Status of Wetlands in Bangalore

 In U.S.A, nearly 54% of the 87 million hectares of wetlands have been lost, primarily through agricultural activities. Twenty-two of the lower 48 states have lost at least 50 % of their original wetland area. Indiana, Illinois, Missouri, Kentucky and Ohio have lost more than 80 %, while California and Iowa have lost nearly 99 % (USEPA, 1995). Conversion of the wetland for agriculture was responsible for 54 % of the loss; drainage for urban development - 5 % and planned development - 41 %. These wetlands are threatened by air and water pollutants, and hydrologic alterations (USEPA, 1994b). In New Zealand, about 90 % of wetlands have been lost over the last 150 years through land drainage and development. In Ireland, only 23,000 hectares of bogs (7.5 %) out of the original 3,11,000-hectares remain (Chatrath, 1992) and about 51 % of wetlands have been lost to forestry and peat mining during the last 3 decades. An average of 61% of wetlands has been lost in six countries (Netherlands, France, Germany, Spain, Italy and Greece) as estimated by the European Commission in 1995. It was noticed that nearly 67 % of mangrove forests was lost in the Philippines over the last 60 years. In Netherlands, only 3.6 % of the original bogs remain. Wetland area has drastically reduced in Belgium, Chile, South America and Africa, mainly due to significant anthropogenic activities that include intensive agricultural activity, drainage etc. In Japan, only 19,200 (nearly 60 %) out of 32,000 coastal wetlands remain. Similar situations apply to the wetlands of U.K and Norway too (Clare Shine et al., 1999).

 Almost 95 % of the wetland coral reefs have been damaged primarily through excess fishing, using dynamites and other poisonous materials. About 20 % of the world’s fresh water fishes were found to be endangered, mainly due to disturbance to their habitat (IUCN, 1994). Fresh water fishes comprise about one-third of all fish species. The diversity of fish species is threatened, since lakes are semi-closed systems and fishes have no means of escaping from lake deterioration, becoming vulnerable to ecosystem disturbances.  Table 11gives the number of threatened fresh water fish species data (The1996 IUCN Red List of Threatened Animals) for 21 selected countries.

Table 11: Number of threatened fresh water fishes

In several countries, 20–30 % of the fish species are threatened at present, with about 81 fish species recorded to have become extinct during the past century. Globally, pollution and habitat modification are the most widespread and pervasive factors known to cause decline in fisheries.

 Totally, 93 lakes were sampled in five continents (Africa, Asia, Central and South America, Australia and Europe). It was found that nearly 55 lakes have declined in terms of quality, particularly those in Asia. Table 12 gives the changes in the lake quality for the five selected continents.

Table 12: Changes in lake condition

Globally, large and long-lived lakes have been known to support high diversity of fishes, molluscs, crustaceans and several invertebrates. Table 13 gives the biodiversity features of major long-lived lakes.

 Table 13: Biodiversity features of major long-lived lakes

Approximately one third of Wullar lake of Kashmir is degraded due to siltation and encroachment, which have also affected many other lakes in India, especially Chilka lake in Orissa (the largest brackish water lagoon in south-east Asia), Kolleru lake (Andhra Pradesh) and Sukhna lake, a man made wetland in Chandigarh. Most of these lakes have lost their water holding capacity in just two decades. Eutrophication (nutrient enrichment) and weed infestation threaten Srinagar’s Dal lake, which is situated in the heart of Kashmir Valley.

Water hyacinth is spreading at an alarming rate in Harike lake (Punjab), having infested 75% of the wetland area. This lake is important for migratory waterfowl and attracts over 20,000 ducks during winter. Nearly 210 species of birds were found in this wetland, out of which three duck species, the bronze-capped teal (Anas falcata), scaup duck (Aytha marila) and white-headed stifftailed duck (Oxyura leucocephala) are rarely seen elsewhere in India (WWF, 1992). Extensive fishing throughout the year has caused considerable disturbance to the aquatic life (especially birds) in this lake.

Loktak lake, the largest natural lake in eastern India (in the southern part of Manipur valley), is seriously threatened on account of unplanned land use practices and over exploitation of the available resources in its catchment. These improper planning approaches have led to unsustainable economic development. Much of the lake is choked with weeds, silted (due to catchment conditions) and encroached from all sides. These anthropogenic activities have resulted in shrinkage in size, pollution and loss of rich biodiversity and other biological resources.

