Newsletter No. 65;
IRBMS
Chennai: The Chennai Aquifer System, the crucial LPA. There are districts where the rate of
source of groundwater for about 1 crore people, is groundwater drafting exceeds the rate of natural
now critical. The Central Ground Water Board recharge.
study shows that Chennai's groundwater resources
are over exploited; it is being extracted at a rate of
185%. Spread across 6,288 Sq.Km, the system
covers Chennai and Tiruvallur districts, besides
parts
of
Kancheepuram
and
Vellore.
The
groundwater table in Chennai is depleting between
10cm and 20cm per year. A 2013 study shows that
groundwater in the industrial belts of Ambattur,
Chromepet and Manali, besides dump yards in
Pallikaranai
and
Kodungaiyur,
have
been
contaminated with heavy metals. Recently CGWB
found that groundwater in the SIPCOT area of
Thoothukudi where Sterlite Plant was located, is
polluted.
(NCT) probably deserves a special mention here as
the scenario looks pretty grim. About 49% of the
region’s wells have suffered from water-level drops,
with about 66% of wells deviating from long-term
decadal averages (2006-2015) by about two metres.
About 12% of wells deviate from the same by over
metres,
groundwater
human factors such as municipal drafting are key
determinants of groundwater availability. Over
half the total draft in the region, goes towards
furnishing domestic needs while irrigation claims
the rest; which amounts to about 42%. In New
Delhi, the stage of groundwater development is
around 170% which underscores the appalling state
of deficit. Out of nine NCT districts, groundwater
development is over 100% in six. In the southern
districts, groundwater development is over 200%.
Keeping in mind that the national statistic for
groundwater development in India is about 61%,
Delhi: The national capital territory of Delhi
four
But other than such supposedly natural factors,
indicating
levels.
major
Recent
depletion
in
meteorological
assessments reveal that cumulative rainfall (CR)
adding up to 21% less than the long period average
(LPA) for the north western states. For Delhi,
this shows how dramatically the NCT deviates
from the national trend. The total annual
groundwater drafting in the NCT approximates
around 389 million cubic meters (MCM) with a net
natural recharge of around 281 MCM, giving rise to
an overdraft of over 100 MCM.
The contamination of groundwater is a major issue
in the NCT, over 30% of the NCT area appears to
be contaminated with high levels of fluoride.
Nitrate appears ubiquitously across the NCT,
largely owing to unplanned domestic sewage
disposal, unlined drains and urban runoff from
Haryana and Punjab, the latter is barely half the
4
Integrated River Basin Management Society