Use Water Wisely: Irrigate with Water Conservation in Mind
Too much irrigation can waste a lot of water
As much as 60% of all household water consumption can go to outdoor uses. Irrigation systems should be designed to minimize the consumption of potable water. A good system is a water-conservation tool that delivers water in the most effective way at the appropriate time. Systems that distribute water indiscriminately are inherently wasteful.
Programmable controls adjust watering schedule
It makes little sense to irrigate during or after a rainstorm, but that’s just what can happen with a basic timer-actuated system. More sophisticated controls can adapt to local weather conditions and adjust the schedule as needed so that plants are watered only when they really need it.
One such device is a controller made by WeatherTrak. Once you’ve programmed it with information on plant and soil types, sun exposure, and slope, it can override the automatic watering schedule based on wireless updates from local weather stations. Systems are available for both commercial and residential landscapes.
Research and observation pay off
Timers and moisture sensors can make an automatic irrigation system dispense water precisely. But that may not help if you don't know how much water your garden needs.
Researching plants and choosing ones that thrive in your region are good starts. An experienced gardener or a local Cooperative Extension Service office can help adjust the watering schedule.
Garden layout also helps. Grouping plants that have similar water needs will make it easier to keep soil appropriately moist.
Consider installing a rainwater-collection system
Using rain runoff is a cheap way to supply drinking water. Harvest H2O Rainwater Harvesting Community
Mulch any perennial beds. Giving planting beds an annual top-dressing of mulch keeps the weeds down and helps retain soil moisture.
The International Residential Code includes requirements for lawn-irrigation systems in Section P2902.5.3. The code requires the system to be isolated from a home's potable water supply with a vacuum breaker or backflow preventer.
ABOUT GREEN IRRIGATION
Start with appropriate plants
Choosing drought-tolerant plants is an effective way to conserve water that would otherwise be devoted to thirstier species. Plants that are adapted to local conditions won't need much supplemental watering, and they should be healthier in general than unfamiliar non-native species.
Even so, some plants are likely to need watering at least occasionally. Automatic sprinklers that are activated by a timer are one approach, but conventional sprinklers are inefficient. Plants need moisture at root level, not on the leaves, and a high proportion of water that is sprayed into the air is lost to evaporation.
Water requirements vary. Water needs vary depending on the plants. A system that distributes water indiscriminately will overwater some plants and underwater others.
Soil also counts. Even with the right plants and an effective irrigation system, soil type plays a huge part in getting the water to the plants. Heavy clay can hold a lot of water but doesn't make it all available to plant roots; sandy soil lets the water pass right through before the plants can grab it. Having the right soil for your plants is just as important as watering them.
A pond can be an irrigation ally. Water for irrigation can be stored in a natural or man-made pond. When the terrain allows it, a gravity fed irrigation system is a low-impact way of providing water for plantings without tapping into potable water supplies. In addition, a pond can be an appealing landscape feature with its own collection of plants.
ABOUT SYSTEM TYPES
Drip irrigation. Drip irrigation and soaker hoses deliver water slowly and directly to plant roots, so none is wasted in evaporation or runoff. Reducing water contact with leaves, stems, and fruit discourages plant disease.
A soaker hose or drip irrigation system can sit on or below the ground, costs between $500 and $1,200 per acre, and can be automated with a timer.
A project for DIYers. Drip irrigation is an easy-to-intermediate DIY project that pays for itself in water savings in one to three years. Even with a filter, however, drip systems should be monitored for leaks and clogs.
Tubing placed belowground can be damaged by gophers and moles. The type and depth of pipe may depend on local climate and may be subject to neighborhood ordinances. Detailed instructions for various drip systems plus product reviews of common irrigation system components are available on-line.
Zoned irrigation systems. Zoned systems dole out different amounts of water for turf and vegetation beds depending on need. Turf is better suited to sprinkler irrigation, while landscape plants are better watered with drip systems.
Different types of plants also need water at different depths: trees, 18 inches to 36 inches; shrubs, 12 inches to 24 in inches; herbaceous plants and turf, 6 inches to 12 inches.
Other factors. Water requirements by species, soil type, and exposure to wind and sun are other site characteristics that affect irrigation planning.
Some zones may require daily watering, while others allow for monthly irrigation, and the right controller can help. A timer can automatically control which zone is watered and when.
Some controls aren't sophisticated enough to meet different watering needs in different zones. More complicated electronic controllers, some with moisture sensors, have these programming capabilities.
ABOUT SPECIAL SENSORS
Smart controllers for irrigation systems do almost all the scheduling work for you. There are several types and styles.
Some include software that draws on historical weather and water-use data to predict when water will be needed and provide it accordingly. While imperfect, these systems can save a lot of water.
Adjusting for on-site conditions. Others use the same data plus a temperature sensor that adjusts watering when conditions veer from the historical norm.
Some systems use off-site information provided by a local weather station, or another source, be it radio, the Internet, or a phone connection. Controllers also can have their own built-in weather stations.
Moisture sensors placed in the ground are another way of determine watering needs. All smart controllers will need fine-tuning for the first few months. The Irrigation Association maintains a list of qualified smart controllers.
The Environmental Protection Agency has a national list of irrigation professionals who have completed a certification process through the EPA's WaterSense program.
- Scott Phillips/Fine Gardening #92
- Ruth Lively/Kitchen Gardener #31
- Jennifer Benner/Fine Gardening #117
Oct 16, 2009 5:57 PM ET