The value of irrigation often fails to reach its potential because of an unclear understanding between the consumer and the contractor during the construction process. A clear understanding between the property owner and the contractor is very important in providing the intended landscape and deriving the maximum benefit from water conservation technology. As design and construction professionals serving the irrigation customer, we bear the responsibility of effectively communicating the whys and what fors to these customers.

Drip and micro-irrigation system consumer advocacy has been sponsored and promoted by the Irrigation Training & Research Center at Cal Poly State University through their General Irrigation and their Drip/Micro Irrigation Consumer Bill of Rights. The designers and constructors are given notice by the "Bill of Rights" that certain minimum standards should be expected by consumers. Designers and contractors would be professionally obliged to institute the implied design and construction practices, should these standards receive sufficient exposure and support.

Putting consumers in control, through educating them on the critical considerations and characteristics of a properly functioning irrigation system they may soon purchase, bodes well for certified irrigation designers. The reason for this should be clear: Functionality, performance, user friendliness, irrigation specialist credibility, system maintainability and robustness are what count, irrespective of the form, color or texture.

By the consumer's setting of standards up front, the designer and the contractor have clearer pictures of the customer's willingness to invest in water conserving irrigation technology. The vast number of small projects, which traditionally have not been considered worthy of a certified irrigation designer's time and effort, now become worthy. By hook or by crook, we all are obliged to deliver a much more uniform product and the minimum requirements of the irrigation system needed to achieve the customer's vision of his landscape. This eliminates a potentially huge barrier to high quality irrigation system construction, the lack of agreement between the designer and the contractor.

Two, Critical Value-Adding Design Practices

Balanced Emitter Schedules -- Certified irrigation designers (CIDs) are well-suited for the often over-looked detail of directing species-specific irrigation rates to the plant materials scheduled by a landscape architect. The CID will usually consider the fact that a variety of shrubs will share a common shrub valve, as will a variety of trees share their respective common tree valves. Because of this, if plants are to receive their appropriate allotments of water annually, they must have delivered to them differing volumes of water.

To carry this concept further, consider the various annual water requirements of the following mature trees:

• Sweet Acacia -- 1,827 gallons per year
• Blue Palo Verde -- 3,000 gallons per year
• Sissoo Tree -- 5,409 gallons per year

This sample represents the widest possible range of annual tree water requirements to be irrigated on parts of the urban freeway system in Arizona. It is part of the entire list of plant water budgets recently derived in harmony with expert input from The University of Arizona, the City of Phoenix, and ADOT's own historical estimates.

Using the lowest water demanding tree, we select a flow rate to direct at this tree, while considering that it is desirable to wet as much of the tree's canopy area as possible, while restricting the number of multi-outlet emitters to one per tree, while being restricted to one particular manufacturer's family of emitter products. The particular emitter family has been widely used in Arizona for a variety of reasons, not the least of which is that it offers five different flow rates from its six-outlet emitter series. Six outlets, at the lowest flow rate emitter of 0.6 gallons per hour (GPH) each outlet will maximize the wetted area, while addressing the other concerns also.

The combined flow to the Sweet Acacia therefore is 3.60 gallons per hour. To satisfy the "Projected-Normal-Mature State" annual water requirement, we would irrigate the Sweet Acacias for 508 hours over the course of the entire year, from 1,827 divided by 3.60. By establishing the annual irrigation hours for Sweet Acacias, obviously we also establish the annual run hours for all of the other trees on the shared irrigation valves, and usually on the shared irrigation system controller as well. The remaining mathematics results in the appropriate flow rates to the Blue Palo Verde and the Sissoo Tree as 6.00 GPH and 10.00 GPH, respectively.

With the projected annual water budgets established for each plant to be used in the landscape, we can predict and project reasonable estimates of annual water requirements for the specific irrigation system before the project is even constructed. This alone should be a new and beneficial piece of information for the consumer- (soon-to-be water manager).

Of course, in most cases separate landscape irrigation metering of water would be very beneficial if we are really sincere about water conservation. But the biggest benefactor is the professional landscape care provider since he now has a balanced, water delivery system under his command. Granted, this is only true up to a point, since the "water budgets" may be in error by some fraction.

Regardless, only through unified adoption of some locally appropriate, expert derived estimates, can we even begin to head towards the eventual refinement of these estimates. In the meantime, we begin to provide water managers with balanced irrigation systems, and leave to their discretion the way in which they allocate those total run hours each year.

As-Built Plans

A smart property owner will demand that the contractor prepare a reasonably well detailed and accurate construction plan of the irrigation system, including proposed locations of all valves and the distances of all trenches, as well as trench contents, from walks, walls, and plant pits. These drawings should additionally denote, through the use of some systematic method, such as the eight points of a compass, the angle of approach of emitter supply tubing and emitter, relative to the shrub or tree, so that future renovations, additions, and maintenance can proceed without first having to do extensive exploration for emitters and supply tubing.

Due to the additional costs of having irrigation system plans red-lined to reflect the as-built condition, consumers may need to perform the red-lining themselves. Consumers should specify to the contractor that he prepare a detailed scheme which utilizes color-coded flags and that these flags shall be carefully placed along (on-top of) trenches during the backfilling process, which provide consumers the verifiable information they need to amend plans.

Thomas A. Reynolds holds B.S. and M.S. degrees from Arizona State University, School of Agribusiness and Resource Management. He has more than 15 years of field and laboratory experience in scientific water management, irrigation system design and marketing. Since April 1997, he has held the postion of Irrigation Designer for the Arizona Department of Transportation. His views in this article are his own, and not those of ADOT.