How Much Water Should I Use?

Outdoor Water Use

Outdoor water use is for irrigation and is much more difficult to manage than indoor water use. There are many variables to consider when deciding how much water to use on landscapes. Variables include:

  • Plant – bluegrass turf, annual flowers, xeriscape shrubs
  • Soil – clay, sand, loam
  • Exposure – full sun, partial shade
  • Irrigation nozzle – rotor, spray, drip
  • Irrigation Requirement

Metro will attempt to simplify the variables above in order to help you determine how much water you should be applying to your landscape.

Choose a selection from the boxes below in the Run-Time for each irrigation zone or station and the run time calculator  to enter on your irrigation controller will be displayed at the bottom of the page. Also , after each selection there will be a description of that variable for your convenience.

A run time is the amount of time to be entered on the irrigation controller for each zone or station. This run time changes each month from May through October and changes year to year. Wait to turn on your irrigation system until late May or early June because the longer plants wait for rain, the deeper their roots grow. The deeper roots grow the more drought-tolerant they become. There are many important maintenance techniques that should be implemented to ensure deep root growth and generally healthier plants.

Plant type – cool-season turf, warm-season turf, perennial, Xeriscape perennial, shrub, Xeriscape shrub, tree, Xeriscape tree, annual

Examples of cool-season turf are Kentucky bluegrass, Tall fescue, Fine fescue,
Examples of warm-season turf are Blue grama, Buffalograss, Tufted hair grass, Bermudagrass
Examples of perennials are larkspur, Oriental poppy, roses
Examples of Xeriscape perennials are chocolate flower, penstemons, hyssop
Examples of shrubs are burning bush, euonymus, boxwood
Examples of Xeriscape shrubs are potentilla, apache plume, fernbush
Examples of trees are maple, ash, cottonwood
Examples of Xeriscape trees are Kentucky coffee tree, oak, pine
Examples of annuals are petunia, pansy, lobelia

Soil type – Clay, sand, loam

Clay soil is usually grayish in color and can be rubbed between two fingers to form a “ribbon.” Sand has larger particles and feels gritty. Loam is usually dark brown or black, has an earthy smell, and has some of clay and sand in it.

If you have clay soils decrease the number of minutes from the run time calculator and “cycle and soak” method of irrigating. Cycle and soak allows the water to infiltrate clay soils that have very small pore spaces which does not allow water to soak in rapidly. To add a cycle to your irrigation clock, simply add another start time. If you have sandy soils, which are unlikely in the Village, then add a minute or two to the run time.

Exposure type – full sun, partial sun, partial shade, full shade

It is important to watch the area in question at many times in a day to get a good idea of the amount of sun it receives throughout the whole day.

Irrigation nozzle type – rotor, spray, drip

Rotors are irrigation heads that go back and forth in a certain pattern. Spray nozzles have a fixed spray pattern and do not go back and forth. Drip nozzles are small emitters on a poly tube.

Irrigation Requirement – 500 to 10,000 square feet in 100 square feet increments

Irrigable land space is determined by calculating the area of the zone or station. Irrigable land space of a square or rectangle is calculated by taking the length multiplied by the width of the area. Irrigable land space of a triangular shaped bed or turfgrass area is half of the height through the middle of the triangle multiplied by the length of the base of the triangle. If the irrigable land space is shaped like circle, then multiply half the length across the circle by itself and then by 3.14.

The Irrigation Requirement is a combination of the local weather conditions. Find this value in the Weather Station Chart at the bottom of the page under the box titled, “Irrigation Requirement.” Use the 7 day value.

Run-Time Calculator, How much water should you use?

How much water should you use?
Irrigation Requirement :
Plant Type:
Irrigable Land Area :
Irrigation Nozzle Type:
Run Time :

The Run-Time value that is calculated in the above table represents the number of minutes that zone should run for that week. However, the amount of time is based on the prior week and therefore will be one week behind. As you track the weekly irrigation requirement, you will realize that the irrigation requirements are similar week to week in each season, i.e. Spring, Summer, and Fall. Take the run-time value and divide it by two to determine how many minutes to program into your irrigation controller on the two watering days scheduled per week.

To schedule an irrigation audit or for more specific information on how to calculate the amount of water to apply to a landscape, please contact the District, (303) 688-8330. The District can also help you program your irrigation controller.

Castle Pines Village Weather Station

The following chart displays the current local weather from Metro’s weather station located at 5880 Country Club Dr. This information is updated daily. The “Irrigation Requirements” section is the amount of water to apply to cool-season turfgrass. This value is slightly higher than what Metro suggests to apply because the amount of rainfall incorporated into the supporting calculation is greater than the typical amount of rainfall that is absorbed in the Village’s mostly clay soil.


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