In a previous article Importance of maintaining surface water bodies (April 2), the role of traditional surface waterbodies, known as eris, in areas of low rainfall was noted. The importance of eris as appropriate irrigation devices for the cultivation of paddy, as flood-control devices, as backup in periods of low rainfall and as crucial to the overall ecosystem was also pointed out.
The eri system is an invaluable treasure that we have inherited from our ancestors. However, in the last couple of centuries, they have been in a state of neglect. In the recent past, eris have been not only neglected but also abused. They are very good rainwater harvesting (RWH) systems created primarily for agricultural purposes and hence very relevant in rural areas.
Neglect of eris in the rural areas has led to the overexploitation of groundwater both through open wells and deep borewells. The open wells, which are sustained through seepage from the eris, have gone dry because of the neglect. Deep borewells tap the deep layer of the aquifer found within rocky strata. This is not easily sustainable by all the recharge activities carried out as part of rainwater harvesting. This has led to borewells going deeper and deeper and has been partly responsible for farmers’ suicides. Rural Tamil Nadu has become water-stressed only because of this. This cannot be reversed unless the eris are given a new lease of life.
An important aspect of the eris is that they should be maintained properly and periodically for them to play a useful role. Maintaining these waterbodies is as important as creating them. This involves desilting of the eris, the inlet and outlet channels, strengthening the bunds, repairing the sluices and the overflow structures. During British rule, the resources of the village communities were taken away and the task of maintaining eris was given to a government department. This led to the inefficient functioning of the eris and ultimately to their decay. Failure to desilt them periodically will result in the reduction of the effective volume of the waterbody, giving an impression that they are full even after a small shower. Once this happens, eris may not be able to supply water even for a single crop when traditionally they would have supplied water for two crops and in some cases even three.
Due to urbanisation, some of these eris located in urban and peri-urban areas may have lost their relevance in agriculture. Still they can continue to play a useful role as reservoirs supplying fresh water to the surrounding areas.
This is evident from the fact that four such eris—Puzhal (Red Hills), Sholavaram, Chembarambakkam and Veeranam—have been important water sources for Chennai. Several others in the CMA (Chennai Metropolitan Area) and the extended area of the city are not freshwater sources as of now but can become supplementary decentralised sources in future. In addition, there are a number of such eris in the neighbouring districts of Chengalpattu, Kanchipuram and Thiruvallur. There should be an effort to pick out those that have lost their agricultural relevance, in order to repair, rejuvenate and use them either as freshwater sources for the immediate use of the neighbourhood and/or as recharge ponds to build up the aquifer.
There should also be an effort to immediately revive the eris that still exist in Chennai. These can be potential sources of fresh water if large quantities of rainwater are made to collect in them. If this is done, they can act not only as freshwater sources and help recharge groundwater but also mitigate floods. And Chennai can become self-sufficient in water.
Many old eris are gradually dying and disappearing into urban extensions and building sites. Such blind and unplanned expansion of urban areas needs to be halted. The city of Chennai is an example of such expansion. What was once a landscape full of eris has been converted into a city and its suburbs, by filling in all the old ones. The result is that there is no way of holding rainwater and recharging groundwater. Instead, during periods of heavy rainfall, entire residential areas become water-logged since they are “low-lying”.
In the extended area of Chennai as well as in the CMA, there are several eris, which having lost their agricultural relevance, are being considered as useless. It is very difficult to even imagine how the eris, which are such magnificent RWH systems, could be ignored, neglected and abused by way of encroachment, and dumping of solid and liquid waste into them. Dumping wastes makes it difficult to revive and rejuvenate them. In several cases, state government offices have come up in eris and the state housing board even promoted a housing scheme in one and gave it the name of the eri!
It must be still possible to harness the run-off waters from a large portion of the semi-arid tracts of India by a proper extension of the indigenous eri technology. Without a proper study and understanding of the eri technology, modern civil engineers will not be able to play any innovative role in providing water to regions in India, which have become perennially “drought-prone”.
T M Mukundan
Founding trustee of Centre for Policy Studies. Also an Yoga instructor & Ayurveda scholar
(t_m_mukundan@rediffmail.com)