First in a four-part Citizen Matters series authored by Bangalore-based Rainwater Club on implementing rainwater harvesting for gated layouts.
Much has been written in recent years about rainwater harvesting. While the literature has certainly elevated interest in this practice, there is very little material to explain in simple terms how people can carry out an informed attempt to introduce RWH in their homes and communities.
This Citizen Matters 4-part series authored by Bangalore-based Rainwater Club shows the way to implementing rainwater harvesting in a particular context: the gated layout.
In the beginning
When residents move into their new homes in a layout, they are occupied with setting up the home and making sure their daily requirements of water, electricity, grocery and other services are met. There is a tendency to assume that the layout developer will ensure proper water management. And indeed they often do manage the water supply, for a time.
Rain barrel. Pic: Rainwater Club.
But more often than not, the developer either does not value sustainable resource management or does not know how to go about achieving it. Moreover, in the absence of a long-term maintenance contract, most developers leave the layout and control of all services in the hands of the residents after the last home has been built. At some point, concerned residents begin to recognize the critical importance of managing the layout’s water efficiently and effectively.
Given that layouts develop mostly on the city’s outer rings, they are off the public water utility’s service grid and must source their own water. Because there is no agency or company to depend upon to secure their future water supply, residents come to see responsible water management not as a choice, but an imperative to protect the investment they made on their new home.
Rooftop RWH. Pic: Rainwater Club.
Rainwater harvesting (RWH), including rooftop collection for domestic use and groundwater recharge, can be instrumental in efforts to achieve water sustainability. To implement this practice throughout the layout, committed residents must come together to carry out a process to familiarise residents with the RWH concept and generate support for it.
Before beginning this process, however, it is important to address some key issues that will arm you with the requisite information to make a strong case for sustainable water management to your fellow neighbours.
3 steps to preparing your RWH efforts
Step 1 - Ask yourself: Why Rainwater Harvesting?
It is important to understand the main objectives of rainwater harvesting in your layout since this will help determine the strategy and design of a Rainwater Harvesting system in
your specific context
- Is it a source of supplemental water (thus reducing demand from your existing sources)?
- Is it to recharge ground water sources as you are dependent on borewells/open wells?
- Is it also as a flood control measure?
Your answers to these questions will help determine the most appropriate RWH interventions. Indeed, in many cases RWH is implemented to achieve all three of these objectives.
About recharge wells and pits
1. What is a recharge pit? Is it the same as a recharge well?
A recharge pit is a hole dug in the ground. Usually it is filled with gravel or jelly to give it structural strength. A recharge well is not filled with gravel. It needs concrete rings installed in it to stabilise its walls.
2. What should be the depth of a recharge well/pit?
If you want to have effective recharge for Bangalore conditions, a 15-20 feet depth is needed. (Provided you do not hit rock before that depth). If you hit water while digging the pit, you need to ask the workers to be careful while they continue digging. The diameter of the pit you choose depends on two things: space available and the quantity of water you will send in. A 3 feet dia X 20 feet pit will ‘hold’ around 4000 litres (for recharging the ground). A 5 feet x 30 feet structure can hold 16000 litres.
3. What are the legal guidelines and their implication for recharge pit sizes?
The law states that you need to store or recharge 20 litres for for every sq.m of roof area and 10 litres for every sq.m of non-roof (ground surfaces such as parking, backyard) area. This is for plot sizes of 40x60 or more. For e.g. if your home has about 100 sq.ms of roof area, and about 50 sq.ms of non-roof area, then you will need to create capacity for at least 2500 litres of water. If you are using a 1000 litre tank to store rainwater for immediate use, you can connect the overflow to a 4000 litre (3 feet x 20 feet) recharge well.
4. How much do recharge pits cost?
Cost of digging a 3 feet diameter x 20 feet deep well is approximately Rs 20,000.
Avinash Krishnamurthy is a member of Rainwater Club.