Geophysical Expression for Groundwater Quality in Part of Chittoor District, Andhra Pradesh, India - Management of Natural Resources in a Changing Environment - page 43

If this prism consists of N parallel and isotropic layers of resistivities, ˁ 1 , ˁ 2 , ˁ 3 , …, ˁ N
and thickness h 1 , h 2 , h 3 , …, h N , when the current is flowing normal to the base, the total
resistance of the prism is

iN =

∑ i

Th h =ρ ρρ ρ +++…+ h h = h / ρ

11 22 33 NN i

i = 1

In the same way, when the current is flowing parallel to base

iN =

i

S =ρ +ρ ρ+ρ / h / h + + / h / h = ρ / h

11 22 3 3 NN i i

= 1

( )

Longitudinalconductance

RTh

t = /

Dar-Zarrouk parameters have been used earlier by some researchers. Zohdy
( 1965 ) developed a technique to interpret the vertical electrical sounding curves by
using the Dar-Zarrouk parameters.
Sree Devi ( 1999 ) prepared a longitudinal conductance map, and noted that lon-
gitudinal conductance is reciprocal relation of resistance and conductance. If a geo-
logical formation is more conductive, it has less resistivity which indicates good
aquifer. Hodlur et al. ( 2002 , 2003 , 2006 ) extensively worked on the Dar-Zarrouk
parameters and used the parameters to develop a technique to improve and update
the resolution of fresh and the saline water aquifers in coastal areas. They showed
the existence of a relation between the Dar-Zarrouk parameters and the natural
recharge. A relation between formation water resistivity ( Rw ) and the longitudinal
unit conductance ( S ) was recognized.
Earlier researchers have not done extensive work to find a relation between the
Dar-Zarrouk parameters and the groundwater quality. In this paper, a modest
beginning is made to successfully unravel the relation between the longitudinal unit
conductance ( S ) and the primary chemical water quality parameters like carbonate,
bicarbonate, total hardness, total dissolved solids and some other parameters.
The qualitative and quantitative correlation of hydrogeochemical parameters
with Dar-Zarrouk parameter, longitudinal unit conductance ( S ) parameters is shown
in Fig. 4a-c to Fig. 7a-c respectively. Tables 2 , 3 , 4 and 5 show the longitudinal unit
conductance ( S ), hydrogeological parameters such as total dissolved solids, electri-
cal conductance, calcium, sodium, carbonate, chloride, total hardness, etc.
The contour pattern of longitudinal unit conductance ( S ) is compared with some
hydrogeochemical parameters and a qualitative correlation in their behaviour has
been recognized. Graphical comparison of geophysical and hydrogeochemical
parameters clearly illustrates a qualitative relationship between the two parameters.
Use of such qualitative relation in the field of groundwater exploration is explained
in this paper.