Pashan Lake – Downfall and Restoration

Prepared by: Nikhilesh Kulkarni

Introduction

Pune is a historic city. References to Pune can be found even from the entries

covering history of last 1500+ years. Like any city, Pune also has a huge need of

potable water. One of the efforts of fulfil l ing the need of potable water apart from

the rivers and wells in the city was the built of many lakes in and around the city.

Pashan lake situated on the urban limits of the conglomerate is one of such

efforts.

Pashan lake is one of the oldest man made structure raised to store water in

India. It is been created by erecting a dam on ‘Ram river’. The lake is surrounded

by residential area, industry and defense institutions.

Lake served as a source of water to old Pashan village, for growing crops all the year round.

Stored water was even pumped and supplied to Governor’s estate situated

downstream where currently University of Pune is situated. After British era, the

water was used to fulfil l the needs of surrounding area. A water treatment Plant

of 1 MLD was set up for that purpose. (Kirloskar Consultants Report, 2005) In

due course of time, plant was closed down as it could not fulfil l the demand of

water of increasing population. Currently, lake is not used for water supply or for

recreational purpose.

This water body being situated on the urban limits of the conglomerate and as a

result of centuries of nutrient and sediment loading had lost its water carrying

capacity. The lake had reached a state of degradation.

PMC estimates that 40,000 people could be provided with drinking water at per capita cost of

250 as compared with the existing per capita cost of 1,500.

Degradation of the lake

The study shows that, there is considerable increase in the chlorides and

phosphate contents of lake water in 10 years. This may be due to sewage

pollution, industrial effluents or daily activities on local people at the lake.

Various reasons behind degradation of the lake are as follows:

1) Deforestation on nearby hills has caused heavy silt formation in the lake. This has

decreased the depth of the lake from at least 50 feet to about 20 feet on account of

the silt collected in it.

2) Ipomea weed is also cited as a major cause of lake's deterioration as it prohibits the

growth of other plants.

3) Washing of trucks in the area contributes to the pollution by adding oil and petrol to

the sewage.

The water quality deteriorated fast as the quantity of sewage water and other effluents mixing

in the water kept rising. PMC worked towards improving the filtration plant but water quality

remained poor. In 1998, Pune Municipal Corporation discontinued providing drinking water

from the lake. However, now the lake is being studied for providing potable water again.

Ecological Impact

F l o r a :

The flora of Pashan Lake includes the terrestrial vegetation along the

periphery of the Lake as well as the aquatic plant species. Total 76 aquatic

species were observed in the vicinity of lake in 1981. However Ipomea weed is

cited as a major cause of lake's deterioration as it prohibits the growth of other plants.

F a u n a :

a) Aquatic Fauna

The water of the lake had many diverse forms of phytoplankton, zooplankton,

aquatic insects, crustaceans, amphibians, reptiles and mollusks. All in one life

stage or another were an integral part of the food chain, necessary to sustain

Lake Ecosystem. The food supply of the fishes was supplemented also by

numerous terrestrial forms, particularly during periods of rainfall or strong winds.

Maintenance of good water quality (relatively free of inorganic or organic

pollutants) was also necessary for the well being of the diverse aquatic

populations but it was not taken care of. Anthropological interventions with

natural ecosystem affected the aquatic fauna and it started depleting. Currently,

as the lake is total ly emptied, aquatic l i fe has vanished.

b) Avifauna

The lake was also known as a birdwatchers’ paradise. Recent studies by Z.W.D.

Li and T. Mundkur, in 2007 say that the presence of 207 bird species which is an

evidence of a healthy ecosystem has now gone down drastically by 80% with

latest bird count of 47 species. The Lake is home to a variety of migratory and

residential birds, which is sure to delight the ornithologists. A dense canopy on

eastern side, good shelter and food available has made Pashan Lake an ideal

place for birds.

T h e R e s t o r a t i o n a n d B e a u t i f i c a t i o n P l a n

The basic objective of the master plan is to restore the lake as a bird’s paradise by

providing breeding and feeding ground for aquatic and avian fauna.

During the financial year 2004–2005 PMC spent 1 crore for de-silting Pashan and Katraj

lakes. Reactivation of Pashan purification plant is also under PMC consideration.

The restoration plan includes the following components:

1. Desiltation of the lake body for the first time since its construction. Part of the

desiltation activities is already completed and this has enhanced the carrying

capacity of the lake.

2. Part of the silt was used to construct a 17 acre island in the lake. 10 acres of

the island is partially submerged and this provides a resting ground for birds

preferring shallow water. The island forms an undisturbed breeding and feeding

ground for the birds. 350 fruit bearing indigenous tree species have been planted

on the island.

3. The island is surrounded by marshland, which is again extremely desirable for

birds preferring to wade or feed in shallow waters.

4. Developments of a wetland system at the inlet of the lake wil l bio-remediate

the incoming water and also provide a suitable ground for birds.

5. The terrestrial birds have also been taken into consideration while planning

for the lake. Hence addit ional 1200 indigenous, fruit-bearing trees and shrubs

have been planted on the embankment around the lake. This will also act as a

buffer for the lake from the anthropogenic or developmental activities

(specifically the highway) being carried on outside the lake premises.

6. Bird hides wil l be built up on trees around the lake for bird watchers.

7. A natural walkway and an Environmental Interpretation Center is also a part

of the plan around the lake.

8. In addit ion to al l the above, the lake restoration plan includes a compound

wall al l around the lake, to prevent unauthorized intrusion.

9. Another important aspect of the restoration of the Pashan Lake includes

strengthening of the Bund which was originally constructed during the British era.

10. Protection of the Ram Nadi in the downstream of the lake by building a 4

km long retaining wall from the spillway is also included.

As of today, the general public is restricted from access into the lakes’ premises.

The restraints would be applicable till the developmental works in the lakes are

completed.