Types of Groundwater Dams

Intense measures are being taken to preserve and harvest rainwater. Rain water harvesting system is being installed in almost all parts of India. Even in areas with heavy rainfall rain water harvesting systems are being used mandatorily. For example each flat in Kerala is now installing the system to save water.

There are a number of modern methods of conserving rain water among which groundwater dams is a new method. There are two types of groundwater dams: the sub-surface dam and the sand storage dam. A sub-surface dam reduces the variation of the level of the groundwater table upstream of the dam by intercepting or obstructing the flow of an aquifer. The structure is built completely under the ground.

The sand storage dam is built above the ground. During periods of high flow sand and soil particles are transported and are allowed to deposit behind the dam. The water is stored in these soil deposits. Constructed in layers the sand storage dam allows sand to be deposited and finer material to be washed downstream.

A combination of these two types can also be used as a groundwater dam. One can increase the storage volume by letting the dam wall rise over the surface while constructing a sub-surface dam in a river bed, thus causing additional accumulation of sediments. Also, while constructing a sand-storage dam it is necessary to excavate a trench in the sand bed to reach the bedrock. This can also be used to create a sub-surface dam.

During the monsoon season the reservoir is recharged and the stored water can be used during the dry season. The excess water replenishes the aquifers downstream.