Rainwater Catchment Effectiveness in Kuria, Kenya
Over a year ago, we launched our Rainwater Catchment Pilot Project to help us answer the question – Is household rainwater catchment a sustainable water supply solution for Kuria? Our Water and Sanitation Field Officers have done a great job of diligently maintaining the units and monitoring the water storage volume, water demand, and the condition of the units. But unexpectedly another project, our Well Buy-In Pilot Project, nudged us closer to the answer to our question.
A very brief summary of the major results of our Rainwater Catchment Pilot Project:
• Here in Kuria it rains a lot of rain most months of the year (40-70 inches per year), but sees little to no rain during 3-4 months.
• A few days of storage during the dry season was about all we could get out of the units. Of course restricted use could change that, but that doesn’t seem to be sustainable according to the community.
• Our rainwater catchment units aren’t able to solve the water problem during the dry months.
• The units are expensive (over $150) and not affordable for a family in this community.
What do wells have to do with this?
If you haven’t been following this blog, we implemented a well buy-in program at the four deep wells we built in August where a small fee is charged per bucket of clean water (2 Kenyan Shillings per 20 Liters) to pay for future maintenance on the pump. The fee is cheaper than any available water treatment method and less than the cost of getting sick from drinking water contaminated with feces. We’ve watched as well revenues have fluctuated during the past 9 months. They were high during the first harvest at the well located in a village near the Kenyan/Tanzania border. But, then when the maize market switched to Kenya customers decreased (no more thirsty loader crews and restaurants in need of water). We also noticed another very interesting pattern that perked our ears – on a plot of rainfall and well revenues, the trend is clear – well revenues drop during high rainfall.
Where were people getting water during the rainy season? The local springs and rivers are very contaminated, which people are aware of after our trainings.
We asked around and found out that most people are able to get all their water needs met by capturing rainfall from their roofs using what they call “traditional rainwater catchments”, essentially a few foot strip of corrugated metal wired to their roof of the same material. During the rains, someone runs out to switch out 100-Liter plastic storage containers or old oil barrels until all the containers in the house have been filled up. We weren’t surprised that people were using these traditional rainwater catchments – that’s where we got the idea in the first place. We were surprised to learn that they were able to meet their water needs using this system. And, it’s not really fair to say that they fully are. More or bigger storage containers would certainly make their lives easier by eliminating the need to switch out barrels in the pouring rain.
But, we learned an important lesson- the simple traditional units are working pretty well for people and our nice improved versions are expensive and potentially not a ton more effective. Our pilot rainwater catchment units have great benefits – 1,000 Liters of storage provides a few days of water during the drought, gutters stretching the length of a the roof quickly transport a lot of water to the tank, and the PVC pipe with cap first flush system effectively keeps the dustier water from entering the tank. But, even the nicer taps made in England (we tried taps made in China first that quickly failed) are showing signs of needing a good amount of ongoing maintenance. And the few days worth of water the large tank gets us doesn’t justify the cost (1,000 tanks cost about $100).
Of course there are numerous potential cost-cutting alternatives that we’ve considered – building concrete tanks, using smaller tanks, using more bricks and mud and less cement in the foundation, and eliminating the first flush system, just to name a few. The concrete tank idea has been tried a lot locally and we often see very large abandoned, cracked concrete tanks. We’re still exploring the cost/benefit of the smaller tank option. We implemented the cement reduction idea and it saved a decent amount. Eliminating the first flush could work since there is very little to no fecal matter on the roofs, the wire mesh in the drain box catches the big stuff and any dirt that gets in end up on the bottom of the tank since the tap is elevated a few inches. However, this would save us just a few bucks, or shillings. After a good amount of analysis by us and our friends at Engineers Without Borders, we have accepted the unfortunate reality that there are few ways to cut costs that don’t seriously compromise the long-term sustainability of the rainwater catchment unit.
And after the realization about the traditional rainwater catchments meeting people’s needs, we found that the traditional style is tough to beat in terms of cost/benefit. And, maybe we don’t need to try to win… Maybe a better solution is to train the community members who aren’t using traditional rainwater catchments how to build them. And/or if storage is the limited factor (since even a tiny strip of bent metal can collect a whole lot of water during the serious rain storms here in Kurialand), maybe selling or loaning out larger tanks would help people most.
Our household rainwater catchment pilot project has done its job well – it produced data that allowed us to make a wise choice about how to move forward. And from here it looks like we won’t be building loads of household rainwater catchment units any time soon. Instead, a better move might be to focus on increasing the impact of the traditional systems that already exist in the community.