Bengaluru: Bengaluru has seen a 1055 per cent increase in concretisation with a concurrent 88 per cent drop in vegetation over the last 46 years, according to a research study done at the Indian Institute of Science.
A decline in groundwater levels down to calamitous depths would be an obvious corollary, says the study authored by Dr T.V. Ramachandra, Sincy V. and Asulabha K. In intensely urbanised areas such as Whitefield, the water table has declined from 28 m to 300 m in some cases, and from 400 to 500m in others over a period of 20 years.
Geo-visualisation of likely land use in 2025 indicates that 98.5 per cent of the Bengaluru landscape would be filled with paved surfaces (urban cover), it states.
Field investigations of 105 lakes conducted by the researchers revealed that 98 per cent of them have been encroached to construct illegal buildings, high-rise apartments, commercial buildings and slums during 2005-16. Ninety percent of them are sewage-fed.
“Also, lake catchments are being used as dumping yards for either municipal solid waste or building debris. Indiscriminate disposal of solid and liquid waste (rich in organic nutrient) has enriched nitrate levels in the surrounding groundwater resources, threatening the residents’ health (thereby increasing risks such as kidney failure, cancer, etc.). Washing, household activities, vegetable cultivation and even fishing was observed in a few of the contaminated lakes,” the research paper says.
The sustained inflow of untreated sewage into the water bodies has led to large-scale fish mortality in recent months, the report states.
Conversion of wetlands into residential and commercial layouts has compounded the problem by removing interconnectivity in an undulating terrain. Encroachment of natural drains, alteration of topography involving the construction of high-rise buildings, removal of vegetation cover, reclamation of wetlands are the prime reasons for frequent flooding even during normal rainfall episodes since 2000.
