BENGALURU: The plummeting water levels in reservoirs across the state – a consequence of consecutive droughts – presage a summer of acute water scarcity. Against such a bleak scenario, district administrative bodies are likely to resort to the most feasible solution: digging up more borewells to slake the thirst of the populace. However, information contained in reports prepared by the Central Ground Water Board and Ground Water Directorate, Karnataka pertaining to chemical concentration in groundwater in the state, could well render the plan of digging borewells defunct.
The reports indicate that concentration of harmful chemicals such as nitrate, fluoride, arsenic is beyond permissible limits in 22 of Karnataka’s 30 districts, including Bengaluru Urban and Bengaluru Rural. Bureau of Indian Standards’ limits for the chemicals are as follows: nitrate (45mg/l), fluoride (1.5mg/l), arsenic (0.05mg/l), iron (1mg/l). Groundwater samples were also tested for presence of three heavy metals: lead (0.01mg/l), cadmium (0.003mg/l) and chromium (0.05mg/l).
Concentration of nitrate, fluoride and iron was found to be above permissible limits in as many as 16 districts. Content of arsenic, one of the most dangerous elements, was found be excessive in two districts, Raichur and Yadgir. But no districts reported excess levels of heavy metal content.
The report on chemical concentration in groundwater, a copy of which is available with TOI, was prepared by testing samples collected from observation wells marked by the department of mines and geology, across Karnataka. Of the 1,167 samples collected by the Ground Water Directorate, fluoride concentration was found to be high in 93, and nitrate concentration was above permissible limits in 271. While total hardness level in water was found to be above safety levels in 111 samples, 136 of them had excess iron.
Director of the Ground Water Directorate, SB Shettennavar attributed the alarming levels of chemical concentration in groundwater to over exploitation. “Failure to recharge groundwater reserves over the years has led to this situation. We have intimated authorities in districts where chemical content is high to be careful in giving permission for new borewells. In fact, in taluks where chemical concentration is above the threshold, we have denied permission to dig borewells,” he told TOI.
Queried about the tenders being called by government agencies, such as Bangalore Water Supply and Sewerage Board, for digging new borewells, Shettennavar said, “Government bodies are exempted. Moreover, they dig borewells to quench the thirst of the public. However, we have asked them to gather data on the quality of water in the specific area where they want to dig new borewells, before staring work.”