Impact of urbanisation on groundwater regime: A case study of Bangalore City, Karnataka, India

Urbanisation causes major problems due to rapid growth and erratic planning. The present paper highlights the impact of urbanisation of Bangalore metropolis on its environment due to rapid industrialisation and the consequential economic and demographic changes. The study area lies between Latitude 12 degrees 48' to 13 degrees 10' and Longitude, 77 degrees 27' to 77 degrees 45', with an areal extent of 762 km(2). The population of the city has increased from 0.16 million at the beginning of this century, to its current level of 4.5 million. This has resulted in shortage of housing and other problems. The indiscriminate conversion of land for industries and residential purposes has also affected the number of tanks and lakes in and around the city. Reduction in recharge zones of groundwater is due to depletion of open spaces and vanishing of water bodies within the conurbation zone. The silted tank beds have been either converted into residential sites or used as dumping grounds for solid and liquid wastes, thus polluting the environment. Rapid urbanisation has led to a shortage of potable water and the city has to depend on external water supply sources. During the early part of the century, rain water was harvested in and around Bangalore and utilised. Now the increased demand for water is met by pumping from the River Cauvery over a distance of 100 km. This is both expensive and unreliable due to various constraints. One consequence is that groundwater is increasingly exploited. Lack of effective management has led to a decline in the water table. This study, in which 140 groundwater samples were collected, has revealed that pollution occurs in many places due to the improper disposal of sewage and industrial effluent. Isogram maps have been drawn to identify areas of gross pollution. Groundwater degradation may be arrested by restoring tanks both to augment supply and to facilitate groundwater recharge. Community water schemes and legislation to prevent over-exploitation should be implemented. Industries must be encouraged to recycle water and waste. The disposal of the solid and liquid wastes of the city should be regulated to prevent environmental pollution.