Kaliveli (in South Arcot district of Tamil Nadu) is one of the largest semi-permanent water bodies of India that has suffered from shrinkage of its water-spread area, mainly due to encroachment by paddy fields. A wide variety of water bird species, including pelicans, storks and flamingos, is poached for meat. This has resulted in the migration of the entire bird population (upto 40,000) of Kaliveli.

Kolleru Lake (Andhra Pradesh) has lost 34,000 hectares of water spread to agriculture. Deepar beel (Assam), Hokarsar Lake (Kashmir) and the Pyagpur and Sitadwar Jheels (near Lucknow, Uttar Pradesh) are just a few of the many wetlands that have shrunk on account of reclamation for agriculture.

Aftab Alam et al (1996) studied the presence of plankton, and the dynamics and effects of varying dominant biota on the plankton population in four freshwater ponds receiving pollutants. The study involved both qualitative and quantitative estimation of plankton by drop count method, and they were identified using standard monographs of Edmondson (1959) and Pennak (1980). ‘A’ pond, which received detergent pollutants, showed less plankton with 13 genera of phytoplankton and 7 genera of zooplankton, the dominant phytoplankton being Microcystis, Tetrapedia, Nostoc, Selenestrum, Euglena, Phacus and certain diatom species and zooplankton such as Branchionus, Filinia, Hexarthra, Euchlanis, Monia, Cyclops and Diaptomus. The poor results for pond 'A' compared to ponds 'B' (showed 24 species of phytoplankton and 15 species of zooplankton) and 'D' (30 species of phytoplankton and 17 species of zooplankton) was attributed to the influx of phosphorus into the water body by washing activities and dominance of certain planktivorous insects. Also, the presence of certain pollution tolerant species of phytoplankton - Oscillatoria, Scenedesmus and Euglena indicated high degree of organic pollution. The study concluded that both eutrophication and macrophytic infestation are responsible for plankton richness of ponds and the dominant biota affected other biota, bringing changes in the biotic composition with few others interfering directly with the biotic community.

 S. K. Khatavkar et al (1995) studied the short-term effect of phosphorus on phytoplankton primary production in two tropical fresh water bodies situated in the Western Ghats region of Maharashtra. The study involved measurements of important physico-chemical parameters. The results showed no significant change in the production after adding phosphorous, except for a marginal increase on few occasions. It was felt that the primary production during short-term exposure might be influenced by the planktonic density rather than absorption of nutrients as P and N. Addition of nutrients in short-term exposure can stimulate phytoplanktonic growth rate only where the phytoplanktons are in the starving condition. However, such conditions occur often in deep, temperate and oligotrophic lakes, where turnover period is longer.

 Kaur H et al (1996) studied the biotic components of a fresh water pond in Patiala, which revealed its eutrophic condition. Plankton analyses were done on monthly basis for six months following the methods of Mellanby and Tonapi. The protozoan fauna consisted mainly of Diffugia sp., while paramecium sp., varied seasonally. Nine species of rotifers were observed as the most abundant of all the planktonic population present, indicating their tolerance to organic pollution. They included Lecane sp., Brachionus sp., Notholca sp., Anuraea sp., Rattulus sp., Cathypna sp., Trichotoria sp., and Notops sp. 

Large tracts of the Sunderban ‘mangals’ have been axed in the last two or three hundred years, reducing the forested area by half. A part of Pichavaram mangroves of Tamil Nadu has been drained and certain mangrove species such as Sonneratia and Xylocarpus have been extensively felled, restricting some areas to pure coppices of Avicennia, severely depleting the species diversity. 75 % of Little Andaman is deforested. The increase in sewage and industrial effluent in mangrove estuaries has also led to the disappearance of many species of flora and fauna. The increase in industrialisation in coastal areas, off-shore mining, dredging, construction, and oil transport have greatly increased the vulnerability of coral reefs in India. It has been estimated that 50–70 % of the coral life of the Gulf of Kutch has been destroyed as a consequence of mining. In the Andamans, widespread and uncontrolled deforestation has resulted in soil erosion and massive siltation in the fringing reef habitats (WWF, 1992).

Hunting and poaching of waterfowl and other animals prevalent in many parts of the country mainly threaten wetland faunal species. It is estimated that about 50% of the ducks visiting the Manjhaul chaur near the Bihar-Bengal border are poached by duck-trappers. Poachers kill about 15,000 – 20,000 waterfowl each year in Chilka lake (Orissa). Poaching of wetland dependent species, in particular, hunting of the endangered Indian rhinoceros in Assam’s Manas and Kaziranga National Parks, while the collection of gharial eggs in Satkoshia Gorge Sanctuary (near Cuttack, Orissa) has greatly depleted the wild populations.

