Nair's Residence: An example of a Sustainable Water Management plan

Mr. Nair, a client who had retired from his active career and a man who enjoyed doing hands-on work approached us with a view to install a rain water harvesting system for his house in North East Bangalore. He could easily be counted as an eco-convert as he himself believed and was interested in many a green thing. He came to us at time when the construction of his house was nearing completion. We saw in this proposition of his an opportunity to address this in a more wholesome manner than just providing a system to satisfy his demand. Read on...

Project facts:
Location: Horamavu, Bangalore
Site area: 568sqm (approx)
Roof catchment area: 198sqm (approx)
Ground catchment area: 285sqm (approx)

Site plan: House on the east and landscaped area on the west 

The site was two plots of land with the eastern section being the house which was being constructed then adjoined by a vacant piece of land to it's west. This vacant land had a small patch of green,fruit and vegetable plants that Mr. Nair painstakingly maintained himself. At the north west corner of the site was a store which was to also include a driver's toilet later.
At IGH we believe that it is immensely more sensible to have a comprehensive strategy which involves reducing the water need first and then managing demand of water (through rain, etc) efficiently than blinker-eyed isolated interventions. Therefore we expanded the scope of just the rain-water harvesting proposition to a comprehensive water management scheme that took into account the following:

• Rain water harvesting- to catch all the rain that fell on the building's roof and the site
• Water conservation measures- to reduce overall water demand
• Grey water treatment- to reuse water that would otherwise be wasted and reduce fresh water demand
• Landscape and irrigation design- to ensure minimal use of water for external use

Comprehensive Sustainable Water management- Nair Residence

RAINWATER HARVESTING
The roof area of the house, approx 198sqm, was large enough to potentially harvest about 1,47,000 lts of water annually in Bangalore. This would meet an optimised water requirement of the Nair household of 5 members for about 9.8 months in a year- which can be a very substantial saving if rain water is managed well. Since the ground catchment area was nearly 1.5 times that of the roof, we suggested that Mr. Nair undertake surface water harvesting too, beyond just limiting it to roof rain water harvesting.

The overall plan was to use the rain water from the roof top for domestic consumption, as this would be relatively cleaner water thus requiring minimal filtration, while the surface rain water (water falling on the ground/ garden) would be harvested for ground water recharge to supplement the aquifer.

Roof Rainwater harvesting system

Roof top rain water harvesting:

The rain water down-takes from the roof of the house were already in place. The exposed roof area had 7 down-takes that were lead into the rear of the house, below ground level and already cemented over. This turned out to be a major limiting factor in the design of the RWH system as it did not allow for an above the ground, in-line system which could have been far sleeker than the underground system which was finally put in place, specially the first flush and filter units..

An important prerequisite for effective roof top rain water harvesting is the regular maintenance and cleaning of the roof. Though Mr. Nair had a 10 kl underground sump that would suffice the requirements of rain water storage, he opted to go for a separate underground tank as he did not feel comfortable about mixing rain water with that in his main sump. The terrace- the catchment for roof top rain water harvesting- he felt, despite his efforts to keep it clean, would have more contaminants than anticipated and so he wanted to play safe in separating the rain water from the main tank.This however, remained a contentious point as the source of his sump water was from a bore-well, definitely of a lower quality. A little more attention to keeping the terraces clean and less money would have been spent.

The rain water harvesting system designed here included:

• Collection chamber to collect water coming from the down-takes via a combination of 3 and 4 inch PVC pipes. A sieve as leaf separator, placed on an incline, was included in this chamber to keep large particles out of the system. An overflow at the top level of this chamber led the water into the first flush chamber. 
• First flush Chamber to flush out a specific volume of the contaminated first rains.The initial rains falling on the roof (especially after long dry spells) is usually contaminated by dust, bird droppings and other particulate matter. Depending on roofing material type, ambient pollution levels and total roof area a certain volume of water from these initial rains needs to be flushed out of the system to keep the system clean. A simple water level dependant float based diversion system was designed to be the first flush here. A dripper driven mechanism ensured that the water from this chamber was drained out over a period of 3 days after which the first flush would reset. The over flow from this would be cleaner water that would enter the filtration chamber. 

