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