Geology Reference
In-Depth Information
7
Various Pumping Tests and
Methods for Evaluation of
Hydraulic Properties in Fractured
Hard Rock Aquifers
J.C. Maréchal, B. Dewandel, K. Subrahmanyam
1
and R. Torri
Water Department, Unit “Water Resources, Discontinuous Media”, BRGM,
Montpellier, France
1
Indo-French Centre for Groundwater Research, National Geophysical
Research Institute, Uppal Road, Hyderabad, 500 007, India
INTRODUCTION
Large tracts of South India are underlained by hard crystalline rock terrain
(granite, gneiss, basalt, etc.). The area is also classified as semiarid to arid,
generally prone to drought conditions, requiring optimal management of
groundwater resources against increasing demands of water for various
activities (agricultural, industrial, domestic). Estimating the hydraulic
characters of water bearing layers is an essential part of groundwater studies.
The most effective way of determining these characteristics is to conduct
and analyse in-situ hydraulic tests. One of the early records of pumping tests
on a large scale in India was done by Vincent and Sharma (1978). The study
indicates that well losses comprise a significant portion of the total drawdown
in a number of low- and high-yielding wells. Karanth and Prakash (1988)
observed that the transmissivity values (
T
) obtained by slug-tests are more
than pump test values for low
T
values, and that they vary from negligible
up to a factor of about three for higher
T
values. Pradeep Raj et al. (1996),
from hydrological tests on dug wells in the crystalline rocks, estimated a
range of
T
values from 26.5 to 56.36 m
2
/d, for the weathered zone based on
interpretation made by Papodopulos and Cooper method (Papadopulos and
Cooper, 1967). Ballukraya (1997), from a study in Karnataka, postulates that
the yield fluctuation in the pre- and post-monsoon periods is largely dependent