Jebanesan et al (1994) paper deals with physico-chemical analysis, metallic and non-metallic pollution of the Cooum river at 9 stations in the vicinity of Madras for a period of three years from June 1985 to May 1988 in an attempt to find the present status of pollution in the river by analysing the chemical factors responsible and the relative abundance of aquatic macrophytes. The results of the various physico-chemical parameters showed heavy pollution due to industrial and domestic sewage at the downstream than at the upstream. The results are expressed as a range at all the 9 stations for the various parameters such as pH, DO, BOD, COD, heavy metals, etc.

L.L.Sharma et al (1992) studied the diurnal fluctuations in some limnological parameters in relation to plankton in Lake Fatehsagar in Rajasthan. For diurnal variation studies, sampling was done on three occasions in the deepest part of the lake. The parameters selected for the study were visibility, air and water temperature, pH, DO, carbon-di-oxide, carbonates and bicarbonates. While comparing data on physico-chemical parameters with planktonic density, it was evident that phytoplankton had higher density at noon coinciding with reduced level of carbon-di-oxide and increased pH, DO and carbonate in the surface waters. Microcystis flosquae, a dominant plankter had maximum density at 15.00 hrs and many rotifers were found on the surface during night. In general, maximum number of zooplankters coincided with the higher concentration of carbon-di-oxide in the bottom waters, decreased pH and lack of sunlight during late night hours.

Someswara Rao et al (1994) studied the quality of ambient air and drinking water in the port town of Kakinada, Andhra Pradesh. The water of river Godavari was analysed before and after treatment (at both the treatment plants constructed by the side of each reservoir). 60 samples across the Godavari river and along the canals were also analysed. The river water was found to be generally soft but turbidity and iron were found to be high in the post-monsoon season. Nitrites were also high indicating pollution due to organic matter and DO was found to be in the range of 5.1-6.5mg/L. Residual chlorine at the tap end was sometimes found to be as high as 0.4 to 0.5ppm (optimum level-0.1ppm) and sometimes, it was absent. Some parts of Kakinada have saline and hard ground water. They reported that the above-said effect could be due to seawater intrusion since the concentration of chloride, magnesium, sulphate and sodium were found to be high near the sea and reduced as one moved away from the sea. The ground water table was found to be at a depth of 1-2.5m, which could lead to pollution of ground water, by sewage inflow. High levels of nitrite and low levels of DO strengthened this claim. Fe, Cu and Zn were found to be in concentrations much higher than the desirable limits. 

Ajai Pillai et al (1996) studied the physico-chemical property of drinking water of Durg Municipality. Samples for analysis were collected from utility points (municipality taps). Raw water and treated water were also collected; the samples were analysed for their chemical and biological characteristics following standard methods (APHA-1985). They reported higher values for the chemical parameters at Police Line and Sindhiya Nagar. The TDS concentration at this place was above the limit (150-10,500). The total hardness was also found to be higher. The fluoride content was found to be much lower than 0.5mg/L and hence there was a deficiency in fluoride. They reported a high coliform (MPN/100ml) indicating a poorly maintained supply system with a possibility of sewage mixing with water supply.

V.N.R.Rao et al (1987-90) studied sewage pollution in the high altitude Ooty lake, its causes and concern. The sampling programme consisted of a series of fortnightly water quality and biological surveys for one year from Nov-87 to Oct-88 and monthly surveys from Nov-88 to Oct-90. Four sampling points were chosen. The physico-chemical and biological characteristics of the waters were estimated according to Standard methods (APHA, 1981) except ammonia, which was determined, by phenol-hypochlorite method outlined by Solarzano (1969). The alkalinity and hardness of the lake was reportedly high. Nitrate-nitrogen fluctuated seasonally and ranged between 0.03-3.07 mg/L, nitrite-nitrogen between 0.01-1.23 mg/L and ammoniacal-nitrogen between 0.01-8.31 mg/L. Phosphate-phosphorus was very high throughout the study period, highest value being 4.97 mg/L (lakes with or above 20 mg/L of phosphate-phosphorus are called eutrophic lakes according to Dillon-1975). The concentrations of metals in the water were low to be considered hazardous. Concentration of DDT in the waters (1.37-3.7ug/l) far exceeded its solubility level suggesting the presence of rich organics in the surface waters. a, B, r and d isomers of HCH were detected in the waters. Carbofuran was observed in the lake and the concentration ranged from 14.22-32.4ug/l. Chlorophyll a concentration in the surface water ranged between 24.7 and 196.8mg/m³. Blue-green algal blooms were observed in summer that indicated eutrophic conditions of the lake. The dominant species of phytoplankton in the lake were Chlorophyceae, Scenedesmus, Chlorella, Crucigenia, Oocystis, Chlorococcum, Pediastrum, Schroederia, Tetrastum and Ankistrodesmus. Total and faecal coliforms were high at the inlet points and gradually increased towards the outlets of the lake. Prevention of entry of raw sewage, dredging the lake and removal of E.crassipes will enhance the self-purifying capacity of the lake.

