Two rivers may pose challenges for water mangers this season

Chennai: After a terrible drought year in 2016, two cheers on Tamil Nadu's water front this year, amid two rivers juxtaposing two images and giving enough tasks for the State's water managers whose diligence could better the food front scenario this year.

The stars hitched to the Cauvery river have already presaged copious inflows in 2017 - the recent 'Cauvery Mahapushkaram' festival along its banks flagged that optimism despite the late release of water for delta irrigation from the Mettur dam and farmers at best hoping to make one late 'Samba' paddy crop to the market. But will this relative cushion Mother Nature has endowed with in 2017 translate into more cheerful outcomes?

While the water level in the Stanley reservoir at Mettur, thanks to the copious Southwest monsoons in the river's catchment areas in Karnataka, hovering around a healthy 95 feet against its full level of 120 feet in October third week and the Northeast monsoon expected to hit soon, reaffirms a positive image of cautious optimism in the delta areas, of greater surprise is the floods in Palar river, which is at best seen as one huge aquifer.

The Palar shares some common descriptions with its Cauvery counterpart. Like the latter, it also rises in Karnataka (Nandi hills), an inter-state river much of which flows through Andhra Pradesh and north Tamil Nadu. The defining waterway of erstwhile North Arcot and South Arcot districts, like the Cauvery, is also governed by an '1892 Agreement' between the erstwhile princely state of Mysuru and the then British government in water sharing. Though these inter-state boundaries have changed after Independence, Palar has always invoked the imagery of a vast sandy stretch, but with a subterranean presence.

'If you are from a household from Vellore district, nobody would come forward to give their daughter in marriage", senior DMK leader Durai Murugan used to quip in the Tamil Nadu Assembly, when pressing for a permanent solution to the water endemic to arid North Arcot region. It was later that an ambitious combined water supply project from Mettur, to draw excess flows from Cauvery all the way to Vellore and other places nearby like Melvisharam and Gudiyatham, was taken up five years ago, logistically similar to the Veeranam lake pipeline link to greater Chennai.

Thus, it came as a sudden surprise that one of those pipelines on the Palar riverbed was recently damaged, as surplus flows from Andhra Pradesh following heavy rains there into the arid river course came as an unexpected 'Palar Pushkaram' bounty for many. As recently as October 12, 15 villagers were reportedly cut off, as a bridge near Ambur in Vellore district was submerged in four feet of water in the Palar, the second floods in the river in two years, the first ahead of the November-December floods of 2015 that deluged Chennai! That was when Palar saw surface flows after 20 years, people living along its course said.

Even as political party leaders including Mr. Durai Murugan quickly made a beeline to study the Palar "in spate", almost all political parties have been clamouring to build a series of check-dams on the river downstream of the point it enters Tamil Nadu so that even such rare bouts of surpluses could be beneficially conserved for a less rainy day.

Mr. Durai Murugan recalled that the previous DMK government had chalked out a massive Rs. 1,700 crore project to construct ten check-dams on Palar at different places to help utilise the surplus waters, similar to the pleas of farmers in the Cauvery delta to construct downstream barrages, as in Mayanur near Karur, to store and divert flood-flows in Cauvery to arid regions of Pudukkottai, Sivaganga and Ramanathapuram districts.

The water managers' tasks in Tamil Nadu in 2017 has thus been equally spread out between the Cauvery and Palar basins, given that the State, as well known water management expert Dr P M Natarajan, a former member of the working group of the State Planning Commission, shared with DC, received about 414.30 mm rainfall from the recently concluded Southwest monsoon season, that is “about 29 per cent more than the average precipitation of this season, only after 1996”.

This year, the inflows into the Palar, Dr Natarajan opines ‘may be about 25,000 cusecs’. And with a normal Northeast monsoon predicted by the weathermen, he reminds us that this figure is not far from the ‘dangerous’ discharge level of about 35,000 cusecs of floodwaters into the Palar during 2015 that had resulted in flood flows of at least 75 tmcft (thousand million cubic feet) into Chennai city that year.
If this is a plausible scenario for the last quarter of 2017 in the Palar river basin, the Cauvery river basin is equally flood-prone during the 2017 Northeast monsoon season, cautions Dr Natarajan. As almost all main reservoirs in the upper riparian Karnataka state already having reached full capacity, the expert pointed out that a good Northeast monsoon is bound to be an add-on to Tamil Nadu's water resources this year. The Bhavani dam has already reached 50 per cent of its capacity and any flood discharge in Bhavani river is very likely to result in floods in the Cauvery also, he underscored.

Hence, Tamil Nadu's water managers need to plan well in advance, before the formal onset of the Northeast monsoon, on options to utilise the surplus flows in the Cauvery and in the Palar as well, Dr Natarajan urged. In the Cauvery basin, the options according to him include diverting the excess flows from Mayanoor barrage to Grand Anicut (GA) and from there through the GA canal to Avidaiyarkovil and Manamelkudi taluks of Southern Pudukkottai district on the one hand, and to the Veernaam tank on the other. Once Veeranam lake is full, greater Chennai city could draw from that source.

“Another approach is to utilise the possible flood flows, diverting the water from Mettur to Coleroon through Thiraiyur and Manachanallur and filling the 185 tanks through this 183-km long route,” suggests Dr Natarajan.

As for the surplus flows in the Palar river this year, which could again get accentuated from the coming Northeast monsoon, one way is to divert the excess flows into Chengalpattu, Uthiramerur and Madurantakam tanks, says Dr Natarajan.

Thus, advance planning, impinging both these river basins simultaneously, is peculiarly called for this year, so that Tamil Nadu is not caught napping once again, he emphasised.