First flush diversion system

• Filter to further clarify the water - Three grades of aggregate (top layer- 40mm, middle layer- 20mm and bottom layer- 10mm) in mesh cages, for ease of maintenance, are placed one over the other as filter media in this chamber. The outlet at the base of the filter leads the filtered water via a levelling chamber into the storage tank. 
• Rain Water Storage tank to store the harvested rain water. A 5000lts capacity tank was designed with its overflow leading into a central water feature meant for ground water recharge. Though BWSSB regulations specify a minimum storage capacity of 20lts/sqm of roof area, which would have meant 3600lts, we thought it prudent to provide for a storage tank that would meet the water requirements of the family for about 7 days. Water from the rain water storage tank is pumped into the main sump from where it would be further pumped into the over- head tank for domestic consumption. Had the rain water harvesting system not been an afterthought, as it turned out to be, the plumbing could have been managed appropriately, integrating the RWH system with the main plumbing, to ensure a single operation of lifting of water from UG sump to the over head tank. 

System Maintenance: Each of the chambers have their own separate access hatches for ease of maintenance and upkeep. The dripper out from the first flush chamber needs to be checked for clogging. Setting the dripper to fully open position and then resetting it to desired flow ensures that it will remain clog-free, provided terrace is well maintained. The filter media (aggregates) is placed within steel meshes. This needs to be removed once in six months, brushed and washed with clean water before being replaced. The rain water storage tank is to be cleaned seasonally, ideally at the end of the monsoon period or along with general maintenance and cleaning of the main sump.

The surface rainwater harvesting scheme integrated into the landscape

Surface rain water harvesting:
Surface rain water recharge
The ground catchment area was about 260sqm. We designed a network of surface water harvesting systems which were a combination of recharge well, boulder trenches and a central pond. These were integrated as elements in the landscape design and for effective ground water recharge. 

Here again the regulation specified a minimum capacity of 10lts/sqm of open area (about 2600lts for this project), but we designed the system to be capable of handling a heavy rain of about 40mm in one day (Bangalore gets an average rainfall of about 16-20mm per day) and so for about 9100 lts. The recharge well can handle about 2000lts, the boulder trenches about 4500lts and the central pond about 2600lts.

WATER CONSERVATION MEASURES

The use of water efficient fixtures can reduce the overall daily water requirement by almost 30% depending on usage. It goes without saying that one can be wasteful even with most efficient of systems.

As we began chalking out measures for water conservation in this project, we made a list of fixtures- faucets and flushes that could help conserve water not knowing initially that Mr. Nair had already procured his sanitary and plumbing fixtures at the time of our engagement on this project. We however, convinced him about exchanging his fixtures- basin/ sink faucets and shower heads mainly, with more water efficient ones. Sadly, he had already gone ahead and installed the flush valves, which prevented us from securing about 15-20 lppd through the use of more efficient options.

Water efficient fixtures 

Extensive market surveys were carried out following which we made our recommendations about fixture selection. We assisted Mr. Nair with procuring recommended fixtures by tying up with suitable vendors. During this process of surveying the market we realized that the choice at the hands of a client was very limited, especially if one were to look for 'made in India' products as being water conserving. On the other hand the market seemed flooded by imported fixtures thanks to stringent water use laws in those countries. 

The few fixtures that met our needs seemed more abundantly available in the product manufacturer's brochure than in the market or the display shelves. Clearly, the consumer saw too little of these products and therefore wanted them even lesser. The general notion of most vendors was that these water efficient fixtures were solely meant for gaining points in green ratings and therefore applicable in large projects- hospitality or offices and hardly for individual homes, which was our area of application. Vendors did not seem too keen on pushing these water efficient fixtures and kept almost no stock of them because these, according to them, were not fast moving items. The sluggishness of the distributor to procure small quantities of these specialized items became increasingly evident as we had to keep moving from one to another.