Gupta.S et al (1992) conducted a preliminary investigation on physico-chemical factors, periphyton and invertebrate communities in a protected water work of Shillong, Meghalaya, to assess the drinking water quality and major environmental changes of the incoming stream water as it passes through the water supply system. High levels of DO, low levels of suspended solids and the absence of molluscs and tubifields indicated high natural water quality of the reservoir.

Nag.J.K. et al (1993) studied trace metal levels in drinking water of Hoogly district. Water samples were collected from 55 locations from tube wells and other ground-water sources used as drinking water in the district of Hoogly, West Bengal. In all samples Hg was absent, Na, Ca, Cr, Pb, As, K (except in one) and Mg (except in two) were under maximum admissible concentration or guide level (GL) recommended by WHO. But the serious cause of concern was the presence of Zn in >65% water samples with a maximum of 33 times more compared to WHO recommended GL. Other heavy metals like Cu and Cd were also found in several samples.

Pandey. D.K (1993) evaluated the water quality of Nainital lake (lentic ecosystem) of Central Himalaya at bimonthly intervals. The study was conducted to determine the impact of seasonal variation on physico-chemical and microbial characteristics of Nainital lake water of Central Himalayan region. Various characteristics of water were evaluated at bimonthly intervals from Sep. 1990 to Jan. 1991. All the parameters except DO of the lake water observed were maximum during the month of September and minimum in the month of January. DO content on the other hand was maximum in Jan and minimum in Sep. samplings. The study showed high pollution load in this water ecosystem at all times.

H.Kaur. et al (1996) studied the abiotic and biotic components of a fresh water pond of Patiala (Punjab). The Sirhindi Gate Pond lies close to thickly populated localities and thus has become a dump for domestic wastes. This pond is located at Vikas colony, a thickly populated locality lying opposite the Sirhindi Gate of Patiala City. Water samples were collected once a month over a period extending from July-1992 to December-1992. Temperature, pH and DO were taken on the spot while the other physico-chemical parameters like alkalinity, chlorides, nitrates, hardness and iron were estimated in the laboratory as per APHA (1989) procedures.

The pH value ranged from a minimum of 7.4 in September to a maximum of 8.4 in August. The alkalinity values fluctuated between 220 mg/L in December to 350 mg/L in August. Total hardness varied from 110 mg/L (July) to 220 mg/L (Dec). The chloride content varied from 200-280 mg/L (permissible limit = 250 mg/L). The Fe content varied from 0-0.7 mg/L and was totally absent in September. The protozoan fauna of the pond was Paramecium species, Difflugia species, Copromonas species, Oxytricha species and Spirostomum species. Nine species of rotifers and 2 species of annelids were present. Crustaceans and insects were abundant in July and August.

M. Parvateesam and Sudha Gupta (1994) studied the physicochemical characteristics of a lake receiving effluents from textile mills in Rajasthan. Drainage of wastes from textile mills alters the physicochemical characters of freshwaters. Hamir lake situated near the industrial area of Kishangarh near Ajmer was chosen for the study. The chemical analyses of the water samples were carried out following the methods recommended by Golterman et.al (1978) and APHA (1989). Temperature ranged from 18.3-34.6 ⁰C, pH from 6.5-8.8 units, conductivity from 1.75-4.0x10^-3 u/cm, total alkalinity from 101-654 mg/L, TDS from 772-1770 mg/L, chlorides from 51.2-161 mg/L, DO from 0.04-12.35 mg/L, dissolved carbon-di-oxide from 0-26.3 mg/L, ammonia-nitrogen from 1.1-3.9 mg/L, nitrate-nitrogen from 0.24-0.84 mg/L, phosphate-phosphorus from 0.9-8.6 mg/L, dissolved organic matter from 280-480 mg/L and BOD from 100-160 mg/L. These values indicate that the lake is polluted. Dissolved organic matter is accumulated in the lake due to textile wastes and oxidation of dead aquatic flora and fauna.

