Weather patterns (including amount of rainfall), plant type, and irrigation system efficiency (a measure of how evenly the irrigation system applies water), are all taken into account when determining how much water the irrigation system needs to apply to keep the landscape healthy. This is known as the irrigation requirement.
The historical irrigation requirement from 2003 to 2008 in the Denver-area was 18 gallons per square foot (GPSF). Years with an irrigation requirement above the historical average of 18 GPSF indicates a hotter, drier year (represented as greater than 100 percent) and years with an irrigation requirement below the historical average indicates a cooler, wetter year (represented as less than 100 percent).
To determine the irrigation requirement for bluegrass in the Denver-area, the following information is used:
- Local weather stations to collect weather data, including rainfall
- An irrigation system efficiency of 75 percent, which is considered efficient by industry standards
- An irrigation season of April 15 through Oct. 15
This chart will be updated on a regular basis throughout the irrigation season.