Saline water intrusion and dumping of solid waste have led to the erosion of water quality in the Manimala river basin in Kottayam and Pathanamthitta districts, a survey carried out by the Centre for Water Resources Development and Management (CWRDM) has revealed.
Surface water samples collected from all the 18 locations in the river basin showed poor quality. The survey was carried out as part of an environmental monitoring programme undertaken by the Kerala Sate Council for Science, Technology and Environment (KSCSTE) in six river basins, namely Kuppam in Kannur district, Karuvannur in Thrissur and Palakkad districts, Manimala (Kottayam and Pathanamthitta) and Kavvayi, Nileswar and Ramapuram in Kasaragod district.
The study found that solid waste from hotels, houses, shops and construction sites was dumped into the Manimala river at several locations. The percentage of E.coli and faecal streptococcal bacterial contamination was high in the post-monsoon season. All the samples collected in the pre-monsoon season and 83 per cent of the samples collected in the post-monsoon period showed that the water required conventional treatment and disinfection to be used for drinking purpose.
The biological analysis of water samples showed high level of algal pollution at Mallapally bridge, Thondara and Mankombu, indicating the approaching eutrophic nature of the water almost round the year.
The water quality index of the Kuppam river basin showed that 56.25 per cent of samples were of marginal water quality, while 43.75 per cent was of poor quality. Samples collected from most stations revealed that the water required conventional treatment and disinfection to be used for drinking. The study reported a very high count for both E.coli and faecal streptococci bacterial population during the monsoon season. The area near the Madakara bridge revealed high level of sewage contamination.
Analysis of water samples from the Karuvannur river basin revealed that 69.23 per cent had marginal quality while 30.77 per cent was of poor quality. However, the majority of water samples were suitable for irrigation. Downstream stretches of the river were found to be organically polluted, primarily by untreated sewage and agricultural run-off.
All the surface water samples of Kavvayi river tested positive for E.coli in the monsoon and post-monsoon seasons. E.coli contamination was reported in 71 per cent of groundwater samples. The study indicated organic pollution in the downstream areas of the Kavvayi, Nileswaram and Ramapuram rivers.
According to Suresh Das, Executive Vice President, KSCSTE, the report is expected to provide a scientific basis for implementing action plans by local bodies and other stakeholders to improve the quality of the rivers.
