Reducing the Loss

March 1, 2000

Among the common complaints of people who live in states where water usage must be controlled because rainfall seems poorly timed, if not inadequate, are the blatant abuses they see related to irrigation. Have you ever driven through town on a day so rainy your wipers can hardly keep the windshield clear to see sprinkler systems merrily spraying away at the hospital, on the golf course, in front of the bank, or outside city hall? Have you ever had neighbors who seem to flush the street gutters (and their debris) more than they feed their lawns, vegetables, and flower beds? Have you seen rural sites where too powerful or poorly adjusted irrigation is destabilizing and washing away the soil, contributing to the death of adjacent trees and shrubs? The sites of waste might be at parks, golf courses, farms, or areas around large buildings, and they might be privately or publicly owned. In those areas where the cost of water for one use is so much more than for another use, the criticism can border on hysterical. With today’s knowledge, it is all so unnecessary.

“If there is water running down the street or causing other damage, somebody has done something wrong,” says James P. Chinni, a designer of irrigation systems in Ohio and a guest lecturer on the subject at Ohio State University. Chinni’s knowledge of the history of irrigation systems and of what is being done today to perfect them is extensive. His own company has been involved in such projects as the South Park Mall in Strongsville and the Solon City Hall Complex, both in Ohio. One of the most interesting projects he describes is at Disney World in Florida, where four weather stations control the watering. Why four stations? Because there are four different climate zones in the big theme park. The weather stations collect data concerning the plants, trees, and shrubs (such as how much moisture they have given off and received in the last 24 hours) and give the results to a computer that determines how much watering is required in the next 24 hours. A most interesting and praiseworthy aspect of the system at Disney World is that it reuses tertiary water. In a similar application for a golf course in Aruba, the sewer wastewater from nearby hotels provides the water for irrigation. Other examples of accuracy and innovation in watering given by Chinni concern an up-market auto dealership where he designed a system that would not spray the expensive cars on display (by using emitter tubing), locations where the right subsoil permits below-the-surface irrigation, and the promising future role of systems whereby the weather controls the supply. To solve one of the most common problems of watering at almost any site, some systems today will not turn on if it is too windy.

A good design is not the last step, of course. “The correct installation of the irrigation system is as critical as a proper design,” adds Chinni. “We install systems to specification and accepted industry standards. If this integral part of an irrigation system is ignored, clients can often incur unnecessary, continuing extra costs after installation.”

Netafim in Fresno, CA, manufactures and markets Techline, one of the subsurface drip irrigation systems mentioned by Chinni. Thus far, Techline has tended to be used in problem areas where a standard irrigation system would have been inadequate or inaccurate. It has been used successfully for such applications as odd-shaped areas, median strips, islands in parking lots, high-wind areas, and steep slopes. To withstand the attacks of fertilizers and chemicals, the tubing and the dripper housing of Techline are made from synthetic elastomers, while the pressure-compensating dripper is completely self-contained and molded to the wall of the dripper tubing itself. An advantage emphasized by the manufacturer is that Techline is continuously self-cleaning during its operation (not just at the beginning and end of a cycle). In the regulating mode, the water flows freely along the center of the housing, keeping debris out of the dripper. To initiate the flush cycle, particles create back pressure and push back the diaphragm so that it flexes and particles are washed out of the regulating chamber. After this flushing, Techline automatically resumes its regulating mode.

Conservation of water is the goal of Toro’s new EZ Drip Series low-volume irrigation system, designed for a broad range of customers: residential, municipal, and commercial. “This system has a variety of components ideal for customizing irrigation for those difficult-to-irrigate areas that require low volumes or various applications of water,” explains Jody Hinkle for Toro in southern California. Among those components is the AGE (Advanced Generation Emitter) that operates at three flow rates and includes pressure compensation for uniform water application. A bug cap is preinstalled and the AGE delivers a large, turbulent flow path. Toro’s Turbo-SC Plus emitters incorporate a self-flushing mode designed to clear debris and prevent clogging. This component also helps give uniform application with its allowance for pressure compensation and, combined with Turbo-Key, operates at three flow rates for good adaptation to specific water conditions. For short distances without slopes, the EZ-2 Emitter could be the best solution. A pressure-regulating multioutlet emitter system offers nine pressure-controlled outlets with flows from 1 to 20 gal./hr. “This easily converts standard sprays to low-volume emitters and is ideal for mixed plant areas and planters,” notes Hinkle. “For customizing water use for varying plant material, our EZ Drip pressure compensating modules are available in six flow rates that deliver from 6 to 25 gallons per hour.”

When it comes to larger applications (e.g., sports fields), the latest improvements to the Toro 2001 Series sprinkler are interesting. A nozzle tree is available for color-identified flow rates, and the nozzles screw in with no need for an adjustment screw. Each sprinkler is complete with six main nozzles and two inner nozzles, while there is a debris seal to lock out unwanted materials such as top dressing and ground debris. Toro is one of several manufacturers that will supply easy-to-understand performance charts for its systems. With so many new control and adjustment components available for today’s irrigation systems, a potential user should study as much performance data as possible and have his distributor or installer explain everything.