An efficient landscape drip irrigation system was outlined as another means of conserving water. The treated grey water was to be reused for landscape irrigation, thus reducing the overall water requirement.

GREY WATER TREATMENT
Mr. Nair had already on his own accord chosen to separate the grey water line from his soil line. So water coming out from the basins & bath areas in the bathroom and the kitchen sink, known commonly as grey water having fewer pathogens was piped out on a separate line. Most waste water treatment systems available in the market do not cater to scales as small as that of an individual home. They also invariably are  mechanical systems that rely on an energy source. We wanted this grey water treatment system to be able to function without consuming power and also blend into the landscape. After much research and deliberation, we decided to go in for a reed bed based grey water treatment system. We worked on that integrated other plant containers apart from the main reed beds, and ensured that the whole system became a part of the overall landscape.

Grey water treatment system

The system we designed had the following sections

1. Grease trap to separate out the grease and oil which would otherwise retard the system's functioning. Kitchen sinks are large contributors to oil and grease. It is important to remove, to the extent possible, these materials. This is achieved by a grease trap which is a chamber that has two baffles. These baffles cause water to flow between them in a manner where grease floats on the top and gets arrested between them. The overflow is grease free and the water is lead into the nest chamber which is a sedimentation tank. Obviously, exercising caution at the source could potentially reduce the loading on the treatment system down the line.
2. Sedimentation tank to separate out large particles. This chamber has a single downstand baffle which assists in sedimentation of suspended solids, that persist in the system, by gravity. The sizing of this tank was based on a two days standing time. The overflow from this chamber is at an upper level and feeds the gravel bed. 
3. Gravel bed to further filter the grey water. A graded gravel bed consisting of three descending grades of 40mm, 20mm and 10mm is used as a first stage filter for the water coming from the sedimentation tank. The partition walls of this filter bed were made as a perforated brick masonry walls with the overflow from here leading into the planted filter bed.
4. Planted filter/ reed bed to oxidise and treat the grey water. A process of secondary filtration, the reed bed system relies on the ability of certain types of plants to decompose the organic pollutants present in the water. The water is held in this planted filter bed for a period of about 2 days before being let out and stored in the treated grey water tank. The plants/ reeds used in this project were sourced from a lake nearby the site itself. 
5. Treated grey water storage tank to store water before being re-used. Water entering this tank is relatively clean and odour-free. It is now ready to be used for landscape irrigation. 

System Maintenance: Each of the enclosed chambers had their own separate access hatches for ease of maintenance and upkeep. The grease trap needs to be checked from time to time and the excess trapped grease removed from the system. General cleaning of the sedimentation and storage tank would ensure the removal of any minimal particle settlement. The gravel bed and planted filter beds need to be kept weed free and de-weeding undertaken as required. The reeds are to be maintained and can be done along with general garden upkeep.
This simple decentralized system of grey water treatment has been functioning efficiently since its completion in early 2010..

LANDSCAPE AND IRRIGATION DESIGN
As mentioned above, the site was actually two individual plots that Mr. Nair owned in a private layout. He built his house on one and on the other he had plans of maintaining a garden.

We expanded this mandate to integrate within the landscaped area the rain water harvesting systems, a reed bed based grey water treatment system and surface water management system apart from a kitchen garden, patches of native flowering plants and fruit trees that would attract various life forms. There was a requirement to have a kennel and a store with a driver's toilet too in this landscaped area.

A view of the landscaped area

The orthogonal grid for the landscape was formed by extending the logic from that of the built, a straightforward, rectangular building. A central water body, the pond (see surface rain water harvesting) with a pervious base was designed as a seasonal water body that would contain surface run off water in it during the monsoons and would dry up in the summer months- much like the tanks that once dotted this city. Around this pond was the permeable walk way which lead from the house to and around the landscaped area. The walkway was paved with open jointed paver stones with grass in intermediate spaces to ensure that it allowed water to percolate into the ground. By the side of the walk way on the south is the boulder trench, again meant for surface rain water harvesting. A secondary path of stepping stones led from this walkway to individual spaces like the store etc,.

