San Luis Obispo County has a Mediterranean climate with hot, dry summers and mild, cool winters with little to moderate annual rainfall. Water shortages are common and within the next five years, more than two-thirds of the states in the nation will likely be short on water, even under non drought conditions. Today’s irrigation systems must be resource efficient and designed, installed and maintained for tomorrows needs in mind.
The ultimate goal of a resource efficient landscape is sustainability. The concept of sustainable landscaping examines the energy and resource inputs (i.e. water, materials, and labor) and outputs (i.e. water runoff, greenwaste, and pollution) and finds ways to minimize both.
In this newsletter, we will examine the many aspects of a residential irrigation system. By following the guidelines listed below an efficient and resourceful irrigation system can be installed at your home.
Evaluate Your Landscape – This involves taking an inventory of the types of plants you have in the landscape. Different kinds of plants require specific amounts of water. Separate plants into hydrozones or microclimate zones which are determined by plant water needs, soil type, exposure and other specific needs of the plant. Each hydrozone should have its own valve and irrigation method to accommodate the specific needs of the plants.
- Lawns –
- Lawns are one of the highest water users in the landscape and represent a separate hydrozone. If possible, eliminate the amount of lawn to conserve water.
- If a lawn is necessary consider alternatives such as drought tolerant Carex praegracilis, synthetic turf, or drought tolerant step-able groundcovers.
- Shrubs, Vines, Groundcover, Perennials –
- Consider the water needs of the plants that are chosen. Some are originally from wet climates and have higher water needs. Group plants within the landscape according to their requirements. Plants with the highest water needs will do best closer to the house, while plants with lower water needs will do well on the perimeter of the landscape. Each grouping is a separate hydrozone.
- Vegetable Boxes, Fruit Trees, Meadow, Pots, Planted Flagstone Walkways, Planted Rock Walls, and Planted Driveways –
- All of the options listed above require different water amounts, or irrigation methods. Each represents a different hydrozone.
Know your soil and how much water it retains. Sandy soil drains quickly, whereas clay soil retains water for longer periods of time. Separate valves by soil type or drainage.
Know the shade patterns around your house and the areas that are subject to wind. Separate plants accordingly.
Break larger areas into smaller ones, if the hydraulics of the system cannot accommodate the whole area.
- All of the options listed above require different water amounts, or irrigation methods. Each represents a different hydrozone.
Methods of Irrigation –
- Rotors –
- Ideal for clay and loam soils, slopes and large areas.
- Utilize for large areas – lawns, groundcovers, and low shrubs and perennials that tolerate overhead watering.
- Often more efficient than spray heads because they utilize less water and often fewer valves to cover the same area.
- Can be utilized with reclaimed water.
- MP Rotators –
- Multi-stream rotor ideal for small to medium lawns, groundcover, and low shrubs and perennials that can tolerate overhead water.
- Water is applied slowly and uniformly to reduce runoff and wasted water. It can use up to 30% less water than a conventional spray or rotor head.
- Tight, high energy streams increase wind resistance and effectiveness on slopes.
- Utilizes fewer valves and controls, less pipe, wire, and labor, thus lowering the cost of installation.
- MP Rotators fit most conventional spray heads.
- Can be utilized with reclaimed water.
- Spray –
- Ideal for small lawns, groundcover, low shrubs and perennials that tolerate overhead watering.
- Body styles come in spray nozzle on a riser, or 2”, 3”, 4”, 6” & 12” pop ups.
- Nozzles come in a variety of arcs and radius’ including side strips and corner strips, making hard to irrigate areas accessible.
- Fixed pattern or adjustable nozzles.
- Can be utilized with reclaimed water.
- Microspray –
- Ideal for small areas of groundcover that need overhead water, seedlings, and annual flower beds.
- Uniform water distribution up to 27 feet.
- Fine mist and flat trajectory.
- Nozzles can clog easily
- Risers usually need to be supported by stakes
- Drip Irrigation –
- Ideal for native plants, trees, shrubs, vines, perennials, fruit trees, pots, and vegetable boxes.
- Highly efficient method for applying the amount of water the plant needs directly to the root zone.
- Emitters come in a variety of sizes ranging from .5 GPH to 10 GPH and some are pressure compensating.
