Rainwater Harvesting (RWH) is the process of collecting and storing rainwater in a scientific and controlled manner for future use.  Rain water harvesting systems are simple to install and operate. Rainwater Harvesting in urban areas include

  • Roof top rainwater harvesting

  • Rainwater harvesting in paved and un-paved areas (open fields, parks, pavement landscapes etc.)

  • Rainwater Harvesting in large areas with open ponds, lakes, tanks etc.

Water is so precious that if and another third World War is to be occurred, then that will be the war of Water.  It is life. Man can live without food for more than one month but without water man cannot live more than seven days

In some cases, rainwater may be the only available or economical water source. Rain water harvesting systems can be simple to construct from inexpensive local materials, and are potentially successful in most habitable locations. Roof rainwater can’t be of good quality and may require treatment before consumption. As rainwater rushes from roof, it may carry pollutants in it such as the tiniest bit of mercury from coal burning and bird feces.

Although some rooftop materials may produce rainwater that is harmful to human health, it can be useful in flushing toilets, washing clothes, watering the garden and washing cars; these uses alone halve the amount of water used by a typical home.

Components of Rain Water Harvesting

Rain water collection may be from roof tops, terrace, courtyard, paved or unpaved open ground etc. But Roof water harvesting system which is the simplest and easiest will be the most suitable method . It has the components like Catchment area, Collecting Gutters, Transportation, First flush, Filter and Storage tank.

Down pipe and first flush arrangement

This is an arrangement to prevent the dust and other unwanted materials that may be seen on the roof, from reaching the storage tank. By fitting a down pipe with an end cap or valve can ensure that the washed water from the roof does not reach the storage tank. It is always safe to ensure that the first flush arrangement remains open during non- rainy days and should be closed after first rain up to the satisfaction of the end user.

Filter unit

The rainwater collected from the roof should be allowed to reach the storage tank only through a filtering mechanism. Rubble, sand and charcoal, as used in the traditional three-pot filtration, can be adopted here. 10 cm thick 20mm rubbles, 10 cm thick charcoal/coconut shell, 15 cm thick coarse sand, 5 cm thick 6mm rubbles etc. may be arranged from bottom to top in the filter unit. The water that is passed through this filter should remain safe for a long period of storage. Charcoal/coconut shell is added to eliminate gaseous pollutants.

Storage tank

Mainly three types of storage tanks are constructed for roof water harvesting. They are above ground, underground or sub surface tanks as per requirement. The storage tank may simply be the collection drums.

Provision for drawing water and spill over

For drawing water from the storage tanks, any method may be adopted provided it shall be drawn only when needed. The easier the method adopted for drawing water, the more will be the chances for its misuse. The adopted methods may be a tap, hand pump or electric pump sets.

Maintenance

  • Before collecting the rain water, the roof, gutters and tank should be cleaned
  • Let the first 2-3 rains flow out through the first flush system
  • Remember to clean the tank once in a year
  • Replace the filtering agents every year
  • Keep the tank and surroundings clean and hygienic
  • Apply white cement on the tank every year
  • Remember to preserve water and use it judiciously

Advantages of Rain Water Harvesting

Rainwater harvesting systems are simple to install, operate, and maintain. It is convenient in the sense that it provides water at the point of consumption and operating costs are negligible. Water collected from the roof catchment is available for use in potable and non-potable applications such as toilet and/or urinal flushing, laundries, mechanical systems, custodial uses, site irrigation and for bathing water. Since rainwater is collected using existing structures, i.e., the roof, rainwater harvesting has few negative environmental impacts.

Benefits of Using Rain Water Harvesting

Rainwater is free; the only cost is for collection and use. It lessens demand on the municipal water supply. It saves money on utility bills. It makes efficient use of a valuable resource. It diminishes flooding, erosion, and the flow to storm water drains. It reduces the contamination of surface water with sediments, fertilizers and pesticides from rainwater run-off resulting in cleaner lakes, rivers, oceans and other receivers of storm water.

It can be used to recharge ground water. It is good for irrigation and plants thrive because stored rain water is free from pollutants as well as salts, minerals, and other natural and man-made contaminants. It is good for laundry use as rain water is soft and lowers the need for detergents. It adds life to equipment dependent on water to operate, as rain water does not produce corrosion or scale like hard water. It can help achieve LEED Green Building Rating Credit.

What are the benefits of rain water collection?

Rain water is the purest form of water. In rain water, we have total control over our water supply. It is very ideal for cities with water restrictions. It is socially acceptable and environmentally responsible. It promotes self-sufficiency and helps conserve water. Rain water is better for landscape plants and gardens because it is not chlorinated. It reduces storm water runoff from homes and businesses. It can solve the drainage problems on your property while providing you with free water.

It uses simple technologies that are inexpensive and easy to maintain. The potential cost savings especially with rising water costs. It can be used as a main source of water or as a backup source to wells and municipal water. The system can be easily retrofitted to an existing structure or built during new home construction. Systems are very flexible and can be modular in nature, allowing expansion, reconfiguration, or relocation, if necessary. It can provide an excellent back-up source of water for emergencies.

For a poor family to construct high quality storage tank may not be possible, therefore the best method will be construction of katcha ponds lining with tarpaulin. Collection of Rain water in the drums is also another feasible way. If the Harvesting is to be done for the whole village, then a bigger ferro-cement tank with roof may be constructed.

Therefore, we should not leave the advantages of Rain water harvesting. A GCI roofing house having a surface area of 30 ft. X 40 ft. can collect about 1,49,500 litres of water per annum while the average rainfall is calculated at 1790 mm and efficiency for 75%.

Rain water harvesting will particularly benefited the hill dwellers as the water problem is more acute for them. The Municipal councils, Small town committees and Panchayats also should have their own Rain water harvesting facilities to help the public supply, to improve the ground water condition and for more greenery.

( Reference: Article by Mr.N Munal Meitei, Range Forest Officer wrote for The Sangai Express. , http://e-pao.net/ )

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