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 about 30 acres and includes more than 1000 apartments, Club House etc. Construction of the township started in around 2004 with the last set
of apartments sold and occupied by 2010.
Water for the township’s requirements is sourced through three sources, 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 within 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 Residents Welfare Association (RWA) got some more borewells drilled. But the yields
of the borewells also started 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 the year 2019 detailed engineering drawings of an
extensive Rain Water Harvesting (RWH) 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 underground network 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 rain-water 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 contractor willing to do this work became extremely 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 projects 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 at a cost of about Rs.37,000.
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. Ideally it should be carried out just after end of winter, say between January to March, (b) the underground channels were inhabited
with snakes and other such creatures. This could be 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 RWHCs
since the whole area was built up and most of the openings were 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 underground connecting pipes from
the one RWH chamber and then after reaching the next he would bang on the cover from beneath 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 rewarded. 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 are 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 for harvesting the rain-water is in place and
functional. We just need to strengthen the water seepage capacity. 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 about 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 billion 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 shallow 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 need 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 the shallow 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 own 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.