10. Energy Balance Flow Relationships  Hydraulic problems
concerning fluid flow are generally handled by accounting in
terms of energy per pound of flowing water. Energy measured in
this form has units of feet of water. The total amount of energy
is that caused by motion, or velocity head, V2/2g, which has
units of feet, plus the potential energy head, Z, in feet,
caused by elevation referenced to an arbitrary datum selected as
reference zero elevation, plus the pressure energy head, h, in
feet. The head, h, is depth of flow for the open channel flow
case and p/figure defined by equation 2-2 for the closed conduit
case. This summation of energy is shown for three cases on
figure 2-3.  Figure 2-3a -- Energy balance in pipe flow.  Figure
2-3b -- Energy balance in open channel flow.  Figure 2-3c --
Specific energy balance.  Figures 2-3a and 2-3b show the total
energy head, H1; for example, at point 1, in a pipe and an open
channel, which can be written as:  eqn (2-19)  At another
downstream location, point 2:  e