METHODOLOGY
The proposed study to suggest suitable restoration techniques for the lakes in Bangalore based on the pollution level. Valuation of lakes is done to ascertain the economic dependency of the people living in the surrounding areas on these lakes. This entails sampling, analysing the lake water quality in the field and laboratory by using appropriate methods, socio-economic aspects of the lakes, depth analysis and volume computations of the lakes using GIS.
Sampling
For physico-Chemical characterisation of lakes, samples were collected at various inlets, outlets and middle part of Rachenahalli and Amruthalli lakes at 15 days interval. Totally four samples have been taken from each lake,every time of sampling using polyethylene containers.
Physico-chemical Analysis
The main objective of physico-chemical analysis is to assess the quality of water and to find out its pollution level.
# Physical Parameters:
Various physical parameters that were analysed were color, temperature, transparency, conductivity, pH, total solids, dissolved solids and suspended solids.
# Chemical Parameters:
Various chemical parameters analysed were alkalinity, acidity, dissolved oxygen, chlorides, sulphate, total hardness, calcium, magnesium, sodium, potassium, nitrates and phosphates. The analysis of these lake water qualities was done as per the standard methods prepared and published by NEERI and American public health association.
Color was measured using visual comparison method; temperature was determined using Mercury thermometer; pH was measured using a pH meter; electrical conductivity,using a conductivity meter; total solids,total suspended solids, and total dissolved solids, was determined using Gravimetric method;D.O was estimated using the Winkler's method. Sodium and Potassium were analysed by using flame-photometer. Alkalinity and acidity were determined by titration method provided by NEERI. Total hardness, calcium and magnesium, were determined using EDTA titration method; chlorides, using Argentometric method; sulphates, using turbidimetric method using Spectrophometer at 420 nms; nitrates, using Phenol Di sulfonic Acid method using Spectrophometer at 410 nm and phosphates , was determined using Ammonium Molybdate method using Spectrophometer at 690 nm.
Socio-economic Survey:
Socio-economy survey was conducted to quantify the values of wetland resources and to determine the economic dependency of the people living in the surrounding areas on these lakes. A random survey of the houses around the lake was carried out using a standard questionnaire format designed for this purpose. Totally five villages were selected in this regard.
Bathymetric Analysis
Bathymetric analyse is carried out to find out the depth profile of the lake. This is done by dividing the lake in to different segments using transects. The depth at various points is found by using plumb bob or by simply a rope tied with a stone at one end and a measuring tape. Volume of the lake can be computed using the depth and area data's that is obtained.
Appilication of GIS and Collateral Data
The Geographic Information System (GIS) is used for spatial and temporal assessment, which helps in identifying and monitoring the impacts, due to point and non-point source(NPS) of pollution. The patial and temporal changes in the surface water bodies are mapped using Survey of India 1:50,000 scale, topographical maps. The technology of remote sensing is used as a monitoring tool for basin management. The SOI 1:50,000 scale, toposheet number 57 G/12 are used for topographical informations, for placing ground truth sites in the field and for the preparation of base maps. Converting topographical information with field data in to digital format creates final maps and various layers of maps are prepared in this regard using Map info software. Integration of thematic layers of water quality and quantity along with socio-economic, land use and population informations are overlaid on the base map to know the Current Status and Socio-economic aspects of the wetlands.
