Water Supply Hydrology. The publications listed in pars. 2.1.1, 2.1.3, and
2.2.1 include information on the hydrologic cycle--that is, the natural distribution and
circulation of water in the earth's atmosphere, on the earth's surface, and below the
earth's surface. These resources present the basic distinctions between surface
waters and ground waters and introduce the principles of hydraulics (volume and flow).
Water Use. Water usage at medium to large military installations is
similar to usage in a modern city. Water is used for residential, commercial, and
industrial purposes, as well as for fire protection. The most important reason for
maintaining continuity of service is to protect public health. To adequately supply all
water requirements, water system operators need to know the magnitude and
occurrence of peak flows.
A discussion of water use issues, as well as emergency and alternative
water sources, can be found in par. 2.1.3.
Groundwater Supplies. Detailed and specific information on groundwater
sources, water well terminology, well location and construction practices, and well
types can be found in the publications listed in pars. 2.1.3, 2.2.1, and 2.2.36.
Aquifer Performance. The three basic calculations related to water well
performance are well yield, drawdown, and specific capacity. These calculations
provide information for selecting appropriate pumping equipment and identifying any
changes in the productive capacity of the well. Paragraph 2.1.1 defines these
parameters and provides sample calculations. Paragraph 18.104.22.168 provides a method
for computing drawdown.
Balancing the Pumping Schedule. When water is pumped from a well, a
depression is produced in the water table as drawdown occurs. When pumping stops,
the water again rises to the static water level. The depth and lateral extent of the cone
of depression depends on the pumping rate of the well. If two or more wells are located
so closely together that their cones of depression overlap, the wells compete with each
other for the groundwater. Then, each produces less water than if operated alone
(Figure 1). Place operating wells as far apart as possible to minimize the effect of
overlapping cones of depression. Operate wells in rotation to equalize wear on