TAMIL NADU

Cauvery delta ecosystem in deep water

The Cauvery eco-system is in deep trouble with the current year being one of the worst drought years that the river has witnessed.

The delta region, known as ‘Marudha Nilam’, can no longer have that nomenclature as it is now shorn of Marudu trees, a native plant. The ‘minimum viable population’ (MVP) size of this tree has gone down and has become virtually an ‘endangered species’.

Frequent loss of flows in the river over the past four decades has resulted in gradual degradation of the eco-system, laments K.V.Krishnamurthy, former Head of the Department of Botany, Bharathidasan University, considered an authority on the Cauvery’s flora and fauna.

Even the migratory birds would shun the State if the current drought-like situation continued, warns S. Balachandran,Deputy Director, Bombay Natural History Society.

Potability of the water along the banks of the Cauvery and the Coleroon is going to be a question mark sooner or later, apprehends V.Ganapathi, advisor, Exnora International.

Indiscriminate sand quarrying all along the banks of the Cauvery has resulted in the gradual loss of water- holding capacity of the river itself, says R.Nandakumar, who has spearheaded a movement against sand mining and has won a major case in the Madurai bench of the Madras High Court recently. “Loss of one cubic metre of sand will result in the loss of capacity to hold three cubic metres of water’, he adds.

Prof.Krishnamurthy told The Hindu that it was during 1970s such loss of flows in the Cauvery started and over the years the phenomenon has resulted in creation of “huge islands of vegetation” all along the course of the river.

“Such an island virtually looks like a forest near Grand Anaicut’, he points out.

The major problem arising out of this situation is that the sand in the river gets reduced and mud is formed. “The typical riverine land structure will be lost”, both with regard to “physical and biological parameters”. “Thus sand will become soil.”

Even in the Coleroon and some parts of the Cauvery such islands of vegetation have formed an aquatic bed and the size of this vegetation patch will gradually increase.” This will become a major problem in due course of time”.

As flow of water has become less, stagnant pools are formed and they give rise to noxious aquatic elements that prevent the flow of water.

Along the banks, the native vegetation is gone and that space is occupied by “alien invasive flora (plants)”. During the last 15-20 years this has been happening substantially. “Thus the threshold value of many of the native plants including Marudu has slumped”, says Prof.Krishnamurthy.

With regard to fauna, he says there were 80 species of 23 fish families in the Cauvery system 40 years ago. Of them five species are exclusive for the Cauvery. Now their population has dwindled and many of them have lost their MVP size. Same is the case with “fresh water prawns”. On the other hand, mosquito population has been on the rise.