How to Build a Groundwater Dam

A groundwater dam interrupts the natural flow of groundwater by intercepting or obstructing it, as well as provides storage for underground water. It's effective in areas like India and Africa which have a large variance of ground water during the rainy and dry seasons. Although there is quite a bit of labor involved in constructing a groundwater dam, it's a functional way to filter and store water.

Difficulty: Moderately Challenging

Instructions

1. Select a site for a groundwater dam that crosses a stream or valley and has bedrock or a stable clay bed. The soil should have a lot of sand and gravel with either rock or some other permeable layer 6 to 8 feet below the surface.

2. Use earth-digging equipment or many people with shovels and dig a trench across a dry riverbed. Dig all the way down to the bedrock. Do this during the dry season, before heavy rains and monsoons.

3. Build a wall of brick or stone at the end of the trench, stopping about 4 feet under the riverbed surface. You can build this wall with any kind of weatherproof material, such as heavy clay, concrete, rocks and sheets of plastic. Pack it tightly to form a solid, waterproof barrier.

4. Place a pipe in the downstream wall of the reservoir which leads to a pump on the side of the riverbank. This provides access to the stored water.

5. Expect the reservoir to fill during the monsoon season so the stored water will be available during the dry season. Overflowing water runs off to refill aquifers downstream from the dam.

Tips & Warnings

• To help find a good place for a groundwater dam, look for an area along a river and riverbank that has green vegetation year around. This is an indication that there is underground water. You also want to dig down a few feet to make sure there's layered bedrock near the surface.

Resources

• Further explanation and drawings at cseindia.org.