Rain Water Harvesiting

8/2/2019 Rain Water Harvesiting

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RAIN WATER HARVESTING

Definition:-

Rainwater harvesting is the accumulating and storing of rainwater for reuse beforeit reaches theaquifer. It has been used to providedrinking water, water

forlivestock, water forirrigation, as well as other typical uses. Rainwater collected

from the roofs of houses and local institutions can make an important contribution

to the availability of drinking water

Why Rainwater Harvesting:-

Major parts of our country have been facing continuousfailure of monsoon and consequent deficit of rainfall over thelast few years.

Also, due to ever increasing population of India, the use ofground water has increased drastically leading to constant

depletion of ground water level causing the wells and tube wells

to dry up.

In some places, excessive heat waves during summer createa situation similar to drought.

It is imperative to take adequate measures to meet thedrinking water needs of the people in the country besidesirrigation and domestic needs.

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How To Harvest Rainwater:

There are several types of systems to harvest rainwater, ranging from very simple

home systems to complex industrial systems. The rate at which water can be

collected from either system is dependent on the plan area of the system, itsefficiency, and the intensity of rainfall

Broadly there are two ways of harvesting rainwater:

(i) Surface runoff harvesting

(ii) Roof top rainwater harvesting

Surface runoff harvesting:-

In urban area rainwater flows away as surface runoff. This runoff could be caughtand used for recharging aquifers by adopting appropriate methods.

Roof top rainwater harvesting:-

It is a system of catching rainwater where it falls. In rooftop harvesting, the roof

becomes the catchments, and the rainwater is collected from the roof of the

house/building. It can either be stored in a tank or diverted to artificial recharge

system. This method is less expensive and very effective and if implemented

properly helps in augmenting the ground water level of the area


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Components Of Roof top rainwater harvesting system:-

Catchment

Transportation

First flushFilter

Catchment:-

The surface that receives rainfall directly is the catchment of rainwater harvesting

system. It may be terrace, courtyard, or paved or unpaved open ground. The terrace

may be flat RCC/stone roof or sloping roof. Therefore the catchment is the area,

which actually contributes rainwater to the harvesting system

Transportation:-

Rainwater from rooftop should be carried through down take water pipes or drains

to storage/harvesting system. Water pipes should be UV resistant (ISI HDPE/PVC

pipes) of required capacity. Water from sloping roofs could be caught through

gutters and down take pipe. At terraces, mouth of the each drain should have wire

mesh to restrict floating material.

First Flush:-First flush is a device used to flush off the water received in first shower. The first

shower of rains needs to be flushed-off to avoid contaminating

storable/rechargeable water by the probable contaminants of the atmosphere and

the catchment roof. It will also help in cleaning of silt and other material deposited

on roof during dry seasons Provisions of first rain separator should be made at

outlet of each drainpipe.

Filter:-

There is always some skepticism regarding Roof Top Rainwater Harvesting since

doubts are raised that rainwater may contaminate groundwater. There is remote

possibility of this fear coming true if proper filter mechanism is not adopted.


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Secondly all care must be taken to see that underground sewer drains are not

punctured and no leakage is taking place in close vicinity. Filters are used fro

treatment of water to effectively remove turbidity, colour and microorganisms.

After first flushing of rainfall, water should pass through filters. There are different

types of filters in practice, but basic function is to purify water.


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Ground Water Recharge:-

Rainwater may also be used for groundwater recharge, where the runoff on the

ground is collected and allowed to be absorbed, adding to the groundwater. In theUS, rooftop rainwater is collected and stored in sump.

Ground water aquifers can be recharged by various kinds of structures to ensure

percolation of rainwater in the ground instead of draining away from the surface.

Commonly used recharging methods are:-

a) Recharging of bore wells

b) Recharging of dug wells.

c) Recharge pits

d) Recharge Trenchese) Percolation Tanks

a) Recharging of bore wells:-

Rainwater collected from rooftop of the building is diverted through drainpipes to

settlement or filtration tank. After settlement filtered water is diverted to bore wells

to recharge deep aquifers. Abandoned bore wells can also be used for recharge.

b) Recharging of Dug Wells:-

Dug well can be used as recharge structure. Rainwater from the rooftop is diverted

to dug wells after passing it through filtration bed. Cleaning and desalting of dug

well should be done regularly to enhance the recharge rate. The filtration method

suggested for bore well recharging could be used.

c) Recharge Pits:-

Recharge pits are small pits of any shape rectangular, square or circular, contractedwith brick or stone masonry wall with weep hole at regular intervals. to of pit can

be covered with perforated covers. Bottom of pit should be filled with filter media.
http://en.wikipedia.org/wiki/Groundwater_rechargehttp://en.wikipedia.org/wiki/Sumphttp://en.wikipedia.org/wiki/Sumphttp://en.wikipedia.org/wiki/Groundwater_recharge


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d) Recharge Trenches:-

Recharge trench in provided where upper impervious layer of soil is shallow. It is

a trench excavated on the ground and refilled with porous media like pebbles,

boulder or brickbats. it is usually made for harvesting the surface runoff. Bore

wells can also be provided inside the trench as recharge shafts to enhance

percolation.

e) Percolation Tanks:-

Percolation tanks are artificially created surface water bodies, submerging a land

area with adequate permeability to facilitate sufficient percolation to recharge the

ground water. These can be built in big campuses where land is available andtopography is suitable.

Surface run-off and roof top water can be diverted to this tank. Water accumulating

in the tank percolates in the solid to augment the ground water. The stored water

can be used directly for gardening and raw use. Percolation tanks should be built in

gardens, open spaces and roadside green belts of urban area.


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Advantages:

Rainwater harvesting technologies are simple to install and operate.Local people can be easily trained to implement such technologies, andconstruction materials are also readily available.

Rainwater harvesting is convenient in the sense that it provides water atthe point of consumption, and family members have full control of theirown systems, which greatly reduces operation and maintenanceproblems. Running costs, also, are almost negligible.

Water collected from roof catchments usually is of acceptable quality fordomestic purposes. As it is collected using existing structures notspecially constructed for the purpose, rainwater harvesting has fewnegative environmental impacts compared to other water supply projecttechnologies.

Although regional or other local factors can modify the local climaticconditions, rainwater can be a continuous source of water supply forboth the rural and poor.

Depending upon household capacity and needs, both the watercollection and storage capacity may be increased as needed within theavailable catchment area.


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Rain Water Harvesiting

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