Wanjiku Mwangi wakes before dawn each day in the red-dirt hills of Murang’a, where she bends over rows of young napier grass, her hands brushing dew-heavy blades that now grow lush where soil once washed away. Just five years ago, her family’s maize withered in cracked earth, and her children often went to bed hungry. Today, her small plot yields enough to feed her six children and sell surplus at market—all because of a simple change: she stopped tilling uphill and began planting along the contours of the land, a technique taught through the Tana-Nairobi Water Fund, Africa’s first water fund.
The Tana River, Kenya’s longest and most vital waterway, supplies 95% of Nairobi’s drinking water and sustains millions downstream. But decades of deforestation, unsustainable farming, and erosion threatened both the river’s health and the people who depend on it. In response, The Nature Conservancy, in partnership with local NGOs, utility companies, and the Kenyan government, launched the Tana-Nairobi Water Fund in 2015. Its mission: protect the river at its source by empowering upstream farmers to become stewards of the land.
Now, over 100,000 farming families across the Tana River Basin have adopted conservation practices like terracing, agroforestry, and riparian buffer zones. These methods reduce soil erosion by up to 60%, increase water infiltration, and boost crop yields. Farmers receive training, seedlings, and tools in exchange for committing to sustainable land use. The results ripple far beyond their fields: cleaner, more reliable water now flows to 9 million people in Nairobi and surrounding regions. In some areas, water treatment costs for the city have dropped by 30% because the river is cleaner at the intake points.
“It helped me feed my six children,” Wanjiku says, standing beside a terraced slope dotted with banana trees and nitrogen-fixing calliandra shrubs. “I used to lose soil every time it rained. Now the water stays, the crops grow, and I have hope.” Her story echoes across the basin, where women’s groups lead reforestation efforts and youth cooperatives monitor stream health. Over 10,000 hectares of degraded land have been restored, and more than 2 million trees—including native species like warburgia and croton—have been planted along riverbanks to stabilize soil and filter runoff.
The water fund model, once untested in Africa, has proven that investing in upstream ecosystems pays off downstream—literally. For every dollar invested, $3.50 in benefits are returned through reduced water treatment costs, increased agricultural yields, and improved public health. As climate change intensifies droughts and floods, the Tana-Nairobi Water Fund offers a blueprint for resilience. With plans to expand into other river basins, this Kenyan innovation shows that when farmers thrive, so do cities—and rivers can run clean once more.