There are a number of ideas that must work together to achieve water-saving landscape design and installation. These include:
Planting – Choose mainly plants that have some resistance to drought and need watering perhaps 1-4 times per month in the summer. Group plants together that have similar watering requirements. Plants that need more water can often be used in special areas, for example to add a touch to entrances.
Hydrozone irrigation group valve circuits so you can irrigate properly for each area.
For sprinkler and rotor irrigation, carefully position and adjust headers to avoid overspray, and use matching rainfall rate headers in each circuit. For drip irrigation, use installation methods that limit the fragility of the system; for example, spaghetti tubing breaks easily. Drip emitter locations should be added and subtracted as plants grow. Consider weather-sensitive “smart” controllers, such as stand-alone or subscription weather sensor packages. With or without these types of controllers, pay attention to the clock setting – this is where more water is wasted than anywhere else (turn it off during the rainy season in Northern California!).
Mulches: Use a 2- to 3-inch depth of bark or tree chip mulch to reduce evaporation and prevent soil from baking. Arbor chip mulch is one way to recycle tree debris. Shredded bark is good on slopes because it doesn’t move downhill as much as bark chips. Avoid “gorilla hair” which can form a mat that water and air have a hard time penetrating.
Compost – Using compost as a top dressing for new and established plants, and in some soils as a soil amendment, will improve the water-holding capacity of soils over time. Compost can be mixed with bark or tree chips as mulch.
Question: Is drip irrigation better than spray irrigation?
Drip irrigation was originally developed for row crops, which are mostly annuals, and later became popular for landscape plantings. Despite its popularity, it does have some drawbacks, and every homeowner or property manager needs to make informed decisions when planning a landscape installation.
Advantages:
- Easy and relatively inexpensive to install. Trenching is often not necessary, since the polyethylene pipe is laid at ground level, under the mulch.
- Requires less training for workers to learn installation
- Reduces evaporation when the system is running, without spraying or fogging to evaporate
- For widely spaced plants, save water as the emitters are placed right at the root ball of the plant.
- Easy to repair.
Cons:
- Brittle and easy to break. Often the problem is not seen until the plant wilts.
- Some plants do better with spray on their leaves.
- In heavy soils, it can cause roots to rot due to sitting in water, as all the water is concentrated in the root ball. Some experts think CA natives are particularly susceptible.
- As bushes and trees grow, it is necessary to change the position and number of emitters, but this is rarely done. A 10 year old tree with emitters right on the trunk is not being helped by the drip system and can be damaged.
A conventional sprinkler system is more expensive and won’t be as efficient, but it will be more durable, require less maintenance, and need less renovation as the landscape matures. the use of bubblers in small areas is also a good option. There is no perfect system.
Question: What is xeriscape?
Xeriscape is a term for low-water-use gardens and landscapes, also called drought-tolerant landscapes (“xeric” means ‘dry’, from the Greek word “xeros”). (Sometimes misunderstood as “zeroscape”). trees, shrubs, and ground cover plants that can thrive with much less water than the typical lawn and azalea design type, which is a style well suited to rainy climates but not much of California with its 6-month dry spell each year, or to the southwestern US in California, many public agencies rely on the WUCOLS (Water Use Classification of Landscape Species) database to classify ornamental plants by high, medium, and low water use.
While there is a stereotype of xeriscape being limited to cacti and succulents, or limited to plants that look scruffy and unkempt, this is not true. Aside from those native to California, there are many useful plants from similar climates, including Australia, New Zealand, South Africa, and Mediterranean countries. While some California natives respond to drought stress by going dormant or semi-dormant in the summer, many will still do well with watering once or twice a month. As in any planting design, attention to soil, exposure, slope, maintenance requirements, and the art of combining plant species will go a long way toward creating a successful low-water landscape.
Question: What is the State of California WELO?
The California State Legislature updated its landscape water conservation law by passing the WELO (Water Efficient Landscape Ordinance), effective January 2010. All new and renovated plants totaling more than certain square feet must meet with the water conservation requirements of the law. This is a model ordinance: cities and counties can adopt more stringent rules but not less stringent ones.
The following projects are subject to the new law (there are some exceptions, but this covers most projects):
(1) new construction and rehabilitated landscapes for public agency projects and private development projects with landscape area equal to or greater than 2,500 square feet that require a building or landscape permit, plan verification, or design review;
(2) new construction and rehabilitated landscapes that are installed by developers on single-family and multi-family projects with landscape area equal to or greater than 2,500 square feet that require a building or landscape permit, plan verification, or design review;
(3) new construction landscaping provided and/or contracted for by homeowners in single-family and multi-family residential projects with a total project landscape area equal to or greater than 5,000 square feet that require a building or landscape permit, plan verification, or design review
Please note that square footage refers to planted areas and does not include hard surfaces.
The law lays out the requirements for what must be included in grading, irrigation, and planting plans (the entire ordinance is 41 pages long!), but most important is the required calculation of MAWA (Maximum Applied Water Allowance, in gallons per year) and ETWU (Estimated Total Water Use), and ETWU has to be less than MAWA. Plant factors for these calculations will be obtained from the WUCOLS (Water Use Classification of Landscape Species) document.
Also of note in the law: Sprinkler irrigation is not permitted in areas less than 8 feet wide. Irrigation clocks should be connected to soil moisture sensors or Et (evapotranspiration) sensors, as well as appropriate rain, frost and wind sensors. Many manufacturers are selling subscription services that download weather information to the controller or stand-alone weather sensors that measure solar gain and rainfall on the site.
