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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Overview of Secondary Water Su~lv Systems <br /> <br />Secondary Supplv Concept <br /> <br />A secondary supply or dual system is basically a utility. Potable water is provided for <br />largely indoor culinary uses and a secondary or "dual system" is provided for primarily <br />outdoor landscape irrigation. <br /> <br />A sound engineered approach to secondary water management includes a detailed <br />design of the infrastructure piping and the irrigation system, and due consideration to <br />long-term system operation and management. The provision of secondary supply may <br />also afford significant opportunities for the ditch company to modernize its 100-year-old <br />plus canal infrastructure. Modernization may include structural or operational <br />improvements, or a combination of these, the benefits of which can complement the <br />ditch company's provision of secondary supply for urbanization. This is expected to <br />materially benefit the larger community, in terms of the water conserved in agricultural <br />uses. <br /> <br />Key engineering design criteria for a secondary system include annual landscape and <br />crop water requirements, water delivery alternatives and constraints, water storage <br />requirements, determination of peak demand flows, pump station and control <br />requirements, primary distribution system layout, service connections for <br />residential/commercial customers, system operation including supervisory control and <br />data acquisition (SCADA) monitoring and control, and system maintenance. These <br />engineering criteria can enhance the overall secondary supply scheme, or conversely, <br />detract from it if they are not properly addressed. <br /> <br />There are basically three ways that secondary supply irrigation systems can be <br />operated. They can be operated on-demand, on a fixed rotation, or some combination <br />thereof. "On-demand" means that the residential or commercial user of the secondary <br />system is allowed to irrigate any time of the day or night. "On-rotation" means a fixed <br />period of time in which certain tracts or divisions of the system are allowed to irrigate. <br />This is similar to municipalities instituting water scheduling during drought. A <br />combination of these two would occur when the irrigation system is operated on <br />demand, but within a fixed time window (night time hours, for instance). <br /> <br />As with any irrigation system, the system capacity is based upon the area to be irrigated, <br />application efficiency, peak season evapotranspiration, days of operation per week, and <br />the allowable daily irrigation window. The major difference between a secondary water <br />system to individual home sites and a large golf course irrigation system is the number <br />of irrigation system managers involved. In the case of a golf course, for example, one <br />irrigation manager is typically in charge of scheduling and operating the irrigation <br />system. This allows the pump station and mainline pipe to be sized to operate at full <br />capacity for a given window of time, say 8 hours per day. This type of user is very <br />predictable and is represented by a relatively flat demand curve over time. The demand, <br />and therefore the flow rate of the irrigation system, ramps up to full capacity over several <br />minutes at the start of the irrigation window, It then runs at capacity until the demand <br />drops off at the end of the irrigation window. <br /> <br />Aqua Engineering, Inc. <br />June 2004 <br /> <br />Canal Modernization Feasibility Study <br />-4- <br />