What is Rain Water Harvesting? Rain Water harvesting means understanding the value of rain and to make optimum use of it when it falls. Rain Water harvesting broadly refers to the collection and storage of rainwater; and also, other activities such as harvesting surface water, extracting groundwater, prevention of losses through evaporation and seepage.

Why Rain Water Harvesting? We currently depend on our secondary sources of water such as Rivers, lakes, and groundwater. The water crisis can only be controlled if everyone is effectively taking part in conserving and saving the available water using Rainwater Harvesting.

Chennai situation: Chennai gets an average of 1200-1300 mm of annual rainfall throughout the year. Due to urbanization it is rapidly becoming a concrete jungle with no to very less open surfaces that would help enhance the recharge of groundwater.

How to Harvest Rainwater? Rainwater harvesting is very simple, we need to collect as much rainwater as possible. There are multiple techniques to do so for majorly two purposes. Water is stored for in containers above ground or below ground which can be instantly used.

Water is pushed to the ground which can be withdrawn later RWH systems to opt for: There are multiple systems to choose from based on your requirement. to Store water which can be bought to use instantly Or pushing it down to help recharge groundwater for future purpose The following are few systems that can be opted in for:

Open well Concept - If you have an open well available at your place you can divert the Rainwater from your terrace using PVC pipes through a filter chamber. This concept recharges the groundwater at a higher rate than any other concept.

Borewell Concept - The borewell is one of the most common sources of water in India. These are wells dug deep into the ground to tap into water-bearing soil or rock layers termed aquifers which can be used to store rainwater which can later be used.

Percolation Pit Concept - A percolation pit is one of the simplest and most effective way to harvesting rainwater. It's just a hole dug into the ground which is loaded with rocks or block jam and stream sand. The hole is securely punctured with solid pieces wherever essential to recharge the ground water.

Recharge well Concept - A Recharge well can be of varying sizes. A typical well is of 3 ft diameter and 20 ft depth which can hold 4000 liters of water. The boundary wall is lined with brick/stone walls with small openings to percolate water down in sandy soil. The top area of the pit can be secured with a cover. Different Methods of Rain Water Harvesting Based on the type of building various methods can be adopted:

Rooftop: Roof-top rainwater harvesting (RRH) is diverting and storing a part of the rainwater that falls on the roof of a house. This can be implemented at houses, apartments or complexes. The following concept are can be implemented:

Sloping Roofs: Transporting or diverting rainwater from the roof to the storage tank using Gutters and channels. Roofs that are made of Iron or Asbestos Sheets, tiles can ustilize this method to harvest the maximum rain water.

Houses with RCC Roof: Houses which has a sloping roof can use half-cut PVC pipes which can be fitted along the side to transporting or diverting to either a sump/open well/bore well or recharge well, depending on the type of house and its location. Setback: The “Setback Area” is the area around the open space in the front/back/sides of a plot/building and the section that is in between the building.

Implementing RWH in these spaces can be very beneficial in reducing the clogging of streets during rain and could conserve the runoff water. Rules and Regulations Now all multi-storied buildings/special buildings need to have RWH then only can get approval/permission from CMDA.

All new construction regardless of its size needs to have RWH implemented in the plan to get license by Chennai Municipal Corporation RWH structures are now mandatory for all, without which CMWSSB will not provide approval for new water and sewer connections. Not only its now mandatory to implement RWH in the construction plan, the owner/owners/occupiers needs to also declare that they would be properly maintaining the structures implemented and should not be dispensed with in the future. In RWH systems for houses.

The collection or catchment method depends on the roof design of the house. We need to elaborate more on the methods of using that water.

Some Examples are

1. Diverting the water from the roof or terrace directly into the ground to recharge groundwater tables.

2. Collecting the water in a sump to be used by the household.

3. Diverting the water into a well or borewell to recharge.