RWH LEGISLATION – TO HARVEST WHAT? (Written in 2003)
A lot has been told about the benefits of rainwater harvesting in the past 10 odd years. Many methods of harvesting the precious commodity – water – have been worked out, tested and established at the micro and macro levels. Now a government in the ‘over ride mode’ (Tamil Nadu government) has enacted a legislation, threatening households of legal action for failure to put up a RWH structure in place, by a deadline.
There are certain realities we have to bear in mind. The quantum of annual rainfall in an area such as Chennai and suburbs – say about 1200 mm per annum, resulting in some 100 crore cubic meters (Some 3500 crore cubic feet) of water – if fully harvested, can almost satisfy the full requirement of water for residential purposes, hospitals, hotels, schools and collages, even after considering the seepage and evaporation losses. Coupled with recycling of used water, treated suitably, for washing and industrial purposes, the harvest can fully take care of Chennai’s water requirement. This is true for many other cities and towns as well to varying extents.
However, this does not mean everyone will get sufficient piped supply of water from Metro water/ Corporation/ Panchayath. The water being let back in to the soil will have to be mined by the individual households by pumping. As of now, at most places the ground water is hardly potable. But with a good recharge of ground water by RWH the quality of ground water can be expected to improve substantially.
However the area covered by all residences in the heart of the city will be hardly 50% and as we go outward it will reduce to less than 10% at the suburbs. The rest of the area are covered by roads, railway tracks, public buildings – schools, collages, hospitals, offices, factories, bus stands, railway stations – parks, rivers, tanks, unused residential plots, beaches etc. Even out of the area covered by the residential premises, hardly 30% to 60% (going from suburbs to heart of city) is covered by the buildings proper. What the legislation is trying to cover now is the 60% of 50% to 30% of 10% area i.e. 30% to 3% area in urban and suburban areas. Even now considerable amount of water falling at the un-concreted area is going back in to the soil only and the excess water from these concreted (30% to 3%) and un-concreted (20% to 7%) areas in residential premises is flowing on to the roads covered by the remaining 50% to 90% public areas under the direct control of the civic bodies. This means practically almost the complete 100% rainwater is at the disposal of the civic bodies, if we assume that the individual residential buildings do not harvest rain.
Many educated and sensible households have already installed RWH systems voluntarily and their response to such a socio – individual cause will be better without legislation, than with legislation. The remaining people, who neither can understand the benefit, nor care for others, are not going to respond the desirable way. They are only going to look for ways to manage (circumvent) the legislation. In simple words the legislation will only end up fattening the pockets of the councilors and other civic body officials. The desirable effect, if any, will be more than offset by the undesirable effects.
Hence instead of harvesting rainwater, the legislation will only end up in making the councilors and civic body officials harvest currency. I leave the amount involved to the imagination of the reader.
If the government means business, efforts should be intensified to harvest the water from the 50% to 90% remaining areas than the built up (residential) areas. Anyway even the un-harvested water from the 50% to 10% residential built up area is only flowing in to the remaining 50 to 90% areas. The water that collects from the overflows from houses in to the road along with that falling on the road it self, can very well be harvested by storm water drains and percolation pits dug at regular intervals. The percolation pits are required in the heart of the city, where the storm water drains have to be lined with concrete. In the periphery and suburbs the drains can be open earth dug up type, which will directly allow percolation. Further the storm water drains on either side of the roads, should be connected at the ends of roads and in turn with the other drains etc. leading to the surplus water draining in to temple tanks and other public ponds. Where there is no such pond (for example T. Nagar area), percolation ponds should be dug at parks and other public grounds (Panagal park etc.). This is not any new idea. This is just reviving the age-old practice of our wise ancestors. Only the greed of the modern man has deprived us of these things and we have to revive the age-old practices at least now, having been driven to the wall. The RWH system in its full form should be implemented at all public premises as listed above. The RWH system for such public premises should be designed not only to harvest the water falling on the roofs, but the complete water falling on the premises. Thus the RWH can very effectively cover almost the whole city.
