The city has gone through a difficult summer as far as water supply is concerned with the GVMC stretching itself and scraping the bottom.
Theoretical physicist Vikram Soni, who is working on sustainable cities, is of the view the per capita water availability in all Indian cities is showing signs of stress. The city's water needs will be around 150 million cubic meters a year, he estimates.
The groundwater recharge depends upon the soil. But even taking the national average of 10 to 12 cm a year and at a conservative estimate the recharge would be between 70 and 140 million cubic meters a year, he says.
“With the kind of red, gravely soil porosity and water assimilation is quite good and groundwater can meet the needs of the city,” Prof. Soni told The Hindu during his recent visit to the city.
It can be further enhanced by water harnessing and all of it can be used, he says. If managed properly and the city is not over-concretized that could be a reasonable quantity of water.
Prof. Soni says tanks will not help much for a city of this size.
“You have to look around in the 680 sq km (of the city) and see where the depressions and catchments are located. If water can be held in some lakes it would help a little bit. It would not help too much if two metres of water is lost by evaporation. The more the depth of the lake, the smaller the surface the more effective it will be for water retention. If there are 15 to 20 lakes with a total area of 5 sq km storing 2 to 3 meters of water it would bring in an additional 15 to 20 million cubic meters that would be a supplementary source,” he says.
On artificial lakes, he says, there must be some depressed areas in the monsoon that become wetlands. If the geography permits artificial lakes can be creaetd by the administration. Since there are no rivers, the balance has to be brought by pipelines or canals. But the major source of water is groundwater, Prof. Soni says.
Because there are lots of hills there have to be depressions. If the porosity is good they can be used as water recharge structures for the groundwater, he suggests. At intervals of five km each, the structure can take 15 to 20 million cubic meters. But more recharge is possible if the underlying area is neither clay nor rock. If the soil is loose gravel, recharge is possible.
The city's water needs will be around 150 million cubic metres a year, says theoretical physicist Vikram Soni
