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, ,;,fr' ;'1 ' I Unlike large automated systems, where most of the adjustments are made by computerized controls, the USU system has relatively few automatic controls. "We're relying on information, not automatic controls, to manage water," Walker says. The system involves sensors at gatehouses and flumes, which measure water depth, salinity, and temperature. This information is transmitted by solar-powered radios to a base station, where it is entered into a database. The watermaster then reviews this information on his computer, and radios the appropriate instructions to the mechanized gates. The irrigation engineers realized substantial savings by purchasing off-the-shelf components instead of complete systems. Dataloggers, widely used in weather systems, are a key component of the system. In addition to compiling data, the devices also offer some control features, enough to execute the commands required to regulate gates, thereby functioning as small canal-side computers. In a heavily automated system, this type of control would require an entire computer, markedly increasing the costs and complexity. "In our system, we have a strong source of intelligence at the control site and a relatively weak source of intelligence at the canal site," Walker says. "This minimal reliance on automatic controls makes it possible to use inexpensive dataloggers." The USU engineers also built their own sensors for about half the cost of commer- cial models. If commercial sensors malfunction, the entire sealed unit must be replaced at a cost of about $500. The most expensive component in the USU sensor is a $125 converter, which is easily replaced, Walker says. Other components are also less expensive than those usually used in automated systems. Walker says some of this equipment may not be as durable as more- 1 08 UTAH SCIENCE