Water management at Adarsh Palm Retreat villas

APR villa complex is located in Bellandur, next to the Devarabisanahalli Lake. The villa complex occupies an area of 110 acres and houses 798 villas. Being a low-lying area, the houses and roads closer to the lake have been facing basement seepage and road flooding issues. This case study looks at how certain individual villas have been tackling this issue with rainwater harvesting.

1.0 Water sources and management at the community level

• The layout has a BWSSB Cauvery connection.
• There are twelve borewells (depth between 1000 to 1100 feet) in the premises,  of which seven are currently yielding.
• Rooftop rainwater harvesting has been implemented in the common clubhouse building.
• The layout has 34 recharge wells and 3 withdrawal wells – the latter are not used.
• During the non-rainy months, the complex is heavily dependent on tanker water.
• All the water is mixed in a common raw tank from which it is passed through the water treatment plant (WTP) and then supplied to individual houses.

2.0 Water management at the individual villa level

Based on anecdotal information, rooftop rainwater harvesting has been implemented in about 40 villas as of 2022. Water from the rooftops is directed into wells that have been dug in these villas for groundwater recharge. Motors with / without automatic sensors have been fitted in some of these wells, and the water is used for various non-potable purposes that include washing clothes, cleaning the house etc. Here are stories of some noteworthy individual villas that have successfully reduced seepage with various techniques of rainwater harvesting and groundwater usage.

For a family of four, assuming a daily consumption of 135 litres/person/day, the annual water demand would be approximately 194 KL. The average rooftop area of a villa is 175 sqm, from which around 153 KL of rainwater can be harvested annually. This would meet 79% of the annual water demand of the family. Combining this with water from a withdrawal well which is also regularly recharged, the family could completely eliminate the need to buy tanker water.

Recharge well in the backyard

3.0 The Hydrogeological study

In 2017, Biome and ACWADAM conducted a comprehensive hydrogeological study to help understand the shallow aquifer of the area.

Hydrogeology and Aquifers: The study found that the shallow aquifer occurs less than 10 metres below ground level and is about 30 metres deep. This shows that a large quantity of water is present as shallow groundwater in this area. The water table eventually cuts through the surface of the ground close to the entrance of the layout forming the Devarbeesanahalli Lake.

Hydrogeological cross-section along E-W direction

Villa layout: The villa layout is divided into three phases. The study found that the eastern part (placed at a higher elevation) forms the recharge zone, and the western part, containing the Devarabeesanahalli Lake, constitutes the discharge zone of the shallow aquifer. The transition from one zone to another occurs approximately at the 4th lane of phases one and two, causing seepage and even flooding in the areas left of this lane (see figure below).

Recharge and discharge zones in APR on the phase-wise demarcation of the villa complex

Flood mitigation using recharge/withdrawal wells: Simultaneous recharge and discharge of the aquifer by using the water in the shallow aquifer can mitigate the flooding/seepage issue. This will further reduce tanker usage, thus reducing the load on the aquifer even further.

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.

4.0 Conclusion

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;

1. Storing and using rooftop rainwater in a sump.
2. Diverting the overflow from the sump to a recharge/withdrawal well.
3. Using the water from the saturated aquifer through withdrawal wells.
4. Reducing the usage of externally sourced water like tankers and Cauvery water to reduce the load on the shallow aquifer.

Here’s the detailed case study of Adarsh Palm Retreat villas.