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World Waternet and NWB Fund support sustainability of drinking water supply in Tanzania

08 July 2024

Mindu Dam is the main source of drinking water for Morogoro, Tanzania. About 80% of the water supplied by MORUWASA, the local water company, comes from this dam.

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The water supply from Mindu Dam is increasingly threatened by the effects of climate change, population growth and intensive agriculture. These factors lead to heavy loading on the surrounding river banks, causing severe soil erosion. To combat this soil erosion, the NWB Fund has released €99,830 for this project by World Waternet in Tanzania. This amount will be used to introduce agroforestry in the Mindu Dam catchment area. This project is a follow-up to an earlier project in which a smart reforestation tool was developed. The project will run until April 2026.

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Regional manager Janette Worm - World Waternet, is very happy and proud with the news: "This development allows us to take new steps towards climate-resilient river basin management and sustainable water supply (IWRM4WASH) together with all stakeholders. Only in this way can our WaterWorX partner, the drinking water company MORUWASA, continue to guarantee a sufficient drinking water supply in the future."

FarmTree tool method

Agroforestry is a sustainable solution against erosion and sedimentation (downstream). Sedimentation occurs due to severe soil erosion where soil washes off and enters the dam as sediment. This process of sedimentation, where sand and gravel accumulate, significantly reduces the storage capacity of the dam as the silt limits the space for water intake. To deploy Agroforestry, World Waternet first uses the FarmTree tool method. This provides a simple interface for entering agronomic, financial and design details of an agroforestry system. Combining water management with agriculture, forestry and the local economy, allows you to retain water better and longer upstream. This is crucial with the climate extremes of recent years. Think here of drought or, on the contrary, extreme rainfall that can cause mudslides.

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Agroforestry as a solution

Combining trees, plants and different types of agriculture has a positive effect on erosion and sedimentation. Trees and vegetation provide stability to the soil through roots, which reduces erosion, slows water flow and filters sediments. These systems also maintain healthy soil structure, promote biodiversity and provide a valuable supplement to the income of local farmers who are much needed to work on successful and sustainable water systems. This results in a more pleasant living environment for the local population.

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Pre-project developments

In the past year, World Waternet, in collaboration with MORUWASA (the local drinking water company), the Wami-Ruvu Basin Water Board (the local water board) and the Dutch company FarmTree, conducted research on agroforestry interventions to reduce sedimentation in Mindu Dam. This project was also co-financed by the NWB Fund. Together with all stakeholders, an agroforestry tool was then developed. This helps to choose the right mix of trees and cashcrops (the so-called, NWB Fund watershed reforestation tool). The follow-up project focuses on the implementation of this tool.

In addition, a roadmap describing various interventions has been drawn up. One example is that local farmers could switch to beekeeping or aquaculture, which would mean less agricultural activity and alternative sources of income. Small sedimentation dams could also be built to capture sediment before it reaches Mindu Dam. In light of recent floods in East Africa, this innovative approach highlights the need for nature-based solutions for water management and conservation in collaboration with local communities.