The cascade from the driver's cabin roof to the central pond

The built- store cum driver's toilet- was designed to have its roof as a water cascade. The surrounding plot of lands were still vacant and so Mr. Nair had already built a compound wall along his plot's boundary. We used two of these walls on the north east corner as the back of this built feature. It's front was a rough hewn stone masonry walls with precast ferrocement troughs inserted for the water cascade. This water cascade was fed by re-circulated water from the central pond, powered by a small solar pump.

After some deliberation on the roof of this built section of the landscape, we decided to go with a ferrocement roofing system which would be supported on steel lattice girders and concrete beams anchored into the boundary wall. On the roof of the toilet was the drip irrigation tank that was fed by the treated grey water.

This project attempts to demonstrate how individual home owners could work towards resource independence- in this case water. By adopting measures first to reduce water consumption, efficiently harvest rain water and finally reuse and manage water sensibly, this project aims to optimally utilise a resource as precious yet heavily abused as water.

The two sides of water

Drought and flood are two sides of one coin, Water. The people of Rajasthan and MP are those who experience the drought while Bihar experience worst o floods in India. But interestingly most other states have both extremes in different parts of the state. In Karnataka the north districts are water scarce while the coastal south districts have flood related hassles. In all cases it is the populated cities that face the worst of all. Certain level of balancing of such a situation is possible if large scale Rain water harvesting and recharging activities are taken up. The cities face water scarcity or flood only due to manmade disruptions. Just look at Bangalore. The networks of beautifully connected lakes have vanished. The city’s eco system has gone for a toss. I fear many of such disruptions are irrevocable and we have to face the fury of weather. We wait for the worst to happen to take the first step.
One unexpected summer rain boosted my confidence about the Rain Water Harvesting and water security. With one day’s rain on 23rd April 2011, the entire 10K litres sump was filled. A straight monetary saving of Rs.400/- that I would have otherwise spent on tanker water. The sight of the filled sump with clean rainwater is an overwhelming experience. While I was checking my sump I saw my neighbour getting his water tanker to fill his sump. I felt one should be ashamed of not harvesting the safest and purest water and depending on subsurface water which would have all kind of toxins in it. In most situations, rain water requires purification for visible impurities and biological impurities by means of a normal UV filter. But the subsurface (borewell) water requires a RO filter in addition to remove the toxins.
The RWH filter that I have installed did its duty of removing all dirt particles and the water appeared just like well water or even cleaner. With such a rain, the water collected in a day could be enough for close to a month! I wish if I had some more extra storage facility to secure all this water.
The very next day I read in the newspaper that in some area there will not be BWSSB water supply for 3 days. And the other news in the same page is about the havoc caused by the heavy rain in many areas including flood. What a contrast!
While the city face severe water shortage and most people worry and blame the BWSSB for failed supply. Very few would have done something to harvest and use the rainwater. In the outskirts of the city I am a happy man without any worries when I read there is no water supply.
On the one hand we let the fresh rain water go down the drain while on the other we face serious water shortage. Individually all of us are responsible for this. Every individual, irrespective of where they live- independent bungalow or apartment, can prevent callous rainwater runoff. A small recharge pit within the compound would be able to percolate a lot of rain water. One could also use the existing sump for collecting the rainwater by using an efficient filter unit. Imagine what the impact of several lakh houses doing this would be! The drainage system will not be overloaded with rainwater and filth that it carries. If government organs like the BBMP could take the initiative in having several protected ground recharge pits along the drainage system that will stop the water from flowing down to the main stormwater drains. Beyond recharging the surface water source such simple design internvetions would also help to avoid flooding in many areas.
If we are serious about solving the water related worries, we must give some focussed attention to Rainwater harvesting. The few thousand rupees that one spends will surely pay its dividends. One need not worry too much about system maintenance as it is not going to be a major hassle. It just requires a nominal care that any such precious resource would demand. Take this from me as somebody who has experienced the joy of being independent (to a great extent) starting with water.

