The electrical power obtained from conversion of potential and kinetic energy of water is called Hydroelectric power

PE=WZ

where
PE= potential energy

W =total weight of the water

Z =vertical distance water can fall

Power is the rate at which energy is produced or utilized:
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Flow through a venturimeter is given by

where
Q= flow rate, ft3/s (m3/s)

c =empirical discharge coefficient dependent on throat velocity and diameter

d₁= diameter of main section, ft (m)

d₂= diameter of throat, ft (m)

h₁= pressure in main section, ft (m) of water

h₂= pressure in throat section, ft (m) of water

ECONOMICAL SIZING OF DISTRIBUTION PIPING.

An equation for the most economical pipe diameter for a distribution system for water is

D=0.215*(fbQ³_aS/aiH_a)^1/7

where

D= pipe diameter, ft (m)

f =Darcy–Weisbach friction factor

b =value of power, $/hp per year ($/kW per year)

Qa= average discharge, ft3/s (m3/s)

S =allowable unit stress in pipe, lb/in2 (MPa)

a= in-place cost of pipe, $/lb ($/kg)

i =yearly fixed charges for pipeline (expressed as a fraction of total capital cost)

Ha =average head on pipe, ft (m)

The steady flow rate Q can be found for a gravity well by using the Dupuit formula:

Q =[1.36K(H ²-h ²)]/log(D/d)

where
Q =flow, gal/day (liter/day)

K= hydraulic conductivity, ft/day (m/day), under
1:1 hydraulic gradient

H= total depth of water from bottom of well to free-water surface before pumping, ft (m)

h= H minus drawdown, ft (m)

D= diameter of circle of influence, ft (m)

d =diameter of well, ft (m)

The steady flow, gal/day (liter/day), from an artesian well is given by

Q=[2.73Kt(H -h)]/log(D/d)

where
t = thickness of confined aquifer, ft (m).

The demand rate of water for fighting fire is very high though the total quantity of water used for fighting fires is normally quite small. The fire demand as established by the American Insurance Association is

G=1020?P(1 -0.01?P)

where
G =fire demand rate in gal/min (liter/s)
P= population in thousands.