Cubbon Park was created in 1870 and spans an area of around 200 acres. The park hosts various botanical species, with a total of 8866 trees. It is a preferred destination for early-morning walkers and joggers and hosts important government buildings like the Karnataka High Court, State Archeological Museum, etc.
The park has seven old open wells that are around 20-40 feet deep. Over a period of time, these wells had fallen into disuse. The well water had become dirty, mixed with the garbage thrown inside. The park also has three ponds, which were filled with silt and were not functioning to their original storage capacity. Most of the water needs were met by sourcing Cauvery water from BWSSB.
Rejuvenation of open wells, ponds and digging of recharge wells
A project to rejuvenate the old wells and ponds in Cubbon Park and also to recharge groundwater was taken up by Biome Environmental Trust, India Cares Foundation (ICF) and Friends of Lakes (FoL), together called the Waterlife Consortium. The concept of this project came from the thought that the park could be self-sustainable for its water requirements and should not have to depend on external water sources. Given the presence of a robust shallow aquifer and open wells, it was planned to see if the park could demonstrate best practices for water management by highlighting the use of the shallow aquifer. The recharge wells and the ponds recharge groundwater, and the open wells are sources from which groundwater can be drawn. The wells can also be monitoring points, which can instruct future groundwater management actions in the park. This project was completed in two phases: Phase I and II.
Phase I was carried out in May 2017, in which the 7 open wells were revived. The water drawn from the wells is used to water trees, the lawn and the rose garden. Within a year, by Sept 2018, the open wells together started yielding 80,000 litres per day.
Phase II was started around Oct 2018, in which 73 recharge wells of 3 ft x 15 ft were dug, and two ponds were rejuvenated. The mud from the digging of the recharge wells was used to create a large mural on one of the walls of the Cubbon Park Metro station, telling the water story of Bengaluru, and depicting the lives of the traditional well-diggers. This was executed in collaboration with the Srishti School of Art and Design, and funded by the Bangalore Sustainability Forum.
When the mural was unveiled to the public, some events were organized involving the well-diggers who dug the wells, including a Kaavya Sanje and a virtual tour of the mural (due to the pandemic), called Namma Ooru Namma Neeru.
Each well has a static volume of around 3 kilolitres (KL), and each well can potentially recharge around 4.5 KL each time it rains (assuming each well can recharge one and a half times its static volume of 3 KL). This means the recharge potential of all the wells is 73 x 4.5 KL = 328.5 KL.
We have around 60 rainy days a year in Bengaluru. Assuming that the wells recharge to their full capacity on at least 30 of those days,
328.5 x 30 = 9855 KL = 9.8 million litres (ML) of rainwater will get recharged annually through the recharge wells (the actual recharge volume is likely to be higher, as rainfall intensity will vary through the 60 rainy days, with at least a few really heavy showers).
Map of 73 Recharge Wells in Cubbon Park
The annual natural recharge that occurs in the park is at least 39.25 ML, considering a recharge rate of 5% from an annual rainfall of 785 ML on the 200 acres.
The two ponds taken up for rejuvenation had areas of 50 and 230 square metres respectively. Assuming a recharge rate of 5 mm/day for the ponds, and assuming that the ponds hold water for at least 240 days (8 months) of the year, the annual recharge volume (in kilolitres) of the smaller pond is at least 60 KL, while that of the larger pond is 1356 KL. The total annual recharge potential of both ponds is 60 + 1356 = 1416 KL = 1.41 ML.
So annually, the total volume of rainwater recharged at Cubbon Park (not considering the third pond) is at least 9.8 ML (from recharge wells) + 39.25 ML (natural recharge) + 1.41 ML (from two ponds) = 50.46 ML, which is several times more than the volume of groundwater drawn (0.55 ML).
Clockwise from top left: Concrete rings with gravel aggregate around them, wire mesh grill in the well, completed recharge well, concrete slab well cover
Ponds being desilted and cleaned
Cleaned pond filled with rainwater
4.0 Conclusion and Next Steps
Situated in the heart of the city, Cubbon Park is one of the areas that has a robust shallow aquifer. The huge volume of rainwater that it recharges helps replenish the groundwater table of not only the park but the surrounding areas as well. Regular monitoring of the well water levels and documentation of the usage of well water for the park’s needs would help greatly in understanding this shallow aquifer’s behavior.
A hydrogeological study of the park and surrounding areas would help delineate this aquifer’s extent and, thereby, its volume. This would provide valuable information on the capacity of this aquifer and its potential to meet the park’s water needs. A study of the borewells and open wells (if any) in the surrounding areas would help in understanding the park’s role in keeping the water table replenished.
Here’s the detailed case study.