- Author: Rho Yare
And then, one day cities began reading those water meters and charging the nice, water loving citizens by the units of water used each month. You could almost tell the day the bills arrived. Neighbors discussed them at the mailbox with anger, frustration, even fear. “How can I afford this every month?” Or “How can I reduce my monthly bill?” And that was the birth (or at least the beginning) of serious discussions about how to be “water wise” or how to conserve water to lower the units of water consumption that consequently will lower the monthly bill.
During this last drought, many people just stopped watering their lawn. This helped reduce their water bill but does little else. In many cases it killed street trees as well.
Not watering grass in our climate guarantees that the grass will die. In its place, however will be weeds. Weeds can live and multiply in harsh, waterless conditions. And all those weeds are spreading seeds that land in your neighbor's lawns. And eventually even the weeds die from normal life cycle or lack of water. Then the wind blows the precious topsoil from your yard. This topsoil mixes with the other air in our valley and adds to air pollution.
What if I want to keep my lawn?
There are a few things you can do if you do not want to give up your lawn completely. Think about reducing the amount of lawn in your yard, which can help you save water and money. Having a beautiful yard without green grass does not mean just rocks, cactus, or artificial turf. Begin by removing a small section of the grass. Check with the Stanislaus Master Gardeners and local nurseries for plant suggestions to replace that green grass with other green, or gray, or yellow plants. Think beyond bark, boulders, and bare ground. The possibilities are endless. This time of the year is a perfect time to begin making plans for that winter yard renovation!
What are some easy tips to save water?
Now, if you are not ready to commit to a grassless or partially grassless yard there are some changes that can help in reducing water consumption. First, examine your current watering system. If you have a sprinkler system, do not assume that it is working properly. Checking weekly during the warm weather is a must, especially after the lawn is mowed and in the daylight. Is everything working properly, sprinklers putting water on the lawn not the sidewalk or street? Are the sprinklers clogged, broken, or even missing? If you have an automatic timer, check the timer, and remember to decrease time and days as the daylight time shortens and weather cools, and turn the sprinklers off when the rains begin. Be an agent of change for the better! Making a few changes now can make a difference in your water bill, landscape, and our world because we are all in it together.
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Join Rho Yare on Zoom for an evening of tips on how to reduce your water bill, yard work, pesticide use, all while having a gorgeous yard on Tuesday, October 27, 2020 from 6:00-7:30 p.m. Sign up at http://ucanr.edu/sustainable/2020 to receive your link.
- Author: Dustin Blakey
As I was driving my kids to school recently, I noticed that a landscape on the way was irrigating its dormant turf. It had rained the night before. That seemed really unnecessary. Later that day I saw another landscape (with green grass) had a head spraying out into the street. I see irrigation problems almost every day but for some reason that memory stuck.
As a community, we tend to irrigate our landscapes poorly, but we can do better. Ideally we should apply just what our plants need plus maybe a little extra to make up for variability in our sprinkler system. It's not uncommon for a landscape in Bishop to use 2 or 3 times the water it needs. Assuming that water makes it on to the lawn. Last summer there was a small creek along the curb in my neighborhood every morning from someone's broken irrigation up the street. And to be fair, I have a head that often gets flipped backward and then waters the driveway.
Maybe in a future post we can cover how much water our lawns need and how often to run the system, but today I think a good place to start is how to make sure your system is working correctly. Rain Bird has a nice spring checklist, but the process should involve a bit more.
A good practice is to begin the season with an irrigation audit. This is a process where we check to make sure everything is working as it should, and we check the output of our sprinklers to make sure they are uniform. Uniform application saves water since we don't have to over apply water to get the dry places wet enough.
All irrigation audits start by running the system and making sure sprinkler heads are working and pointing over grass. This is usually simple to address. You may need a small screwdriver to make some adjustments but that's about it.
From there you can choose how complicated you want to be. Commercial turf managers will audit their systems using at least 20 special catch cans to measure the system's output and variability. That's probably over-kill at home.
Oklahoma State Cooperative Extension has a very simple version of this test that will tell you each sprinkler zone's output in inches per hour using tuna or cat food cans. This will allow you to set your sprinkler system to water just the amount the lawn needs rather than "15 minutes every day" type scheduling. They even include a short video. SIMPLE AUDIT LINK.
If you use this system I'd recommend looking at each can to see if they are about the same level. If they vary a lot, you may need to consider some maintenance on the system. As a rule, most sprinklers are designed to have head-to-head coverage in their pattern. If your system does something else--that's common around Bishop--expect a lot more variability.
