Groundwater in Bangalore has been utilised beyond the critical limit, with more than 85 per cent of groundwater being used. The groundwater utilisation is far higher (1997-2003) when compared to previous assessments (1994-1997), the Department of Mines and Geology has found out.

In its latest five-year systematic groundwater resource status report, the Department has found out that 21 watershed areas in the State, including Bangalore, have been categorised as over-exploited areas.

The report analyses groundwater availability, utilisation and the balance potential available for utilisation.

According to the report released recently, 16 watershed areas fall under the ‘critical’ category, with over 65 per cent groundwater utilisation.

While an additional 47 watershed areas have been categorised ‘semi-critical,’ where utilisation is less than 65 per cent, about 296 watershed areas in the State are ‘safe’. The report covers and assesses all 380 watershed areas in the State.

The groundwater in Karnataka is usable as far as irrigation is concerned. However, certain pockets in different parts of the State have been identified as problem areas with regard to potability of drinking water, the report says.

The report points to increase in fluoride, nitrate and total dissolved solids (TDS) content due to over-exploitation, contamination and drought. Urbanisation and industrialisation have also affected the quality of water.

Lack of proper underground drainage and sewerage systems add to the increase in the nitrate content. Parts of Bangalore, Chitradurga, Hassan, Tumkur, Kolar, Bellary, Bijapur, Raichur and Gulbarga are facing excess nitrate contamination, with nitrate content exceeding the permissible limit of 50 mg per litre.

Fluoride content, which is hazardous to bones and teeth, has increased because of over-exploitation and depleting water levels in parts of Kolar, Tumkur, Chitradurga, Raichur, Gulbarga, Bellary, Bangalore, Belgaum, Bijapur and Bagalkot districts.

These districts have thrown up far more fluoride content in the samples collected from observation borewells, with fluoride in drinking water crossing the danger limit of 1.5 mg per litre. Untreated effluents from industries located in and around Bangalore, Kunigal, Nanjangud, Anekal, Hassan, Sedam and Gokak have polluted both surface and groundwater.