Eliminating Run-off and Overspray

Run-off occurs when water is applied too fast, or in too great an amount. Most soils absorb water much slower than sprinkler systems apply the water to the landscape. It is best to use multiple, short duration watering times (cycles) with enough time between each cycle to allow the water to soak into the soil.

Sloping and poorly graded land can cause run-off. Terracing and shallow watering basins can help prevent run-off on sloped areas. Broad, shallow basins are generally better than deep, narrow ones; the wider the basin, the wider root area you can soak.

Once your sprinkler system has run through all the cycles, let the landscape rest and have a chance to completely absorb the water for at least a day before repeating the process. Determining the length and frequency of watering for your landscape is a simple process. Visit the Plant List and note the hydrozone designation (level of water use and sun/shade necessary) for each of your particular plants. Next visit the Irrigation Guide. Match the hydrozone designations to the watering schedules. The Plant List and Irrigation Guide can be found on the Main Menu.

1.	Do the runoff test – see Getting Started for details – then adjust your irrigation schedule accordingly.

2.	Check the pressure of your system and adjust to the manufacturer’s recommendations.

3.	Retrofit sprinklers with rotary nozzles, which emit water slower so the soil has a chance to absorb it.

4.	Retrofit sprinklers to drip irrigation or subsurface drip irrigation.

Overspray is the water that lands beyond the planted or target area. When overspray lands on sidewalks, driveways, and other hard surfaces it can, and does, empty into the streets and local waterways. Garden beds and irrigation systems should be designed to avoid overspray onto impervious surfaces. Lawns should be held back from streets and driveways. Overhead irrigation should not be used in planting areas directly adjacent to streets, driveways, and waterways.

Water running off the landscape carries pesticides and fertilizers to the street. Once in the street, oil, and trash may also be picked up by the water. Even ‘clean’ water can be deadly to aquatic life because it is chlorinated.

•	Paying for water that is not needed, or used, in the garden.
•	Accelerated deterioration of asphalt driveways and parking areas.

•	Damage to fences, siding, patios, walks, and other garden structures.
•	Ocean clean up and watershed restoration projects.

1. If your landscape is composed of individual plants, such as shrubs, rather than continuous groundcover like turf; convert your spray system to drip irrigation.

2. Relandscape with individual plants (one-gallon size or larger) and convert the spray system to drip irrigation.

3. Replace all the plant material with a permeable, non-living groundcover such as gravel, rock mulch or decomposed granite that will not require irrigation.

4. Install a buffer strip of permeable, non-living groundcover such as gravel, rock mulch or decomposed granite between the plant material and the hardscape and move the sprinkler heads inward to the edge of the planting bed. (See drawing below) Because of the possibility of wind and misadjustment, this solution is not fool-proof.

5. Install a subsurface irrigation system such as ECS or Wick. Note that these systems are relatively costly.