Hyderabad: It is estimated that the groundwater in TS has been recharged by 400 tmc ft due to the monsoon rain. By comparison, the Srisailam dam has a total capacity of 215 tmc ft.
According to department officials, the exact quantum of groundwater recharged will be known after a few weeks but a rough estimate based on the number of rainy days and presumed precipitation conveys the picture that the groundwater table was rising despite rains having stopped for the last few days.
“It is difficult to assess the total quantum of rainwater now. It will take a few more weeks for us to make studies at different places using various parameters but our rough estimate is that it would be around 400 tmc ft,’’ Mr G. Sambaiah, director, groundwater department told this newspaper.
There is a universally accepted approach to assess rainwater. It is taken that 42 per cent of rainwater is lost to ‘evapotranspiration’, or due to evaporation and by transpiration from plants and is estimated at 1,400 tmc ft.
Another 40 per cent, or 1,300 tmc ft is taken to be run-off, the draining away of water from the surface. Six per cent or about 200 tmc ft goes into irrigation tanks and small reservoirs and the remaining 12 per cent is considered as recharge of groundwater.
Run-off water also includes inflows at all major reservoirs and water pouring into rivers from streams and rivulets.
Mr Sambaiah said that depending on the surface, soil, and weather zone, the recharge of ground water will take a minimum of three days to a maximum of 20 days after each rain. It is not instantaneous as people think. “There was rain every day in September. That really helped groundwater recharge to its full capacity,” he said....