Baruah. B.K. et al (1996) studied the effect of paper mill effluent on the water quality of receiving wetland. The Nagaon Paper Mill, located at Jagiroad in Central Assam, employs bamboo as raw material, various chemicals like alkali, sodium sulphate, chlorine etc. and water for the manufacture of paper. The mill releases effluents at the rate of 2100 m³ per hour containing numerous organic and inorganic chemicals, polluting a wetland called Elenga Beel. The analysis of effluent flowing out of the ETP and Beel water was carried out as per Standard methods of APHA (1985) and Trivedi and Goel (1986). The paper mill effluent revealed that most of the parameters and components of the effluent had crossed the standard permissible limits, specifically in respect to pH, DO, BOD, COD, hardness, alkalinity, chlorides, sulphates, Ca and residual chlorine. The Elenga Beel water quality before confluence with the effluent showed normal values of the water parameters. The pH of Beel water after confluence recorded high in pre-monsoon season. Further study revealed absence of DO and high BOD and COD. Analysis further revealed that the high load of alkalinity, hardness, chlorides, Ca, Mg, Na, K and sulphate of the effluent caused remarkable increase in values of all these parameters in the Beel water. The findings clearly indicated that Nagaon Paper Mill effluent has extremely polluted the Elenga Beel.

Sabu Thomas and Abdul Azis P.K (1996) studied the spatial and temporal distribution of nutrients in the Peppara reservoir-a man-made ecosystem in the Western Ghats. Water samples were collected from 4 stations that were monitored and analysed following techniques and procedures (Golterman 1969; Jhingran et al 1988). The concentration of nitrate-nitrogen in the reservoir ranged from 0-1ug/l at the surface and 0.08-0.85ug/l at the bottom. Maximum value was observed in Jan at the intermediate zone of the reservoir. Phosphate-phosphorus concentration ranged from 0-1.51ug/l. Silicate concentration ranged from 1ug/l to 36.95ug/l for surface and bottom water. The major supply of phosphorus in the reservoir comes from agricultural areas and plantations in the watershed of the reservoir. When the nutrient values in the present study were compared with those from other reservoirs in Kerala, it was found that the concentrations of nitrates, nitrites and phosphates were almost the same and that of silicate was higher.

H.C. Kataria et al (1995) carried out an assessment of water quality of Kolar reservoir in Bhopal (M.P). The samples were selected from 6 sampling stations at different stations of the Kolar dam. The samples were analysed according to APHA (1985), Trivedi and Goel (1986) and NEERI (1986). Temperature, pH, turbidity, electrical conductivity, total solids, suspended solids, nitrites, nitrates, phosphates, chlorides, total alkalinity, total hardness, calcium hardness and magnesium hardness were analysed on the same day. BOD was determined by dilution and incubation method. Temperature varied from 22.4 to 33 ⁰C and pH ranged from 7.5 to 8.1. Turbidity ranged from 6.0 to 38.2 NTU. Nitrite ranged from 0.002 to 0.080ppm and nitrate ranged from 0.026 to 0.840ppm due to organic pollution and use of fertilisers and industrial effluents mixing into the dam water by run-off water. Phosphate concentration varied from 0.006 to 1.2ppm. Phosphate concentration was found to be higher in summer and lower in winter. Chloride content ranged from 22.2 to 34.8ppm. Total hardness ranged from 112 to 136, 86 to 102 and 26 to 42ppm, respectively in different sampling points of the dam. BOD and COD ranged from 2.0 to 3.6 and 18.2 to 92.8ppm respectively. Fluoride ranged from 0.030 to 0.123ppm. Sulphate ranged from 38.4 to 72ppm. These results show that the reservoir is severely affected by various domestic and industrial effluents flowing into the dam at various points.

