HYDERABAD: What recharges groundwater of Hyderabad? It is sewage, effluents from industries and leakages from drinking water supply network. In fact, urban sources like sewage transported in nallas which crisscross the city and leakages from water supply network of Hyderabad Metropolitan Water Supply and Sewerage Board (MMWS&SB), recharge city’s groundwater aquifers ten times more than natural groundwater recharge sources like rainfall or surface run-off water.
This is a finding of a study titled, ‘Impact of urbanisation on groundwater recharge and urban water balance for the city of Hyderabad, India’ conducted by researchers from RWTH Aachen University, Germany and National Institute of Technology, Patna. The study by Hemant Wakode of RWTH Aachen University, mentions that the net recharge of groundwater in Hyderabad due to urban components like sewage and leakages was estimated to be approximately 568 millimeter per year (mm/yr), whereas recharge due to natural components was just 53 mm/yr.
While one is taught in schools about ‘water cycle’, of evaporation followed by rainfall that recharges groundwater, the reality is different. As urban areas are becoming concrete jungles, percolation of rain water into ground through open spaces decreases. However, network of sewage and leakages in drinking water supply lines that run underground ensures percolation of water all round the year.
Sewage water polluted with contaminants like detergents and heavy metals seeping into groundwater is a major cause of concern. About half of the 1,450 million liters per day (MLD) of sewage water generated in Hyderabad is not even treated in sewage treatment plants.
Dr Himanshu Kulkarni, executive director of Advanced Center for Water Resources Development and Management (ACWADAM), says “While I don’t think that a figure can be arrived at, as to by how many times urban recharge component is higher than natural recharge but it is true that there is a trade off between reduction in natural recharge of groundwater through percolation versus leakage of unnecessary water into aquifers, which will have undesired consequences. Mapping of aquifers need to be done in cities along with identification of natural recharge areas. Waste water should be systematically treated and channelised to these areas.” He added, “While state governments are trying to channelise drinking water from rivers to cities, they cannot wish away dependence on groundwater as the cities grow at a rapid pace. Groundwater will continue to be an important source of drinking water.”