Infochangeindia kids section

Imagine a situation where there is no more potable water on earth. Riverbeds will dry up, taps will run dry, people will fight for a handful of water. There will be riots over water. How will you bathe, wash, cook, build houses, run your industries, generate electricity, and most important, what will you drink?!

Water is the source of life. All our civilisations sprang up next to rivers. Over the years, rising populations, growing industrialisation and expanding agriculture have pushed up the demand for water. New technology like borewells and water pumps help us suck water out from great depths beneath the surface of the earth. At the same time, we do not replenish this water. In urban areas, the construction of houses, footpaths and roads leaves very little exposed earth for water to soak in. Forests have been ruthlessly chopped down, hillsides stripped of all their greenery, thus allowing rainwater to flow down slopes unchecked. Floodwater quickly flows into rivers, which dry up soon after the rains stop. If this water could be held back, it could seep into the ground to recharge groundwater.

Subsurface water is like a bank account. If money is continuously withdrawn without any deposits, the account will empty out. In the same way, aquifers are becoming bankrupt because more water is being withdrawn than is being replenished.

According to Colonel Shashikant Dalvi, a retired army officer who has set up the consulting firm Parjanya, in Pune, “40 years ago, Pune had a percolation rate of 45%. But now with increased areas under concrete and tarring, the rate has gone down to 8%”.

The idea of recharging groundwater through rainwater harvesting is becoming popular

in many Indian cities. Rainwater harvesting (RWH) essentially means collecting rainwater and storing it for later use. Not only does this stop groundwater depletion, it also raises the watertable and helps augment water supply. This artificial recharging stops the drop in groundwater levels and conserves surface water run-off during the monsoons.

While town planners and civic authorities in cities are slowly introducing by-laws making rainwater harvesting compulsory in all new structures, a lot still remains to be done.

It’s time for us to follow the saying, “The best helping hand is at the end of your arm,” and tackle the problem ourselves. A few concerned and responsible citizens, schools, colleges, hospitals and industrial houses have already begun the task and have taken the leap towards ecological resuscitation.

How you can implement rainwater harvesting

Rainwater harvesting is a way to capture rainwater, store that water above ground or charge underground aquifers and use it later. While this happens naturally in open rural areas, in congested, over-paved metropolitan cities we need to create methods to capture rainwater.

All you need for a water harvesting system is rain, and a place to collect it. Airports, temples, roads, highways, flyovers, parks, schools, colleges, hospitals, shopping arcades -- all can be drawn into the net.

Typically, rainwater is collected on rooftops and other surfaces and the water carried down to where it can be used immediately or stored. You can direct water run-off from this surface to plants, trees, lawns, or even to an aquifer.

If you have a roof, you already have 80% of your rainwater harvesting system in place. You just need to re-orient the plumbing. The present design for houses takes all the rainwater from the roof and ground-level areas around the house and directs it towards the street where it flows into drains. Of course these days it usually floods the streets as stormwater drains become clogged with dirt and plastic!

Bring rainwater down from your rooftop using closed PVC pipes and direct it to a sump. The sump is a deep hole (about two feet square and 16 feet deep) dug into the ground. Fill this up with a simple filtration unit consisting of sand, brick jelly and broken mud bricks. If you do not have a sump, use a well. In many parts of the country, old wells are used as garbage dumps when they dry up. Clean the well and direct rainwater into it. If you do not have a well, construct a baby well (about two feet in diameter and 16 feet deep, based on the soil structure).

It’s important to select your site carefully. If you are installing your rainwater harvesting system in your garden, choose a corner that is the most low-lying. This will ensure that water flows into the site when it rains.

Drill a hole in the ground, 3-12 inches in diameter. Depending on the terrain, as little as five feet or as much as 30 feet deep.
Drop stones or (preferably) bricks into the hole so that the channel always remains open.
Cover with a one-foot-by-one-foot, preferably double, stainless steel or galvanised mesh.
Put a layer of small pebbles onto this.
Cover with loamy river silt/garden soil; NEVER black cotton soil.
Cover with brick cobbling/paving.

When it rains, water flows into this hole, gradually sinking in until it reaches the bedrock. The level of the underground water slowly rises, increasing with each year’s rainfall. This is your storage. The steel mesh and layers of pebble and soil are the only filter you need. Now install a pump to draw out the water. If the rainfall has been good, the water will be enough to last you throughout the year.

If you had not installed the water recharging system, all this precious rainwater would have flowed out onto the streets!

Total time to complete the project: Two to four hours, if a drill is used.
While this is the simplest form of water recharging, Milind Kulkarni runs a special consulting firm, Hydro Bio-Tech Systems, in Pune, which installs rainwater harvesting systems on a larger scale. The company has set up systems in a number of buildings in the city.

Kulkarni says: “For a terrace with an area of 1,000 square metres and rainfall of around 600 mm in one season, 50,000 litres of water can be saved in a single season.

Installing a rainwater harvesting system works out to be very economical; the cost can be recovered in around one-and-a-half years. Installation cost is minimal since the basic infrastructure already exists. What is needed is technical expertise.

According to Kulkarni, rainwater harvesting systems can be used on concrete flat roofs, inclined roofs, earthen tiled roofs and industrial sheds.

He explains the requirements and feasibility of installing a rainwater harvesting system.

An average individual requires 135 litres of water. Below is a percentage split-up of this amount:

Flushing toilets
Laundry
Washing cars and floors
Construction activities
Industrial process usage
Gardening
Fountains and lakes

Rainwater quantity available in one monsoon season = A x R x C, where A = Area of rooftop in square metres; R = Average rainfall in one monsoon season; C = Coefficient of run-off (usually 0.9) for a concrete terrace.

Pipes/rainwater gutters must be firmly supported.
Minimum four-inch-diameter pipes must be used for a terrace area of up to 4,000 square feet.
In the case of PVC rainwater gutters, minimum gutter diameter should be 180 mm.
Above-the-ground PVC pipes should be the SWR type.
Below-the-ground PVC pipes should be concrete-encased.

Is filtration necessary?

Filtration of harvested roof water is a must if the water is stored in a tank or recharged directly in a borewell, well or any other waterbody. Filtration of rainwater is essential in any rainwater harvesting system, otherwise wells or storage tanks will silt up.

Specially developed rainwater harvesting purifier filters can help remove dust and particles present in rainwater.

RWH Purifier To remove dust accumulated in the filters, an in-built backwash system is provided.

The filter is made from PVC material so there is no problem of corrosion. It can be installed in existing rainwater drop pipes.