In addition to these, a very cost effective way to do RWH will be to stop the water flowing through the rivers and nullahs, draining in to the sea, as all the surplus water after whatever is absorbed by earth from the whole metropolis drain in to these rivers and nallahs only. Check dams constructed at a number of places such that water remains stored in the river up to a height of just a meter below the neighboring land mass will ensure immediate increase in water table. Anyone doubting the cost effectiveness of this can just visit a couple of villages near Chennai itself, to see for himself how cost effective this can be. Using just the available rocks and gravel at these places and cheap labour (may be even free labour – shramdan), many such structures have been built in every rivulet and nullah apart from enveloping the hillocks by a water retaining bund. No need to mention the benefit. When the Government says ‘building check dams in Adyar, Coovam and Buckingham canal is not cost effective’, they should only be meaning ‘not cost effective for the ministers, legislators, councilors and officials’.
The Government finds it worthwhile putting up a flying train (MRTS) spending several thousand crores, pouring in millions of tons of concrete, only for a few railway employees traveling with free passes, finds it not cost effective to harvest some 100 crore cubic meters of water flowing through these nallahs, by constructing check dams, spending a fraction of what it costs to build the concrete junk of MRTS. Only people both living and working at walking distances from the stations find the MRTS of any use. Even that diluted by the fact that the frequency of the trains is much lesser than the bus service and the bus service covers a lot of interior areas and we have about 40 to 50 bus stops for every train station and lastly the bus charges are much lesser than the MRTS charges.
Apart from ensuring a very effective RWH as a long-term benefit, the check dam project will give work to a huge labour force for a few months. Needless to mention that such a project should be implemented with maximum use of labour force and absolute minimum of machinery. To make the project even more cost effective, the check dams should be masonry ones initially. They can be concrete lined in due course and in phases. It will be better to entrust this work to NGOs like Ramakrishna matt, Satya sai trust, Exnora, Sarvodaya etc. so that the benefit reaches the poor unemployed labour force and the contractors are not allowed a bumper ‘harvest’. By making it a labour intensive project, the Government can utilise this opportunity to apply a little bit of balm on the gashes created by the World Bank/ IMF regimes, the Globalisation and liberalisation process.
Needless to mention that the check dam building should be preceded by the installation of drainage pipes along the banks of the rivers and to ensure that the river water is not polluted by sewerage. This work is anyway long overdue and the cost of the work need not be considered as RWH cost. In fact after installing the drainage pipes, de-silting and putting up the check dams, the stored water can even be treated and supplied for secondary domestic use initially and even for drinking purpose subsequently.
In fact these RWH at public places will be much more cost effective (for the public) than the RWH at every house. The RWH in every house will mean spending Rs 1000 or so, by some 20 lakh households or so (i.e Rs. 200 crores) just to harvest a fraction of the precipitation, as against harvesting 100% by the RWH in public places costing much lesser than the above 200 crores plus what the government will have to anyway spend for RWH at other places. The benefit will far outweigh the cost.
As for the RWH in rural areas are concerned, quite some work – as mentioned above – have been already done in many places. This work should be further intensified. The government legislation now is calling for harvesting those few liters of water falling on the roof-tops of tiny huts in villages, which is anyway falling on the ground and is getting absorbed by earth. The cost of putting up such RWH structures in village huts as a percentage of the cost of the hut itself will be prohibitive and will yield no tangible result, as the area covered by roof-tops in a village will not be even 1% of the total area.
When in doubt, just ask the elders in the village about watershed management. They will teach our MBAs and IASs, the what, how, why and who of it. No need to refer to World Bank report on this. We have enough local wisdom on this issue as in many others. A conscious effort in this direction may one day even result in eliminating dependence of water flowing down the Cauvery from Karnataka for cultivation. The rainwater falling on the landmass of Tamil nadu, if harvested fully by local absorption – by check dams etc. (not by harvesting roof top water, which anyway falls on the ground and gets absorbed) – may be sufficient for Tamil nadu’s irrigation needs with suitable adjustments in cropping pattern.
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