Why rainwater harvesting should be stepped up in urban areas

In many neighbourhoods in Nairobi, you will hardly fail to come across the ubiquitous yellow 20-litre jerricans stacked high on a pushcart operated by water vendors. Water vendors have become a vital part of life in such neighbourhoods where taps run dry more often than not.

As Nairobi continues to experience rapid population growth, it is struggling to keep up with the increasing water demand. Water rationing has become the norm in many parts of the city. In some estates, residents go for days without running water. Yet every rainy season, millions of litres of clean rainwater go to waste. Isn’t it time we started harvesting rainwater in a more strategic manner to alleviate water shortage in the country in general and in our urban centres in particular?

According to the Kenya Demographic and Health Survey 2022, about 91 per cent of urban households use improved water sources. However, this figure hides important inequalities. Piped water access is limited – only 33 per cent of households have access to piped connections – and informal settlements remain chronically underserved.

Urban areas like Nairobi already face a daily water shortfall. With a population of around five million and a daily water demand of 120 litres per person, Nairobi needs roughly 219 billion litres annually. Studies show that if rooftop rainwater harvesting was implemented across formal and informal settlements, the city could collect up to 44 billion litres of water yearly. This is 20 per cent of the total annual demand, which is one in every five litres of water we need.

While the government has implemented frameworks and policy measures such as the Water Act of 2016, Sessional Paper No. 1 of 2021 on National Water Policy, and the National Water Master Plan 2030, progress has been slow. Growing urban populations, failing infrastructure, and climate change continue to strain Kenya’s water supply.

The Constitution and Sustainable Development Goal 6 both enshrine the right to water, but translating policy into reality remains a challenge. The government has done well in developing large-scale water supply systems like dams and boreholes. But they are stretched thin, expensive to expand, and vulnerable to climate shocks. We need rainwater harvesting to complement them.

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Untreated rainwater may not be ideal for consumption but can serve uses like cleaning, irrigation, and flushing toilets. By handling these day-to-day demands, it frees up piped water for drinking and cooking. And because the water falls directly where it’s needed, there are no distribution costs.

So, what’s holding us back? The gap lies in policy and political will. Kenya’s legal framework contains strong water policies, but these do not adequately prioritise or enforce rainwater harvesting. While the National Water Master Plan 2030 mentions water-saving technologies, rainwater harvesting is not treated as a central pillar.

The government can initiate reforms by ordering rainwater harvesting for new constructions, especially multi-storey apartment blocks and commercial buildings. Counties can also invest in shared tanks for informal settlements.

Let us learn from countries like Singapore, where rainwater collection is built into urban planning. The entire city is treated as a catchment area, with rooftops, drains, and canals channelling rain into reservoirs that supplement the national supply.

Mr Ochieng is the CEO of The Kenya Alliance of Resident Associations