The discovery of Tungabhadra river water turning green was predominantly due to various forms of algae and it is not ‘toxic’ or poisonous has come as a big relief to the people of Ballari, Koppal and Raichur districts.
This has been revealed in the latest report of the Indian Institute of Science (IISC) after conducting a detailed water analysis.
Since 2008, the water augmented in the Tungabhadra reservoir was turning green in colour causing concern among public, especially after reports of fish kills, apprehending that it would affect the quality of drinking water. The water analysis done then at the Regional Centre of Pollution Control Board had revealed that the water was unfit for drinking unless treated.
With the river water turning green becoming a regular feature, the District Environment Office here had IISc conduct water analysis.
The report, a copy of which is available with The Hindu , said that the study team could identify that the green colour was predominantly various forms of algae and collected water samples for further analysis and identification of algal species in order to use them as indicator species.
Anacyctis, Microcystis, Nitschia, Microcystis Phormidium were the dominant algae found.
The report said that “all the green floating ‘oily’ mass were algae that had formed flocs and none of the algal species recorded are considered toxic or poisonous as reported in various media”.
“All the algal blooms, predominantly Microcystis among others are a response to high nutrient influx into stored dam water”.
“At the time of visit (of the team) most of the flocs appeared to be at the death phase of the algal bloom phenomenon. The nature of extensive blooms that were reported earlier (3-4 weeks) had gradually receded when we had visited and only small floating flocs were seen. This suggested that the large nutrient influx was perhaps a one time event and could be from many causes that are point and non-point sources”.
“The source of nutrient influx could be both from sewage and agricultural origin and therefore needs to be properly examined”.
“The Committee recommended that a thorough study of the various sources of nutrients needs to be carried out by a team that would trace the source and origin of the large nutrient loads. The study should partition these loads (and quantify them) into the ones from agricultural run-off, mixed treated and untreated sewage and natural inflow through the riverine processes. By doing this it will be possible to suggest control measures. No quick recommendation, including use of algicides into agricultural waters, will be appropriate”, the report said.
