Geology Reference
In-Depth Information
6
Pumping Tests: Planning,
Preparation and Execution
K. Subrahmanyam and Haris H. Khan
National Geophysical Research Institute
Hyderabad - 500007, India
INTRODUCTION
The most important aspect of groundwater studies in an area is to determine
how much groundwater can be safely withdrawn and also for management
of the available source. This determination involves
(i) Transmissibility and storage coefficients of the aquifers
(ii) The lateral extent of aquifers and the nature of the boundary conditions
(iii) The effect of future developments on recharge and discharge
All the above information can be obtained by conducting pumping tests
in the field. A pumping test involves the bailing out of water through a
pumping well (Pw) and the measurement of water level changes induced in
one or more observation wells (Ob well/s) located in the vicinity of the
pumping well. In general, two types of tests are conducted in the field. A
long duration test known as the aquifer performance test (APT) is for obtaining
the characteristic features of the aquifer. The second type of test, step-draw
down test (SDT) is for determining the optimal capacity of the well and to
install proper pumping equipment. A step-draw down test is conducted with
different pumping rates in three or five stages, each stage being of the same
duration. The specific capacity versus the yield relationship is determined on
a designed production well.
Since a pumping test is a costly proposition, an attempt has been made
in the following paragraphs to briefly discuss the most important aspects of
selection of a test site, preparation and procedures to accomplish the tests.
