Drought

Nearly all areas of California are under a Drought Watch with some either in or about to enter a Drought Alert.  When there is an impending or actual water shortage, local water suppliers adopt drought response plans that include measures intended to reduce water demand.  The water use reductions and measures vary by the severity of shortage and are classified by stage.  Stage 1 is known as a Drought Watch and usually asks for voluntary actions to reduce water use up to 10%.  It relies on a public information campaign but can include enforcement of local water waste ordinances.  Stage 2, a Drought Alert, mandates a 20% water use reduction and involves a more intensive public information campaign, enforcement of local water waste ordinances, and specific mandatory water use restrictions.  Stage 3, a Critical Drought, requires up to 40% reduction in water use, and Stage 4, a Drought Emergency, requires more than 40% reduction in water use.  Stages 3 and 4 often require site-specific water allocations and/or severe landscape irrigation restrictions.

In the summer, about 1.5 to 2 inches per week is needed for tall fescue and other cool-season grasses and 1.25 to 1.5 inches per week for bermudagrass and other warm-season grasses to grow well.  To get a more precise answer based on your site, see the Lawn Watering Guide for California at http://ucanr.org/landscapewater.

A lawn will likely survive, but may not have optimum appearance or wear tolerance.  It will likely show brown areas, be less green, and thin out.  Exactly how well it looks and performs will depend on several factors: the climate, the type of grass involved, the performance characteristics of the irrigation system, irrigation application techniques, and the turf maintenance practices followed.  In this scenario, sites in moderate coastal climate areas of the state will likely see better turf performance than those in hot inland valley or desert areas.  Warm-season grasses (bermudagrass, buffalograss, st. augustinegrass, zoysiagrass) are more drought tolerant and likely to perform better under this situation than cool-season grasses (tall fescue, ryegrass, kentucky bluegrass).  It is critical that the irrigation system distributes water very uniformly and that it functions well at all times.  The irrigation manager must carefully set irrigation schedules so that on a watering day enough water is applied to wet the root zone of the turfgrass, which can be at least a few feet deep for warm-season grasses and up to a foot or so for cool season grasses.  It will require multiple irrigation cycles during the early morning or evening hours of an irrigation day to accomplish this.  The lawn should be mowed at the correct height – 2.5 to 3 inches for tall fescue, 1.5 to 2 inches for other cool-season grasses, and about 1 inch for most general use warm-season grasses.

Be sure to water at night, ideally between 9:00 PM and 6:00 AM.  Doing this reduces evaporation and the chance that wind will be strong enough to interfere with sprinkler patterns.  Next, walk through the area while the irrigation system is running and watch how well the water is applied.  Adjust sprinklers to get water completely covering the ground from one head to another and to eliminate overspray onto pavement that leads to runoff.  Repair any misaligned or broken sprinkler heads, fix leaks at heads or valves, and prune away any plant material that blocks sprinklers.  Be sure to add mulch 2 to 4 inches of coarse mulch around shrubs, trees, flowers, and newly planted plants to reduce evaporation.  Finally, adjust the runtimes in your irrigation controller every month to account for changes in the average weather conditions.  Doing all of these things can reduce by up to 10% the amount of water needed to adequately irrigate a landscape.

Although claims of 20 percent water savings are often purported, there is no guaranteed amount of water savings after installing one of the new smart or ET controllers.  Very few well-designed studies have been conducted that quantified the amount of water saved and simultaneously quantified performance of landscape plants after one of these devices was installed.  Installing a smart controller can result in more, less, or the same amount of water applied to a given landscape depending on a number of factors.  Critical factors include how much water was previously applied to the landscape (i.e. was the landscape over or under watered or watered correctly), how accurately the device was setup, and how well the irrigation system performs.  A copy of an early UC Cooperative Extension study on these devices and links to studies by others are available at http://ucanr.org/landscapewater.

As a general rule, established non-turf landscape plants need less frequent irrigation than a lawn area.  Many trees, shrubs, and groundcovers will perform acceptably when watered every four to ten days in the summer.  However, enough water must be applied to fully wet most of the root system at each irrigation.  This means running the irrigation system long enough to wet the soil at least 12 inches deep.  If drip irrigation is used, more frequent irrigation may be needed since only a portion of the root system is usually wetted with these systems.

Gather at least six straight-sided containers of the same size (used pet food or tuna cans work very well) and set them evenly space in the lawn.  More containers often produce more accurate test results.  Run the sprinkler system for 20 minutes and use a ruler to measure the depth of water (in inches) in each container.  Total the water depths for all containers and divide by the number of containers to determine the average depth of water applied.  Multiply the average depth by three to determine how many inches of water the system applies per hour.  Use the results to set the runtime in your irrigation controller.  While running the irrigation system for this test, note the time at which runoff begins.  This is the maximum number of minutes the system should run for a cycle.  In many instances, the irrigation system will need to run more minutes than the time to runoff in order to apply enough water.  Scheduling multiple cycles separated by several minutes to an hour on an irrigation day will accomplish this without creating runoff and water waste.

Yes.  Lawns of bermudagrass, buffalograss, st. augustinegrass, and zoysiagrass (warm-season grasses) need about 20% less water than tall fescue, ryegrass, and kentucky bluegrass (cool-season grasses).  Also, warm season grasses typically require less frequent but deeper irrigation than cool-season grasses.

Take a long screwdriver, similarly shaped tool, or a special soil probe and probe the soil in several spots an hour or so after an irrigation.  The depth that the screwdriver or tool can be easily pushed into the soil is the depth that the water has penetrated.  If deeper wetting is needed to wet plant roots, then additional irrigation cycles are needed.  It the soil is wet beyond plant roots, then irrigation runtime should be reduced.  Checking the soil moisture each day with this technique and watching the plants for signs of wilt or water stress will enable you to see how long it takes for soil to dry to the point where water must be replaced.  This is the maximum interval between irrigations for the current season.  Ideally, irrigation is applied just prior to the onset of plant stress, so irrigation should be scheduled about one day shorter than the estimated maximum interval.

ET is a widely used abbreviation for the term “evapotranspiration”, which represents the amount of water lost from a planted area due to the combined processes of evaporation from the soil surface and plant transpiration, which is the loss of water from plant foliage.

The primary things affecting a landscape’s ET rate are the local climatic factors (sunlight, temperature, wind, relative humidity), the type of the plants present, and how wet the soil is.  Regardless of plant type, the ET rate is higher when there is bright intense sun, warm temperatures, wind, low relative humidity, and plenty of water in the soil for plants to take up through their roots.  This is because evaporation from the soil is generally greater under these conditions as is water loss from plants (transpiration).  The actual rate of transpiration is regulated by the physiology of each species, thus the ET for plantings of different plants can vary somewhat.