Irrigation Unit Descriptions
Area | Distance | Flow | Power | Precipitation | Pressure | Salinity | Speed | Volume
Area
acre – 43,560 square feet
hectare – metric measure of area = 10,000 square meters (100m x 100m area). There are about 2.5 acres in one hectare.
sq. cm – square centimeters
sq. ft – square feet
sq. in – square inches
sq. meter – square meters
sq. mile – square miles. There are 640 acres in a square mile.
Distance
cm – centimeters
ft – foot (singular), feet (plural)
in – inches
km – kilometers
mile – 1 mile = 5280 ft
mm – millimeters
m – meters
y – yard
Flow
acre-ft/day – flow that would cover a perfectly flat acre of land one-foot deep in one day
acre-in/day – flow that would cover a perfectly flat acre of land one-inch deep in one day
acre-in/hr – flow that would cover a perfectly flat acre of land one-inch deep in one hour. This is approximately equal to 1 cfs.
cfs – cubic feet per second. There are about 450 gpm in 1 cfs. 1 cfs is about 1 acre-in/hr. In other words 1 cfs will cover 1 acre in 2 feet of water in one day.
cfm – cubic feet per minute
cms – cubic meters per second (1 cms is a lot of water! About 16,000 gpm.)
cu. m/hr – cubic meters per hour
cu. yd/min – cubic yards per minute
gpd – gallons per day
gph – gallons per hour. Typically used for drip emitter flow rates.
gpm – gallons per minute
mgd – million gallons per day
lph – liters per hour
lpm – liters per minute
lps – metric liters per second. 1 lps is about 16 gallons per minute.
Power
btu – British thermal units per hour
btm – British thermal units per minute
hp – horsepower
kw – kilowatts
Precipitation
cfs/acre – cubic feet per second per acre
cm/day – centimeters per day
cm/hr – centimeters per hour
cm/month – centimeters per month
cms/ha – cubic meters per second per hectare
gpm/acre – gallons per minute per acre. This is commonly used to design irrigation systems. 7 gpm/acre is a common design number for Eastern Washington.
in/day – inches per day
in/hr – inches per hour. This is a common measurement of an irrigation system’s application rate. It is important to know to understand how long to leave the irrigation system on.
in/month – inches per month
lps/ha – liters per second per hectare
mm/day – millimeters per day
mm/hr – millimeters per hour
mm/month – millimeters per month
Pressure
atm – Atmospheres. Equal to about 14.7 pounds per square inch.
bars – 1 bar is 100 kilopascals of pressure.
ft of water – Feet of water. Also known as feet of head. The pressure at the bottom of the given depth of water in feet. Used by engineers to design systems. About 2.3 feet of water is equivalent to 1 psi.
in of Mercury – Inches of mercury. Pressure at the bottom of the given depth of mercury in inches.
in of water – Inches of water. Pressure at the bottom of the given depth of water in inches.
kPa – Kilopascals. 1000 pascals. 1 pascal = the force of 1 newton on 1 square meter.
m of water – meters of water. The pressure at the bottom of the given depth of water in meters. 1 m of water is about 9.8 kPa.
psi – pounds per square inch. Sometimes referred to colloquially as “pounds of pressure”.
Salinity
dS/m – deci-siemens per meter. A measurement of electrical conductivity (EC). Salty water conducts electricity more readily than pure water. Therefore as salinity increases, EC increases.
microS/cm – micro-siemens per centimeter
mg/l – milligrams of dissolved salt per liter of liquid. A measurement of total dissolved solids(TBS) equivalent to parts per million (ppm).
mS/cm – milli-siemens per centimeter
ppm – parts per million. Parts of salt per million parts of the total solution. Equivalent to milligrams per liter.
tons/acre-ft – tons of salt per acre-foot of water
Speed
ft/hr – feet per hour
ft/min – feet per minute
ft/sec – feet per second
in/min – inches per minute
km/hr – kilometers per hour
meters/hr– meters per hour
meters/min – meters per minute
meters/sec – meters per second
mph – miles per hour
Volume
acre-ft – amount of water that would cover a perfectly flat acre of land one-foot deep
acre-in – amount of water that would cover a perfectly flat acre of land one-inch deep
cu. ft. – cubic foot of water
cu. in – cub inches
cu. meter – cubic meters
cu. yd – cubic yards
gals – gallons
gal UK – United Kingdom (UK) gallons
hectare – mm – Amount of water that would cover a perfectly flat hectare that is one millimeter deep.
hectare – m – Amount of water that would cover a perfectly flat hectare that is one meter deep.
liter – liters. 1000 liters fit inside a cubic meter.
ml – milliliters, a thousandths of a liter
