Future of Nairobi's water depends on Upper Tana's health

A water reservoir at Hola irrigation and settlement scheme, Tana River County. Over 5,000 acres of land are under irrigation-agriculture in the area.[Nehemiah Okwembah, Standard]

Nairobi County is approaching the limits of its water supply. Demand is rising, rainfall is more unpredictable, and groundwater is not a long-term solution. To secure the city’s water future, the rivers that supply it must be protected at their source.

Over the past decade, despite mounting pressure on the water supply, Nairobi’s taps have not run dry. That resilience is not accidental. Sustained investment and collaboration to protect the Upper Tana watershed, where 95 percent of Nairobi’s water begins its journey, has made a difference. Today, 42 million more litres of water flow to Nairobi daily than 10 years ago.

This is what happens when we protect water at its source, using nature-based solutions. Stretching across Murang’a, Nyeri, Nyandarua, and Laikipia counties, the Upper Tana basin is a lifeline for Kenya. It quenches Nairobi while supporting rural households, agricultural production, and underpins about 65 percent of the country’s hydropower generation. What happens upstream, on farms, forests, and riverbanks, directly shapes the reliability, quality, and cost of water delivered downstream.

Ten years ago, the warning signs were clear. Soil erosion, degraded land, and climate variability were not only undermining farm productivity but also increasing sediment loads in rivers and reservoirs that supply Nairobi. This meant higher water treatment costs and growing uncertainty. It required a shift in mindset. Instead of focusing only on downstream infrastructure, partners chose to invest upstream, where nature provides cost-effective water infrastructure. In 2015, government agencies, water utilities, private sector partners, and community organisations came together to act at the source through the Upper Tana Nairobi Water Fund (UTNWF), Africa’s first water fund built on a public-private partnership model.

The idea was simple but powerful: fix problems at the source, rather than paying for the damage downstream. The model was successful in the city of Quito, Ecuador, in Latin America, where it was pioneered by The Nature Conservancy. Since then, the scale of impact has been remarkable. Farmers across the watershed have been supported to adopt practical land management measures that strengthen productivity and water security.

These include terracing, agroforestry, grass strips, and the protection of riparian zones along rivers and streams. Such practices hold soil in place, improve water infiltration, and reduce sediment flowing into rivers. Farmers have also been supported to construct thousands of water pans to capture rainwater and surface runoff for use during dry periods. This reduces pressure on rivers while strengthening resilience.

More than 260,000 farmers have been reached. Some 470,000 hectares of farmland are under improved management practices. More than 5.9 million trees have been planted to stabilise soil and restore degraded land, while 980km of riparian areas have been protected.

These landscape-scale improvements have delivered tangible benefits for both rural communities and urban water users. This is conservation that works for people, for nature, and for cities. At the same time, sediment risks to rivers and reservoirs serving Nairobi have declined by 41 percent. As Nairobi increasingly turns to groundwater, the importance of healthy landscapes is even clearer. Aquifers are replenished by rainfall infiltrating through soil and vegetation. When land is degraded, that recharge declines. Protecting the Upper Tana is therefore essential, not just for surface water, but also for groundwater.

Ajagbe is the Regional Managing Director of The Nature Conservancy’s Africa Programme, and Njoroge is a Trustee and President of the Upper Tana-Nairobi Water Fund Trust