1.0 Introduction
Deccan International School is located on 18th Main Road, Brindavan Layout, Padmanabhanagar in the south of Bengaluru. The overall area of the school complex is 10 acres. The school consists of junior and senior schools, an ashram school, a playground, the Nettakallappa Aquatic Centre and the vehicle parking area all of which are at different levels topographically. There is a contour drop of 10 m within the campus.
Fig 1: Deccan Internation school and its location on the map
2.0 Summary and context
The school campus is situated in a low-lying area near the dry Chikka Kalasandra lake. Hence, during heavy rain, many areas on the school campus get flooded causing a lot of inconveniences. At the same time, the school regularly faced water scarcity issues, particularly in maintaining their large swimming pools and would often resort to buying tanker water to meet their daily demand.
This story focuses on how the school has solved this paradoxical problem of water scarcity and abundance by using 11 recharge wells that direct a large part of the 13801 KL (13.8 million litres) rainwater runoff generated every year into the ground.
Fig 2: Area covered by the school and its proximity to the Chikka Kallasandra lake
3.0 Water usage
The school needs water for drinking, handwashing, gardening and flushing the toilets. A significant amount of water is also needed for the swimming pools in the aquatic centre.
4.0 Water demand
A half-day workshop was conducted with the staff to determine the water demand of the school based on their daily activities. This revealed that the school needed about 35KL/day to function smoothly.
5.0 Sources of water
5.1 Borewells
The main source of water for the school are the 4 borewells which are all currently in good working condition. The table below depicts their details and locations.
Table 1: information about the four borewells
BW1 was drilled when the open well in the campus had dried up. Subsequent borewells were drilled to meet the increasing water demand, and also because the water in BW1 had become silty. Water from all the borewells is used to fulfil all the needs of the school including the swimming pools. However, apart from BW2, all the borewells would go dry in the summer. After recharge wells were dug, they have been yielding throughout the year.
When BW1 dried out, direct borewell recharge was implemented. This was not appropriately filtered, causing the borewell to discharge muddy water. This has now been corrected with appropriate silt traps and recharge wells.
Fig 3: The 4 borewells in the school campus (clockwise from the top BW1, BW2, BW3, BW4)
5.2 Water tankers
Even with BW2 working, the school had to buy 12 KL of tanker water per day in the summer (2 tankers 6 KL each). This was mainly used for the swimming pools.
However, after the recharge of BW1 was corrected and revived, the need for water tankers had come down significantly by 2018. The school hasn’t bought any tanker water since 2020 owing initially to low demand due to Covid. Subsequently, this reduction in dependency has been attributed to the increase in yield of the borewells after recharge wells were dug.
5.3 Cauvery water
The school also gets Cauvery water from the BWSSB – about 2 KL per day. This is mainly used for drinking purposes, after filtration.
6.0 Flooding issue and solution
The primary issue the school faced was flooding during heavy rain. Its position in a low-lying area near a lake caused water from the surrounding area to flow through the campus and flood certain areas within the school. Six to twelve inches of stagnant water used to be the norm in these areas. The areas that were most prone to flooding have been listed below. The solution for each of these areas was tailored slightly differently.
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Flooding area 1 – the parking lot
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Flooding area 2 – Junior school courtyard
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Flooding area 3 – Open area behind Ashram school (previously called grape garden area)
Fig 4: Areas of flooding and directions of runoff
The best way to deal with excess water is to send it into the ground. This has the double benefit of preventing flooding and enhancing the groundwater level. A similar approach was taken up at Deccan International School. The next sections describe the tailored approaches for each of the flooding areas.
6.1 Total runoff from different catchment areas
Table 2: Total runoff
Hence, the volume of water generated with runoff in the entire school is calculated to be 13801 KL annually.
