With summer heat and deepening drought upon us, the stringent outdoor watering restrictions adopted July 15 by the State Water Resources Control Board present many homeowners with a conundrum: how to keep their landscaping alive while staying compliant. The good news is that a new generation of "smart" irrigation systems, designed to increase water-delivery efficiency and minimize waste, is available today, often at reasonable cost.
This includes sophisticated controllers that read real-time site conditions and deliver just enough water to keep plants healthy. Sensors that deliver water based on the amount of moisture in the soil. Sprinkler heads that maximize penetration and limit drift and runoff. These innovations have enough potential to address the state's extreme drought that government agencies are willing to pay for homeowners to install them.
The Environmental Protection Agency has calculated that replacing the standard clock timer controller found in most yards with one of its approved "smart" irrigation controllers can save an average home nearly 8,800 gallons of water annually.
The most sophisticated of the "smart" systems are the so-called weather-based irrigation controllers, or WBICs. These take in real-time weather data, either captured on-site through roof-mounted weather sensors or from historical and local satellite-fed data. The controller applies the information to the preprogrammed specifics of the garden — soil type, sun exposure, plant type, slope — to deliver a specific quantity of water. WBICs range in sophistication from ones that simply shut off when there is rain to a micromanager's delight, allowing a homeowner to control every move at every station from the convenience of a home computer.
A second, although more limited, option is the soil moisture sensor, or SMS. These measure the amount of moisture at root level and transmit the information to a controller, which adjusts the watering accordingly. Since only one sensor is installed, SMS systems work best in yards that receive a uniform amount of light.
Of equal importance to the controllers are the sprinkler heads themselves, and there is improvement there too. Irrigation experts call the advent of Hunter's MP Rotator head revolutionary. Rotator nozzles deliver multiple, rotating streams of water at a slower rate than conventional sprinkler heads for better soil penetration, less runoff and up to 30% water savings.
Smart irrigation systems, including the rotator heads, often can work off an existing layout. Many can be installed by a somewhat savvy do-it-yourselfer. However, the more sophisticated the system, the more it may be worth the investment to have an irrigation specialist install and program it. Franklin Gaudi, landscape irrigation specialist at Cal Poly San Luis Obispo's Irrigation Training and Research Center, tested six different WBICs for 14 months in his laboratory, using outdoor sensors. His takeway?
"The high-end smart controller will do a better job, but only as good a job as the initial data input," he says. "They still rely heavily on user input to get them to work right. If someone puts in the wrong numbers to begin with, it's garbage in, garbage out. My suggestion is, find somebody in your area who can identify and install the right information and is willing to handle phone calls."
Products to save water come with rebate offers
Weather-based irrigation controller
WBICs automatically adjust the irrigation system's watering times based on an on-site sensor-based control or a signal from local weather stations. They deliver water according to need rather than on a preset timer. Most WBICs take into account such site-specific variables as soil and plant type, sun exposure and slope, which are programmed into the system. Three basic types of WBICs are stand-alone controllers, add-on devices and plug-in devices. The latter two connect to, and modify the watering schedule of, standard clock timer controllers.
Pro: They react to real-time weather conditions, watering only as needed.
Con: They must be programmed to work correctly, taking into account the current watering restrictions of eight minutes per station and three days per week. The WBIC will ratchet down from there, depending on rainfall. Otherwise, the WBIC will exceed limits on watering.
Average cost: $300. SoCal WaterSmart rebate* starts at $80 a controller for less than 1 acre of landscape.
Soil moisture sensor
A soil moisture sensor, which is placed into the ground, measures the amount of soil moisture in the active root zone. If the soil moisture content registers above a pre-programmed point, it signals to the irrigation system controller to bypass a watering cycle.
Pro: They tie watering to the real-time need at an area's root level. SMSs work best in areas that have a uniform sun exposure and the same water requirements.
Con: Since only one SMS can be linked to the controller, the SMS can give inaccurate information in yards with a mix of sun and shade areas. Some sensors are also prone to corrosion from fertilizers.
Average cost: $155. SoCal WaterSmart rebate is $80 for less than 1 acre of landscape.
Rotator sprinkler heads
Rotator-style sprinkler heads, rather than spraying water, shoot out multiple streams of water at a steady rate. The slower application allows water to penetrate more deeply and evenly, and it minimizes runoff, resulting in 30% less water use than traditional heads. Rotators can be installed onto any conventional spray head body. Hunter introduced the MP Rotator head to the market; Toro, Rainbird, K-Rain and Orbit have approved heads as well.
Pro: Rotator heads deliver water where it is intended to go, eliminating drift and runoff, which the July 15 water-use restrictions will fine at $500 per day. They're excellent for use on slopes.
Con: They must be spaced exactly according to manufacturer specification because they are not forgiving.
Average cost: $7 per head. SoCal WaterSmart rebate: $4 per head, minimum 15 heads.
*Rebates subject to availability of funds