CHENNAI: Tamil Nadu is facing a water deficit
of 11%, says a report. This is bad news, coming as it does at the
beginning of a torrid summer. While the current total water demand in
the state, for domestic, irrigation, livestock and industrial needs, is
1,867.85 tmcft (thousand million cubic feet) a year, the total
availability, from all resources, is only 1,681.78 tmcft.

This
deficit will rise to 17% by 2045, said the report, jointly prepared by
several central and state government agencies, including Tamil Nadu’s
public works department and the Central Water Commission.

Water experts say a 11% deficit at present means that the state is set
for an acute water crisis in the coming years, and blame the situation
on the lack of serious conservation efforts.

Experts who helped
to conduct the study said that the overflows into the sea during the
monsoon can alone meet the drinking water requirement of the entire
state. The excessive extraction of groundwater in the coastal areas has
resulted in sea water intrusion, the report said. Extraction of
groundwater has increased manifold in Chennai, Cuddalore, Chidambaram,
Nagapattinam and Tuticorin districts, where industrial and institutional
activities have increased and population has shot up, it said. As per a
recent classification, 139 revenue blocks, one third of the total
blocks in the state, have recorded overexploitation of groundwater.

“These findings are not surprising,” said Prof S Janakarajan, a water
expert with the Madras Institute of Development Studies. “Apart from
agricultural use, there is a rise in demand for water due to
urbanization and industrial development,” he said. “River aquifers have
lost their capacity to recharge due to excessive sand mining. This has
resulted in huge overflows into the sea during the monsoon,” he said,
suggesting that water bodies be restored to store the surplus flows
during heavy rain.

Tamil Nadu, which had three reservoirs in
the pre-independence era, has added 82 reservoirs in the last six
decades and boasts of 39,200 tanks now. At least 17,879 of them, big and
small, are on the coastal belt, and their status is either ‘good’ or
‘normal’. But an alarming 80% of overflows from rivers is wasted, said
the report based on a study on ‘Effective utilization of northeast
monsoon’.

The report has proposed 13,560 crore for works in the
next decade to rectify the system. About 130 tmcft of water flows into
the sea from at least 10 rivers, including the Cauvery, it said. Compare
this to Chennai’s drinker water needs — 1 tmcft every month.

Sedimentation has reduced the capacity of several reservoirs between 2% and 59%. Built in 1934, Mettur reservoir,
the lifeline of Cauvery delta, loses 11 million cubic metres of storage
capacity a year due to sedimentation. The water tanks lose 40 to 50
million cubic metres of storage capacity each year. The report
emphasised the need for consistent efforts to desilt water bodies. The
silt can be used either for construction, agriculture or river
restoration, it said.

“Thanks to the new reservoirs and better
management of water tanks in parts of the state, either by PWD or local
bodies, the deficit could be managed over the years. But the demand is
shooting up every year,” said a water manager. The report suggested it
would be prudent to link the rivers within the state by short canals to
divert the occasional flood flows to the adjoining basins. The state
often witnesses a situation in which one river is in spate and other is
bone dry.

The state will now be compelled to augment the
capacity of existing storage structures in coastal regions, construct
check dams and new reservoirs, and link rivers, wherever possible, as
suggested by the report.

“Unless this is done, the future looks
pretty bleak. With a majority of the rivers being interstate,
dependence on neighbouring states should end,” a member of the study
team said. The good news is that the 41-year data shows there is no
dramatic change in the trend in the onset of northeast monsoon.