Ecosystem under pressure as River Tana basin water level drops

Wednesday January 18 2017

Workers at the Northern Collector Tunnel water project in Murang’a, central Kenya. PHOTO | FILE

Kenya is struggling to ensure the sustainability of the Tana River Basin, with dependence on the water source for food production and energy generation and other needs on the rise.

The Tana River Basin is used for drinking water, hydroelectric power, fisheries, agriculture and biodiversity.

The basin ecosystem includes forests, arid and semi-arid lands, mountain vegetation, freshwater and wetlands, marine and coastal areas and agrosystems.

According to a report by Wetlands International, in addition to the government planning massive infrastructure projects and irrigation schemes along the basin to drive economic growth, poor land use practices, pollution, soil erosion, overgrazing and deforestation are now taking a toll of the basin’s ability to provide essential services.

There are fears of conflict as communities living downstream on River Tana complain of falling water levels that drop further during the dry season.

Already communities that depend on the mangrove ecosystem, which provides fish, firewood and flood protection, are feeling the impact as 38 per cent of the mangroves in the delta have been lost.


“The Tana river basin is facing a number of challenges, potentially undermining the continuous provision of ecosystem services,” states the report, titled The Economics of Ecosystem Services of the Tana River Basin.

The report assesses the impact of large infrastructural interventions along the Tana River Basin.

River Tana is a socio-economic lifeline for Kenya. Originating from two of Kenya’s major water towers — Mt Kenya and the Aberdares — it is Kenya’s longest river, traversing seven counties.

The river supplies 80 per cent of Nairobi’s water needs, and accounts for 70 per cent of Kenya’s hydroelectric power generation and 38 per cent of the country’s power supply.

The basin has fertile highlands for food production and cash crop farming in the upper region, while the downstream region along the Tana Delta offers vast opportunities for irrigation.

According to the Wetlands International report, although development plans along the Tana River Basin have positive socio-economic impacts, they also pose serious negative risks.

“Several planned developments projects fall short in terms of economic efficiency,” the report notes.

In efforts to drive the attainment of Vision 2030, the government has unveiled various projects along the basin that are exerting further pressure on the basin’s ecosystem.

Apart from the Northern Collector Water Tunnel project, which is being implemented at a cost of $64.8 million and is designed to boost the Nairobi water supply to 700,000 cubic metres a day, the government is implementing the High Grand Falls (HGF) hydropower dam, which will be Kenya’s biggest dam, with a capacity to generate between 500 MW and 700 MW of electricity.

While the government says that the $1.4 billion project will help in flood management, power generation, and supply of irrigation, drinking and industrial water, there are fears its reservoir, which has a capacity of 5.6 billion cubic metres of water, will adversely affect downstream areas.

“The negative downstream effects of the HGF dam often outweigh the positive effects of the dam upstream,” states the report, adding that while the outcome does not imply that the dam should not be developed, there is a need for proper dam management regimes to mitigate the negative effects downstream.

“Contrary to the popular notion that the flooding havoc in the delta is caused by excess rainfall upstream, local communities believe that before the dams on the Tana River were constructed, they used to cope well with natural flood events,” the report states.

The government also intends to start an irrigation scheme in the Tana Delta. The project involves development of one million acres of irrigated land to boost food security.

“Overall water resources at Garissa are greatly reduced, almost to a constant level of natural minimum flow with hardly a flood peak left,” states the report.

The greatest pressure on the basin will be from supplying water to the Lamu Port and Lamu Southern Sudan-Ethiopia Transport Corridor project.

As the single largest infrastructure investment in Kenya, there are concerns that the massive water supply needs of the Lamu port/city will lead to an over-abstraction of water in the basin.