CONTENTS-
Abstract
Introduction
Materials and Method
Results and Discussion
References

The Langlier's index, which is an indication of the corrosive tendency of water has not been studied during the recent years. The present study was conducted on the water quality of Dalvoi lake and Karanji lake of Mysore during 1999 – 2001. The Langlier's index can be used as a measure of pollution to determine the scale forming or corrosive tendency of water. Physico-chemical parameters, Langlier's index and planktonic forms have been employed for the assessment of water quality. The nature of pollution in Dalvoi lake is mainly due to city sewage entering into it regularly. It shows the tendency of water to form light scale deposition and is dominated by mixed blooms of blue-green algae; desmids are completely absent and the water body has become eutrophic. Karanji lake supports certain species of diatoms, coupled with paucity of desmids. It is not much contaminated as most factors are within  standard limits. The   water has neither scale forming nor corrosive tendency. Assessing these factors is useful in corrosion control programme and in preventing calcium carbonate scaling in piping and equipment such as in industrial heat exchanger or domestic water heaters.

Water pollution as known today is relatively a new phenomenon. The natural aquatic environment has been affected adversely by man's activities, mainly by over crowding. It has been reported that in India 50-70% of the pollution load of lakes, rivers and stream is from domestic sewage. Water bodies are being increasingly polluted in the urban centers like Mysore. An effort has been made to evaluate the extent of pollution using the calcium carbonate index. However, instances are too numerous, varied and common to warrant special attention that it has become necessary to prevent and control water pollution against its ill effects on   flora and fauna and perhaps the quantifiable contribution to the deterioration of the quality of life. The present work was undertaken with the objective of elucidating lake water and establishing interrelationship between various physico-chemical parameters including the calcium carbonate saturation index and its influence on phytoplankton.

Karanji lake is situated on the eastern part of the Mysore city and is about 6 km away from Manasagangothri campus. It is a major water body measuring about 0.7 km long and 0.8 km broad. It has an oval shape. It is a perennial water body. Rain water is the major source of water but at times sewage water enters into the lake. The water is light green in colour. Dalvoi lake is situated in the southern part of Mysore city and is about 8 km away from Manasagangotri campus. It is a big water body measuring 1.0 km long and 1.2 km broad. The maximum depth when full is about 8 m and normal depth of 6m. It is oval in shape. It is a perennial lake and a huge amount of city sewage flows into it. The method of collection, preservation, enumeration of phytoplankton and estimation of physico-chemical parameters are same as described by Hosmani and Vasanth Kumar (1996) and Trivedy and Goel (1984), APHA, AWWA (1995).

The seasonal variation of physico-chemical parameters, phytoplankton and calcium saturation index are presented in Table 1 and Table 2. The calcium carbonate saturation index in Karanji lake had the tendency of hard water with light scale deposition (+ 1.46 and +1.04). Dalvoi lake water had a tendency of light scale deposition during all seasons apart from rainy season (+0.637). Many physico-chemical factors are said to influence the distribution of desmids. Amongst them pH, total solids, calcium, nitrates phosphates, organic matter and temperature are the most important factors. Puttaih and Somashekar (1987), Velacha and Bhatnagar (1988), Swarnalatha and Rao (1994) observed that most waters had tolerance limits of physico-chemical parameters avoiding all polluted waters. Euglenoids have been noticed in both the lakes where there was   low content of dissolved oxygen. In Dalvoi Lake, the low concentration of CO 2 appears to have a positive impact on the abundance of euglenoids, where the water had a tendency to form light scale deposition. The least number of Euglenoids occurred when the tendency of water was very low during rainy season (+ 0.285) and the organisms were 3675 organisms/l in Karanji lake. Highest Euglenoids were found during summer 2000 and 2001 (9450, 11550 organisms/l), while the tendency of water was to form light scale deposition.

The maximum Bacillariophycea were observed during summer 2001, (10395 organisms/l) when the tendency of water had a light scale deposition (+ 1.04), while the minimum number of bacillariophyceae was observed during winter 1999 (58880 organisms/l). Low concentration of calcium influenced moderate number of diatoms in Karanji lake, corresponding to the lowest calcium (46.03 mg/l) whereas their higher number was noticed in Dalvoi lake. Similar observations were made by Hosmani and Bharathi (1975), Rao and Selvarani (1989). pH was inversely related to the distribution of cyanophyceae and is a highly tolerant organism, when the water tends to form light scale deposition. Blue green algae dominated during the summer season followed by summer. Hegde and Sujata (1997) observed that blur green algae are maximum during winter. With this, it can be concluded that the Langlier index would be useful in determining the quality of water, which favours the growth of phytoplankton and reduce the pollution strength of lakes. This also helps in usage of water for industries and other domestic purposes. The maximum growth of phytoplankton was highly tolerant in light scale deposition.

APHA, AWWA, WCPF, 1995: Standard methods of Examination of water and wastewater. 19 th Ed.

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Hosmani S.P. and Bharti S.G. (1975) Hydrobiological studies of ponds and lakes in Dharwad III occurrence of Euglenoid blooms. K.U.J. Science 30: 151-156.

Hosmani S.P. and Vasanth Kumar L (1996) Calcium carbonate saturation index and its influence on phytoplankton. Poll. Res. 15 (3) 285-288.

Puttaiah E.T and Somashekar R.K. (1987): On ecology of desmids in lakes of Mysore city. Geobios New Reports 6:132.

Rao V.N.R. and Selvarani V (1989): Phosphate uptake in Amphora coffeeae formis (Agardh) Kutz, Navicula pelliculosa (Breb) Hilse and Thalassiosira Fluviatilis Hustedt, Phykos 28(1&2):216-230.

Swarnalatha N and Narsing Rao A (1994): Assessment of water quality and pollution in lentic environments. J. Swamy. Botl. Club 11(1&2): 44-47.

Trivedy R.K. and Goel P.K. (1983): Chemical and Biological Methods for water pollution studies. Environment Publication. Karad.

Velecha V and Bhatnagar G.P. (1988) Seasonal changes of phytoplankton in relation to some physico-chemical factors in lower lake of Bhopal, Geobios 15:170.

DOS in Botany
*DOS in Environmental Science
University of Mysore,
Manasagangotri,
Mysore – 570 006.
Karnataka. India.