The eco-restoration of Lake Pashan in Pune is a good showcase for the partnership between experts and municipal authorities
Lakes in and around cities should be a major source of attraction for those living in urban areas. From morning walkers to romantic couples longing to get away in a boat,to the elderly who simply want to sit and watch the world go by,lakes cater to us all. And,of course,when associated with wetlands,they provide an opportunity to make our children and grandchildren into amateur naturalists. What many of us dont know is the vital role these water bodies play in maintaining the sustainability of our environment.
But in India we have come to dread water bodies in our cities only because instead of rainwater,it is sewage and effluents that are filling up our urban lakes and ponds. Rather than controlling the rate of run-off in our cities,we find our lakes carrying the load of garbage,sewage and encroachment by land grabbers.
It need not be that way. Pune has shown the way. The Pune Municipal Corporation (PMC),working closely with the Institute of Environment Education and Research,Bharati Vidyapeeth University (BVIEER),funded by the Jawaharlal Nehru National Urban Renewal Mission (JNNURM),launched an eco-restoration project that has successfully brought Lake Pashan and its surrounding wetlands back to their original glory. I could share the joy as Dr Erach Bharucha gleefully informed me that in the winter of 2012-13,a pair of grey herons nested successfully at Pashan,after a long,long time. A surgeon by profession,Dr Bharucha is passionate about environmental sustainability,and has found a second vocation as the director of BVIEER. He and his team have worked closely with the PMC in restoring biodiversity in the region.
Pashan lake and the surrounding wetlands used to be a major attraction for bird watching. The legendary Salim Ali was a frequent visitor. Bird counts were regularly taken by the World Wildlife Fund and Ecological Society of Pune. As late as the 1950s,the lake hosted flamingos,storks,nucta ducks and a host of waders. In winter,morning birds used to come to Pashan and return to the Mula-Mutha river bed (a 1 km stretch between Bund Garden and Koregaon Park) in the evening to roost on islands and rock bunds made by traditional fisherfolk. The lake was created by an ancient dam across Ramnadi,a tributary of the Mula river of Pune city. The ecosystem was an undisturbed habitat for aquatic birds with a full complement of raptors,such as Marsh harriers and Bonellis eagles. The water flowed through an extensive forested tract of babul trees and scrubland on the surrounding hills. Scrubland is often looked upon as wasteland. Just because it does not produce crops and does not yield revenue,does not mean that it has no value. The terrestrial babul thorn forest and scrubland had significant value for rich bird and insect life in the region.
The lake was the source of water to Pashan village. But more important,the wetlands helped retain water during dry periods,thus keeping the water table high and relatively stable. During floods,they reduced flood levels downstream and trapped suspended solids and nutrients in the aquatic system,thereby creating conditions of rich biodiversity. Even in the early 1980s,Pashan was a major wintering site for waterfowl.
There was a precipitous drop in these visitors to the lake between 1989 and 1994. The increased human activity in and around the lake,including washing clothes and bathing cattle,took its toll on the environment. Pune also saw an investment upsurge on the western side of the city in the aftermath of the Mumbai blasts of 1992-93. The upstream debris from construction in the catchment area of Ram nala (originally Ramnadi),11 km away from the lake,destroyed the natural babul forest. It added to the problem of rapid siltation and reduced the depth and water storage capacity of the lake. As the lake became shallow,the fringe reed beds gave way to Ipomoea (commonly known as the besharam plant,which wipes off everything,growing itself into a thick shrub),which covered about a third of the previous water spread.
The second half of the 1990s saw another major investment boom in Pune,led by the IT Park in Hinjewadi. A number of villages in Bavdhan Khadan,covering an area of a little over 6 sq km on the western side of Pashan,and another collection of villages,covering 8.4 sq km in Baner on the eastern side,were added to the Pune municipal area in 1997. As the housing and construction boom took off just as water and sewerage infrastructure was being laid,Pashan lake and the wetlands were at the receiving end of these developments. The debris from construction activity found its way to the lake and the wetlands.
With the deteriorating conditions at the lake,the movement of local birds stopped,and the region turned into only a halting or roosting site for a few migratory birds. Raptors (birds of prey that sit at the apex of the food pyramid) such as Marsh harriers,once common in Pashan,became only occasional visitors. As the mud banks were lost,waders dependent on gradually tapering water levels at the periphery also abandoned the region.
It was then that the PMC turned its attention to Pashan to undo the damage. The lake was fully drained in May 2005 with a view to dredging and removing the silt. Recognising the need for scientific inputs,BVIEER was requested in 2006 to prepare a full-fledged eco-restoration project for Pashan. At a total cost of Rs 16.7 crore,the project was sanctioned under the JNNURM in 2006,and the contract for implementation was given to a private company,NERIL,based on competitive bidding. The government of India contributed 50 per cent of the funds,the government of Maharashtra 20 per cent,and the PMC,30 per cent. The project has been completed in six years with a close partnership in continuous monitoring of progress by the PMC and BVIEER. As Mahesh Pathak,municipal commissioner,Pune,put it,this project is a good showcase of partnership between experts and municipal authorities.
The objective of this eco-restoration was to create wetlands where the Ram nala meets Pashan lake. This required adjusting the depth of water. The lake had to be drained a second time to get this right. The desilting has been designed such that the lake would have open water,a shallow submerged shoreline with emergent floating vegetation,and banks covered with typha. Bamboo clumps have been planted to screen the water from external disturbances. A buffer is provided by planting 1,200 trees on the embankment. In addition,350 indigenous fruit-bearing trees have been planted around the lake and on the island,contributing to the terrestrial ecosystem.
Part of the silt was used to construct a 17-acre island within the lake. Of this,10 acres are partially submerged when the lake is full. This provides roosting and feeding ground for birds preferring shallow water during the summer drawdown. The islands are now a favourite secluded site for storks,herons,cormorants and migrant ducks. The islands and the babul trees that remain now constitute a roosting colony. The lake is re-inhabited by fish,crustacea and molluscs,which shows that the ecosystem is on the way to rapid restoration.
Besides strengthening the dam and spillway,increasing the depth of the lake by 1.5 metres and creating the island,the project also involved building a gabion wall (3 km long),a walkway,and putting the plantation in place. An Environment Interpretation Centre has been set up for visitors. A nursery at the lake sells plants suited to the local environment,but is not expected to generate any significant revenue. The annual operation and maintenance cost is estimated at Rs 25 lakh,which must be provided for by the PMC to ensure the long-term sustainability of what has been achieved.
There is still need for the proper disposal of sewage and debris from the Ram nala,and for a mud bank ecosystem at the inlet and at the periphery,which currently has steep embankments,but the flora and fauna have voted for the new regime. After a gap of over two decades,storks,ibis,spoonbills,large flocks of cormorants and ducks such as shovellors,pintails and pochards have come back home to Pashan.
The writer is chairperson of ICRIER and former chairperson of the high-powered expert committee on urban infrastructure services