We could have been the 'People of the tanks'

I guess most of us will be saying, "what is he talking about?" But, that is just it. Bangalore is set in a landscape of a 100 tanks (for a lovely insight read the book "Deccan Traverses'), has had a history that recorded for over 400 years.

Many of us know of the lakes around Bangalore, but that is part of the change brought in by the limited understanding of our administrators and planners. The system stretches from beyond the Northern boundaries of our city limits and goes beyond the point where Cauvery plummets many levels at Sangam, making all of us in the lands of Ramnagaram, Maddur, Mandya and Srirangapatnam inhabitants of this landscape. Even more significant is the fact that this fabric of tanks is a result of human actions. Yes, all of this is man-made! The will of the people made this landscape and it is the lack of it that is fast erasing it.
So why 'tank people'? Well, it formed the very life fabric that sustained this slice of civilisation. Each village/ hamlet had a tank of its own or shared a large one. These tanks would fill up during the monsoons and drained out water through a system of overflow valleys. The tanks would loose their water through the dry months, some completely and would leave large amounts of silt behind (a result of sedimentation). This silt formed crucial building material, for mud mortar/plaster and even for earthern walls, and was also used for agriculture as a nutrient rich soil. Most importantly, these tanks would help in recharging the ground water table. Potentially, these tanks can help in sustainably recharging rainwater for over twice the current population!! The landscape would change with the cycle of seasons, the tanks filling up during the monsoons and transforming into silted depressions for the drier months. This was the same space that we now occupy.
So where is this land that our city is in today?
The death knell was sounded by some interventions during the colonial rule... the closure of tanks, the conversion of drain valleys into narrow nallahs... stone lined channelways. Then came the babus and state government planners (post independence) who did more damage in the last 60 years than in the 200 plus years that the British occupied this land. Closure of tanks, treating them as lakes (completely misunderstanding their purpose and characteristics), and reducing this system to a pale reminder of the past.
So what is different?
The most significant change is that of identity and association. The link between tank and habitation has been forgotten. We no longer see them as great catchments of precious rainwater runoff. The nallahs, once percolating drain valleys, have been concreted and thinned clogging the system, or, encroached upon... causing great damage to both life and property every time we have even a good shower. The change in attitude is very visible in the health of these nallahs and tanks. They stink, sewage flows illegally into these systems in innumerable points. Many tanks have also been converted into permanent water bodies.. with stone masonry walls and pretty landscaped gardens to 'beautify' them. Probably the greatest change was the import of water to feed this city's population (executed during British times) from over 100 kms away near Mysore and therefore pumped up to over 900 feet! .... something that was never done for centuries before. Arguably, the population has also increased multifold over the last 100 years, but how do we explain that we had a water management system that could cater to twice the current population? This turning of our backs on a constant sustainable rainwater collection and recharge system combined with a callous and greed driven boring of our aquifers has resulted in falling groundwater levels.
This has changed the very way we live... our water comes from an unseen source (almost magical) so we dont see the link between these tanks around us and the water in our taps. The governments constant crowd pleasing statements of increasing supply 'to' the city has always conveyed the message that the solution for our water woes lies outside this system. This complete faith in long piped systems is also reflected in the city's wet waste treatment plants, large systems that are supposed to handle and treat the sewage from large quadrants of the city. This has also had an impact on the water equation of our city. Nearly all the water consumed by the city's inhabitants is drained out (inefficiently) only to be treated and led away from the city. In the original system, all waste water would find its way into the ground, filtered through rear yard broad leafed high-capillary plants and through the various layers of the earth.
Just take a look at that. Water was captured right around where people lived, allowed to filter into the ground, drawn out through open wells... and was recycled after consumption through a biological treatment system, again within the habitation limits. (of course, people did not waste great volumes of water in flushing)
This is what we today call a sustainable water loop. There is still hope, i think. The steps are obvious.

All it took was the will to do something....

Here is something to exemplify our mindsets towards easily addressable, everyday issues. The community that I recently shifted into (Aug 2009) was where most of the residents knew each other for over 15 years.