Complete flood irrigation for crops and plants used to be most popular in dry regions or those places where the timing of irrigation is especially sensitive (cranberry bogs in Wisconsin, garden crops in California, and alfalfa and winter wheat in Montana and North Dakota) but is less favored now, not only because of the cost of water but because much of the water applied was wasted. Pumps, such as those manufactured by Crisafulli in Glendive, MT, have retained their popularity for this kind of irrigation (and stormwater or flood control) because there are power options and configurations developed for today’s applications that have eliminated some of the perceived disadvantages of yesterday. Such pumps transfer large volumes of water in a short time, with 10,000 gal./min. from a 16-in. pump quite normal for large areas. The 8-in. discharge size, still transferring several thousand gallons per minute, has proved most popular in southern California’s Imperial Valley. At some sites, the unused water used to drain away to wastewater streams, but there are efforts today to design drainage systems that take that water back up to the original acreage. With flood irrigation, if the field supplied has a high point and a low point, the water may be captured at the low point and taken back to the high point for reuse. A perceived negative side of flood irrigation has also been its tendency to contaminate underground aquifers by leaching down pesticides and chemical fertilizers. Drip irrigation (applied at the roots of the plant and usually well regulated) is more popular now. Sprinkler irrigation has been criticized because it can place water where it is not needed, and there is loss to evaporation. Poorly controlled sprinkler systems and manual watering with garden hoses in urban and suburban areas are the culprits for those streams of water flowing down the gutters. Their effect is similar to that of storms: overloading drainage systems and carrying garbage and pollution downstream.

Flood irrigation is not dead, but the method of using it to its best advantage has changed. In California’s Imperial Valley, careful planning is making this economical method less wasteful than it has been. “Some farmers have dug pits with backhoes by the drop boxes at the low point in their fields and installed pumping systems to transfer the water back to the top for reuse,” says Eddie Reed, a representative at Jordan Implement in Blythe, CA. Reed’s parents were farmers in the Imperial Valley, and he has seen many changes and some good progress. “Mixed with the fresh water, the water from the drop boxes is suitable for further irrigation and even helps to save money on fertilizers and chemicals.” There has never been a shortage of water for the Imperial Valley, with supplies coming from the Colorado River, but the needs of San Diego with its growing population have inspired some new thinking about its usage and marketing. Historically, the water used for irrigation would go down into a drain ditch and then to two rivers that feed the Salton Sea. There the water stagnated and evaporated. There is drainage tile underground in the Imperial Valley, and water that gets down there is too salty for reuse. The surface water that flows down the fields is acceptable, however, and it is the best use of the surface water that Reed and his farmer friends have found in about a decade of research.

If yesterday’s waste and soil damage are the bad news, there is encouraging good news in all the research, testing, and commitment found today in public and private efforts to make poor soils economically productive and more environmentally stable. DRiWATER is a patented concept in plant irrigation. Basically it is water bound in the form of a gel (98% water by weight and 2% alum and vegetable gum). It dissolves back into water at a controlled rate of flow when placed in contact with the microbiological life forms found in soil. Then the product drip-irrigates a seedling or plant for a length of time that depends on the size of the application; the quart size will irrigate for three months or more. It is interesting that irrigation by DRiWATER does not depend on relative humidity or temperature. This product, therefore, should not be confused with polymers (cross-link polyacrylamides), whose release rate might be unpredictable because they are affected by high temperatures or low humidity. In California, DRiWATER was a factor in the award for Water Conservation Honors won by Caltrans for a revegetation project in Amador County. Some savings reported in the use of this product come from a reduction in the labor required to establish plants in their first three to five years and from the reduction in the requirements for watering equipment and the transportation of water. A University of Idaho research project seems to indicate that DRiWATER may be a practical help in erosion control and roadside slope stabilization. Not only has the survival rate of plants at testing sites been encouraging, but the plants were planted in poor soils and 90ºF weather, with no manual watering and little rainfall. In other parts of the world where the scarcity of water is a major concern-Saudi Arabia, Egypt, and Jordan, for example-this technology is becoming increasingly accepted as the way to turn deserts into useful land where food, plants, and trees can be grown.

What happens above ground is the obvious part of watering, whether its source is irrigation or rainfall. What happens below the surface is less obvious but equally important, as mentioned above in the case of flood irrigation, where the water can drive pollutants in unwanted directions. Soil erosion is another obvious result of inaccurate watering. Less visible is the effect on one of our most expensive, publicly funded ground conditions: the highway. Most of the potholes in streets are caused by water. Stormwater attacking the road base of a major highway can cause bewildering expenses for repairs. An important aspect of the I-15 interstate project in Salt Lake City, UT, is the drainage installed to handle stormwater and channel it away from the roadbed. A one- or two-person crew has been installing lightweight, corrugated polyethylene (PE) pipe from Advanced Drainage Systems (ADS) of Columbus, OH. The long “stick” length of the pipe reduces the number of joints required and, thus, the cost of labor and installation time. Most of the ADS pipe-33 mi. of it-is 24 in. long x 30 in. in diameter. The installation contractor, Wasatch Constructors, estimates that the use of this type of PE pipe will save them about 15% in labor, materials, and time costs, compared with other pipe materials.

