Water Well Manual (USAID).pdf - The Water, Sanitation and Hygiene

Water can be found almost anywhere under the earth’s surface. There is,
however, much more to ground-water exploration than the mere location of
subsurface water. The water must be in large quantities, capable of sustained
flow to wells over long periods 7-t reasonable rates, and of good quality. To be
reliable, ground-water explorat!on must combine scientific knowledge with
experience and common sense. It cannot be achieved by the mere waving of a
magic forked stick as may be claimed by those who practrce what is variously
referred to as water witching, water dowsing, or water divining.
Finding the right location for a well that produces a good, steady water
supply all the year round is usually the job of scientists trained in hydrology.
These scientists are called hydrologists. Their help may be sought from
geological survey departments, governmental and private engineering organi-
zations. and universities if and when available. These experts should always be
consulted for large scale ground-water development schemes because of the
great capital expenditures usually involved. However, it should be apparent
from the remaining sections of this chapter that a sufficient number of the
tools of the hydrologist is based upon. the application of common sense,
intelligence and good judgement to permit their reasonably successful use by
the average individual interested in the location of small wells. The
interpretation of geologic data may present problems though, with some help,
these need not be totally insurmountable to some of our readers. The use of
well inventories and surface evidence of ground water location should be
much less difficult and find greater general application.
The following sections describe the simpler tools of the hydrologist and his
use of them. The more sophisticated methods of exploration involving the use
of geophysics are considered beyond the scope of this manual and, therefore,
have been excluded. It is sufficient to note that they are available to the
hydrologist to provide him with additional information on which to base his
selection.
GEOLOGIC DATA
Before visiting the area to be investigated, the hydrologist seeks out and
studies all available geologic data relating to it. These would include geologic
maps, cross-sections and aerial photographs.