Mellen Nyabuto
Underground Tanks are storage structures that are constructed below ground purposely for water storage. They can be designed to collect and store water from ground catchments such as open lands, pavements, and footpaths. Water from roof gutters can also be channeled into this tank. In most cases, the water collected is used mainly in agricultural practices such as irrigation of small land plots and watering animals. They can be constructed in different shapes and sizes at a good cost and offer large storage for small scale farming.
Testimonies from farmers
“It’s hard to tell when it’s going to rain, even if it does, we don’t know exactly when. Last year I experienced challenges, I couldn’t plant in time because the rains delayed and because of that I suffered some losses since we couldn’t be able to supply as much vegetables as we usually do to the market. I intend to look into building underground water tank surfaces that can harvest water from runoffs and gutters to use in the farm during the dry seasons,” says Peninah a vegetable farmer in Murang’a County.
“In this time of unexpected rainfall and season changes, this tank comes in handy as I am able to monitor and water my greenhouse plants during the dry periods using water collected in the tank during the rainy season,” says a seedling producer from Thika.
How to construct underground water tank
Below is a stepwise description of how an underground water tank can be constructed.
- Site Selection: Choose an appropriate location for the underground water tank. The location should be level, free from obstacles like rocks, trees, or underground utility lines, and should have good drainage to prevent waterlogging.
- Design: Determine the required capacity and dimensions of the water tank based on the water demand, the available space, and the budget. Engage a qualified engineer to design the tank and specify the materials and construction methods.
- Excavation: Excavate the site to the required depth and size of the tank. The excavation should be slightly larger than the size of the tank to allow for the installation of reinforcement and formwork.
- Foundation: Prepare a strong foundation for the tank by leveling the base and pouring a layer of concrete.
- Reinforcement: Install steel reinforcement bars inside the excavation to provide structural support for the tank. The reinforcement should be placed in a grid pattern and secured in place with wire ties.
- Formwork: Build a formwork to the shape and size of the tank using plywood or steel sheets. The formwork should be strong enough to withstand the pressure of the concrete during pouring.
- Plumbing and Electrical: Install the necessary plumbing and electrical lines inside the excavation. This may include pipes for water inlet and outlet, drainage pipes, and electrical conduit.
- Pouring the Concrete: Pour the concrete into the formwork in layers, ensuring that each layer is properly compacted using a vibrator. The concrete should be of the right mix and consistency, as recommended by the engineer.
- Curing: Allow the concrete to cure for at least 28 days. During this time, keep the concrete moist by sprinkling it with water and cover it with a plastic sheet.
- Waterproofing: Apply a waterproofing membrane or coating to the interior of the tank to prevent water seepage. The waterproofing material should be compatible with the type of water stored in the tank.
- Backfilling: Backfill the excavation around the tank with soil or sand, compacting each layer as you go.
- Access and Ventilation: Install an access hatch and ventilation pipe to allow for inspection, cleaning, and ventilation of the tank.
- Testing: Conduct a leak test to ensure that the tank is watertight before use. This may involve filling the tank with water and observing for any signs of leaks.
Overall, constructing an underground water tank can be a complex and time-consuming process. It is important to engage the services of a qualified engineer and contractor to ensure that the tank is constructed to the required standards and specifications.
Mellen Nyabuto is a plant pathologist woking with International Institute of Tropical Agriculture Email: mellennya96@gmail.com