May 31, 2002

Irrigation Water Management with IRWD

Please note:  This article was addressed to our customer base within the Irvine Ranch Water District, and some items are specific to that condition.  Also, the charts mentioned are not posted here.  If you would like copies of those, please contact us via email.

Notes on Irrigation Water Management Within the Irvine Ranch Water District


As an IRWD reclaimed water customer, I’m sure you are aware that the district is quite proactive in the area of water conservation. Through the years, there have been many manifestations of IRWD’s programs as their reclaimed water policy has metamorphosed. As one of the leading water agencies in conservation programs in California, IRWD has enacted their 5-tiered billing system, the Et-based allocation system, the infamous Operation Outreach educational and rebate program, all in conjunction with a growing water reclamation project and customer base.

The rates IRWD charges for reclaimed water remain unchanged since 1995. The lowest tiers continue to be lowest rates in Orange County. The labels for the billing tiers have changed and are less offensive now: Low Volume Discount, Conservation Base Rate, Inefficient, Excessive, Wasteful. IRWD continues to conduct educational seminars regarding water conservation and its policies. Most recently, their concern has been the reduction in runoff in response to new regulations assigning possible liability for runoff that reaches the ocean. This year, IRWD sends its customers the Landscape Water Management Performance Report. Since no one likes to get a “C”, let alone an “F”, the monthly Performance Reports, which assign a grade of “C” to a property using 100% of its allocation, have set off a buzz. IRWD remains at the forefront of creating strategies that can engineer better human behaviors! The thing to notice about the new grading scale is an “A” is awarded only to those using less than 80% of allocation. That is analogous to your child being required to obtain more than 20% extra credit to get an “A” in a class, or receiving a “C” for getting all the questions correct on a test! But, it definitely gets your attention.


We must conserve water. For the sake of economic growth, improved quality of life, protecting quality of the environment, and also to preserve the value in your property, water conservation makes sense. It also saves money on the water bill. We support the efforts of government agencies and the private sector to develop meaningful policies, programs, infrastructures and products that support conservation of water. We have cut water use at our sites by incredible percentages since 1988, and continue to reduce the use of water. IRWD says that “drip” is the most water conserving system you can install. We have many sites that prove the statement that GOOD drip irrigation systems save water. We are good at drip irrigation, and the reason we have taken the time to understand these systems is we care about water conservation. We have suggested in the past the idea of IRWD giving its irrigation customers an annual water allotment, based upon historical Et and then adjusted up or down for actual recorded Et for the year in question. Then, a customer would have the ability to budget use more proactively. For instance, if you host an important conference at your site in mid-September you would want your lawns and plants looking their best. There is no denying that green lawns still have an emotional impact on all of us and portray a sense of prosperity and well-being. An annualized budget scheme would allow you to allocate more water during late July, August and early September to optimize the appearance of your landscape for the conference. Then, you would budget less water at another time of year when landscape appearance wasn’t as important to you. In the present IRWD scheme, August and September are the most challenging months for keeping up the appearance of lawns. The weather is still hot, but the Et is going down as are other factors involved in the allocation formula. The average weekly allocation September 2001 was 35 ccf while it was 47 ccf in July. IRWD has not entertained the idea of annual water allotments for irrigation customers so far.

We use horticultural practices that both improve landscape quality and tend to reduce water use. Aeration, mulch, specialized fertilizers, timing of trimming, growth regulation, and lawn clippings recycling are among the services we make available to your property.


Centennial Services, as a part of our landscape maintenance service to your property, reads your irrigation water meter weekly. We compare this data with the allocation data from the IRWD website at least once monthly. We adjust your irrigation controller to deliver water appropriate to the needs of your landscape within certain bounds of allocation. Our philosophy has been to consider the overall cost of the water used, and the benefit received from that water instead of only focusing on penalty charges. As a rule of thumb, unless directed otherwise by the property manager or owner, Centennial Services uses 120% of Eto as a benchmark or do-not-exceed goal. (See the green chart enclosed, which shows annualized water cost under various percentages of allocation) We know at that level, your cost of water overall begins to increase dramatically due to the billing policies of IRWD. But, this additional water can be beneficial to your landscape: It acts as a buffer to sudden weather changes. For example, the Et for the second week of April (a time of year when plants are actively growing and getting ready to bloom) increased almost 50%. Inefficiencies in the irrigation systems at some properties are alleviated by increases in usage to deliver the quality of landscape desired. During certain times of the year, such as when deciduous trees are leafing out, there is an increased draw on soil water especially when the trees are growing in lawns. If a special system to water the trees is not provided (rare in older landscapes), the additional water the trees need at this critical time must come from the lawn irrigation system, unfortunately. In winter, in the non-penalty period of the year (December through May) we do not manage the water use at your site as aggressively, unless directed by the owner or manager. During this period, your use percentage might be high, however bear in mind the allocation is at its smallest to begin with (Dec through March). April and May are high demand months where using more water really pays off in enhanced plant appearance. Another reason we might use additional water in spring is to build up soil capacity, which serves as a bank of available water for your plants. The IRWD does not officially agree with any of these horticultural principles, however, so they grade you harshly for using water above the “80% of Eto level”. As summer progresses, we monitor your irrigation water use, and may send a technician out to “emergency tweak” your controller if it appears the use is going to generate a lot of penalty charges. If the customer has provided a water bill copy to us and has requested this service, we can monitor the water used during a billing period, and even cut off use so as not to exceed a pre-set limit defined by the customer. Remember, too, that weather trends can be generalized but are still unpredictable. The allocation you get weekly is based upon the previous week’s weather. Even if your controller were adjusted weekly to a theoretical 100% of allocation (don’t forget those irrigation inefficiencies, sloped areas, night winds, compacted soil patches, etc etc etc) you might over use water the following week due to a change in weather. Or you might end up with diminished plant quality (dry patches in lawn, wilting perennial or annual color, stress on shrubs and trees) due to a change in weather.

