Defining Rain Water Harvesting
The collection of rainwater from the catchment area for later use is known as rainwater harvesting. The population of India is almost 18% of the total world population that has access to just 4% of the world’s total water resources to fulfil the needs, that can further deplete due to over-utilisation and ever-increasing population. This sheds light on the importance of water conservation using rainwater harvesting systems – it involves two main techniques:
- Collecting the rainwater directly for future use.
- Artificial recharge to improve groundwater storage.
Benefits of Rainwater Harvesting
- Rainwater harvesting helps in preventing rainwater pollution.
- It helps raise the groundwater level.
- A rainwater harvesting system helps cater to the water demands during the dry season.
- It helps in checking rainwater flow that in turn prevents soil erosion.
Components of a Rainwater Harvesting System
It is a simple rooftop water collection system that would work with the minimum requirements viz PVC pipes, mesh to cover the inlet and outlet openings, tanks or pits and pebble filters (used to remove big and small debris and sediments) – a proper combination all these will result in a highly efficient rainwater harvesting system.
Common Components:
Pits
These pits are constructed to recharge the shallow aquifer.
Construction Specification-
- Width – 1m to 2m
- Depth – 3m
- Back Fill- Yes, with boulders, gravels, and coarse sand.
Trenches
Constructed when the permeable stream is available at shallow depth.
Construction Specification-
- Width – 0.5m to 1m
- Depth – 1m to 1.5m
- Length – 10m to 20m
- Back Fill – Yes, with filter materials.
Recharge Wells
Constructed to recharge the deeper aquifers and water is passed through filter media to avoid choking of recharge wells.
Construction Specification-
- Diameter – 100mm to 300mm
- Back Fill – Yes, with filter media.
Recharge Shafts
Used to recharge the shallow aquifer located below the clayey surface.
Construction Specification-
- Diameter – 0.5m to 3m
- Depth – 10m to 15m
- Back Fill – Yes, with boulders, gravels, and coarse sand.
Lateral Shafts with Bore Wells
Used to recharge upper as well as deeper aquifers.
Construction Specification-
- Width – 1.5m to 2m
- Length – 10m to 30m
- Back Fill – Yes, with boulders, gravels, and coarse sand.
Apart from these 5 components, a spreading technique is used to spread the water in streams by making check dams, Nala bunds, cement plugs, gabion structures, or a percolation pond may also be constructed. The dug wells and handpumps can also be utilized to recharge aquifers.
Brief History of Rainwater Harvesting
The tradition of water harvesting in India dates back to almost 2 millennia. This is evident from various ancient texts that tell us about the water harvesting systems. The Vedas, Puranas, Mahabharata and Ramayana along with various Buddhist and Jain texts provide references to canals, tanks, embankments, and wells.
Dholavira a major site of the Indus Valley Civilization lies in an arid area, that receives an average annual rainfall of 260mm. There is no source of water to cater to the needs of the people and the subterranean water is brackish and saline, hence the inhabitants of Dholavira created several reservoirs to collect the monsoon runoff flowing down the flanking streams of Manhar and Mansar.
Relevance in Today’s Age
There has been a decline in the rainwater harvesting practices mainly due to reasons like-
- The State has become a major provider of water that replaced the community and household management of water.
- Currently, rather than relying on rainwater and floodwater, we have shifted to the use of surface and groundwater, even though Rainwater and floodwater are more abundantly available.
So, with the growing population and the dynamic use of the water makes the rainwater harvesting systems as the need of the hour. The rainwater harvesting systems can be used in personal as well as apartment dwellings and the collected water either can directly be sent to the ground or can be used for horticulture or it can even be used to wash your cars and bikes. Water is a very important resource for any country but with the current unsustainable use of water we might be running out of it pretty soon. If collective constructive efforts are taken we can surely avoid this situation and keep this issue at bay.
Remember people, together we can and we will Save the Water and Save the Environment.
Sources:
- (1)– National Water Policy (2012)
- (2)– CPWD, A Handbook of Landscape
- (3)– pubs.iied.org, Making Water Management Everybody’s Business: Water Harvesting and Rural Development.
