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Irrigation Management Before, During, and Following Drought in Colorado |
By Laura Pottorff and David Whiting, Colorado State University Cooperative Extension, Horticulture
Precipitation, snow pack, stream flow, and reservoir levels are significantly lower than historic averages throughout Colorado and the Rocky Mountain region. During normal precipitation years, landscape irrigation comprises 50% or more of urban water use during the growing season in the Rocky Mountain region. In anticipation of restrictions in irrigation that may be imposed by water utilities, communities, and other water-management entities, suggested irrigation management practices are offered.
The following practices allow you to have a green lawn, healthy landscape and still reduce water consumption
Improve Irrigation Efficiency
Make sure that the irrigation system is operating properly.
Replace broken or missing sprinkler heads and straighten to vertical.
Check that rotor heads are turning properly.
Adjust heads so that water is not thrown onto streets and driveways.
Check nozzles for plugging and clean filters.
Place containers on persistent dry spots to determine if poor sprinkler coverage is the problem.
Regulate the pressure at individual zone valves to spray droplets instead of a mist that drifts and evaporates, wasting water.
- Never water if the soil is still wet.
Water to meet the needs of plants. Review how to set irrigation days, zone start times and run times so adjustments can be made for the season and weather. Newer irrigation controllers allow dialing down water applications to a lower percentage and increasing them during peak summer heat to close to 100 per cent.
Water as infrequently as possible, without causing undue stress to the lawn and other landscape plants.
Turn the irrigation controller to the "Manual" position (from "Automatic") and learn how to operate it manually.
Don’t irrigate on a set schedule (every 2 or 3 days); plant water use can vary greatly from one day to the next.
Lawns may need water every three or four days during the heat of the summer, less in cooler times of year. Shrubs and trees may need water only once every few weeks, while perennial flowerbeds may need water only once a week. Plants growing in sandy soils may need more frequent watering.
The roots of trees, shrubs, and flowers may rot if watered on the same schedule as the lawn. Water-logged conditions do not favor the growth of healthy plants. Over-watered plants with root damage need more water in the heat of the day.
Irrigate when footprints or mower wheel tracks become easily visible on turf and large areas of the lawn take on a bluish-gray color.
Place straight-sided containers (such as soup or bean cans, etc.) around the yard and measure output so that you know how long it takes to apply ¼ to ½ inch of water. Apply ¾ to 1 inch of water, slowly enough that runoff and puddling does not occur. Cycle through irrigation stations or frequently move a sprinkler around the yard to allow water to soak in more thoroughly and evenly.
Don’t water again until abundant signs of water stress (footprinting, blue/gray coloration) appear in the lawn.
Hand-watering small or isolated dry spots can allow extending the time between watering by another day without watering the entire lawn.
Water between 9 p.m. and 9 a.m., when it is cooler and there is less wind.
Designing an irrigation system
- Sprinklers should be zoned properly so lawns can be watered separately from trees, shrubs and flowers. Also water vegetable beds and rose gardens separately from lawn areas. Place trees and shrubs in areas separate from lawns. Position woody plants on higher ground if they are in the lawn area.
- Design sprinklers to "line out" driveways, walks, roads and non-irrigated areas. Sprinklers should be next to hard surfaces to throw water onto landscape areas. Avoid a design where the sprinkler heads shoot from the center towards pavement.
- Design irrigation zones so water from one head touches the neighboring head(s). Too much space between sprinkler heads creates dry spots. Sprinklers are best installed in a triangular or square pattern with water from one head touching the neighboring two heads. Sprinkler heads that do not overlap cannot be expected to properly water the intended area properly.
- Install only as many heads on an irrigation zone as the water pressure will allow. Irrigation heads are calibrated to apply a certain amount of water over a specific area at a set water pressure. Installing more heads than the water system will handle results in dry spots. Symptoms of low water pressure often appear as donuts of green grass around the sprinkler head with dry areas between heads.
- Avoid oscillating sprinklers and sprinkler heads that produce mists or fine sprays.
- Do not install different types of sprinkler heads in the same irrigation zone.
- Rotary, spray heads and impact sprinkler heads put out different amounts of water. Impact sprinklers heads may put out as little as ½ inch of water per hour, while pop-up spray heads may apply up to two inches of water per hour.
- Install the same type of head with the same precipitation rate within each zone. Otherwise water will be wasted.
- Long sloping turf areas may require several different sprinkler zones; each line of sprinklers, controlled by a valve, is called a zone.
- Irrigation zones should be installed along the top of the slope, rather than up and down the slope. The slope may require two or more lines of sprinklers, each controlled by its own valve. Adjust sprinkler zones running along the middle and bottom of the slope so they apply progressively less water than the sprinklers at the top of the slope. Water runs down hill. Reduce the amount of water in each zone accordingly. Watering for the same amount of time in each zone wastes water.
- If possible, install water-conserving devices such as check valves, pressure regulators or climate sensors (i.e. rain, temperature and wind sensors). These will suspend irrigation when unfavorable weather conditions exist.
Maintenance Practices for Managing the Changing Water Needs of
Plants
- Reset automatic controllers according to seasonal needs of plants. Controls should be inspected at least once a month to adjust run times. This seasonal information is available in most communities from the city or water supplier.
- Winter watering can be a critical tool to minimize stress to trees, shrubs, flowers, and turf in areas receiving low winter precipitation and subject to drying winds.
- Application of water once a month during dry winter periods will allow plants to emerge from winter healthier, requiring less water in the spring. A commonly seen situation is overwatering in spring in a vain attempt to help plants recover from winter drought stress. Timely winter watering avoids this.
- Plants mature and change. Add or relocate system components as needed to maintain uniform distribution of water. Ensure that system modifications do not exceed the system watering capacity.
- Drip irrigation installed at the base of large transplanted trees should be moved as the tree root system expands. Drip irrigation that is not relocated over time, wastes water because the fine roots that pick up moisture have grown away from the base. Tree roots spread outward, two to three times the width of the tree canopy. Drip irrigation located at the base of the tree does not deliver water to roots five or more feet away from it.
- As a landscape matures, more shade develops from trees. Plants growing in shaded conditions often use less water.
Photos: Carl Wilson, Judy Sedbrook
