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Water conservation plays a huge role in sustainability. Precipitation in San Diego often falls short of the seasonal average of about 11 inches per year with extended periods of drought. Nearly all landscapes are sustained by additional irrigation water which must be imported to supplement the shortfall and to survive the dry spells. Most projections for the future include increasing scarcity for this essential resource.
Virtually all landscapes in Southern California are sustained by additional irrigation. This requires that 80-90 percent of our water must be purchased by local water suppliers and transported via canals from the Colorado River & from reservoirs north of Sacramento.
Key irrigation concepts include:
Most irrigation systems are in-ground systems, which means that everything is buried below the ground surface. The system is connected to a water source, usually a water main line provided by a local utility, city or county. Water then moves under pressure through pipes called mainlines from the water source to valves and then through lateral lines to the sprinkler heads and emitters. Most systems use a pressure regulator to control water pressure at the source, and a check-valve or back flow preventer to prevent water in the irrigation lines from being pulled back into and contaminating the clean water supply if the water pressure drops.
Most irrigation systems are divided into zones or hydro-zones which are comprised of a single irrigation valve and one or a group of drippers or sprinkler heads. Irrigation systems are divided into zones to work with the available water pressure and to control the amount of water and frequency of water application. Each zone valve is controlled by wire connection to an irrigation controller or electrical device that signals a zone to turn on at a specific time and keeps it on for a specified amount of time. A Smart Controller is a recent term used to describe a controller that is capable of adjusting the watering time by itself in response to current environmental conditions which are relayed by satellite. Soil moisture sensors, a rain sensor, a satellite feed weather station, or a combination of these provide the data that the controller uses to adjust the application of water.
Spray heads that pop-up are the common sprinkler type used in most residential and small commercial landscape projects. They provide a continuous spray of water over the entire distribution pattern of the spray head. Manufacturers offer effective adjustable nozzles, square patterns, center strip, end strip, close-in watering and low-angle nozzles for windy locations.
Gear-driven rotors are now the most widely used sprinkler type for medium to large-scale areas. An important factor to consider for landscape applications is the precipitation rate or the amount of water that each head delivers. Rotors apply water at a much slower rate than spray pop-ups and prevent puddles and runoff. The best reasons to use gear-driven rotors are variety and versatility. A variety of radius and flow options, uniformity of water distribution, easy access, serviceability and durability are all factors in favor of rotor type heads.
Traditional irrigation systems are installed to spray or bubble water over large areas and are designed based on the amount of water they discharge in gallons per minute (GPM), and the amount of water pressure they require for optimum performance. In contrast, drip irrigation systems discharge in gallons per hour (GPH) and require very little water pressure for performance. Due to the low water pressure requirements, drip irrigation emitters or micro-irrigation systems can function with gravity-fed rain harvest or storage tank systems.
Simple drip emitters have outputs ranging from 1 to 16 gallons per hour (GPH) and deliver water very slowly to specific spots of up to 3 feet in radius. Other drip emitters include micro bubblers that emit a lot of water to a single planting area, misters with flow rates of 1 to 8 GPH for humidity-loving plants, and adjustable low-volume emitters that attach to quarter-inch tubing with flow rates of 0 to 29 GPH for flowers, shrubs and container gardens.
As water supplies become more limited through increased population demands, droughts, and climate change, city, water district, and state level regulations and codes are beginning to encourage, offer rebates with use, or mandate significantly reduced water allowances making low-volume irrigation systems mandatory.
This web site is supported by Carl D. Perkins VTEA IC funds through the System. Office, California Community Colleges,