Deweeding

Both the lakes, with large human habitation within its catchment areas, are subject to various anthropogenic pressure, important being inflow of nutrient in the form of agricultural waste, solid and liquid municipal waters resulting in nutrients enrichment and luxurious growth of shoreline and aquatic vegetation.

The sub-project is aimed at harvesting nutrients through removal of shoreline, emergent, submerged, floating weeds and algal blooms from the shoreline, shallow sections and thereby improving water quality of the lakes. The deweeding operation envisages complete removal of in Vader species like Ipomea fistulosa and controlled removal of other types of weeds to reduce nutrient level as well as maintain the ecological balance of the lakes. In the Upper lake, deweeding works is spread over an area of 59.5 sq. km. which include water spread area and its fringe area where as in Lower lake it is limited to water spread area only. 

The deweeding operation has started from February 1999, with target of complete removal of shoreline weeds from 430 ha., controlled removal of emergent, submerged and free floating weeds in 4 cycles and removal of algal bloom as per requirement.

The target and achievement of deweeding operation are as follows:

S.No.	Weed Type	Quantity to be removed (Target)	Achievement
1	Shoreline (Ipomea fistulosa)	223 ha	357 ha
2	Emergent (Scirpus royalie & Cyprus rotandus)	714 ha. (3cycle)	380 ha. (2cycles)
3	Other Emergent (Ipomea aquatica, Polygonum glabrum, etc)	174 ha. (3cycles)	222 ha. (2cycles)
4	Floating  (Water hyacinth)	27023 tonnes	24039 tonnes
5	Submerged Weeds	101856 tonnes (3 cycles)	66427 tonnes (2 cycles)

This sub project is likely to be completed by March 2002, and then maintenance deweeding operation would continue for another 3 years under the DPR.