Earlier studies carried out by the Department of Mines and Geology during 1994, 1995 and 2003 on the groundwater quality of Bangalore Metropolis had found that the groundwater pollution in the city has mainly been due to sewage disposal and recommendations have been made to prevent pollution from sewage and industrial wastes. The supply of the required quantity of water to the population continues to remain a big challenge to the concerned authorities in Bangalore.
The report is divided into three sections:
- Part I: Urban groundwater hydrology
- Part II: Groundwater quality
- Part III: Quality of lake waters
In the current study, over 3000 groundwater samples were collected over an area of 800 sq kms in and around Bangalore city. The study area was divided into four quadrants and each quadrant was made into one sq km grid. Two or three samples were collected from each such grid and analysed in the chemical laboratory at the Directorate of Mines and Geology at Bangalore.
The study found that:
- The growth of the city over the last few years, the ever increasing demand for water and deficiency in the public water supply system has developed a heavy strain on the groundwater aquifers of the city
- The over draft of ground water has resulted in a steep decline in groundwater level, drying up of unconfined aquifers and mining of groundwater situation in many parts of the city
- Total dissolved solids and fluoride content in groundwater on higher side from deeper bore wells are the signals of deterioration of the quality of groundwater
- Among 2209 of the groundwater samples analysed, the nitrate content in excess of the desirable/permissible limit is found in 638 samples (29%), iron in 214 samples (10%), total hardness in 185 samples (8.5%) and fluoride in 14 samples (0.6%)
- There has been a high presence of heavy metals in groundwater attributable to the infiltration of effluents from the industrial waste disposals, higher content of NO3, low and high values of pH and the presence of e-coli and total coliform bacteria due to discharge of untreated sewage waste into the natural drainage system
- The causative factor for groundwater pollution is more anthropogenic than being geologic. Groundwater, once polluted/contaminated is difficult to bring back to the required drinking water standards. The cost of treatment of contaminated water is predicted to be enormous in the city of Bangalore
- The best option is to avoid disposal of solid, liquid domestic and industrial waste within the city premises
- As per IS 2003 drinking water specification, 31% of the city groundwater is non potable as against 50% found in the previous study conducted in 2003. This has been due to the remedial measures implemented earlier to prevent groundwater pollution
- Top priority needs to be given to conservation of rainwater through appropriate rainwater harvesting measures
- Creation of greater awareness among the public towards economical social and health implications of pollution of water resources and judicious use of available potable water resources is the need of the hour
A copy of the report can be downloaded from below: