Farm Radio International provides information about different ways to capture rain. They state, "some people catch rainwater from roofs and hold it in tanks or cisterns. Others build dams, or collect water in shallow pans, terraces, or other small structures. The water is then available for use in the dry season. Water captured in the rainy season can be stored above ground – in cisterns, tanks, dams, and other containers. Or it can be stored underground. Building an earth bank is one way to store water underground."
This article explains how to build a series of earth banks on the farm to harvest rain water that can be used all year round to grow crops and to use in the household. Earth banks are useful because they can help a farmer to grow food all through the dry season, when fresh food is scarce. They work because they capture rainwater and store it in the soil.
But how do earth banks store water in the soil? Earth banks are able to do this because of how they are built. They should be built on the lower part of a gentle slope. When rainwater runs down the slope, the earth banks slow the water down so it can seep into the soil, instead of running over it and in this way crops get more water.
How to build an earth bank
Earth banks are simply low mounds of earth.
NB: It is very important to note that there has to be a slope so that the water runs downhill. But the slope shouldn't be too steep, or the flood water will wash away the earth bank. Just a gentle slope works best. However, if there is a stream on the land, more water can be captured in the soil and in the well. Earth banks can also be eroded by rain and run-off water, so regular work is needed to keep the soil in place.
Before attempting to construct an earth dam, it always wise to look around and try to find someone who has already built an earth bank. Asking other farmers if they know people who have tried improves the success of the project significantly.
Information source: Farm Radio International, "Harvesting Water Using Earth Banks", Package 71, Script 8, June 2004, www.farmradio.org