By Duncan Mboyah

Kenya’s Tana River Basin is expected to receive over 40 percent increase in rainfall due to climate change, a report recently released in Nairobi by International Water Management Institute (IWMI) says. The basin is home to 18 percent of Kenya’s population, and provides food and jobs for close to seven million people.

 The report notes that the basin that has been facing perennial declining rainfall and periods of droughts is set to benefit from changing weather patterns. “The large increase in the amount of water available in the basin will translate into more hydropower, water supplies and irrigation,” Matthew McCartney, leader of IWMI’s Water Futures Research Group says.

“The rainfall in the basin will likely increase over the rest of the 21st century with a change of up to 43 percent in mean annual rainfall,” the report says

The report observes that though this will serve as a boost to the basin and all who depend on it, there are new challenges that include destructive floods outweighing benefits without proper planning.

He notes that, the report confirms, the findings of previous studies and are consistent with reports from the Intergovernmental Panel on Climate Change (IPCC).

In the upper Tana River Basin, ecosystem services influence the delivery of water to dams and hence the provision of water for hydropower and irrigation as well as domestic and industrial use.

In the lower basin, water-dependent ecosystem services, including fisheries, cultivation and cattle grazing on the river’s floodplains, support the livelihoods of many hundreds of thousands of people.

The impact of climate change on these ecosystem services depends greatly on how natural and built infrastructures interact and are managed under future climate conditions.

“Climate change is acknowledged to be a significant threat to the future development of Kenya,” Prof Eric Odada with the African Collaboration Centre for Earth System Science (ACCESS) at the University of Nairobi says.

He notes that how Kenya responds to both the opportunities and the challenge will make an enormous difference to people and the environment.

The don says that new infrastructure can provide some solutions but will not by itself be sufficient.

“Kenya’s specialists in water policy and practice must gain a better understanding of the role that natural infrastructure plays, and how natural and built infrastructure can work in tandem to ensure resilient and sustainable development in an era of climate change,” he observes.

Odada says that the basin provides 80 percent of population Nairobi with water and delivers 70 percent of the country’s hydroelectric power and 35 percent of its total electricity supply.

James Dalton, coordinator of global water initiatives with the Global Water Program of the International Union for Conservation of Nature (IUCN) notes that more frequent floods resulting from increased rainfall variability could undermine new development opportunities.

He says that working in both the basin and West Africa’s Volta River Basin, project researchers aim to demonstrate how “nature-based” solutions can contribute to climate change adaptation and sustainable development.

The study results provide a helpful reminder that water is the primary medium by which economies, societies and landscapes will experience the impacts of climate change,

Researchers used a hydrological model, called the Soil and Water Assessment Tool (SWAT), to simulate processes affecting river flows in the future.

Climate change input came from an ensemble of six models, simulating different greenhouse gas emission scenarios.

The researchers then evaluated climate change impacts by comparing these scenarios with the basin’s current situation.

The study was conducted by researchers under a project called WISE-UP to Climate (Water Infrastructure Solutions from Ecosystem Services Underpinning Climate Resilient Policies and Programs led by IUCN.

It focused specifically on ecosystem services that shape the ability of built infrastructure to deliver its intended benefits. These services typically correspond to key hydrological features of a river basin.

WISE-UP to Climate has been working closely with decision makers, water managers and other stakeholders in the basin over the past 4 years. Approaches and results have been discussed with local experts, including from the Kenyan Meteorological Department.

The project will present a wealth of practical findings and insights when it officially closes in early 2018.