On Water and its Management : Experience with Rain Water Harvesting

I live in a large “gated community” in Hyderabad, designed and built by one of the country’s top most construction companies. It is spread over more than 30 acres and includes more than 1000 apartments, Club House etc. The township was constructed starting around 2004 with the last set of apartments sold and occupied by 2010.

Water for the township’s requirements is sourced mainly through HWSSB (Hyderabad Water Supply and Sewerage Board – Manjeera Water) and borewells. When both these fail to supply sufficient water, recourse to tanker water is taken which is both costly and of suspect quality.

The township also has three Sewage Treatment Plants (STPs) with aggregate daily processing capacity of 1,100 KL of sewage and generates around 600 KL of treated STP water every day. This water is used for flushing and irrigating the gardens and plants in the township. This still leaves a daily surplus of around 200 KL of STP treated water even during peak summer, which is currently disposed into sewer lines. Finding a regular buyer would give some regular additional income and the same is being actively pursued.

The developer had provided for a few borewells initially, but within a few years yields of most of these borewells started dwindling. Thereafter the RWA got some more borewells drilled. But the yields of the borewells also kept on dwindling and became meagre and all of them used to go totally dry by the time summer approached.

The RWA then approached outside consultants for advice on Rain Water Harvesting. All the consultants advised to go in for harvesting of terrace rain water and use that water for recharging existing try borewells. A sum of nearly Rs.30 lakhs was spent for this purpose but there was absolutely no improvement in the yield of the borewells. This resulted in severe water crises during summer months with large dependence on costly water tankers.

Around 2019 detailed engineering drawings of an extensive Rain Water Harvesting system built by builder was serendipitously discovered. This system has been designed and built to harvest every drop of rain water falling inside the township plus water from a small monsoon-fed rivulet flowing along the boundary of the township. All the rain-water from terraces and open areas feed into a network of surface storm water drains, which in turn feeds into the RWH system.

The RWH system consists of 15-16 RWH Chambers each 2 meters by 2 meters wide and 4 meters deep. All the RWH chambers are linked to each other by concrete hume pipes ranging from 3 feet to 5 feet diameter, with water flowing under gravity from one end to the other and meanders all through the township. The system is designed to only let the water which does not get harvested to flow into the adjoining lake, which in turn acts as a natural harvesting pit.  Enquiries with sources in builder revealed that the RWH Chambers (RWHC) have been built at sites where percolation was expected to be good as per soil testing carried out by them.

Our records showed that the entire RWH system had not been desilted for the last 12-14 years. A couple of attempts had been made in the past to get it desilted, but the work turned out to be both challenging and expensive and as such further action was abandoned.

There were various challenges in getting the RWH system desilted. First, was whether desilting was operationally feasible with many residents being of the opinion that it was not, since no one had much idea of exactly what was the actual layout like (all of it being deep underground). The second challenge was whether getting it desilted yield any positive results based on the futile attempts made earlier. That is, would the costs justify the results – increase in yield of our borewells. Third, there was also a strong feeling that once the harvested water percolated into the local aquifers, there was no way one could be sure that the water would benefit the borewells within the township, which would be a waste of both effort and money. It might help others but not us. Lastly, was finding competent contractors who could undertake this kind of specialised work.

After a lot of internal deliberation, it was decided to get only three of the RWHC desilted on an experimental basis. As luck would have it, by this time the March 20 lock down took effect and finding any kind of contractors willing to do this work became difficult.

Incidentally, of the many contractors we contacted, one turned out to be the consultant who had advised us to get new RWH systems constructed (mark you this firm has quite a reputation in handling RWH in the local market). When we questioned him as to why he had advised us to get fresh structures constructed when desilting of existing structures would have been much cheaper and hopefully more effective, he gave some evasive responses and then promptly disappeared. It was obvious that the option he gave us would have much better margins for him – he had a perverse incentive in giving wrong advice while we lacked the knowhow to discern this.

We then turned lucky and found a contractor who was willing to do the desilting work. He lacked sophistication but more than made up for it through his practical and earthy approach. In this way we were able to get three of the RWHC desilted (2020-21) and in the process understood the intricacies and challenges of the work. The work consisted of basically sending labourers down into the RWHCs and physically remove the silt from them and the connecting pipes, and then disposing the silt. The silt removed was used to fill up some low-lying areas in the township. What we did find was that the entire RWH system was virtually choked with silt and a total of around 750 cft of silt was removed from just three RWHCs.

The learnings from this experiment were, (a) the work could not be carried out during monsoon months since a humongous amounts of water flowed during this period. (b) the underground channels were inhabited with snakes and other such creatures. This was handled by lighting smoky fires inside the pipes and bursting crackers which drove away any snakes which were there.  (c) the biggest challenge (which turned out the easiest to resolve) was to locate the locations of the RWHCs since the whole area was built up and most of the openings covered. The drawings indicated their existence, but locating the exact position was difficult. This is where our unsophisticated but earthy contractor showed his real worth. He arranged for one of his workers go down the connecting pipes from the one RWH chamber that we could easily locate to the next and after reaching it bang on the cover with his pick-axe. This way we were able to easily locate all the RWH chambers. The connecting pipes being of around 3 to 5 feet diameter it was not difficult for the workmen to move underground from one RWHC to the next.

