The water management practices of an individual house in Bengaluru, Vijaya Bank Layout are described in this post. This house is in the Bilekahalli ward of Bengaluru and receives BWSSB water supply twice a week.
Before delving into the details, it was essential to actually understand the layout and structure of the house. For this, a layout diagram of the house was made.
C1 & C2: Grated collecting pipes for rainwater
T: Overhead tank for storing water
S1: Borewell of approx 250’ depth
S2: Sump for storing BWSSB Kaveri water
S3: Recharge well of 6’ depth
M: Water meter
C: Connecting pipe for rooftop collected rainwater
From this layout diagram, it can be seen that the house has a sump for storing the BWSSB water which is then pumped onto the terrace and used for their daily needs. There is also a borewell of 250’ depth. But the water in this borewell had gone dry about 5 years ago. This time when the borewell was inspected, there was water at a depth of about 56’ from ground level, which means a total of 194’ of standing water! But how did this happen?
This is where the humble recharge well comes into the picture.
Testing the water level in the borewell
Recharge well
If one looked at this recharge well, they would never be able to say that it’s capable of recharging about 1893 litres of water in one day! With a depth of 1.83 m, this recharge well has shown us that size really doesn’t matter. It was dug about 3 years ago. Water from the rooftop is collected and flows into this recharge well which has an unlined bottom. This means that the water from this well recharges the groundwater.
Recharge well with the inflow pipe
Representative sketch of the recharge well
After monitoring the rate of recharge in this well, we have found that it recharges water at the rate of 0.023 litres/sec, and even on days with extremely heavy rainfall, this recharge well has never overflowed.
Now, after 3 years of digging this well, we have seen that the water in the borewell has increased. While it is also important to monitor the rainfall of the city and understand if there are any other sources of recharging the borewell, it is also pretty clear that this recharge well has an important role to play in this.
One of the most fascinating things that was learnt from this analysis is that although the BWSSB Amendment Act states that households with the requisite rooftop area must have a recharge well of 10 ft depth, we see that this 6 ft recharge well does just as well as any other recharge well.
Water demand
Finally, the water demand and areas of usage was analysed. And it showed that this household has a daily water demand of 191.5 litres/capita/day, which is slightly on the higher side. But several recommendations to reduce the water demand were given. Further, it was also suggested that the borewell water be used for the non-potable purposes in the house, to reduce reliance on BWSSB water.
References
Rain Water Harvesting - Bangalore Water Supply and Sewerage Board. Bwssb.karnataka.gov.in. Retrieved 17 September 2021, from https://bwssb.karnataka.gov.in/new-page/Rain%20Water%20Harvesting/en
Gayathri Narasimhan
