WATER MEASUREMENTS & FACTS
There are two conditions under which water is
measured--at rest and in motion. Volume units are used for water at
rest. Water in motion is described in units of flow.
Volume Volume units describe how much space a given amount
of water will occupy. Water in tanks and ponds is an example of water
at rest. Common units of volume are gallons, acre-inches, acre-feet,
and cubic feet. These units are defined as:
Acre-inch--the volume of water that would cover an acre one inch deep.
Acre-foot--the volume of water that would cover an acre one foot deep.
Cubic foot--the amount of water that would fill a container one foot
wide by one foot long by one foot deep.
Flow Flow units tell how fast a given volume of water
is moving past a fixed point. They can be used to describe the discharge
of a pump, flow in a canal or river, and discharge of a sprinkler, gate,
or siphon tube. Flow units frequently used in irrigation are gallons
per minute (gpm) and cubic feet per second (cfs).
Gallons per minute--the rate of flow necessary to fill a gallon container
in one minute.
Cubic foot per second--the amount of water that would flow in a stream
one foot wide by one foot deep and moving at a rate of one foot every
second.
Water Equivalents data
“A normal” water year or snow year is
a moving, 30 year average that is adjusted every 10 years. The present
range is 1971 to 2000.