With the knowledge gained in desilting three RWH chambers a comprehensive plan to desilt the entire system was drawn up and approval for required funds taken. The decision to get the desilting done was also supported by a very knowledgeable consultant, who advised that to maintain the effectiveness of any RWH structure, it should be regularly desilted. Ideally annually, but at least once every two years.

Finally, the entire system was comprehensively desilted during 2023-24 at a cost of Rs.4.40 lakhs and a total of over 4,500 cft of silt was removed. But the proof of the pudding is in eating it, and we were still not sure that desilting would improve yields of our borewells and by how much.

We then waited with our fingers and toes crossed, trying to avoid the snide comments of the nay-sayers, to see the effects of this exercise.

But our faith was awarded. Starting end of 2024 (ie post monsoon) one by one some of our borewells which had gone completely dry started yielding water. We estimate that the value of water we drew from our borewells was more than Rs.30 lakhs during 2024-25. A pretty good return on investment of Rs.4.40 lakhs.

Encouraged by this, we next got the rest of our borewells surveyed and found that as many as 6-7 of them have substantial water yielding capacity. Due to long disuse these borewells had become dysfunctional and lacked pumps, pipes, electrical wiring etc. This is being addressed now, three borewells at a time. The challenge remains as to how permanent is the improvement in yields of these borewells and as such it is considered advisable to go forward with caution.

In future, we are planning to drill recharge borewells in the existing RWHCs to help recharge the local shallow aquifers so as to further improve the capacity and yield of our borewells. This is a low-lying fruit, since the entire structure harvesting the rain-water is in place and functional. Since presently we are not very sure on the cost-effectiveness and modalities of drilling recharge borewells, it is proposed to get 3-4 recharge borewells drilled every year at an annual cost of Rs.2 lakhs and see its effects and slowly extend it to all the RWHCs.

The Ecological Implications.

The Deccan plateau is one of the oldest geological formations on earth and are approx. 3.5 million years old. (The Himalayas in comparison are only about 72 million years old). Over this long period the rocks of this region have got much fractured due to both tectonic movement as well as through erosion / weathering. This is not to say that at various places there are massive sheet rocks. Due to this, nearly the entire underground aquifers around Hyderabad has large water holding capacity. Water which has percolated down over millions of years. However, since we have been drawing out the ground water much faster over the last century than its percolation, the water table has been falling rapidly. This leads, over time, to dig deeper borewells and it also costs much more to draw the ground water from these depths. At many places the shallow aquifers have gone totally dry. Moreover, the deeper we dig to draw out ground water, the worse the quality of water becomes due to contamination with nitrates, arsenic etc.

Furthermore, due to urbanisation and consequent covering of much of the land with buildings, asphalt, and concrete the natural percolation of rain-water has been greatly impeded. This gives a double whammy to recharge of aquifers. To start with we are drawing ground water faster than the percolation and moreover, the natural percolation is hindered.

Another adverse effect from the falling water table is the consequences on local flora and fauna. The native trees of the area have evolved over millions of years to have roots which go down to the existing water table. With rapidly falling water tables, the roots of native trees are unable to evolve fast enough to go deeper to reach the water table. This in turn results in slow emaciation of many of these trees which has started to manifest itself in the phenomenon of their shedding their leaves much earlier in the year than what they did even 10 years ago. An immediate effect of native trees dying out is that the insects and birds who survive in them are bereft of means of survival and this cycle inexorably impacts our very survival.

Some concluding remarks

Availability of good quality water in adequate quantities and at low cost is essential for life to survive. History is full of examples wherein entire civilisations have collapsed due to paucity of water. Much closer temporally, we know that Akbar had to abandon his newly built grand capital Fatehpur Sikri due to lack of adequate water in that area.

Transporting large quantities of water over long distances is expensive and is hardly a viable solution. Such water may be used for specific uses, such as irrigation or supplying drinking water, but just cannot make up for the water the local flora and fauna are used to and have evolved on over millions of years, and thus its continued use adversely affects the local ecology. It is well known that use of canal water for irrigation over time increases salinity and reduces fertility of the soil. It is therefore essential for sustained development and progress to harvest and use local rain water effectively.

And our experience gives us much hope that it is simple, easy, and inexpensive way to nurture our ecology and ensure our own survival.      

In this adventure I initially faced much resistance from within my community as most people were unconvinced on the effectiveness of the effort or the financial expenditure. It would not have reached its fruition without the unstinted support and advise of three of my neighbours and good freinds, Dr. Raghavendra Shivane, Mr. G V Prasad, and Mr. Uday Bhaskar. I am immeasurably indebted to all of them.