JOIN USUnplanned, rapid urbanisation post-2000 witnessed large-scale conversion of watershed area of the Bellandur lake into residential and commercial layouts and this has altered the hydrological regime and enhanced the silt movement in the catchment.
This is what Prof Dr T V Ramachandra and scholars Bharath Aithal, Vinay S and Aamir Amin Lone from the Indian Institute of Science (IISc) conclude in their study, “Conservation of Bellandur Wetlands: Obligation of decision-makers to ensure inter-generational equity.” The authors are part of IISc Wetlands Group under the Centre for Ecological Sciences.
The declining vegetation cover, says the study, has lowered water yield in the catchment, affecting the groundwater recharge. Alterations in ecological integrity is evident from reduced water yield, flash floods, contaminated water, obnoxious odour, copious growth of invasive floating macrophytes, disappearance of native fish species, rising mosquito menace and other disease vectors, etc.
A major portion of untreated city sewage (500+ million liters per day) is let into the lake, beyond its neutralizing ability and this has hampered its ecological functioning.
The study makes it clear that land use change such as conversion of watershed area, especially valley regions of the lake to paved surfaces, would alter the hydrological regime. Removal of drain (Rajakaluve) and reducing the width of the drain would flood the surrounding residential (areas) as the inter-connectivities among lakes are lost.
There are no mechanisms for the excess stormwater to drain. Thus, the water stagnates, triggering floods in the surroundings.
Dr Ramachandra points out that the lake cannot also be revived if there is alteration in landscape topography since it alters the integrity of the region affecting the lake catchment. This would also have serious implications on the stormwater flow in the catchment. Dumping of construction waste along the lakebed leads to alteration in the lake natural topography, thus rendering the stormwater runoff to take a new course.
Eventually the water would get into the existing residential areas.
Besides, alteration of topography would not be geologically stable. It leads to soil erosion and siltation in the lake, the study notes.
Loss of shoreline is another factor that may make revival of the lake difficult. It was apparent from the field investigations for the study that illogical land filling and dumping in the Bellandur lake bed had gobbled up the shoreline. This loss results in destruction of habitat for most of the shoreline birds that wade in this region.
The study warns that shoreline wading birds such as stilts and sandpipers will be devoid of their habitat forcing them to move out.
As far back as 2005, it was known that local people were dependent on the lakes for wetlands for fodder, fish etc. The study estimates that this activity provided goods and services worth Rs 10,500 per hectare per day 10 years ago. Now the earning would be higher.
The Bellandur lake terrain is relatively flat and sloping towards south of the city. This water body has been a lifeline sustaining the livelihood of settlements in the catchment and command areas. Agriculture (rice and vegetables) practised since long in the downstream continues even today.
Three main streams join the tank, which form the entire watershed. Three chains of lakes in the upstream join Bellandur lake with a catchment area of about 148 square kilometres (14,979 hectares) and overflow of this lake gets into Varthur lake, from where it flows down the plateau and joins the Pinakini river basin.
Dr Ramachandra describes wetlands as lands that are transitional between terrestrial and aquatic eco-systems. Here, the water table is usually at or near the surface or the land is covered by shallow water. Wetlands are the most productive and biologically diverse but very fragile ecosystems.
They function as the kidneys of landscape due to remediation of contaminants (which include nutrients, heavy metals, etc). These fragile ecosystems are vulnerable to even small changes in their biotic and abiotic factors. In recent years, there has been concern over the continuous degradation of wetlands due to unplanned developmental activities.
Proposed steps to revive lake
* Ensure adequate vegetation cover around lake and if possible enhance the same
* Protect ecological integrity of lake by ensuring normal water flow in it
* Do not allow untreated city sewage into the lake
* Don’t allow change in land use and hydrological regime of the lake
* Dont remove and reduce stormwater drain in lake vicinity to ensure easy water flow
* Take measures to avoid lake siltation and soil erosion
PAST
A water source for farming, fishing, drinking
* Bellandur lake served Bengaluru’s water needs right upto the 1970s. The water was used for drinking, household purposes, agriculture and fishing
* Its waters were also used for irrigation. A variety of crops, including rice and ragi besides vegetables were grown. So were pulses and spices
* Fishing was significant in the lake. An estimated 100 families depended on fishing and lived in communities near the lake’s northern shore
* Industrial growth from the 1970s, coinciding with supply of Cauvery water triggered neglect and abuse of Bellandur lake.
*Untreated sewage from South Bengaluru began to be pumped into the lake during this decade
* During the 1980s, chain of tanks/ lakes leading to Bellandur were encroached upon to form housing layouts
PRESENT
Rampant pollution, encroachment, SEZ plans
* Besides rampant pollution due to entry of untreated sewage, Bellandur lake faces the threat of a proposed SEZ. Petition pending before National Green Tribunal
* A Lake Development Authority report submitted to High Court says the land acquired by KIADB for the SEZ is one of the catchment areas of Bellandur lake
* This area between Agara lake and Bellandur lake had been classified as a sensitive zone in the draft CDP Master Plan 2015. However, the final master plan had the classification changed to mixed residential category
* High Court has directed LDA to call a joint meeting of all stakeholders to formulate methodologies to revive both Agara and Bellandur lakes
* HC has directed KIADB to ensure water channels for flow of excess water from Agara to Bellandur lake. BDA is to resurvey Bellandur lake and fix boundaries
FUTURE
Remove encroachers: Dr T V Ramachandra
* To stop the change in Bellandur lake ecology, “eliminate encroachers on all sides of the lakes and their encroachments. Once the stone, sand, metal and other waste is removed, the original size and shape of the lake can be restored.” Locals can approach pro-active courts to initiate action against violators.
* To eliminate sewage from the lake, “identify points where the sewage has been let in, physically remove them. Identify spread of the sewage and eliminate
accordingly.”
* To eliminate metals from lakes, evolve a large project. “Vegetables we eat are metal-laden and poisonous. Their chemical
content should be eliminated.”
* Take steps to prevent dumping of construction waste along the lakebed as this would alter the lake’s natural topography, thus rendering the stormwater runoff to take a new course.