We also do not simply use the “percent key” to adjust your irrigation program seasonally. We have a comprehensive plan that deletes watering days, start times, and uses special programs to make adjustments through the year. This level of management requires a minimum level of sophistication in the irrigation controller that some properties lack. We also recommend upgrades of irrigation heads that are high-gallonage, non-matched precipitation rates, or have uneven application patterns. We are able and ready to provide irrigation retrofit consultation and installation at your property.

Please have a look at the Allocation Formula sheet enclosed. This graphically explains the components that make up your allocation, and shows the places where you and we can exert some control over the water use at your site.


We recognize that urban runoff from all sources is degrading our environment and should be controlled as much as possible with good management practices. We divide our water times into 2 to 4 blocks per watering day/night so as to allow the allocated water to soak in between waterings. A big contributor to runoff is backspray from pop up spray heads used to water shrubbery, where the spray fan hits the foliage and rebounds onto the pavement and down the gutter. Using drip irrigation on hedges and shrub beds that abut pavement is a good idea because the application rate is so slow (1 or 2 gallons per HOUR instead of per MINUTE) that runoff does not occur when the system is operating properly. Irrigation should not result in runoff, but sometimes does because equipment or planting upgrades have not been installed to offset inherent tendencies in the site toward runoff.


An important change in reclaimed water billing will occur this year, as far as information I have indicates to date indicates. IRWD has proposed that the no-penalty period for reclaimed water customers should end. This means that during the December through May use period, penalty charges will apply as they do the rest of the year. The scenario I have charted (see the white chart enclosed) for you property shows how your water cost for the year might work out at various levels of use under this new billing plan. As you can see on the chart, 120% really is the point where the cost of the water you buy increases dramatically and beyond what businesses in other water districts are paying overall. (Please, bear in mind this chart assumes the year-round penalty scenario. The cost of water in the past would be less—see blue block below chart for details on this). One challenge for landscapes under this new plan will be the accumulation of salt in the soil. Reclaimed water is becoming higher in salt. It was already above recommend limits for landscape in the last water quality report I had available (from 1988, published on the IRWD website). As stated in the article on the water quality report, salts tend to accumulate in the waters (and soil) as we use them. A way to rid soil of salts is by leaching. Leaching is an application of water that flows through the soil column carrying salt with it. We sometimes get leaching from winter rains. However, all too often we receive little rain, such as in 2001/2002. We used to apply water during the non-penalty period as a leaching operation and to build up soil capacity after the low allocation periods in October and November. Under the new plan, this would not make sense to do in winter, since that is when the allocation is the lowest. Affects of salt build up on plants are poor growth, poor uptake of nutrients resulting in discolored leaves and poor bloom, leaf drop, lower disease resistance, limb death in trees and shrubs, and death eventually.


We want you to know that we are concerned about both conservation of water and the plants in your landscape. Our natural tendency, as gardeners, is to lean towards using water if we feel it will improve plant quality and appearance. Unless directed otherwise by the property owner or manager, we try to balance what we feel is best for the plants and the property as a whole with the cost of water at the given time of year. This balancing act will be more difficult with penalties being assessed year-round. The water district’s point of view is to promote reduced water use, partially for the sake of conservation, but also to generate more production capacity for an expanded customer base. But, your point of view as the property owner or user is the most important of anyone’s.

We are concerned about your needs and expectations for performance in the landscape. If your highest concern is water cost containment, we work with you to develop a strategy to avoid penalties on water bills. If you are interested in irrigation upgrades, we’ll meet with you to discuss what can be improved and what the costs and benefits will be. If you would like to prioritize landscape quality while minimizing cost, we’ll identify the payment level you’re budgeting for and the landscape quality you like. Some things aren’t possible (Luxuriant lawns at 80% allocation with inefficient irrigation systems, for example), but we are available to provide services to identify and realize your water management goals for your site.

Please call with any questions or concerns.

Centennial Services Inc.

April 2002

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