By Stephen Asante
Accra, Oct. 23, GNA – Water research scientists say a study of the Pra River Basin has shown marked increases in extreme rainfall indices in recent decades, particularly between 2011 and 2020.
The Basin was also experiencing temperature extremes, revealing consistent warming, with more frequent warm days and nights and fewer cold events, Dr Emmanuel Obuobie, Principal Investigator of the Building Climate-Resilience into Basin Water Management (CREAM) Project, noted.
That development, he said, had heightened risks to water security, agriculture, health, and ecosystems.
“The study highlights the urgent need to revise and implement Integrated Water Resources Management (IWRM) strategies in the Pra Basin to adapt to increasing climate extremes and enhance resilience across sectors,” he told the Ghana News Agency (GNA) in an interview, in Accra.
Dr Obuobie was giving a spatiotemporal analysis of past and future precipitation and temperature extremes in respect of the Basin.
Research scientists from the Water Research Institute of the Council for Scientific and Industrial Research (CSIR-WRI) have been engaging stakeholders in recent times under the Danish-funded CREAM Project, aimed at building climate resilience into basin water management in Ghana.
The Project, being implemented in the Pra and Densu River Basins by a consortium of nine partners led by the CSIR-WRI, have seen water research scientists assessesing the historical and projected changes in climate extremes using thirteen WMO-recommended rainfall and temperature extreme indices.
A concept note copied to the GNA states that: “Simulations from four CORDEX-Africa regional climate models under RCP4.5 and RCP8.5 scenarios were analysed for three future periods: near-term (2026–2045), mid-century (2046–2065), and late-century (2066–2100), relative to a 1991–2020 baseline.”
Historical trends were derived from high-resolution historical data developed under the project.
Over the period of implementation (2019-2025), the project has worked closely with key stakeholders in the water, environment and agriculture sectors at the National and Basin levels, and co-developed significant outputs (results, data and tools).
The expectation is that the outcome could guide government ministries and agencies, Non-Governmental Organisations, civil society organisations, research organisations and academia, to inform and improve current basin water decisions, management and research.
Dr Obuobie said findings from their study showed very intense rainfall events had doubled over the last decade.
“Projections indicate these trends will persist,” he noted.
He said the CSIR-WRI’s science engagements highlighted tools and data developed by the CREAM Project, shared in brief key results, and fostered dialogue among stakeholders for inclusive and data-informed water governance.
The concept is to integrate climate change scenarios, land use and land cover changes, and shared socio-economic pathways into water management decisions and practices.
Dr Obuobie explained that understanding the spatiotemporal distribution of climate extremes at the river basin scale was crucial for sustainable water resource management, especially under changing climate conditions.
“In Ghana’s Pra River Basin, where livelihoods are tightly linked to climate variability, shifts in extreme rainfall and temperature events can have significant socioeconomic impacts,” he said.
In a related development, Mr Mark Osei-Owusu, a Principal Technologist at the Surface Water Division of the CSIR-WRI, has cautioned that, if the land use and land cover degradation continued, the future would likely see increased runoff and sediments entering the Pra River channels.
“This has the propensity for higher flood risks.
“We have seen an astronomical increase in terms of sediments due to human activities,” he told the GNA.
Mr Osei-Owusu’s work on the CREAM Project focuses on ‘Modelling the Influence of Climate and Land Use/ Land Cover Changes on the Hydrology of the Pra River Basin Using the SWAT Model’.
That encompasses the integrated effect of climate and land use changes on the streamflow in the Pra River Basin, which were key indicators in determining how the future rainfall and streamflow look like.
He said there was the need for an integrated study of both climate and the land use and cover changes for effective water resources management since their separate study provided a partial picture of their impact on streamflow.
“Climate and land use changes go hand in hand.
“In the era of present climate change and variability, understanding land use and cover, and the dynamics of water basins, is crucial for achieving the goal of successful sustainable ecosystem development,” he emphasised.
The Water Resources Commission says the unfavourable effect of human disturbances in the Pra River Basin has resulted in extensive variations in the ecosystem, necessitating varied research activities and studies to address the situation.
A Soil and Water Assessment Tool (SWAT) deployed for hydrological simulation, for instance, revealed that there was a continuous increase in cropland, settlement and mining at the detriment of forest areas.
The Pra River Basin is located in southwestern Ghana with a drainage area covering some 23,200 km2. It has thirteen (13) rainfall stations, three sub-basins (Offin, Birim, and Main Pra), a natural lake (Bosomtwe), and one drainage station (Shama).
The River originates from the Kwahu Plateau in the east and flows into the Gulf of Guinea at Shama in the west, encompassing a catchment renowned for mining activities in the Western, Ashanti, and Eastern regions.
It has a bimodal rainfall pattern with its main season in March and July and September to the first dekad of November for its minor.
It has a mean annual rainfall range between 1200 and 1700 millimeters, and an estimated mean annual discharge of 214 cubic meters per second, and a mean temperature between 25° and 27 °C.
GNA
Edited by Samuel Osei-Frempong