How to secure the future of Nairobi’s water

Sustained investment and collaboration to restore and protect the Upper Tana watershed, where 95 percent of Nairobi’s water begins its journey, have made a measurable difference. Today, 42 million more litres of water flow to Nairobi every day 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 translated into higher water treatment costs and growing uncertainty about the future. It required a shift in mindset.

Instead of focusing only on downstream infrastructure, partners chose to invest upstream—where nature provides some of the most cost effective water infrastructure. Analysis showed that investing $10 million in watershed restoration could generate more than double the value in avoided costs and wider economic and community benefits.

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, 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 had already proven 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 during droughts.

More than 260,000 farmers have been reached through the programme and 470,000 hectares of farmland are now under improved management practices. More than 5.9 million trees have been planted to stabilise soil and restore degraded land, while 980 kilometres of riparian areas have been protected to safeguard waterways.

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 its core, the Water Fund model is about shared responsibility. Government provided policy leadership and early financing. Private sector partners invested to protect the water systems their businesses depend on. Farmers co-invested labour and resources for on-farm improvements, ensuring that conservation also improved household incomes and food security.

The economic impact has been substantial. Investments linked to improved farming systems and agricultural value chains have generated significant income across the watershed.

Fruit production has generated more than $117 million over the past decade. In addition, more than 22,000 green jobs have been created. These outcomes demonstrate that environmental conservation and economic opportunity can advance together.

At the same time, sediment risks to rivers and reservoirs serving Nairobi have declined by 41 percent. This has helped to protect the performance and lifespan of dams, pipelines and treatment plants that form the backbone of the city’s water system.

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 groundwater.

To secure these gains for the long term, the Upper Tana Nairobi Water Fund Trust has been established as an independent institution dedicated to safeguarding the watershed for generations to come. The trust provides a long-term platform for partnerships, financing, and coordinated action.

Watershed restoration is not a “nice to have,” but a critical infrastructure. 

Forests, soils and rivers store and filter water, regulate river flows and reduce risks from droughts and floods - functions no amount of concrete alone can replace. 

Protecting these natural systems also protects the billions invested in dams, pipelines and treatment plants, while supporting rural livelihoods and climate adaptation.

As we mark 10 years of the Upper Tana Nairobi Water Fund, the lesson is clear—not just for Nairobi, but for cities across Africa: Water security cannot be engineered alone. It must be stewarded—upstream, together, and over the long term. The future of Nairobi’s water supply begins far upstream and protecting it must remain a national priority.

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