The night I moved in I discovered (to my sheer horror) that if it rained even the least bit the entire area in front of my house gets flooded. I spent the next few days engaging with my landlord, my neighbours and the 'residents association' determining the magnitude of the problem and what their plans were to solve this. Beyond the usual discoveries of a bad layout plan, encroachment on land and blocking off of natural drainage, I also found out that the six families (of the 82 that formed the enclave) that stayed around me had tried in vain to address this but their cries for help fell on deaf ears. Replies ranged from, ".... we have forwarded the complaint to the BBMP", to, ".... how is it my problem?" and "...nobody will pay so much when it does not affect them".

The situation had reached such a stage that my neighbours had started modifying their lifestyles to 'live' with a flooded situation for a few months in the year. While some waded through the water to cross over to dry land, the more inventive ones had placed stepping stones to hop across their watery frontyards. My landlord had even been ill-advised to put up a metal mini gate to hold back the water... a kind of check dam!! My neighbour had increased the height of her sump cover to ensure that water did not enter. The more desperate amongst them (tenants like me) had simply shifted out. This situation had now lasted for over 4.5 years.

I gave my landlord and myself about a month to try the 'reaching out' one final time. When a month and a half passed I called my landlord and requested him to organise a meeting of other landlords and tenants to discuss possible solutions. No one was interested. Some had given up. There was an underlying fear that any solution would cost a lot. This was further influenced by their conviction that resolving such things was the problem of the authorities that be.

So I went ahead with finding a solution myself. I had been taking pictures of the flooding over the month or so that I had been here. I determined the local drainage and slopes, the volume of water that collected on different days and scoped out areas where I could divert the water. I had two choices- one, to drain out the water away from this low-lying portion of the enclave, or, two, to percolate the water into the ground. The latter seemed the more attractive and easier choice (sort of).
The volume of water to be tackled (about a 40,000 litres of water in a moderate shower of rain), the area required and the percolation properties of the soil there were my variables. I found that the land sloped across the road to a common, neglected strip of land (about 3 metres across and about a 100 metres long), and I found through a simple infiltration test which showed me that I could percolate about 3,000-4000 litres of water an hour.
I employed a team of 4 labourers, cleared the common land across the road. This had become a dumping ground for all kinds of muck from the very same homes. It took us 5 days to dig a trench about 1.5 metres in average width, about 0.6 metres in depth and about 15 metres long, another day to make a detail (using some waste drain pipes) to divert the water into the trench, yet another day to line the trench with gunny sacs (reject from a local departmental store), and a final day to clear the road and surrounding area from slush generating silt/earth and fill the potholes with 10 mm stone jelly. In all it took 8 days.
To increase the percolation, two concrete rings (3 feet in diameter) were inserted in the wider section of the trench. A layer of stone jelly was filled around the concrete rings adding a filtering medium of about 10 cm. Care was taken to provide a block at the holes on the ring to keep the jelly from pouring in.Now I intend planting around the entire trench, providing a couple of benches made from waste stone and construction debris (from a house being built nearby).... creating a positive space for the community.
Does it work?? Well, it handles a normal rain of up to 8 mm in a couple of hours with ease. Heavy rain showers do create the ponding effect, but it all this water percolates over the next few hours (I have added the picture in another post). The system has been tested by many days of rain, and the nearly an entire rain cycle in the year.... We dont have the nightmares of water standing around for days (yes, we do have to live with that for a few hours)... and the community now recharges about 40,000 litres of rainwater in a normal rain shower.
What else can we do to better this system? To solve the issue of any ponding (once and for all), we would need to increase the capacity of the initial holding system. Which would mean percolation pits, tanks, wells that would hold a volume of about 40,000 litres of water. I have plan to start on that soon.

All it cost me was Rs 5,600/-... the irony was that this was less than what it cost my landlord with his mini check dam and my neighbour's sump cover remodelling.
A return to normalcy, a reduced mosquito menace.... an end to about 5 years of woes.