An aquifer test is a controlled field experiment to
determine basic aquifer parameters such as
transmissivity (T) and storativity (S) in the vicinity
of a pumping well (Bear 1979). It is a commonly
used tool for characterising systems of aquifers,
low permeable layers and flow boundaries. This
chapter focuses on the factors to be taken into
consideration when performing aquifer tests in
buried valleys.
Introduction
Aquifer tests are usually performed by pumping
from an abstraction well at a constant rate for at
least 24 hours. The duration of the test varies and
depends upon the aims of the investigation –
short tests describe hydraulic properties close to
the abstraction well, while longer tests describe a
wider radius.
The drawdown (after initiation of pumping) and
recovery (after cessation of pumping) of the
hydraulic head in the test abstraction well, and
surrounding monitoring wells are measured. To
obtain an idea of the general changes in the
hydraulic head in the monitoring wells it is
recommended that the wells should be
monitored prior to and/or following the pumping
test. Neighbouring abstraction wells may affect
the hydraulic head in the test abstraction well
and in particular in the monitoring wells.
The head in the test abstraction well during
drawdown and the recovery after initiation and
cessation of pumping, respectively, is measured
at very short time intervals (e.g.: 1, 10, 20, 30, 60
or 90 sec). After a while the hydraulic head is
instead measured every five minutes.