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SCADA concepts Generic definitions are appropriate to help describe basic SCADA concepts. The "central system" is microcomput- er based and interface software is used to communicate with remote sites. The software that provides an umbrella over everything is called a "human- machine interface" or HMI. The key hardware at remote sites is a "remote terminal unit" or RTU. The HMI software can be proprietary and published by the manufacturer of the hardware or it can be more and not the higher communication speeds that are now possible. Remote terminal units are essentially a small computer that can be programmed for the specific requirements at individual sites. The RTU is also the point at which sensors are connected. A site with only one requirement, e.g. monitoring the water surface elevation in a flume or weir, would have a water level sensor wired to it. The RTU then communi- generic and published by software companies that write Cates to the central system or conversely, the HMI programs that are compatible with the hardware of central system can initiate a call to the RTU. many manufacturers. Flexible and broadly compatible The preferred communication is two -way programs are known as Wonderware, Lookout, and Intel- communication. In other words, the central lution, as examples. can call the RTU or the RTU can call the Communication can be via wire line (hard wired), tele- phone, fiber optics, or radio. Radio for most canal opera- tions is preferred although the canal easement does pres- ent the potential for easy fiber optic installation. (The Dolores Project in Cortez, Colorado utilizes fiber optic communication.) The SCADA industry has standardized largely on a communication protocol called "Modbus" which is quite flexible but also considered antiquated by many because it was developed for wire line applications This rated canal section is remotely monitored using a SCADA system. RTU equipment is 12 -volt DC powered from a solar panel that maintains a charge on a battery. Communication with the site is by radio. central. It is important to note that the RTU can be monitoring one or more sensors and perform logical operations and even create an exception report or alarm. If flows or water levels exceed a pre -set limit at a point in the canal system, an alarm can be raised or ac- tion can be taken in the form of gate or check adjustments. Alarms can appear at the central computer or even be transmitted to a cell phone or pager. Four levels of SCADA implementation can be described by their respective function and utility to the canal company. • Monitoring (only) • Remote manual operations • Local control • Fully automated operations Each level results in increasing capability within the SCADA system, but each level costs more. The additional cost is largely at the remote sites, not at the central worksta- tion. The central workstation becomes a fixed cost except for HMI upgrades and the inevi- table computer hardware upgrades. A simple SCADA monitoring site is installed in a rated canal section historically used by the New Cache la Poudre Irrigating Company - — 5