Context:

• waters in the Chaliyar, the fourth longest river in Kerala that originates in Wayanad and flows through Malappuram and Kozhikode districts, turned blue-green at several places, people panicked.
• A similar phenomenon has been observed in the Iruvazhinji river in Kozhikode. Scientists blamed it on the sudden spike in summer temperature, which turned the river waters warmer and thus hospitable to blue-green algae, or cyanobacteria.

Toxic algal blooms

• Algal blooms, though not all, can be toxic, warns Mr. Sukumar. Blooms could be harmful to people’s health, fish and livestock. So, it would be wise to keep off the waters until the blooms are washed downstream, which takes time though. 
• Algal bloom has been spotted in the Iruvanjippuzha, one of the Chaliyar’s six tributaries.
• The 169-km-long Chaliyar, which is called the Beypore Puzha in the lower reaches, does not go dry in summer, unlike the Bharathapuzha. It has served the water needs of the people living in its basin for ages. For centuries until recently, the river phas served as a conduit for the timber from the Nilambur jungles. Rafts carried mighty teak logs down the river to Kallai near Kozhikode. Thousands worked in the logging industry, and the local economy flourished.
• The timber also fuelled colonial Britain’s railway expansion as teakwood was used in laying rail tracks. But now, the timber industry is down in the dumps, and the Chaliyar, like other rivers in Kerala, is polluted and shrunken.

Source:TH