Phase I

Siruthuli constructed 150 Nos of rainwater harvesting structures in the initial phase during 2004-2005 with the financial assistance from the Coimbatore Corporation. The structures have been constructed in areas where water logging was observed in four zones of the city.

Impact of RWHS:

The data collected from a locally established drilling company reveals the following facts, which prove the worthiness of the project implemented. The average static water level, yield and cost of drilling in Coimbatore city for 3 years is given in the following table:

The average static water level of Coimbatore city during the year 2003 was about 90’ with 1.5” yield and the cost of borewell amounting to Rs 8,675/- per borewell and for 6½  inch borewell amounts to Rs. 17,028/-. During 2004, due to the monsoon failure in 2003, the average static water level of Coimbatore city went down to 122’ – 131’ and also the average yield of the borewell reduced to 1.3”. The average drilling cost per borewell went up to Rs. 11,250/- for 4½ inch borewell and Rs. 23,222/- for 6½ inch borewell. The average static level in 2005 in the city has risen to 63’ with an average yield of 2” and the cost of drilling for 4½ ” and 6½ ” borewells have come down to Rs. 6,285/- and Rs. 14,166/- respectively.

The above data reveals that in spite of cost escalations and higher rate of drilling in 2005, the average yield and Static water level of bore wells increased with very high reduction in average drilling cost of bore wells.

Thus the Rainwater Harvesting Structures proved efficient in recharging the groundwater table and hence from 2005 onwards it was observed that the water levels of Coimbatore city have risen in all zones. The present static water levels are between 10 ft to 40 ft depth in all the zones. This shows the efficacy of the rainwater harvesting structures constructed during 2004-05.

The failed bore wells and open wells started yielding enough water for the farmers and industrialists. This change in water levels and the cost reduction in Coimbatore city happened due to the above mentioned activities.

Rejuvenating the 150 RWHSs

While the rain water is getting harvested through Road Side & Open Space Rain Water Harvesting Structures, filter materials on these water harvesting structures are constantly filtering out dust and every other impurities that are carried away through the run off rain water. In due course of time, after a couple of rainy seasons, those materials get heavily silted up and it blocks almost all the water that which tries to get in. Thus, due to the silting factor, the very same harvesting structure hinders water reaching the ground and hence the efficiency of the water harvesting structure is getting reduced in due course of time.  

In order to retain optimum efficiency, these structure demands rejuvenation after a period of time. During rejuvenation, the following things are done in sequence.

1.    Removing reinforced concrete slabs from the top of the structure
2.    Removing filter materials along with the silt from the filter chamber
3.    Washing filter materials
4.    Refilling washed filter materials
5.    Shortfalls of filter materials are topped up
6.    Repositioning same concrete slabs in place

While doing the above towards rejuvenation, water levels and water samples are collected from all these bore wells.  

Among the 150 RWHSs constructed in the Phase I, 100 Nos got a new facelift in 2009, with the financial assistance of various Rotary Clubs of Coimbatore.