H.F. Mogal and H.C. Dube (1990-92) studied the distribution of faecal indicator bacteria in mud and water at Dandi Sea coast. Mud and water samples were collected aseptically at bi-monthly intervals from June 1990 to April 1992. Both types of samples were serially diluted for the enumeration of E. coli by pour plate method on eosin methylene blue (EMB) agar medium. The examination of coliforms was done by the multiple-tube-fermentation procedure as a most probable number (MPN) index. It was determined by consulting the PMN chart (APHA, 1985). Using azide dextrose broth, a presumptive test was performed to enumerate faecal streptococci (APHA, 1985). The total coliform population builds up from June onwards reaching a maximum in April. E. coli was present in least numbers in June and the highest counts were obtained in December. The faecal streptococci were also at their lowest in June and rose steadily reaching highest numbers in December. The study showed that the total coliforms outnumbered the E. coli and faecal streptococci. The faecal pollution of human origin noted in the mud and water can be safely ascribed to sewage effluents having coliform bacteria.

 Bangalore – Case studies

 Hebbal lake, situated on NH-7, has been severely affected by sewage and industrial effluents from BEL factory and Vidyaranyapura. The lake was eutrophic due to excessive sewage inflow. High chlorides, sulphates, COD, phosphate and solids damage the quality of water. The preliminary socio-economic survey carried out in the region surrounding Hebbal lake through Contingency Valuation Method showed high level of dependency on wetlands for ground water, food, fodder, fuel, etc. The lake has been restored now. The lake, even in its present state, supports irrigation and acts as a source of fodder to the livestock in the surrounding areas (Ranjani and Ramachandra, T.V, 1999).

 Madivala lake, a perennial tank located in south eastern part of Bangalore City, has been reduced from 114 ha to around 100 ha due to encroachment by the BDA for a road and illegal development of private layouts. Direct discharge of domestic sewage from parts of Jayanagar and J.P Nagar has increased the pollution of the lake. Low DO, high alkalinity, hardness, coliform bacteria, and predominance of Microcystis, pollution indicating algae, are deteriorating the water quality (Ayesha Parveen and Ramachandra, T.V, 1998).

 Ulsoor lake, one of the important lakes of Bangalore, has very broad and deep feeder channels through which sewage and sullage flow in. The runoff and discharges from Commercial Street, automobile workshops, aeronautical industries and Lakshmi talkies affect the lake. Fishy odour, high TSS, alkalinity, hardness, phosphates, coliform population and predominance of Microcystis, damage the quality of water (Priyadharsini and Ramachandra, T.V, 1998).

 Amruthalli lake, situated in Bangalore north taluk, has now attained eutrophic condition due to excessive input of nutrients and organic matter through sewage, storm water, industrial effluents and dumping of organic waste matter from surrounding areas. The lake water is severely polluted by phosphates, TSS, alkalinity, hardness, odour, weed infestation and low DO. Socio-economic survey showed the economic dependency of people residing around the wetland to be about Rs.20/day. The lower value was due to the lake being eutrophic and unusable (Rajinikanth and Ramachandra, T.V, 2000).

 Rachenahalli lake, situated in Bangalore North and South taluks, has been polluted due to discharge of wastewater from nearby institutions and dumping of organic waste materials from the surrounding areas (mainly poultry wastes). Its quality has been affected by parameters like nutrients, alkalinity and hardness. Socio-economic survey showed the economic dependency of people in the surrounding villages to be about Rs.10,435/day [during cropping and fishing season] (Rajinikanth and Ramachandra, T.V, 2000).

 Kiran. R, et al (1998) carried out a comparative water quality assessment of Yediyur and Bannergatta lakes of Bangalore. A periodic monitoring for 12 months (once a month) was done. The physical parameters analysed were colour, odour, temperature, transparency and turbidity. The chemical parameters were pH, electrical conductivity, solids, hardness-Ca and Mg, nitrates, phosphates, potassium, sulphates, dissolved oxygen, BOD, COD, free carbon-di-oxide, fluorides, Na and heavy metals like Cu, Pb, Fe, Cd, Ni and Cr. A qualitative assessment of plankton was also carried out. The study revealed high degree of pollution in Yediyur lake as indicated by high values of COD (84-378 mg/L), BOD (14-32 mg/L), chlorides (96-109.8 mg/L) and higher values of solids. In its present condition, the lake acts as a breeding ground for mosquitoes. On the contrary, Bannergatta lake has no major source of pollution and the major parameters like COD, BOD, pH and chlorides were found to be within the permissible limits prescribed by the Central Pollution Control Board for surface waters. This lake satisfies the drinking water quality standards also.

 Decline in the number of water bodies has a serious impact on ground water level. This is evident from a recent study that the level of ground water table has decreased from 35-40 feet to 250-300 feet in 20 years due to disappearance of lakes (Deepa et al, 1997).