Pollution Status and Conservation lakes without any prior treatment. of Lakes in Coimbatore, Tamil The present study undertaken in Nadu, India Coimbatore during May 2008 on four urban lakes / wetlands namely 1 2 K.A. Nishadh ,​ Rachna Chandra ,​ Ukkadam, Perur, Kurchi and ​ ​ P.A. Azeez2 Chinnakulam reports the water ​ 1- Department of Environmental quality of these water bodies with Sciences, Bharathiar University, reference to the pollution from Coimbatore-641046, India various sources. The pH for water 2- Environmental Impact Assessment samples ranged between 7.64 and Division, Sálim Ali Centre for 8.62. EC and TDS ranged from ​ Ornithology and Natural History 303.67 - 4456.7 μS/cm and 169 - (SACON), Anaiatty (PO), 2079.3 mg/L respectively and were Coimbatore-641108, India positively correlated with chloride and sulphate (P < 0.05). Ukkadam Abstract lake, surrounded by textile dyeing industries, municipal markets, dumped domestic wastes was the Economic development is most polluted among the lakes accelerating the changes in the land studied. This lake receives sewage use pattern and land-cover waste along with effluents from conversion almost throughout India dyeing industries through various at an unprecedented rate. Wetlands channels. In view of the findings, and lakes especially those situated in recognizing the various ecological the vicinity of urban centres have services these wetlands offer to the been facing rapid degradation due to city and its environs regular liquid or solid waste disposal, filling monitoring of disposal of solid / and reclamation, real-estate ventures liquid wastes and sewage discharge and industrial development. is imperative for their conservation. Coimbatore, a rapidly developing city in the western part of Tamil Nadu, has several wetlands and lakes Key words: Lakes, wetlands, in and around its limits. This city Coimbatore, pollution, water quality wanting facilities for treatment of industrial, municipal, domestic and hospital waste has open drainage and Introduction sewerage systems which joining these 1 Rivers, wetlands, lakes and other buffering capacity, and biotic water bodies are important resources inhabitants. Sediment dwelling in close association with human organisms, their environment being existence for centuries. They have the final deposition of pollutants, are made enormous contributions in over much subject to these pressures human development; industries, [2]. agriculture and culture. However, the Coimbatore, the second largest same crucial contributions that they city in Tamil Nadu, has 36,579 made to human kind have become a industrial units of which 2,462 units major cause of their degradation and are within city limits. The growing decimation. Lakes and wetlands, industrialization and rise in appreciated for their water resources, population pose considerable strain ground water recharges, habitats of on basic amenities of the city. The wide variety of fauna and flora, are city faces serious scarcity of water, is facing varying degrees of pressures drought prone and has maximum and consequently environmental number of bore wells in the country. degradation throughout the country. The river Noyyal, formerly a Such degradation is caused due to the perennial one, flows through the city. urban, industrial, agricultural effluent Currently, there are 22 lakes present discharges and hydro geomorphic in and around the city largely fed by changes of canals and rivers linking river Noyyal, and act as storage and these lakes. Due to anthropogenic percolation tanks. The prevailing pressure of several types and drainage and sewers in the city are magnitudes and also inflow of open type joining these lakes and wastewater from several sources river Noyyal without any prior wetlands are gradually enriched by treatment [3, 4, 5]. Canals feeding the nutrients exceeding their assimilation lakes prodigally acted as natural and carrying capacity [1]. Several drainage courses and served as storm pollutants play a major role in water drains for the city. However, environmental degradation ranging currently many of these channels are from oxygen demanding organic dysfunctional for encroachments and pollutants, nutrients, heavy metals to unauthorized constructions. The increased siltation. These pollutants river, a monsoonal one, during lean affect the dissolved oxygen level, months goes dry thus, serving as a turbidity, and chemical contents of dumping yard for garbage and the lake environment thus directly industrial wastes. Moreover, many of affecting its auto regulating capacity, these wetlands are also in part being 2 used as garbage dumping yard, and in and also other hydrophytes occupy a the danger of complete filling in due large area of this lake seasonally course. The present study was forming thick mats over the water undertaken to assess the pollution column. The second lake, the Perur status of wetlands in Coimbatore lake (L2) has