Adarsh Palm Retreat (APR) is a layout in Bellandur with both villas and high-rise apartments and occupies 128 acres of land. It lies adjacent to RMZ Ecoworld and borders the Devarabisanahalli lake.
The villa complex occupies an area of 110 acres and houses 798 villas. This case study focuses on water management strategies implemented at the individual villa level in APR.
Figure 1: Adarsh Palm Retreat villa complex (left: map location, right: google earth view)
1.0 Background
APR villa complex is located next to the Devarabisanahalli lake. Given this low-lying area, many of the houses have been facing basement seepage and road flooding issues during the rainy season right from its inception in 2004.
To tackle this issue, some of the villas have implemented water management strategies that included rooftop rainwater harvesting, digging recharge/withdrawal wells and reuse of STP-treated water for the gardens in the common areas.
2.0 Sources of water and its storage
The layout has a BWSSB Cauvery connection. There are also twelve borewells in the premises, of which seven are yielding. The depths of the borewells range between 1000 and 1100 feet. The layout has also implemented rooftop rainwater harvesting in its common clubhouse. All the water from these sources is mixed in a common raw water tank. During the non-rainy months, the complex is heavily dependent on tanker water, which is mixed into the raw water tank. Water from this tank is then passed through a water treatment plant (WTP) and supplied to all individual villas.
There are three withdrawal wells (about 25 feet deep) in the common areas from which water was intended to be pumped and sent to the raw water tank. Since these are placed between some Royal Palm trees, the roots have been making the maintenance of these wells difficult. Hence, the community has been unable to use these wells efficiently.
Table 1: Water sources in APR
3.0 Water management in individual villas
Rooftop rainwater harvesting has been mandated by the association and based on anecdotal information, has been implemented in about 40 villas as of 2022. Recharge wells have also been dug in many villas for groundwater recharge. Many of these houses have channelled the rooftop rainwater into their recharge wells directly.
Automatic motors help pump out water from these wells once it reaches a certain level. In some houses, the same water is pumped into an overhead tank for non-potable use in the household. Hence, these recharge wells are converted to withdrawal wells whenever they are able to hold water during the year.
Here are stories of four villas that face seepage issues regularly. None of the houses in the stories captured below have an underground basement.
3.1 Swathi’s house (Villa 298)
Swathi is an avid gardener and has a large rooftop garden in her house. Due to this, the water harvested from the rooftop is not being stored in a separate sump and is being channeled directly into a two-year-old recharge well in her backyard.
She does not have an underground basement but has been facing seepage on her ground-floor walls. Biome visited her house during the heavy rains of September 2022. A month and a half prior, she had installed a motor inside the recharge well to use the water for gardening purposes. This helped reduce the seepage to some extent.
At the time of the visit, she was in the process of installing a dual plumbing system for her flush tank and also connecting the well water to her washing machine inlet after passing it through a DIY mesh-based filter suggested by the plumber. She is hoping that these measures would help eliminate the seepage issue in her house completely.
3.2 Vasanthi’s house (Villa 92)
Vasanthi does not have any seepage inside her house. However, her garden area has been continuously water-logged during the August-September 2022 rains which are causing a lot of her plants to wither and die.
The piping for rooftop rainwater harvesting has been done recently and this water is being led into the storm water drains as there is no rainwater sump yet. According to Vasanthi, this is being planned for. There is no recharge well either in her house currently.
Figure 2: Water stagnation causing grass to die
3.3 Mumu Pande’s house (Villa 118)
Mumu Pande had been facing seepage inside her house for many years. She implemented rooftop rainwater harvesting in 2020. This included the digging of two recharge/withdrawal wells in her backyard and one well in her front yard. The harvested rooftop rainwater is directed into these recharge/withdrawal wells. Water is pumped from these wells and used for all non-potable purposes in the household. After implementing measures to use the recharge/withdrawal well water within the premises, the seepage has completely disappeared.
However, there is a small patch on the north-western side of her backyard that is logging a small amount of water. This could be a potential place for another withdrawal well or a water body element as a part of the garden.
She does not have an automated motor to pump out water when it reaches a certain height. Hence, seepage always occurs if the water is not used up which often happens when they are away. Hence, she plans to automate the pumping system in the near future.
Water quality has not been formally tested but is perceived to be extremely good. Ms Pande also claims to have tasted the water on occasion and found it very tasty. She has also observed that the recharge well yields at least a couple of months after the rains and does not feel the need to construct a rainwater sump.
Water from the main supply is utilized during the non-rainy parts of the year and to supplement their needs during the rains.
Figure 3: Recharge well in the backyard
3.4 Shalini’s house (Villa 247)
Shalini’s house is located on the first street of phase one, which is extremely close to the entrance of the villa complex (the discharge zone of the aquifer), and consequently to the Devarabeesanahalli lake. This is the lowest area of the layout and even average rainfall results in flooding this street with at least one inch of stagnant water.
