The Nexus of Changing Climate and Impacts on Rainfed Water Supply and Fresh Water Availability for the Inhabitants of Densu Basin and Parts of Accra - Ghana, West Africa

Abstract

Hydrological modelling with downscaled climate data from a Regional Climate Model (RCM) was undertaken to determine the impact of climate change on the surface water resources of the Densu River Basin. This basin is largely a rural one that is the source of potable water supply to many parts of Accra and also provides life support for the communities living in and close to it. The aim of the study was to assess the resilience of the city of Accra to impacts of climate change on its water supplies. The adequacy of streamflows in the Lower Volta Basin as a source of water supply to Accra in the future under climate change was also ascertained. This river currently supplies about half of the water requirements of the Greater Accra Metropolitan Area (GAMA).Results of the study show that the Densu Basin streamflow is currently under stress conditions due to high water abstraction from the river for municipal and industrial water supplies. The climate change impact analysis indicates a reduction in streamflows in 2050 from the 1961-1990 baseline period as a result of general drying conditions projected for the basin. This future drying condition could result in rural agriculture in the basin shifting from largely rainfed at present to more irrigation. The result would be a substantially more upstream water abstraction from the Densu river system with dire consequences for downstream water supply to the city of Accra. However, the assessment of the streamflows of the Lower Volta River showed that these were adequate to meet the water supply requirements of GAMA even under climate change.It is recommended that an Integrated Water Resources Management (IWRM) plan be fully developed and implemented in the basin for the proper management of the water resources. In addition, the Lower Volta River, which has substantial flows, could be considered as a more reliable source of water supply to Accra.

Keywords: Densu Basin, Lower Volta, Streamflows, Rainfall and Climate Change