At the very least, run your system and watch it for a few minutes. Put a catch can or 2 of any type with straight sides on for one cycle to confirm how much water you're applying. Sticking a ruler in is a good way to measure. You may be applying more or less than you think!
If you are interested in figuring out out to properly schedule up your irrigation, the Master Gardeners can help with that, but we will need to know each zone's output in inches per hour. You can contact us at immg@ucanr.edu.
- Author: Gerry Spinelli
- Author: Michael Cahn
Determining how long to run your irrigation system can be challenging because typical recommendations on how much water to apply are expressed in units of inches (or feet) of water depth. Knowing the application rate of your irrigation system will allow you to convert these recommendations into the time (hours) to operate the irrigation system.
The application rate is the depth of water that the irrigation system applies during a period of time, and is typically expressed in units of inches per hour (in/hr). An application rate of 0.27 in/hr means that when the system is operated for one hour it will apply 0.27 inches of water to the field; if it is operated 45 minutes, 0.2 inches (0.27 in/hr × 45 min ÷ 60 min/hr) are applied and so on.
Note that the application rate is independent of the number of acres irrigated. In other words, an irrigation system would have the same application rate on a one-acre or a five-acre block. For raised bed crops such as vegetables and strawberries, the application rate includes the area of both the furrows and the bed tops.
Determining the application rate of drip systems
The variables determining the application rate of drip systems are: 1. bed width, 2. number of drip lines per bed, and 3. flowrate of the drip tape. The flow rate of the tape (also referred to as the discharge rate) corresponds to a specific pressure, usually 8 or 10 pounds per square inch (psi). The flow rate of the drip tape is usually specified on the label of the tape roll (Fig. 1) and is often expressed in units of gallons per minute per one hundred feet of tape (gpm/100 ft).
Figure 1. Examples of a drip tape label with flow (discharge) rate information.
Some tape manufacturers provide the discharge rate of the emitters and the emitter spacing rather than the flow (discharge) rate of the tape. The discharge rate of the emitters is usually expressed in units of gallons per hour (gph). To calculate the tape flow rate from the emitter discharge rate, use the following equation:
Tape discharge rate (gpm/100 ft) = Emitter discharge rate (gph) × 20 ÷ emitter spacing (inches) [1]
Example (from Fig. 1): emitter discharge rate = 0.16 gph; emitter spacing= 8 inches
Tape discharge rate (gpm/100 ft) = 0.16 gph × 20 ÷ 8 inches = 0.40 gpm/100 ft
The application rate of a drip system can be determined from the tape flow rate (gpm/100 ft), bed width (inches), and number of drip lines using the following equation:
Application rate (inches/hour) = tape flow rate (gpm/100 ft) × number of tapes × 11.55 ÷ bed width (inches) [2]
Example: tape flow rate = 0.45 gpm/100 ft; bed width = 48 inches; 2 drip lines per bed
Application rate = 0.45 gpm/100 ft × 2 drip lines × 11.55 ÷ 48 inches = 0.22 inches per hour
Table 1 also summarizes application rates of some common drip system configurations for strawberry. The application rate of the drip system can be estimated by finding the row with the flow rate that is closest to the tape that you use, and then reading the application rate under the bed and drip line configuration used at your farm.
Table 1. Application rate (in/hr) of drip systems for common drip tape flow rates and bed widths in strawberry.
Determining the application rate of solid-set and hand-move sprinkler systems
To estimate the application rate in sprinkler systems (aluminum hand-move pipes) one needs to know the spacing of the lateral lines, the sprinkler nozzle size and pressure at which the system is operated. For hand-move sprinklers, the distance that the sprinkler line is moved between irrigation sets is the lateral line spacing. Pressure can be measured at the sprinkler nozzle using a with a pitot tube fitted with a pressure gauge. Alternatively, a gauge or Schrader valve can be added to a riser so that the pressure can be measured on the lateral line. Discharge rate of sprinkler heads will increase with higher pressures and larger nozzle sizes. Most manufacturers provide data on discharge rate for each sprinkler head model. Table 2 shows the range of discharge rates for the Rainbird 20JH model.
Table 2. Discharge rates of Rainbird 20 JH sprinkler heads at varying nozzle sizes and pressures.
From the discharge rate, lateral pipe spacing, and discharge rate, the application rate for a sprinkler system can be estimated using the equation:
Sprinkler application rate (inches/hr) = discharge rate (gpm) × 96.3 ÷ [lateral spacing (ft) × head spacing (ft) [3]
Example: Sprinkler head = Rainbird 20JH with 7/64 inch nozzle operated at 45 psi; lateral spacing = 40 ft; head spacing = 30 ft.
