SPOTLIGHT | Sponge cities
Soaking up the water in Kenya
Recently, experts in different fields relevant to establish Sponge Cities gathered for a two-day ‘write shop’ to write chapters for the Guidelines on 'How to create a sponge city?'.
A sponge city is a town that absorbs the water when it rains: either by capturing and storing it, or by giving the water more time to sink into the ground, thereby recharging the groundwater reserves. In Kenya, the rain can fall heavily once the dry season ends. Because of the dry earth and heavy rain, the water normally flows away; creating floods, gullies and landslides. In a sponge city the water is captured to be used later on in the dry season.
In water sector terms, this means a sponge city works on 3R: recharge, retention and re-use of rain water. There are several (combinations of) methods that can be used, such as diversifying the water supply through water harvesting from roofs, roads or runoff. The water can also be safely redirected to recharge, through tree planting and ponds. And it can be re-used, for instance in kitchen gardens or domestic use.
VIA Water happens to have two sponge cities in its portfolio: Kajiado Sponge City and Sponge Towns Kitui. The two projects initially started as separate innovations that came up with similar plans simultaneously, but with different approaches due to different circumstances. They agreed on working together from the start. One of the results of this cooperation is the writing workshop in which the two projects combine their respective learnings on working on sponge cities. This will lead to the development of Guidelines for Sponge Cities, which will give readers a quick overview and stepwise approach on how ‘you can Sponge yourself’. In spring 2019, the two projects are planning an event in which the guidelines will be presented.
Practical activities the projects are employing to ‘sponge’ are for instance a workshop on ‘kitchen gardening’. That means the residents of KwaVonza (Kitui) work towards a garden that can provide them with fruits and vegetables. To grow them, they use recycled materials such as old tires. These make sure the water used does not flow away into the ground but instead just keeps the plant moist.
The project in Kitui is focusing on diversifying the water supply for KwaVonza residents through a combination of retention, recharge and re-use techniques. These combined techniques allow for a diversified water uptake and release, giving residents multiple options and sustaining the water resource over a longer time. The citizen platform is playing a key role in all activities: the citizens themselves highlight the problems and the desired solutions, and ensure implementation of those solutions within their own community groups and households.
In Kajiado the project is focusing on enhancing the availability of ground water supply and on improving water quality. To achieve this, they also use 3R techniques. The project is for instance working together with the local mosque, which has a large roof surface from which the rain water previously flowed away towards latrine pits, ultimately polluting the groundwater supply. This practice has been stopped and the water is being used for storage.
In another activity, trees have been planted to ensure water is retained better and also to prevent dust from blowing around town in the dry months. This also helps in beautifying the urban environment. The project also constructed weirs across a gully with high infiltration rate to slow down surface runoff and enhance infiltration. A monitoring borehole is being constructed to monitor ground water flows as part of the monitoring tools.