Assessment of the Seasonal Water Quality Changes in Semi-Urban Surface Tanks of Noyyal River Basin

Aims: The history of Noyyal river in Coimbatore is known for water quality and taste since the colonial period. The river water is used mainly for drinking, irrigation and industrial purposes to districts of Coimbatore, Tiruppur and Karur with many anaicuts and tanks. In the recent past due to urbanization and industrialization the river water has been polluted in the greater extend.

Place and Duration of Study: The study was conducted to investigate the water quality status of five important upper reach semi-urban tanks of Noyyal river basin in the year 2020 -2021.

Methodology: We have collected the sample season wise in the five tanks and analyzed for pH, EC, TDS, TSS, total hardness, alkalinity, chlorides and sulphates as well as heavy metals such as zinc, copper, cadmium and lead.

Results: The results of our water quality analysis showed that most of the parameters are above the maximum permissible limits of CPCB standards for drinking water in India. The heavy metals concentrations were many folds higher than the CPCB permissible limits. The correlation analysis, Anova and PCA showed that the EC and TDS, alkalinity and sulphates, chlorides and sulphates and alkalinity and chlorides had higher correlation in the water quality analysis and they are interrelated to one another. In the monsoon season the pollution status is less and during summer season the pollution load is higher in the all tanks. During the monsoon season because of intensive water flow dilute the pollution load as well high rate of degradation due to high dissolved oxygen content of river water. Since, he Noyyal river is seasonal river, during summer, there would be very less or no flow of water into the tank increase the pollution load. The Narasampathy tank had comparatively less pollution than other tanks, since, it is the first tank in the upper reach of the Noyyal basin and has less inhabitants and industry.

Conclusion: We concluded that the tanks are polluted due to urbanization and industrialization in and around the Noyyal basin and there is an urgent need to tackle this problem by making eco-friendly and economically viable treatment system to sustain the water quality.