study used six Landsat 8 Operational Land
Imager images covering the study area. Histogram thresholding technique was used to
delineate the waterbodies from their adjacent uplands. Accuracy assessments were done
through field observed data and Google Earth images. The method used produced a positional
accuracy of 94%. The study estimated that there are approximately 254 small reservoirs of surface areas between 1 and 53 hectares in the sub-basin. The combined surface area and
volume of the small reservoirs were estimated to be 1585.265 hectares and 21.154x106 cubic
meters respectively. The study estimated only 35% of communities within the sub-basin have
access to small reservoirs. The study concluded that cluster of communities and population
density are the general determinants of the distribution of small reservoirs in the sub-basin.
However, rainfall distribution and suitability of soil for large-scale crop production may also
be some important factors dictating the distribution of small reservoirs in the White Volta
sub-basin in Ghana.
