| RESTORATION OF LAKES IN BANGALORE :
The term restoration means the reestablishment of predisturbance aquatic functions and related physical, chemical and biological characteristics. The objective is to emulate a natural, self-regulating system that is integrated ecologically with the landscape in which it occurs. Often, restoration requires one or more of the following processes: reconstruction of physical conditions, chemical adjustment of the soil and water; and biological manipulation, including the reintroduction of absent native flora and fauna.
The conservation and protection involves not only buffering wetlands from direct human pressures, but also maintaining important natural processes that operate on wetlands from outside, which may be altered by human activities. Management towards this end should emphasize the long term sustenance of historical, natural wetland functions and values. Restoration is thus a good opportunity to manage wetlands for broad wildlife goals, as restored wetlands provide enhanced wildlife benefits, in addition to other benefits, concurrently.
Most of the developmental activities are currently concentrated in and around Bangalore city. This has led to large scale migration of people from rural and other areas. This increase in population (due to the short sighted planning strategies) over the last two decades has created lot of pressure on the existing waterbodies. The Bangalore Water Supply and Sewerage Board is unable to meet the requirements for potable water in the city due to dwindling water resources (lakes, wells, etc.). Disappearance of lakes in the city is responsible directly for lowering the ground water table, which is evident from the lowering of levels from 80 feet to 300 feet in certain localities. Increasing demands for potable water in the city necessitates the search for environmentally sound alternate water sources. Otherwise, it will be difficult to meet the water demand for the next decade (leading to water disputes among families within and across streets!). Reclamation with an emphasis on health protection, technical feasibility and economics could be a viable option in this context.
The preliminary step that has to be implemented in restoring lake for their long-term sustenance includes:
- Pollution impediment: Wastewater, solid and semi solid wastes entering in to the lake from external sources must be stopped before any restoration work is implemented.
- Harvesting of Macrophytes: Water hyacinth and other nuisance vegetation present in the lake, causing eutrophication, must be removed manually or mechanically. Weed infestation can also be controlled by applying chemicals like methyl-chlora-phenoxy-acetic acid, hexazinore, etc., and biological control by means of introducing Pila globosa (trophical snail), Chinese grass carp (fast growing fish) etc. that feed on many aquatic plants.
- Draining the water: Water present in the lake must be cleaned or drained completely.
- Desiltation: Dredging of the sediments in the lake to improve the soil permeability, water holding capacity and ground water recharge. Recent technological developments do permit wet dredging. Studies in Kolar district reveal that desilting of waterbodies helps in lowering fluorosis in borewell water (ground water).
- Constructed Engineered Wetlands: A constructed wetland is a water treatment facility that has gained importance in recent years for treatment of lakes. Duplicating the processes occurring in natural wetlands, constructed wetlands are complex, integrated systems in which water, plants, animals, microorganisms and the environment (sun, soil and air) interact to improve water quality. Constructed wetlands mimic nature by mechanically filtering, chemically transforming, and biologically consuming potential pollutants in the wastewater stream. These are shallow pools constructed on non-wetland sites as part of the stormwater collection and treatment system. They provide conditions suitable for the growth of emergent marsh plants. These systems are primarily designed for the purpose of stormwater management and maximum pollutant removal from surface water flows through physical, chemical and biological mechanisms. They are often used in sequence with a sediment basin or stormwater pond.
As an extension of the restoration programme, watershed management practices are essential for proper land use, protecting land against all forms of deterioration, conserving water for farm use, proper management of local water for drainage, flood protection and sediment reduction and increasing productivity from all land uses. Key steps for best management practices include:
- Pollution alleviation practices to reduce the engendering of non-point source of pollution (mainly agricultural and storm runoff) through source reduction, waste minimisation and process control.
- Afforestation with native species in desolate areas around the wetland (catchment area) to control the entry of silt from run off.
- The shorelines of the lakes are lined with bricks or stones in an attempt to control shoreline erosion.
- Constructed wetlands for the purpose of stormwater management and pollutant removal from the surface water flows.
- Infiltration trenches for reducing the storm water sediment loads to downstream areas by temporarily storing the runoff.
- Extended detention dry basins for removing pollutants primarily through the settling of suspended solids.
- Gyration of crops rather than monocultures to reduce the need for N and assist with pest control and help in aeration of soil.
- Promoting public education programs regarding proper use and disposal of agricultural hazardous waste materials and regular monitoring of lakes, which are rudimentary.
The restoration programs with an ecosystem approach through Best Management Practices (BMPs) helps in correcting point and non-point sources of pollution. This along with regulations and planning for wildlife habitat and fishes helps in arresting the declining water quality and the rate of loss of wetlands. These restoration goals require profound planning, authority and funding along with financial resources and active involvement from all levels of organisation (Governmental and Non-Governmental Organisations (NGOs), research organisations, media, etc.) through interagency and intergovernmental processes all made favourable in innovating and inaugurating the restoration programs. Network of educational institutions, researchers, NGO's and the local people are suggested to help restore the fast perishing wetland ecosystem and conserve those at the verge of extinction by formulating viable plans, policies and management strategies.
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