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Conservation and Management Plan for Dal- Nagin Lake
3.2 Sewerage and Sewage Treatment
Sewerage and Sewage treatment constitutes a major component of the plan for preventing the pollution of Dal Lake. Over a number of years, an intergrated sewerage system in the peripheral area was under debate . JKUEED had even started work and some components viz. Trunk sewers and pumping stations have executed . Top
The Dal lake receives waste water from fifteen drains and inflow from Telbal nallah . The drains bring in around 40 mld of sewage and join the lake at locations indentified elsewhere in the detailed report . Two alternative plans for sewage treatment where envisaged. One proposal conceptualised a centralised sewage treatment where in all the waste will be collected by sewers (gravity mains) and trunk sewers with 15 intermediate pumping stations (IPS) and a main pumping station , at Brarinambal. This unit of about 41 mld wil treat the sewage through an activated sludge process and release treated waste effluent through Brarinambal . This unit of about about 41 mld will treat the sewage through an activated sludge process and release treated waste effluent through Brarinambal cut into Jhelum . This system,though theoretically very sound has some inherent weakness , such as power dependence (in pumping and treatment), large size trunck sewers and large distance of transport. The power scenario in Srinagar town is dismal and utilizing it for pumping sewage as against domestic requirment seems a far cry . Moreever, failure of system or any component will put the entire machinery out of gear . further a centralised sysytem would entail large operation and maintenance costs. To obviate these difficulties a decentralised system is preffered and has been proposed . This bulk of the sewage will flow by gravity and pumping will be resorted to only when, there is no waste would ensure that the effluent satisfies the standard s and would have substantially reduced level of E. coli and nutrients. Top
3.3 solid Waste Management
The solid waste generated in human settlements within the lake and on the periphery of the lake is one of the contributory factors for the deterioration of the lake environment . Nearly 38000 people reside within the lake and with a capacity of nearly 10,000/- persons the population within the lake contributing to the solid waste could go to about 48000, specially during the tourist season . Apart from this about 2,20,000 people live on the periphery of the lake, who also, directly/ indirectly contibute to the pollution of the lake, through indiscriminate disposal of solid waste into the lake water. Top
A survey of the existing practice indicated that the solid waste Management sytem is not well organised the following gaps cloud be indentified.
 Provision of open dumps for collection in the peripheral areas . These are not conveniently accessible due to large distance & result in a lot of littering due to the activities of rage pickersc animals, birds, rodents and parasites.
Garbage is unnecessarily handled several times and even put on ground before begin finally transferred to the tractors, tippers or trucks .
Disposal by land filling at saidpora Achen does not follow the norms desirable in sanitary land filling practices.
The menace of substantial quantity of polythene bags, which are non bio- degradable is unchecked
community participation and awareness is lacking . Top
Other measures proposed include provision of proper Community bins, “ Garbage Gobblers” etc and the design of the same as well as the areas where they can be provided has been indicated.
The collection of solid waste from houses and its haulage to the disposal will continue to be the responsibility of Srinagar Muncipal Corporation.
3.4 Hydraulic Aspects
The main source of water inflow to the Dal Lake is the Telbal Nala. This also is the main source of sediments inflow and hence to control the sediments entering the lake. a selling basin has been contructed just before the Nala enters the lake . The water from Telbal nala is diverted to the settling basin from where it flows over a 70 m long weir back to the Nala & then to the lake . The dversion weir on the Telbal nala is still to be constructed . The detailed hydraulic and structural design of this work has been given. Top
The flow conditions through the settling basin have been examined and from these the pond level required for diversion of the flow has been worked out. The maximum probable 100yr.flood in the Telbal Nala was estimated as 141.6m3/s and the HFL corresponding to this flood has been worked out on the known cross-section and slop the Nala . It is found that the embankments built on the Telbal Nala will have to be raised tp prevent overtopping during such a flood . Some walls of the settling basin may also need to be raised. the design of the diversion weir is based on the data as mentioned above. Top
The carrying capacity of Nala Amir Khan will be dependent on the water located in the Anchar lake and the opertion of the gated control just upstream . conditions ubder wich the Nala will be able to carry its design of 37m3/s have been indentified. TOP
It is wel known that increasing the inflow of water to alake always. help maintaining the lake in a healthy state and Dal lake is no execption . From consideration , it was felt that it would be worth while if some additional water to be brought from Sindh Nala through the Padshahi canal or Sindh Extension carrying the Dal lake. It wasfounf that about 2 m3/s of water can be brought to the Dal lake through the Padshahi canal. TOP
3.5 Restoration and Development
In order to permit the use Dal lake for aquatic sports, navigation and other desired uses, a case has been made out for removal of excessive biomass of macrophytes by mechanical harvesting . There is no denying that in some areas of the lake weed growth is excessive, which presents a degraded view of the ecosystem. The most sound and reasonable management approach is, however, the control of macrophyt vegetation in the Dal lake rather than its eradication. It is wel known that macrophytes are bio-indicators of pollution . they effectively remove nutrients from the sediments and this helps in pollution abatements. At the same time excessive growth of macrophytes impedes transport, hinders irrigation and increase sediments deposition. Thus an assessment of the advantages and disvantages of mechanical harvesting before selecting an approach is necessary. This has been carried out;- Top
Dredging can be a successful lake restoration technique if there is pre implementation evaluation of the lake setting , proper equipmet and disposal sites are elected and the effects it will have on lake ecology and long term providivity evaluated. If seems that no preliminary studies were undertaken before dredging was started in dal Lake . It suggested that dredging should be very selective and should address the following aspects:- Top
 It should be carried out to deepen those parts of the lake which obstruct free flow of water.
Except when solid land mass or shoals are being removed dredging should aim at removing only upper 20 cm of the sediments which is rich in nutients.
Proper selection of disposal sites is very important. The major adverse impact of present dredging is the filling up of wetland area which used to border the lake and act as a biofilter. This should be avoided at all costs and efforts made to restore these wetlands. Top
Reed beds comprising native species such as Phrgmites Communis, Typha angustata, Juncus and Scirpus need to be planted along the northern foreshore road to act as a filter for the nutrients that may leach from the dykes.
Macrophytes which have established on the silted up areas on the Hazartbal Bain should be dredging out and not allowed to trap silt as is the case at present.
3.6 Circulation & Contaminant Transport Modelling Top
In order to assess the impact of the interventions proposed . It was decided to develop a circulation and contaminant transport model for the Dal lake . The model,which utilizes the inflows and outflows as forcing functions and permits projections of velocities or species concentrations within the lake domain for assigned lake physiography, is based on solving the governing differential equations. The equations were solved numerically by the finite difference method using an iteractive scenarios have been projected using the model. It has been found that removal of the Nishat pipeline bund is not likely to have much of an impact. It is aslo found that operating the Brari Numbal Cut is likely to result in a considerable improvement of the water quality in its vicnity . The other proposed interventions appear to have a significant impact on the water quality in the lake, as the results show a considerable decrease in the BOD and concentration of Nitogen and Phosphorous in the post intervention scenario |
