28-01-2013, 02:46 PM
Groundwater quality and its suitability for domestic and agricultural use in Tondiar river basin, Tamil Nadu, India
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Abstract
Assessment of suitability of groundwater
for domestic and agricultural purposes was carried out
in Tondiar river basin, Tamil Nadu, India. The study
area covers an area of 315 km2 and lies in a semiarid
region. Groundwater is the major source for domestic
and agricultural activity in this area. Groundwater
samples were collected from 45 wells during premonsoon
and post-monsoon period in the year 2006.
The water samples were analysed for physical and
chemical characteristics. Suitability of groundwater
for irrigation was evaluated based on salinity hazard,
sodium percent, sodium adsorption ratio, residual
sodium carbonate, US salinity diagram, Wilcox’s
diagram, Kelly’s ratio and permeability index. Ca-
HCO3, mixed Ca–Mg–Cl and Na–Cl were the
dominant groundwater types. High hardness and
electrical conductivity in this area makes the groundwater
unsuitable for drinking and agricultural purposes.
Concentration of trace elements (Mn, Cu, Zn,
Pb and Ni) did not exceed the permissible limit for
drinking and agricultural purposes.
Introduction
Groundwater is the major source of water for
domestic, agricultural and industrial purposes in many
countries. India accounts for 2.2% of the global land
and 4% of the world water resources and has 16% of
the world’s population. It is estimated that approximately
one third of the world’s population use
groundwater for drinking (Nickson et al. 2005).
Therefore, water quality issues and its management
options need to be given greater attention in developing
countries. Intensive agricultural activities have
increased the demand on groundwater resources in
India. Water quality is influenced by natural and
anthropogenic effects including local climate, geology
and irrigation practices. Once undesirable constituents
enter the ground, it is difficult to control their
dissolution. The chemical characteristics of groundwater
play an important role in classifying and
assessing water quality. Geochemical studies of
groundwater provide a better understanding of possible
changes in quality.
Materials and methods
Groundwater samples were collected from 45 representative
dug wells, dug cum bore wells and bore
wells (Fig. 1) during pre-monsoon (May) and postmonsoon
(January) during 2006. Electrical conductivity
(EC) and hydrogen ion concentration (pH) were
measured using Eutech digital portable meters in the
field at the time of sampling. The pH meter was
calibrated beforehand using 4.01, 7 and 10.01 buffer
solution, and the EC meter was calibrated using 84
and 1,413 μS conductivity solution. All solutions and
instruments were procured from Eutech Instruments.
Groundwater samples collected were transported to
the laboratory on the same day. Calcium (Ca2+),
magnesium (Mg2+), carbonate (CO3
2)−, bicarbonate
(HCO3
−) and chloride (Cl−) were analysed by
volumetric titration methods, sodium (Na+) and
potassium (K+) were measured using the flame
photometer, sulphate (SO4
2−), nitrate (NO3
−), boron
(B−), fluoride (F−) and silica (SiO2) were determined
by spectrophotometric technique as per the methods
described by the American Public Health Association
(APHA 1995).
Result and discussion
Evaluation of water quality for drinking
Quality of groundwater determines its suitability for
different purposes depending upon the specific standards.
Chemically, the water used for drinking should
be soft, low in dissolved salts and free from toxic
constituents. The drinking water standards of WHO
(1996) and Bureau of Indian Standards (BIS 2003)
was the basis for the groundwater quality evaluation
for drinking use.
Evaluation of water quality for irrigation
The suitability of groundwater for irrigation purposes
depends upon the effect of mineral constituents of
water on both plants and soils. The general criteria for
assessing the irrigation water quality are: total salt
concentration as measured by EC, relative proportions
of Na+ as expressed by %Na, SAR, RSC and boron.
Water quality criteria can be used as guidelines by
farmers for selecting appropriate management practice
to overcome potential salinity hazard.
Conclusion
Groundwater in Tondiar river basin is generally
alkaline, hard to very hard and fresh to brackish in
nature. The concentrations of major ions in groundwater
are within the permissible limit for domestic
purpose except for a few locations.