- Low evaporation rate from wind.
- Covering the drip tubing with mulch decreases soil evaporation and protects the tubing from deterioration from the sun.
- In line Drip (Dripperline or Emitterline) –
- Ideal for trees, shrubs, perennials, groundcover, vegetable boxes, fruit trees, planted rock walls and walkways or patios, turf, sports turf and areas next to sport courts, areas subject to vandalism and high wind areas.
- Can be installed subsurface for turf (4-6” deep) or on the surface in a grid pattern or evenly spaced contours or plant ring layout. On surface applications require mulch to protect the tubing from deterioration from the sun.
- Minimal water loss from wind and soil evaporation.
- Highly efficient – applying the amount of water needed directly to the root zone.
- Netafim Techline CV Dripperline has PC emitters built into the drip tubing and are spaced at either 12”, 18”, or 24” intervals. Tubing diameter is available in ¼”, ½”, and ¾” and the flow rates are .26, .4, .6 or .9 GPH to accommodate a variety of watering needs. Pressure compensation range is: min.14.7 to max 70 PSI. Each dripper has a 2PSI check valve so all drippers turn on and off at the same time. They have a continuous self flushing dripper design which flushes away any debris detected throughout its operation and a built in root barrier to prevent root intrusion. Purple-colored dripperline can be used with reclaimed water.
Components –
- Controllers
- Indoor and Outdoor Models – Comes with multiple stations, programs and start times.
- Battery Operated Controllers ideal for areas that do not have outdoor access to electricity.
- Smart Controllers – (weather based) combines current ET weather data from a location specific weather station with landscape specific parameters such as plant type, soil type, slope and sun exposure. The result is a scientifically calculated irrigation schedule tailored to your landscape that adjusts automatically.
- Valves –
- Anti-siphon
- Inline
- Filters –
- When utilizing water other than city water a filter is always needed.
- Mesh Screen
- Disc
- With root block
Sprinkler Design –
- Head to head coverage: Spray from one sprinkler should reach the next sprinkler. For full coverage, each area should be covered by three sprinklers.
- Adjust nozzles to prevent overspray.
- Layout pipes so that they have the fewest turns (most direct route).
- Check water pressure and flow rate (GPM) to determine how many sprinklers can run on one valve (size valves according to demand).
- Don’t mix different types of sprinkler heads. (rotors and spray or MP Rotators).
- Once installed, check your irrigation system periodically for leaks, malfunctions
Water Conservation Basics
- Water in the early morning or at night when the wind is low and the day is still cool. This helps prevent water loss due to evaporation.
- Utilize one kind of irrigation method for each valve. Different methods require different amounts of pressure and watering time to work efficiently.
- Water only the amount of time needed to avoid water loss due to runoff, while thoroughly wetting the root zone horizontally and vertically. Water in 2 sessions if needed. Most drought tolerant plants prefer longer, deeper watering and less often. This will promote deeper root growth and less need for water in the future.
- Cover bare ground with mulch to help conserve soil moisture, suppress weeds, preserve drip irrigation tubing, and keep the soil cooler.
- Remove weeds from the landscape regularly. They steal water that is needed for your plants.
- Add rich compost to your soil to improve its ability to retain moisture and add nutrients for your plants.
Water Audits – assesses your existing irrigation system to make sure that your watering practices and irrigation devices are as efficient as possible. Recommendations are made to improve water scheduling, irrigation devices, and plant material so that your landscape will conserve water and save you time and money.
- What to expect from a Water Audit
- Site inspection and system tune-up.
- System check involving turning all stations and recording observations.
- Calculate a base watering schedule based on observations.
- Basic Water Audit Procedures
- Turn on all stations and check for leaks and problems.
- Make any necessary repairs.
- Measure sprinkler water consumption with a catch can test. Cans are strategically located throughout the irrigating space to catch water from the sprinklers. The information gathered from the catch cans is then used to determine the distribution uniformity (DU) of water coverage over the area.
- Other irrigation methods are by evaluated by turning on the system and observing whether the appropriate amount of water is being distributed to the plants.
- Evaluate the type of plant material and the type of irrigation that is watering the plants to determine if there is a more efficient way of irrigating the plants or if plant material is inappropriate for its location or type of irrigation being used. Create an updated and more efficient watering schedule based on observations and information gathered.
