Wetlands
South Chennai
Solid Waste Management / Sewage Outfall
Pallikaranai is the heart of the south Chennai wetlands and it is in this part that the major rape of the ecosystem is underway at a breakneck speed. The STP is totally defunct (there is no Power Supply), save for the Pipeline system that brings the Sewage to the treatment plant and is allowed to discharge itself of its load directly into the wetland without even the basic filtration process. Ironically, this is hailed as a ‘Natural Treatment’ by the authorities. Added to it, a part of the STP has been allotted to the Corporation of Chennai to dump the Garbage of the city. This is aimed to be used a land filling arrangement. The Alandur Municipality Dump Yard is also proximate and employs a similar strategy sans any scientific way of Solid Waste collection and Disposal system and thus, most of it finds way into the waters of the wetlands and affects the entire biotic ecosystem. The data about the Garbage disposal in the study area speaks volumes about the content of the solid waste and the harm that it can cause.The Physico-Chemical components of the Solid Waste Sample when interpreted with the water quality, give tangible results that prove that the wetlands of South Chennai are being affected by the harmful practices of humans. For the detailed table of the Water Quality Analysis and the Four Year Data on the Garbage generation of the city, refer to the Appendix
Remote Sensing and GIS Integration
Remote sensing refers to the acquisition of information about an object without physical contact (Lo & Yeung, 2002). Data Analysis of the wetlands was done both visual and digital interpretation. The image analysed was a LISS-III (IRS-1C) of 25.5m resolution. The capture date was 3rd may 2000. Erdas Imagine 8.4 and ENVI RT 3.5 were used for rectification and classifications while Arc View 3.2 and Arc GIS for GIS analysis. 17 village maps (1:5000) of the study area were collected. To bring them into the GIS environment, Ground Control Points (GCPs) by aid of Global Positioning System (GPS). These were analysed for Area spread and land use / cover delineation. These were used to Geo-reference the sat img and extraction of study area. Supervised Classification based on in situ support and training sites bought to light the plight of the wetlands. Vegetation, Turbidity and Habitat mapping further projected the damage. The region is a wetland of diverse character with only the region around the pallikaranai village being saturated with water throughout the year. The rest of the region towards the south of this patch is Non-Perennial in nature and thus in spite of the Ground truth knowledge the supervised classification gave the regions as a new class which we had to name dry beds. Upon completion, in the process of the Table Lookup Classification, the class was merged and thus the wetland identified. In all, Nine Land use classes were identified and plotted as a map. The classes were identified as deep water, shoreline vegetation, dry beds, shallow water, thick vegetation, contaminated vegetation, built up areas, , landfills, open areas. A turbidity classification was carried on over the image, to analyse the turbid character of water, which pictured the encroachments and disturbances caused t the wetlands. This was done by subtracting band 1 with that of the FCC and classified. The classes obtained were low medium and high
Water Quality
Turbidity is the result of suspended particles in water. It is the expression of the optical property that causes light to scatter. Turbidity increases when topsoil or effluents are induced into the aquatic environment and in turn decreases the light penetration and thus affects photosynthesis. Groundwater is less turbid due to filtration. Measured in Nephelometric Turbidity units (NTU), high turbidity values were recorded in the study area STP-83.2NTU, along Vel-Tamb.Rd-26.9NTU, Thoraipakkam -66.9 this is way beyond the permissible limits of 5NTU (GOI) for drinking water. Hydrologists put the average turb.value at 30-35 (2002).
The Total Dissolved Salts possess a complimentary relationship with turbidity and include calcium ions, bicarbonates, chlorides, nitrates, phosphates, ferrous ions, sulphates, potassium, magnesium and other ions. These determine the flow of water in and out of the cells of organisms and are essential at certain levels to maintain the aquatic life. High TDS content leads to Eutrophication. TDS levels are above the permissible limits of 2000mg/l at 3036 and 2840 mg/l proximate to the Thoraipakkam intersection, where both the sewage and the garbage coagulate and enter the vast wetland that as yet is untouched and virgin in nature. In comparison, to the on the same area, TDS has increased considerably from 1410 (TNPCB 1995) to 2704 and from 1720 to 3036mg/l. Electrical Conductivity mic S/cm is the capacity of water to conduct electricity and is an indirect measure of the salt concentration (Salinity). High conductivity leads to high amount of ions such as sodium (Na+) calcium (Ca+) magnesium (Mg2+), chloride (Cl-), sulphates (So2-4), bicarbonates (HCO3-) and carbonates (CO32-) in water. Polluted waters have high conductivity. Here EC was at a high 4236 and 3895 mic S/cm giving a clear indication of the high pollution levels.
pH: ‘P’ stands for Negative logarithm (to the base ten) of and ‘H’ stands for the hydrogen ion concentration. The permissible limit is 6.5 – 8.5 (<7- acidic &> 7 basic GOI). The study area gave a pH value ranging from 6.99-7.96. Most of the aquatic flora is supposed to flourish within the pH value on either side of 7. Thus the study area is a good wetland with rich biodiversity. Barring the STP (6.99) the rest of the study area has a basic (above 7) character to it.
Alkalinity is the measure of the concentration of such ions in the water that would react to neutralize hydrogen ions and is thus a measure of the ability of water to neutralize or assimilate acids. In this wetland values as high as 808 (200mg/l GOI) and 788mg/l were attained. High alkaline water gives a bitter taste and makes it unpalatable.
Hardness and Calcium are associated with the ability of water to precipitate soap or react with soap and is due to the presence of divalent cat ions such like calcium, magnesium, strontium, ferrous iron and manganese ions. Bicarbonates & carbonates of calcium and magnesium cat ions cause Temporary Hardness, while sulphates and chlorides of calcium and magnesium cause permanent hardness. Natural hardness depends upon the geologic nature of the drainage basin. The water here is Hard with values of 720 and 670mg/l is, while the permissible limit is only 200mg/l (GOI) and 300 mg/l (USGS). Thus, it is deemed unfit for Human use. High hardness of the region can be attributed to the discharges of the industrial effluents rich in calcium with a high content - 200 and 188 (GOI-75).
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