Environmental Engineering Reference
In-Depth Information
Velocity head:
V
2
/2
g
= 1 ft
Head loss:
h
L
= 19 ft
TDH = 100 ft
Static head:
Z
= 80 ft
Suction lift
figure 2.13 Components of total dynamic head.
velocity head
—The amount of energy required to bring water or
wastewater from standstill to its velocity. For a given quantity of
flow, the velocity head will vary indirectly with the pipe diameter.
Velocity head is often represented mathematically as
v
2
/2
g
(see
Figure 2.13).
2.9 Well and WeT-Well hydrauliCs
When the source of water for a water distribution system is from
a groundwater supply, knowledge of well hydraulics is important to the
operator. Basic well hydraulics terms are presented and defined in this
section (see Figure 2.14). Also discussed are wet wells, which are impor-
tant both in water and wastewater operations.
2.9.1 Well hydraulics
Cone of depression
—In unconfined aquifers, water flows in the aquifer
from all directions toward the well during pumping. The free water
surface in the aquifer then takes the shape of an inverted cone or
curved funnel line. The curve of the line extends from the pumping
water level to the static water level at the outside edge of the zone
(or radius) of influence (see Figure 2.14).
drawdown
—The difference, or the drop, between the static water level
and the pumping water level, measured in feet. Simply, it is the dis-
tance the water level drops once pumping begins (see Figure 2.14).
Pumping water level
—The water level when the pump is off. When
water is pumped out of a well, the water level usually drops below
the level in the surrounding aquifer and eventually stabilizes at a
lower level; this is the pumping level (see Figure 2.14).