Factors to Consider When Scheduling Controllers
- Soil Type
- Climate
- Time of Year
- Time of Day
- Type of Plants
- Type of Irrigation
- Right Amount of Time
- Water Restrictions in the Area
Water Sources
- City Water –
- Most expensive and most common source
- Cleaner and can be used on any type of plant material. Filters are not always necessary.
- Well Water –
- Less expensive, but requires electricity to pump for use.
- Not as common as the city water, but can be used on any type of plant material.
- A filter is usually always necessary.
- Non-Potable Water/ Reclaimed Water –
- Treated waste water that can be utilized for irrigating landscapes. It can not be utilized for drinking water, bathing, irrigating edible parts of edible plants, or filling pools for recreational use.
- It is clear and odorless and saves a considerable amount of water by recycling.
- Purple pipes, tubing, nozzles & valve boxes indicate use of reclaimed water for your safety (non potable).
- Graywater –
- Graywater – untreated household wastewater that has not come in contact with toilet or kitchen sink waste (blackwater). Wastewater from the washing machine, bathroom sink, shower, and bathtub.
- Graywater makes up 50 – 80% of all wastewater of a residential home. Reusing this water is an excellent way to utilize resources that would otherwise be wasted. It can be utilized to irrigate small to medium sized areas of the landscape in close proximity and down slope from the source.
- Trees, fruit trees, shrubs, perennials, non edible parts of vegetables and any salt tolerant plants may be watered using graywater.
- Graywater is ideal for sites with good soil percolation, drain pipes that are not buried under a concrete foundation (raised floor), and for families that utilize the washing machine, sinks, and showers often.
- Graywater can also be used for toilet flushing. Either plumb a bathroom sink directly to toilet tank for immediate use or collect and treat Graywater in a central location and redistribute to all toilets in the house.
- Must use organic soaps that have lower salt content. Avoid products with sodium compounds, boron, chlorine, high pH, and other toxins found within body cleansing products.
- Special Considerations Before Installing a Greywater System
- Access to drain pipes
- Slope of the land
- Drainage/ Infiltration of the Soil
- Proximity to creeks and waterways (minimum 100 ft. away)
- Quantity of graywater produced
- Irrigation needs of plants (suitability for graywater)
- Desired maintenance level
- Permit needs and budget
- Types of Greywater Systems
- Laundry to Landscape – Washing machine pumps graywater directly to plants (no storage tanks).
- Laundry Drum – Washing machine pumps graywater to a barrel which then drains from the barrel through a hose and out to the landscape.
- Branched Drain – Gravity causes graywater to flow outside through pipes to mulch basins around plants. Must be on a slope with adequately sized outlets.
- Pumped System – Graywater drains to a surge tank where it is pumped out to landscape plants.
- Constructed Wetlands (Reed beds)-Graywater drains through a constructed wetland which removes nutrients and transpires water. Best when soil percolation is slow, space is limited and large volumes of water need to be treated.
- Sand Filter to Drip – pressurized system that removes particles with a sand filter, which allows the water to be clean enough for use in a drip irrigation system.
- Rainwater Harvesting –
- Water can be collected from downspouts to Barrels or Cisterns (storage tanks) for later use, or from runoff in the landscape into, drainage swales, terraces and retention basins for more immediate use.
- Not as beneficial for areas that have low annual precipitation rates.
- Benefits of harvesting rainwater: reduces flooding, decreases erosion, minimizes water pollution, prevents areas for mosquito breeding, generates irrigation water & drinking water (if treated), enhances soil fertility & lowers utility bills.
- Using your Landscape to Collect and Use Rainwater
- Retention basins are created in the area with the lowest elevation. The remainder of the landscape is developed to drain into the basin. This can be accomplished through the use of berms, terraces, drainage swales, creek beds or drainage pipes.
- Terraces with diversion swales to direct water runoff from hardscapes to plant material.
- Reducing non permeable hardscape areas decreases the amount of runoff in the landscape.
- Mulch increases water retention for use in a landscape by acting as a sponge to water runoff, decreasing evaporation from the soil, and by limiting soil erosion.