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Drastic fall in groundwater recharge
The city received 49.5 mm rainfall on Tuesday, the highest in July but the groundwater got recharged by only 5-6 per cent, according to groundwater department officials.
Hyderabad: The city received 49.5 mm rainfall on Tuesday, the highest in July but the groundwater got recharged by only 5-6 per cent, according to groundwater department officials.
Ten years ago, there used to be 10 per cent groundwater recharge in Hyderabad, but due to rapid urbanisation and mushrooming of concrete structures the percentage has fallen.
Flash rains for a couple of hours do not help. Consistent drizzle in sporadic regularity helps a great deal in recharging groundwater, says K Dhanunjay, joint director, Groundwater Department, Telangana.
In normal conditions, 42 per cent goes in evapotranspiration, 40 per cent goes in runoff, 8 per cent gets into reservoirs and 10 per cent helps in groundwater recharge but with the number of apartments and shopping complexes going up in the city, the groundwater recharge has fallen from 10 per cent to 5-6 per cent, says Dhanunjay.
Flash rains bring in 30 to 40 mm, but due to lack of rainwater harvesting pits, runoff accounts for nearly 40 per cent. Unless rainwater is channelised into borewells and rainwater pits increased, the city would not have sufficient water, says N Raji Reddy, deputy director, Groundwater Department.
Another reason the Groundwater Department officials put less percentage on groundwater recharge is due to copious rains in a matter of hours. This trend is being witnessed in the last five years. In the past, there used to be rains sporadically from June to September in the South West monsoon.
Flash rains do not help, say officials. Dhanunjay says 70 per cent of the rainfall that the city receives is from the South West monsoon. Till date we have had normal rainfall. There are two more months to go for the rainy season.
Water percolation does not take place in the first rain and it takes 15-20 days for water to percolate. Rocky terrain in the region too does not help, says Raji Reddy. Topography, intensity of rain, timely arrival and duration of the spell all play a vital role in groundwater recharge.
The new trends that the city is witnessing are that there are flash rains more often and rainfall is not uniform. If it rains in Uppal, there is no rainfall recorded in Begumpet. With the rainfall behaviour becoming erratic, officials warn people that if they do not go in for rainwater harvesting pits it would become difficult in summer. “A pit as small as 100 sq m has the capacity to harvest 51,000 litres of rainwater,” they said.
