1.0 Overview and Background

Madiwala lake is situated in BTM layout in East Bangalore, and is part of the Koramangala-Challaghatta valley. It is a part of the Varthur lake series. It is one of the biggest lakes in Bangalore spread over an area of 282 acres and was built by the Cholas in a day. It is home to many migratory birds. The lake comes under the administration of the Karnataka State Forest Department which carries out the routine maintenance of this lake. There is a children's park as well.

Location of the Toilet Block

Near the main gate of the lake there is a toilet provided for the visitors. The toilet block has a rainwater harvesting system. The downpipes were connected to a 6000L sump for storing the rainwater and pumping this water into the overhead tank. It was observed that the sump was damaged and hence could not store water. There was no other water source for the toilets.

Toilet building at Madiwala

2.0 Rain Water Harvesting

The toilet block has a rooftop area of 100 sqm

Taking the average annual rainfall as 974.5 mm, the actual harvestable rainfall for the rooftop is 44 KL (50 sqm x 0.9 x 974.5 mm). The rain that falls on this roof used to be diverted into the sump. It was found that the sump was damaged and could not hold water. Hence, a plan to dig a 5ft x15ft well was decided. The rooftop rainwater was diverted to the open well which was dug by the well diggers.

3.0 Work done

With the help of funding from Puravankara CSR, Ramakrishna and the team dug an open well in June 2022, over a period of 4 days. Roof top rainwater was diverted to the well as the sump was not functional.

A 5ft diameter and 15ft deep recharge well was dug at the Southwest corner

23 concrete rings of 9” height each was added
A silt trap of 3ft diameter and 3ft deep is provided
Water from the rainwater harvesting pipes of the building is diverted into this well through a silt trap.
A grill has been provided at ground level and on the top, for safety purposes
A 1 HP, 0.76 KW, single phase submersible pump has been installed in the well. Water from the well is pumped to the OHT to use in the toilets.

Location for the well Well diggers in action

Water hit at 6 ft Silt trap and the well

Ramkrishna and his team

4.0 Water usage from the wells

The water level is up to 6ft below ground level in the well i.e. there is 5KL of water in the well. The water from the well is used in the toilet by pumping it to the overhead tank in the toilet.