To reduce some load on the shallow aquifer, rooftop rainwater harvesting with a first rain separator has been implemented in the house. The harvested rainwater is stored in a sump to be used for all purposes except cooking and drinking. Shalini has been actively working with her community to implement water management best practices for a long time. She believes that proper water management practices at the community level as well as at the individual household level are essential to tackle the flooding/seepage issues faced by APR currently and hopes that her community soon understands their unique position to turn the problem into a great opportunity.
Figure 4: Seepage through walls
4.0 The Hydrogeological study
In 2017, Biome along with ACWADAM conducted a comprehensive hydrogeological study to help understand the shallow aquifer of the area and mitigate these issues. Below is a quick look at its findings.
4.1 Hydrogeology and Aquifers: APR falls in the northern part of the Yamalur watershed. The study found that the groundwater table i.e. the shallow aquifer occurs less than 10 meters below ground level and is about 30 meters deep. Hard and fractured rock was found further below this level. This points to the fact that a large quantity of water is present as groundwater in this area.
Being in a low-lying area, this relatively thick shallow aquifer remains saturated for most of the year. The water table eventually cuts through the surface of the ground close to the entrance of the layout forming the Devarbeesanahalli lake.
Hence, many villa foundations and basements often cut into this high, thick and saturated water table, making them susceptible to water seepage and flooding. The management of the shallow aquifer becomes extremely critical in such a scenario.
The hydrogeological cross-section of the area is depicted in figure 5 below.
Figure 5: Hydrogeological cross-section along E-W direction
4.2 Villa layout: The villa layout is divided into three phases. As seen in figure 5, the lay of the land is such that the eastern part of the layout is at a higher elevation than the western part. This allows the eastern part to recharge water into the ground, making it the recharge zone of the shallow aquifer. The groundwater table rises closer to the surface eventually cutting through the ground in the western part, which makes it the discharge zone of the shallow aquifer. Approximately the 4th lane of phases one and two is where the transition from one zone to the other occurs causing seepage and even flooding in the areas left of this lane (see figure 6 below).
Figure 6: Recharge and discharge zones in APR on the phase-wise demarcation of the villa complex
4.3 Flood mitigation using withdrawal wells: Simultaneous recharge & discharge of the aquifer by using the water inside the premises instead of sending it out will keep the water in the aquifer balanced and mitigate the flooding/seepage issue. This will also reduce tanker costs which are a regular source of water for many houses in the layout, further reducing the load on the aquifer.
Currently, water from many withdrawal wells is being pumped out into the stormwater drains which flow into the Devarabeesanahalli lake.
4.4 Water quality: The study also found that the TDS of the water varies throughout the layout. However, leveraging the vast area of APR by artificial & natural recharge with rainwater will improve the overall water quality over time.
5.0 Water Demand Management for a single villa
For a family of four, assuming a daily consumption of 135 liters/person/day, the annual water demand would be approximately 194 KL, as shown in the table below.
Table 2: Water Demand for a single house
5.1 Rainwater harvesting potential
Calculating rainwater harvesting potential is a method of estimating how much rainwater can be harvested from rooftop and surface runoff annually by assuming that 90% of rooftop and 70% of paved area runoff can be harvested.
Assuming that the average size of a villa is 4000 sqft (371 sqm) - 175 sqm of rooftop area and 196 sqm of paved area - the following table represents the rainwater harvesting potential of one villa in APR.
Table 3: Rainwater Harvesting Potential
Based on these calculations, one villa has the potential to harvest ~ 287 KL of rainwater annually which is more than sufficient for a family of four.
As seen above, about 80% of the total water demand can be met by rooftop rainwater harvesting alone. Combining this with water from a withdrawal well or community borewell (based on the location of the house) will be sufficient to meet the needs of a family of four without depending on tanker water.
Assuming simultaneous recharge & discharge during the 90-120 monsoon days, one withdrawal well will yield 16200-21600 KL of water. This is 5-6% of the total tanker supply in a year for the entire villa complex.
6.0 Conclusion
The hydrogeological study concluded that “Water seepage and flooding problems are a blessing in disguise. This problem can be turned around to the benefit of the residents by systematic pumping of water contained in the shallow aquifer and its formal utilization.”
To mitigate the seepage/flooding issue as well as to become water-sufficient, a housing complex that is sitting on a saturated aquifer like APR needs to reduce its load on the aquifer while making sure it is sufficiently recharged for the dry season. This can be achieved by;
Using rooftop rainwater directly before it is sent into the aquifer.
Using the water contained in the aquifer with the help of withdrawal wells.
Reducing the usage of externally sourced water like tankers and Cauvery water.
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