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, \, I . PROPOSED DEMONSTRATION PROJECT FOR ET BASED IRRIGATION CONTROLLER Background The water world is still looking for a simple and inexpensive way to provide wide area irrigation scheduling for customers who currently are over irrigating their landscapes. Many systems have been developed and marketed, but most of these are either too complex or too expensive for any but the largest and most high value uses (such as large parks, golf courses, recreation complexes, campuses etc). Aquacraft, Inc has been part of the search for the irrigation "holy grail" starting in 1990 when we began experimenting with use of gypsum blocks wired into standard irrigation clocks using 24 volt relays. These devices actually worked quite well for a season or so, until the current in the system broke down the gypsum block. . Our next approach was the use of a more refined resistance type sensor made by the Irrometer Co of Riverside, California, the Watermark™. We performed extensive field tests of the Watermark system (mostly funded by the City of Boulder Water Conservation Office), and found that it generally worked well, had a low failure rate and limited irrigation to an average of 80% ofET 0 The results which we reported with soil sensors were not sufficient to convince irrigation professionals to embrace the technology, so it remains largely unused to date. Soil sensor systems are also subject to unauthorized field adjustments and disconnection by maintenance personnel who feel the systems are not working properly. During 1998 we looked seriously at a Cable TV based ET controller, however, the costs for the individual controllers, and the monthly signal access charges were too high, in our opinion, to make the system economical. Also, we felt there were major problems and obstacles associated with linking the irrigation clock to the nearest cable TV outlet. Following this, we investigated a broadcast based ET controller using sub-carrier frequencies on local FM radio stations. In this case the charges for use of the frequencies were too high, or no stations were willing to discuss their lease at any price. The Pager Based ET Controller Now comes the Network Systems Company, from Petaluma California who has developed a system which promises to solve many of the problems associated with the previous equipment. Their product is called the Water Right ET Signal Controller. This system uses pager technology to transmit the ET information to specially designed controllers on site. The controllers read the encoded ET information broadcast over the pager system. They then adjust the applications to each zone based on that zone's: plant material, soil type, slope and precipitation rate specified by the installer when the system is set up. .