Thursday, 16 August 2018

Tamil Nadu Lacks Management of Surplus Water in Cauvery

It is paradoxical that we toggle between the demand for Cauvery water in Tamilnadu from Karnataka, and then let most of it go waste. With at least 2 lakh cusecs of water being let into the Bay of Bengal every day, through the Cauvery or its tributary Kollidam, the State's water management system draws serious criticism.

One often comes across the allegation against the State government that it is ineffective in managing surplus water. With farmers and PWD officials having a difference of opinion, here's my report on the reality at ground zero.

About three decades ago, Tamil Nadu government drafted a plan to link rivers Cauvery - Sarabanga - Ayyar to expand the area of the river in the north, including areas in Namakkal, Salem and Erode. In the south, the plan of linking rivers Cauvery - Vaigai - Gundar was also drafted 15 years ago. However, both schemes did not take off.

Tiruchi district secretary of Tamil Nadu Vivasayigal Sangam, Aiylai Sivasuriyan, said, 'As much as Rs 921 crore is supposed to have been spent on both projects. But, what is the current status of the projects?'

According to Sivasuriyan, like this year, Cauvery has witnessed floods twice or thrice in a decade. ‘Last time, in 2013, when floods occurred in the river, 17 tmc ft of water drained into the sea.'
If not a linking project, at least more dams should be constructed across the river to stop water from being wasted, he said.

Not possible

However, PWD officials defend the current situation saying construction of dams is not possible owing to the topography of Tamilnadu. 'We are totally in the plain. The last possible location for us to build a dam was Mettur - that already has a reservoir. On plain land, we can construct only check-dams like Kallanai. And, it is evident that Kallanai's capacity is not more than 0.5 tmc ft,' said a PWD official.

What about check-dams?

But, Ma Pa Chinnadurai of a farmers association reminds the alternative methodology. 'A team of retired PWD officials drafted a plan and suggested 15 locations between Mettur Dam and Kallanai for construction of check-dams. But, there was not even an acknowledgement from the government,' he said, and added that had these check-dams been constructed, between 30 to 80 tmc ft of water could have been saved. 'The estimated cost of each check-dam, with 2 to 5 tmc ft capacity each, as indicated by the officials, was between Rs 3 and 5 crore,' Chinnadurai claimed.

However, the problem of the State is not just because of the absence of dams but the maintenance and management of the water bodies said a retired PWD official. 'There were 41,127 tanks in the State that source water from the Cauvery. Do you know how many are left? Not even 20,000,' was his shocking revelation.

Pointing to encroachments by commercial and residential establishments on these irrigation tanks, the retired official said, 'That is where we fail.'

Tank irrigation shrinks

Similarly, professors from the Department of Economics, Narayanamoorthy from Alagappa University and Alli from Vellore Institute of Technology, who jointly worked on rural management, said, 'Tank irrigation area in Tamil Nadu has dropped from 9.36 lakh hectares in 1960-61 to 4.38 lakh hectares in 2015-16.' Likewise, they say, canal irrigation area has gone down from 7.88 lakh hectares in 1950-51 to 6.72 lakh hectares in 2015-16.

Chennai’s water source

One out of three glasses of water a Chennaiite drinks is sourced from the Cauvery. 'The river supplies 1.45 tmc ft of water to Veeranam lake that is one of the major sources of water for the State's capital,' said a PWD official. However, according to farmers, the path that connects Veeranam and the Cauvery was last desilted in the early ‘90s.

Groundwater management

There are 354 litholog well locations in the whole basin (as per available records) of which 145 well locations fall in the Cauvery lower sub-basin while 210 well locations fall in the Cauvery middle sub-basin. These litho wells are predominantly placed in Tamil Nadu because of its topography and plain nature.

Significance of Mettur Dam
Cauvery Mettur Major Irrigation Project provides irrigation potential of 1,11,700 hectares and covering a cultivable command area of 1,03,600 hectares benefitting the districts of Thanjavur and Pudukkottai alone.

In general, Mettur Dam irrigates 24.71 lakh hectares in Salem, Namakkal, Erode, Karur, Tiruchy, Thanjavur, Ariyalur, Perambalur, Tiruvarur, Nagapattinam, Pudukottai and Cuddalore districts. All these 12 districts put together had 700 lakes. 'But, the pathetic condition is that only 400 survive now of which over 300 lakes have not been desilted for decades,' said a retired PWD engineer.

A study was carried out by ISRO to assess the existing status of the irrigation commands. As per data established by the Ministry of Water Resources of two different seasons: pre-monsoon (2005) and post-monsoon (2004) - were used for delineation of waterlogged and salt-affected areas of major and medium irrigation commands of the basin. The total waterlogged area within these occupies 21,969.33 hectares whereas salt-affected area has been extended to 14,038.85 hectares.

River's geography

The Cauvery basin constitutes three sub-basins - Cauvery upper, Cauvery middle and Cauvery lower sub-basin. The Cauvery upper sub-basin covers 10,958.8 sq km and consists of 18 watersheds, Middle sub-basin, having an area of 57,280.98 sq km, consists of 86 watersheds, and lower sub-basin, covering an area of 17,386.45 sq km, consists of 28 watersheds.

The entire lower sub-basin and most of middle sub-basin lies in Tamil Nadu. The dependable yield for the basin is utilised under a number of major, medium and minor irrigation projects. Irrigation is being carried out in the area under these projects viz., dams, barrages, diversion structures and other lift irrigation systems. According to a statistics, the mineral value of Cauvery water is capable of earning Rs 50 crore through paddy economy which is the highest in south Asia.

Important dams across the Cauvery in Tamil Nadu

  1. Navapatti
  2. Chekkanur
  3. Poolampatti
  4. Kuthiraikalmedu
  5. Lower Mettur Barrage Urachikottai
  6. Bhavani Kattalai Barrage
  7. Vandipalayam Barrage
  8. Pasur Dam
  9. Mayanur Check-dam
  10. Mukkombu Upper Dam
  11. Kambarasanpettai Dam
  12. Kallanai - Splits Cauvery into Vennar, Kollidam, Cauvery Canal
  13. Anaikarai Dam / Lower Anaicut dam (source of water for Veeranam tank)
- Santhosh Mathevan,
Chennai, August 16, 2018.

A part or complete version of this article by Santhosh Mathevan has appeared in All data seen in the article are sourced from the Ministry of Water Resources. Images are sourced from the Internet.