There are a number of ideas that need to work together in order to achieve a water-saving landscape design and installation. These include:
Planting-choose mostly plants that have some drought resistance and need watering perhaps 1 to 4 times per month in the summer. group plants together which have similar watering requirements. Plants that need more water can often be used in special areas, to give some punch to entries, for example.
Irrigation-Group valve circuits by hydrozones so you water appropriately for each area.
For spray and rotor irrigation, carefully layout and adjust heads to avoid overspray, and use matched precipitation rate heads on each circuit. For drip irrigation, use installation methods that limit the fragility of the system-spaghetti tubing, for example is easily broken. Drip emitter locations should be added and subtracted as plants grow. Consider weather-sensitive "smart" controllers, such as subscription or stand-alone weather sensor packages. With or without these kind of controllers, pay attention to the programming of the clock-this is where more water gets wasted than anywhere else (turn it off during the rainy season in Northern California!).
Mulches-use 2 to 3 inches depth of bark or arbor chip mulch to slow evaporation and keep the soil from baking. Arbor chip mulch is a way to recycle tree waste. Shredded bark is good on slopes as it does not move down the slope as much as bark chips. Avoid "gorilla hair" which can form a mat that water and air have hard time penetrating.
Compost-Using compost as a top dressing for new and established plants, and in some soils as a soil amendment, will over time improve the water holding capacity of soils. Compost can be mixed with bark or arbor chips as a mulch.
Question: Is drip irrigation better than spray?
Drip irrigation was originally developed for row crops, which are mostly annuals, then became popular for landscape plantings. Despite its popularity, it has some drawbacks, and each property owner or manager needs to make informed decisions when a landscape installation is planned.
A conventional spray system is more expensive and will not be as efficient, but will be sturdier, require less maintenance, and need less renovation as the landscape matures. use of bubblers in small areas is also a good choice. There is no one 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 "). (It's sometimes misheard as" zeroscape ".) There are many trees, shrubs, and groundcover plants that can thrive on much less water than the typical lawn and azaleas type of design, which is a style well-suited to rainy climates but not to much of California with its 6-month dry period each year, or to the US Southwest. In California, many public agencies rely on the WUCOLS database (Water Use Classification of Landscape Species) to classify ornamental plants by high, medium, and low water use.
While there is a stereotype of xeriscape as either being limited to cactus and succulents, or limited to plants that look scraggly and unkempt, this is not true. Aside from California natives, there are many useful plants from similar climates such as Australia, New Zealand, South Africa, and the Mediterranean countries. While some California natives respond to drought stress by going dormant or semi-dormant in the summer, many will continue to look good with once-or-twice monthly watering. As in any planting design, attention to soil, exposure, slope, maintenance requirements, and the art of combining plant species will go far in creating a successful low-water landscape.
Question: what is the California State WELO?
The California State Legislature updated its landscape water conservation law by passing the WELO (Water Efficient Landscape Ordinance), effective in January 2010. All new and renovated planting that totals over certain square footages must comply with the law's water conservation requirements. This is a model ordinance-cities and counties may adopt stricter rules but not less strict rules.
The following projects fall under 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 a landscape area equal to or greater than 2,500 square feet requiring a building or landscape permit, plan check or design review;
(2) new construction and rehabilitated landscapes which are developer-installed in single-family and multi-family projects with a landscape area equal to or greater than 2,500 square feet requiring a building or landscape permit, plan check, or design review;
(3) new construction landscapes which are homeowner-provided and / or homeowner-hired in single family and multi-family residential projects with a total project landscape area equal to or greater than 5,000 square feet requiring a building or landscape permit, plan check or design review
Note that the square footages refer to planted areas, and do not include hardscape.
The law sets out the requirements for what should be included on Grading, Irrigation, and Planting Plans, (the whole ordinance is 41 pages!) 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 are to be gotten from the WUCOLS (Water Use Classification of Landscape Species) document.
Also of note in the law: no overhead irrigation in areas narrower than 8 feet wide. Irrigation clocks must be connected to soil moisture sensors or Et (evapotranspiration) sensors, as well as appropriate rain, freeze, and wind sensors. Many manufacturers are selling either subscription services that download weather information to the controller, or stand-alone weather sensors that measure solar gain and rainfall on site.