From Table 2 the discharge rate of the sprinkler head = 2.63 gpm.
Sprinkler application rate (inches/hr) = 2.63 gpm × 96.3÷[30 ft ×40 ft] = 0.21 inches/hr
Alternatively, Table 3 can be used to estimate the application rate of an irrigation system using the Rainbird 20JH sprinkler heads.
Table 3. Application rates for sprinkler systems using Rainbird 20 JH heads at varying pressures, nozzle sizes, and lateral and head spacings.
Using the application rate to determine how long to irrigate
The application rate can be used to determine how long to irrigate a crop from estimates of crop water use. For an average year in the Pajaro Valley, a strawberry crop needs one inch of water during a typical week in August and about 28 inches for an entire crop cycle. A grower with an application rate of 0.22 inches/hour will need to irrigate four and a half hours (1 inch ÷ 0.22 in/hr = 4.5 hr) during a week in August and a total of 127 hours (28 in ÷ 0.22 in/hr = 127 hr) during the entire season.
Summary
Accurately estimating the application rate of an irrigation system requires precise knowledge of the discharge rate of the drip tape or sprinkler nozzle. Over time, nozzles become worn and drip emitters clog, or the pressure of the system may not be operated at the specifications of the manufacturer. The best way to accurately know the application rate is to directly measure it in the field. For direct measurements of the application rate, schedule an on-site irrigation evaluation with the RCD of Santa Cruz County at: 831-464-2950, info@rcdsantacruz.org.
- Author: Dennis Pittenger
[From the August 2015 issue of the UC IPM Green Bulletin]
A. Landscape irrigation accounts for only about 9% of total statewide developed water use, but the percentage varies widely among communities. Water applied to landscapes is estimated to account for about 50% of residential water consumption statewide, but the amount varies from about 30% in some coastal communities to 60% or more in many inland suburban communities.
Q. Does a landscape have to be re-planted with specific drought resistant, native, or California- Friendly plants to save significant amounts of water?
A. No. Field research studies indicate that traditionally used landscape trees, shrubs, and groundcovers have considerable drought resistance and perform acceptably with about 40% to 60% of the water required to maintain the average lawn in good condition. This is comparable to the water required by so-called drought resistant, California Friendly, and native plants to perform acceptably in landscapes. The common perception is that plants traditionally grown in landscapes are not drought resistant, so they are usually over watered.
Q. How much water can be saved by removing a lawn?
A. Water savings depends on how effectively the lawn has been irrigated, the type of turfgrass removed, which plants and how many will replace it, and how effectively the water applied to new plants is managed. If a lawn is removed and plant material is changed but the irrigation system and water management practices are not improved, then little water savings will be realized. If the lawn has been over watered and irrigation was poorly managed, then maximum water savings are possible by removing the lawn. However, in such situations keeping the lawn and simply improving irrigation management and improving or replacing an inefficient irrigation system will also generate substantial water savings without the trouble, cost, and the loss of aesthetics and functions that occur when removing the lawn.
A. As with lawns, it depends on the amount of water currently being applied. Plantings that have been maintained with high soil moisture content can usually maintain acceptable performance with a 20-40% reduction in irrigation by extending the interval between thorough irrigations as described above. Additional 10- 20% irrigation reductions to theses plantings or to plantings that have already been irrigated below optimum will usually allow plants to remain functional, but they will grow less, possibly wilt and drop some leaves. It is important to gradually reduce water over a few to several week period by extending the interval between irrigations and applying enough water to wet most of the root system at each watering.
A few deep, root-zone wetting irrigations spaced 3 to 6 weeks apart from spring through fall can be enough to keep most trees and shrubs alive when water is in short supply. Many tree and shrub species will drop leaves, wilt, or suffer dieback of some branches under severe water shortage, but will survive.
Q. When should trees, shrubs, and other landscape plants be planted in a dry year or if drought is expected?
A. Hold off planting until fall or winter to take advantage of cool weather as well as fall and winter rains. The planting site may be prepared in spring or summer, however.
To access this article in it's entirety, see the August 2015 issue of UC IPM's Green Bulletin or visit the UC Center for Landscape and Urban Horticulture
- Dennis R. Pittenger, Area Environmental Horticulturist, UC Cooperative Extension Los Angeles County/UC Riverside, dennis.pittenger@ucr.edu
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