Rainwater harvesting as method of utilizing rainwater for domestic and agricultural use is already widely used throughout the world. Rainwater harvesting is a method which has been used since ancient times and is increasingly being accepted as a practical method of providing potable water in development projects throughout the world.
Rainwater Harvesting; Importance
Water is a precious natural resource that needs to be managed and used wisely. There are many reasons why rain water needs to be harvested. Some of the reasons are;
- Water is a scarce natural resource and hence it should not be wasted
- It can supplement our domestic, industrial and other water needs.
- If rainwater harvesting is incorporated at the design stage of any construction project, the investment is low, and the water collection is large,
- Centralized systems of water supply are under stress to cope with huge water supply demand of cities
- Ground water is constantly getting depleted and polluted in large areas.
- Water is not only becoming scarce but expensive as well.
- The link with the hydro-logic cycle is re-established leading to efficient and effective use of water.
- It can be an individuals contribution to reduce the “ecological water footprint” i.e the distance water has to travel to reach a house.
Rainwater Harvesting; Process
Water can be collected from either rooftops or from ground or a combination of both. It may involve the simple collection of rainwater from the rooftop of a house, for use in gardening or collection from a large industrial campus for reuse in industrial process or for recharging into the ground .
Rainwater Harvesting; Systems
Ground catchments systems channel water from a prepared catchment area into storage. Generally they are only considered in areas where rainwater is very scarce and other sources of water available. They are more suited to small communities than individual families.
Roof catchment systems channel rainwater that falls onto a roof storage via a system of gutters and pipes. The first flush of rainwater after a dry season should be allowed to run to waste as it will be contaminated with dust, bird droppings etc. Roof gutters should have sufficient incline to avoid standing water. They must be strong enough, and large enough to carry peak flows.
A subsurface dyke is built in an aquifer to obstruct the natural flow of groundwater, thereby raising the groundwater level and increasing the amount of water stored in the aquifer.
Rain water can also be used for ground water recharge, where the runoff on the ground is collected and allowed to be absorbed, adding to the groundwater.