“About 4 to 6 inches of granular fill is placed into the trench as pipe bedding,” notes Tony Radoszewski, vice president of sales and marketing for ADS, which is “virtually a standard for all pipe installations. The granular fill depth depends on the amount of clay in the soil. The crew then lays pipe sections into the trench and pops them together. Twelve inches of fill is placed over the pipe and packed down, and then we backfill the trench with native or onsite material.”

One of the characteristics of this kind of pipe for drainage is that it is flexible and transfers live and dead loads to the surrounding soil. The smooth inside of the ADS PE pipe keeps water moving rapidly to prevent surface runoff from accumulating, and the secure joints defeat soil infiltration. “The good hydraulic properties of this pipe should minimize silt buildup,” observes Donald Clark, roadway engineering oversight coordinator for the Utah Department of Transportation.

The storms and floods of 1999 have demonstrated the ability of nature to produce its own powerful irrigation system and the problems that result if there is inadequate drainage. On a less visible but no less dangerous scale, excess water from irrigation systems can become a nightmare for soil engineers and property owners. An inch of water over a surface area of 1 ft.2 equals 0.62 gal. of water.

“To simply bury perforated pipe below ground with a matched volume to carry the anticipated surface load is not enough,” asserts Jonas Z. Sipaila, president of Evaporative Control Systems (ECS) in Reno, NV. “The surface water must first enter the interior of the pipe in order to be transferred away to a desired location. It’s like the bathroom sink, which works well most of the time, transferring as much as 6 gallons per minute into a small 1.25-inch-diameter pipe. Should the drain access be restricted by obstructions at the pipe’s access opening, drainage slows or may completely stop.” ECS says subsurface drainage pipe can react in the same way if blockages limit infiltration rates, regardless of the pipe’s diameter or shape. “There are three physical factors in drainage-pipe design that determine the infiltration rate into a subsurface drainage pipe,” explains Sipaila. “The first factor is the total area of surface openings in the collector pipe. The other two are the inherent blockage created at the available surface area and the water pressure at the interface area.”

At an installation earlier this year in a residential backyard, an ECS system required only 32% of the water required by the front yard at the same residence, which had a preinstalled sprinkler system. “The grass was better in the backyard too,” states a spokesperson for ECS. Good drainage, then, can be an integral part of a good irrigation system. ECS says its systems is suitable for golf courses (with renowned pro golfer Patty Sheehan a new public relations spokesperson for the company), athletic fields, commercial and residential landscaping, specialized farming operations, and septic systems.

Clik-Clik-Clik may be a good solution for controlproblems in irrigation. Hunter Industries in San Marcos, CA, offers the Mini-Clik rain sensor that automatically shuts off sprinklers during rainstorms, a feature that more and morecommunities are requiring.Built of high-impact thermoplastic and aluminum to withstand harsh weather conditions, Mini-Cliks can be adjusted to respond to levels of rainfall ranging from 0.125 to 1 in. Typically this product is mounted out of sight on a fence or roof fascia, but there is also a sensor guard available for public areas where vandalism is a threat. The SG-MC (Sensor Guard-Mini-Clik) has the sensor enclosed in stainless steel with mounting bolts and drill template. Hunter’s Wind-Clik shuts off irrigation systems during times of high wind (with adjustable shutdown points), then automatically resets the system when conditions improve. This development will help ensure that the irrigation water goes where it is intended, instead of being blown away or off its intended target to soak buildings, vehicles, and people. For locations where temperature swings can be dramatic (especially overnight), Hunter’s Freeze-Clik sensors will automatically prevent a flow of water if the temperature goes down near freezing and will reset the system when the temperature rises above your set point.

We will be addressing the subject of irrigation again in a few months, but it seems clear that there are solutions available (and affordable, often because of their engineered simplicity) to most of the problems that have irritated and frustrated both users and neighbors in the past. These solutions apply to irrigation systems of all sizes-from the individual’s front garden to the grower’s multithousand-acre operation-and they are not only new products and new materials, but they’re techniques and technologies developed by people and companies that have learned from their experience in the field. Water is probably the world’s most precious commodity for ensuring a decent standard of living, and the statistics about its unavailability in so many places are appalling. It is good to know that the careless waste of water and the damage that some irrigation systems have caused to the soil are becoming errors of our past. From our research and questioning of people involved, we perceive that irrigation is entering a new era of efficiency and consideration. 
About the Author

Paul Hull

Paul Hull writes on topics related to technology and construction.