a water spread area of which are facing the pressure of 264.8 acres and attracts several avian varying degrees of urbanization. It species [7] and is surrounded by was also aimed to check the changes agricultural land, villages and roads. that have happened in water quality One third of this lake is occupied by with the situation as reported almost a Acacia growth facilitating nesting of decade back [6]. many birds. This wetland is proposed to be developed as a bird sanctuary. Materials and Methods The third lake, the Kuruchi lake (L3) with a water spread area of 343.96 acres, receives municipal sewage and To assess the pollution status of is being used for garbage dumping Coimbatore, four lakes viz. Ukkadam from residential colonies around its lake (L1), Perur lake (L2), Kuruchi vicinity. This lake has least water lake (L3) and Chinnakulam lake (L4) storage capacity although it was in and around the city limits were desilted some years back. selected for water quality evaluation Chinnakulam Lake (L4) has a (Figure 1). Of these, two lakes (L1 shallow long stretch of water spread and L2) were addressed during the forming a discontinuous wetland earlier studies [6] and the other two during lean months. (L3 and L4), whose pollution status Water samples from the above was not known were included in the four lakes were collected in present study. Ukkadam lake (L1) triplicates during May 2008. The having the largest water spread area samples were collected in pre cleaned among Coimbatore lakes and situated bottles, labeled, and immediately very near to municipal market and transferred to ice boxes. The samples one of the busiest bus terminals, were then transferred to the receives effluents from industries laboratory, stored at 4°C in dark till involved in electroplating, dyeing and further processing and analysis. jewel making foundries, urban Physico-chemical parameters namely sewage and other municipal waste pH, Electrical Conductivity (EC, including solids and garbage. Weed µS/cm), Total Dissolved Solids species such as Eichhornia crassipes ​ (TDS, mg/L), Biological Oxygen 3 Demand (BOD, mg/L), Chemical Demand (BOD) in the lake waters Oxygen Demand (COD, mg/L), varied from 2.1 - 4.96 mg/L. BOD alkalinity (mg/L), chloride (mg/L), was highest in the waters of L3 and phosphate (mg/L), sulphate (mg/L), might be due to release of higher ammonia nitrogen (mg/L) and nitrite levels of oxygen demanding waste nitrogen (mg/L) were examined from the near by residential colonies. following standard methods [8, 9]. The Chemical Oxygen Demand (COD) varied from 60 - 430 mg/L Results and Discussion and was highest in Ukkadam lake (L1). This could be associated with higher levels of inorganic wastes The pH of the lakes varied from being discharged into the lake 7.64 - 8.62 (Table 1). The highest pH inducing the COD level. However, was seen in the case of Ukkadam the COD levels in all the lakes were (L1) lake and exceeded the WHO well within the permissible limits. [10] permissible limits (6.5 - 8.5). The values for alkalinity ranged from Conductivity and Total Dissolved 23.3 – 470 mg/L. However, the Solids ranged between 303.67 and phenolphthalein alkalinity was absent 4456.7 μS/cm and 169 - 2079.3 mg/L in L3 and L4. The highest value for and were also highest in Ukkadam alkalinity was seen in Ukkadam lake lake (L1). The TDS values exceeded (L1). The values for chloride varied the WHO [10] permissible limits of from 70.9 - 964.4 mg/L. The value 1000 mg/L in L1. The high TDS in for chloride in Ukkadam (L1) Ukkadam lake is associated with the exceeded the permissible limits of effluents from dyeing and bleaching 250 mg/L [10], probably due to the industries which contain very high effluents from bleaching industries salt [11] and are being discharged which join the lake. into the lake. The nutrients i.e., phosphate and Dissolved Oxygen (DO) did not sulphate varied from 0.12 - 1.6 mg/L vary much and was in the range from and 9.3 - 102.9 mg/L respectively. 4.21 - 5.56 mg/L. The lowest DO was The high phosphate and sulphate recorded in Kurchi lake (L3). This values were recorded in Chinnakulam lake is surrounded by much lake (L3) and Ukkadam lake (L1) household / domestic waste and respectively which may be due to the sewage from its vicinity flow down additional input from agricultural which would have lead to the low DO runoff. The high levels of phosphate content. The Biological Oxygen may also be attributed to the animal 4 waste. Ukkadam lake is located of serious concern and poses besides one of the biggest fish market considerable impact on aquatic biota, of the city and many slaughter houses public health and ground water are also available in its immediate quality. Although the river Noyyal territory. The phosphate values during rainy season gets flooded, exceeded the permissible limit (0.1 during drier months it carries mg/L) of United States Public Health enormous amount of sewage waste.