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Vol. XXIX No. 18, January 1-15, 2020
Making Chennai water sustainable
Indukanth S. Ragade
isragade@yahoo.com
Apropos your report on Making Chennai Water Positive (MM, XXIX, Volume 16, December 1st issue), may I submit that the various seminars held periodically on the topic of Chennai’s water problem do not talk about the basic factors that contribute to Chennai’s citizens being starved of water which, if addressed, would dramatically transform Chennai’s water scenario! Instead, many bureaucrats and experts in the field advocate the inefficient, costly and environmentally unfriendly desalination as the solution! Listed below are the basic factors to be considered seriously and also the ways of tackling them, derived from my own first-hand experience in the field.
At the Macro-Level
1. Totally inadequate reservoir capacity
Chennai gets abundant rainfall, amounting to 125 cm/year (averaged over 100 years). If fully harvested, it can give a whopping 135 litres per citizen per day! The official claims that failure of monsoon is the reason for citizens being water starved is totally false. The rainfall between 2011 and 2018 was over 100 cm (except in 2018) and exceeded 120 cm in several years.
Unfortunately, this falls over only 55-60 days in the year. We had four reservoirs in 1943 when the population was only 10 lakhs. Today, it is 47 lakhs and we still have only those four. A proposal in 1978 to build two more reservoirs in Ramancheri and Thirukandalam dragged on for 20 years and was given up on grounds of ‘opposition from the local population’. The Veeranam Lake, 200 km. from Chennai, which is supposed to feed the city, is itself fed by the Kaveri River whose water is a bone of contention between Tamil Nadu and Karnataka and is itself often dry. Water from the Kandaleru Reservoir (also 200 km. away) comes only for a few days and half of that is taken away by the farmers en route!
And a new reservoir is yet to emerge!
2. Even the existing reservoirs are heavily silted
All the reservoirs are heavily silted. Even though they went bone-dry several times, no desilting has been done. So the volumes reported to be in them as per the heights quoted are inflated figures! Instead of desilting them on an emergency basis, water is brought in by trains from Jalarpet once or twice to show off the apparent concern of the water authorities for the plight of the citizens!
3. Augmenting the shallow water table
There are many large open spaces – school and college play grounds, public open spaces like the island grounds, areas around the memorials on Gandhi Mandapam Road. If on the lowest point or other suitable places in them, irrigation wells are dug and covered with heavy duty covers with perforations, they will collect huge amounts of rain and enrich the shallow water table. Similarly, in the Public Parks rainwater can be easily channelised into irrigation wells. In fact, I had suggested to the Corporation Commissioner that with the soil level in the Jeeva Park in T.Nagar being below the adjoining road level, the water flowing through the storm water drain can be diverted to the well in this park. Instead, the well was closed down! Such initiatives by the Corporation and the P.W.D. can enrich the water table and enable the neighbourhood to get more groundwater.
At the Micro-Level
1. Efficient and Comprehensive RWH
Although Chennai can claim to be the pioneer in having enacted rules in 2003 making ‘rainwater harvesting mandatory in every building, new or old’, people experienced in the field were not consulted and simple, efficient and proven methods of harvesting were not given in the rules. And hardly three weeks were given to the citizens to install them. As a result, a good percentage of the harvesting structures installed are either defective in design or have gone defunct.
Besides, the rules mandated only harvesting the rainwater falling on the terrace. In many places, the area of the open spaces around the buildings is greater than the terrace area. Since most of them are paved and slope towards the gate(s), all the rainwater can be easily trapped at the gate and got for use by a trench connected to a pit.
Such comprehensive rainwater harvesting can easily yield 35% of their water needs in well-constructed complexes.
2. Implementation has been desultory
Metro Water personnel themselves have little experience in RWH at the micro-level and they are the enforcers of the rules! No wonder that most of the structures installed are of little value. The seriousness given to the implementation is exemplified by the fact that most Government Buildings themselves have not put up RWH structures. Two glaring examples are: (1) the 800 flat complex in the SAF Games Village where senior IAS officers (inclusive the Metro Water Director) and (2) the huge Rajaji Bhavan Complex in Besant Nagar where the Southern Headquarters of the Central Ground Water Board itself is located!
3. Recycling of water used for bathing and washing of clothes
Few are aware that the 2003 RWH Rules also mandate that ‘Every building, old or new, shall treat the water used for bathing and washing of clothes by mechanical or other means and use it for flushing and charging the water table’.
This water constitutes 60% of our total use and if recycled, can make a huge difference in meeting the water needs of the residents. While grandly including this rule, the Government has not given any treatment method. It has therefore remained a dead rule! I have established a simple method to do the job in the garden using no power or chemicals but only soil, sunlight and water-loving plants like Cannas, Banana, Hidechium, Cyperus etc. The CMWSSB has tested both the feed water and the treated water and found that the water is indeed cleaned and is re-usable. However CMWSSB has not shown any interest in promoting it. This water can be charged into the soil when it will get fully cleaned and reach the dug well (see next section) or can be physically collected in large flat complexes and safely used for flushing and gardening.
4. Revival of the traditional dug well
Chennai’s sub-soil is favourable for storing and sourcing water at shallow depths. In fact, it was the dug well that was the main source of water for all citizens before piped water became available. It progressively became extinct because, with the introduction of sewerage, the sewage which went to the septic tank within the premises went into the town sewerage. After the flat complexes came, all the used water went into the town sewerage and wells became dry.
These must be revived because, (1) They can be very easily charged with all the rainwater falling over the premises; (2) The recycled water will also go to the well fully cleaned; (3) Pumping costs will be low; (4) They need to be cleaned only once every four or five years; (6) Borewells cannot be easily or efficiently charged with rainwater, and so cannot yield on a sustained basis and (7) Generally, water at shallow depths is of good quality whereas borewells often yield poor quality.
I have personally provided dug wells in more than 150 complexes built by the company where I was working. They are serving the residents well.
5. Installing a three-compartment O.H.T. instead of the two-compartment tank
If the ubiquitous two-compartment overhead tank invariably provided by builders is replaced, within the same space, by a versatile three-compartment O.H.T. with a set of valves, it will be able to store one, two or three different qualities of water and supply them for appropriate use. Such a tank enables the safe storage of the recycled water and it’s exclusive usage for flushing and gardening in both sewered and unsewered areas.
6. Bad Management of Water in Large Complexes in Unsewered Areas
In most large complexes without sewerage, the sterile 60% of grey water is mixed with the 30% harmful sewage, thereby not only poisoning the 60% but unnecessarily trebling the volume to be treated in their S.T.Ps! The treated water is more than what is needed for flushing and the excess is sent out in tankers to be let off in some waterway. Some even get the untreated sewage itself disposed in waterways!
If only the grey water is treated within the premises and re-used, the capacity of the costly STPs can be reduced sharply. In fact, they can even be done away with and replaced by Up-Flow Filters which clean sewage close to the standards of the T.N. Pollution Control Board for discharge of the effluent on un-irrigated soil. I had introduced it in an 80-flat complex in Tambaram fifteen years ago and it has been operating smoothly since then. Strangely, few sanitary engineers seem to be aware of them!
