Rain Water Harvesting - a Visionary Scheme from the Government of Tamilnadu

The Rain Water Harvesting movement launched in 2001 was the brainchild of the Honourable Chief Minister. It has had a tremendous impact in recharging the groundwater table all over Tamil Nadu. Amendments made to Section 215 (a) of the Tamil Nadu District Municipalities Act, 1920 and Building Rules 1973, have made it mandatory to provide RWH structures in all new buildings.   To consolidate the gains, various measures have been taken up for rejuvenation of RWH structures created already in both public and private buildings, besides creating new ones.  IEC activities will be continued in the Town Panchayats to sensitize all the stake holders to sustain the momentum. During 2011-12, in order to give a fillip to this laudable programme, the Town Panchayats have undertaken the construction of new RWH structures and renovation of old RWH structures. IEC activities are being carried out in Town Panchayat areas to sustain the momentum of the programme.

There are  1821 water bodies maintained by Town Panchayats with an extent of 6286.84 acres. In order to restore the 243 water bodies Rs. 55.52 crore has been allocated for the years 2011-12 and 2012-2013 under IUDM and NABARD. Similarly, during 2013-2014, 561 improvement works such as desilting and strengthening of bund and sluice works have been taken up at a cost of Rs.18.40 crore under General fund. Proposed to taken up 88 water body improvement works in 68 Town Panchayats at an estimated cost of Rs.28.15 crore.

Total number of buildings in Town Panchayats is 23,92,457 out of which 22,94,342 buildings are provided with Rain Water Harvesting facilities as mentioned in the following table.   

Type of Buildings	No. of Buildings	No. of Buildings providing RWH structures so far	Balance
Government Buildings	24116	23190	926
Residential Buildings	2208377	2114294	94083
Commercial Buildings	148170	145064	3106
Industrial Buildings	11794	17794	0
Total	2392457	2294342	98115

Action Plan for IEC Activities

·         Vigorous IEC campaign would also be adopted to bring awareness among the public

·         Conduction of awareness programme  with the  coordination of Self Help Groups, Welfare Associations,  NGO s and school children.

·         Erection of  hoardings displaying  the importance  and benefits of the Rain Water Harvesting.

·         Door to Door campaign on  Rain water Harvesting  with  the participation of  SHGs, NGOs.

Action plan for harvesting campus rain water

·         Provision of rain water harvesting structures would also been monitored under Section 215 A of the Tamil Nadu District Municipalities Act, while giving plan approval.  

·         Rain Water Harvesting Structures have already been  provided  in respect of buildings, belongs  to Town Panchayats Department. 

·         Necessary action taken to provide adequate Rain Water Harvesting structures belongs to other Government department. 

·         Now, in order to  make use of the forthcoming North East monsoon, the Executive Officers of Town Panchayats  have been instructed to take necessary action  to rejuvenate existing Rain Water Harvesting structures.

Rain Water Harvesting structures in Ooranies

RAIN WATER HARVESTING TECHNIQUES :

There are two main techniques of rain water harvestings.

Storage of rainwater on surface for future use.

Recharge to ground water.

The storage of rain water on surface is a traditional techniques and structures used were underground tanks, ponds, check dams, weirs etc. Recharge to ground water is a new concept of rain water harvesting and the structures generally used are :-

Pits :- Recharge pits are constructed for recharging the shallow aquifer. These are constructed 1 to 2 m, wide and to 3 m. deep which are back filled with boulders, gravels, coarse sand.

Trenches:- These are constructed when the permeable stram is available at shallow depth. Trench may be 0.5 to 1 m. wide, 1 to 1.5m. deep and 10 to 20 m. long depending up availability of water. These are back filled with filter. materials.

Dug wells:- Existing dug wells may be utilised as recharge structure and water should pass through filter media before putting into dug well.

Hand pumps :- The existing hand pumps may be used for recharging the shallow/deep aquifers, if the availability of water is limited. Water should pass through filter media before diverting it into hand pumps.

Recharge wells :- Recharge wells of 100 to 300 mm. diameter are generally constructed for recharging the deeper aquifers and water is passed through filter media to avoid choking of recharge wells.

Recharge Shafts :- For recharging the shallow aquifer which are located below clayey surface, recharge shafts of 0.5 to 3 m. diameter and 10 to 15 m. deep are constructed and back filled with boulders, gravels & coarse sand.

Lateral shafts with bore wells :- For recharging the upper as well as deeper aquifers lateral shafts of 1.5 to 2 m. wide & 10 to 30 m. long depending upon availability of water with one or two bore wells are constructed. The lateral shafts is back filled with boulders, gravels & coarse sand.

Spreading techniques :- When permeable strata starts from top then this technique is used. Spread the water in streams/Nalas by making check dams, nala bunds, cement plugs, gabion structures or a percolation pond may be constructed.

DIVERSION OF RUN OFF INTO EXISTING SURFACE WATER BODIES

Construction activity in and around the city is resulting in the drying up of water bodies and reclamation of these tanks for conversion into plots for houses.

Free flow of storm run off into these tanks and water bodies must be ensured. The storm run off may be diverted into the nearest tanks or depression, which will create additional recharge.

Urbanisation effects on Groundwater Hydrology :

Increase in water demand

More dependence on ground water use

Over exploitation of ground water

Increase in run-off, decline in well yields and fall in water levels

Reduction in open soil surface area

Reduction in infiltration and deterioration in water quality

Methods of artificial recharge in urban areas :

Water spreading

Recharge through pits, trenches, wells, shafts

Rooftop collection of rainwater

Roadtop collection of rainwater

Induced recharge from surface water bodies.

Benefits of Artificial Recharge in Urban Areas :

	Improvement in infiltration and reduction in run-off.
	Improvement in groundwater levels and yields.
	Reduces strain on Special Village Panchayats/ Municipal / Municipal Corporation water supply
	Improvement in groundwater quality
	Estimated quantity of additional recharge from 100 sq. m. roof top area is 55.000 liters.