6.2 Flooding area 1 – The parking lot
Since the land slopes towards the school from the neighbouring Telecom layout and beyond, two recharge wells of dimensions 5ft x 30ft were dug to recharge the runoff coming from this area. One recharge well (RW1) was dug in the SWD which is very close to the boundary near the Telecom layout. The overflow from this was directed to the second recharge well which is located in the area where the parking lot meets the playground (RW2). The overflow from RW2 has been directed into a chamber from which all the water is directed into the main SWD of the school. Multiple recharge wells are present in this SWD. This line of recharge wells in the internal SWD lies uphill of BW1 and BW2, and the consequent recharge could be a significant contributor to the revival of these borewells.
Fig 5: One among the series of RWs in the SWD
Fig 6: Placement of recharge wells for flood management in flooding area 1 (the blue arrows show the direction of water flow)
Fig 7: Parking area
6.2.1 Future plans
Since the volume of water coming into this area has been observed to be high in the last 2 years, the school is now also considering diverting a part of the runoff towards the open well near the ashram school through the same chamber as shown in Fig 6.
Fig 8: Open well near Ashram block (12 ½ ft dia, 55 ft deep)
6.3 Flooding area 2 – the Junior School courtyard
The Junior School courtyard used to flood when water overflowed from the stormwater drain, and also from the runoff from the elevated play area to the southeast. The runoff volumes for this area are calculated to be 199 KL /annum.
But since the recharge wells in the SWD were dug, this flooding has reduced significantly. A cattle trap drain has also been made (as seen in figure 9) downhill of the courtyard to take any excess water from this area into the SWD.
Fig 9: Junior school courtyard (left: the school side, right: opp the school with cattle trap drain)
6.4 Flooding area 3: the grape garden area
Being an open area of 7792 sqm, a fair amount of runoff even in mild rain (47 KL) used to be generated here. It also directly receives the runoff from the Telecom Layout and extension roads, the parking area, the path next to the playground, the Ashram school rooftops and ground, through a large culvert that opens out into the grape garden area. But after the two recharge wells described in section 6.2 were dug, the school hasn’t seen any flooding in this area. A basketball court has now been constructed in this area and has not faced any water logging to date.
Fig 10: Grape garden area
7.0 Map with important areas marked
8.0 Next steps – Rooftop rainwater harvesting
After successfully managing the flooding issue and reviving their borewells with 11 recharge wells, the school is now looking at its water security in the long term. Anecdotal evidence suggests that a significant amount of water is still running off the property from the exit points marked in figure 4.
8.1 Open well
After the heavy rains of 2021 and 2022, the old open well near the ashram block that had run dry has now started to hold water. This is the biggest motivation for the school to consider recharging this well. The school plans to direct the rooftop rainwater from the ashram building into this well and also direct some of the water coming from the parking lot in its direction as described in section 6.2.1.
Fig 11: Downtake pipe not connected to the open well yet
8.2 Rainwater harvesting tank
A rainwater tank of 80 KL capacity exists near the junior block that is currently taking in a lot of silty water from a part of the rooftop of the building. This has recently been cleaned once, the stored water from which was used in construction activities in the school. The sump is however still taking in silty water. This silt is a result of the surface runoff that gets into the cattle trap drain that carries the rooftop runoff. The school plans to correct this as well. This water is planned to be used for gardening purposes in the future.
Apart from the above, rooftop rainwater harvesting is being planned for the rest of the buildings as well. This water is planned to be used to supplement their domestic needs and further reduce the pumping of borewell water.
9.0 Conclusion
Deccan International School has successfully tackled its flooding issue by using recharge wells to send the excess water into the ground. This has also added the benefit of the revival of all its borewells, eliminating the use of tankers for the last 3 years.
This effort can be furthered by setting up rooftop rainwater harvesting for all its buildings. This will help reduce purification and pumping costs for the school and also help revive the open well for long-term water security. Revival of this large old well also has the added benefit of preserving our heritage artefacts. Since this is a school, this and the rest of the water management system could be great learning for the protection and optimal usage of our natural resources for its students.