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I I I I I I I I I I I I I I I I I I I Service Area and Future Urban Landscape Water ~uirements Service Area and Irriqated Area As conceptualized, the pressurized pipe system will serve an area of approximately 7,570 acres. This area was determined from the current Lower Boulder Ditch Company service area as shown in aerial photographs and GIS maps and as outlined by members of the Board of Directors, Several assumptions were made to determine the water use requirements and overall sizing of the pump stations and pipelines, The first assumption is the actual future irrigated area to be served by the system. The irrigated area is the fraction of total service area to be irrigated with landscape irrigation systems. These areas include parks, open spaces, rights-of-way, golf courses, streetscapes, commercial lots, schools and public spaces, multi-family housing areas, and individual residential lots. For the water requirement elements of the study, it is assumed that the actual irrigated area is 30% of the total service area, or about 2,270 acres. Typically, experience has shown that irrigated area can range from 20% to 40% of a development site and is dependent on the type of construction and local development and landscape requirements. For instance, a commercial development may only have 20% of the area irrigated while an "estate" type residential development may have 40% of the area irrigated. Considering a mixed land use development, assuming 30% of the total area will be irrigated is a reasonable assumption for this level of study and accounts for parks as well as subdivision residential lots. Water Requirements The peak season daily water use was calculated for 2,270 acres. It is assumed that irrigation will occur over an average 12-hour watering window, seven days per week. Water requirements were calculated based on historical averages, turf water requirements, and assumptions made during this modernization feasibility study. Peak season daily application rate in the Longmont area is estimated to be 0.29 inches for bluegrass turf. The crop coefficient used for turf is 80%. The crop coefficient is a parameter used by various irrigation scheduling methods to scale potential evaporation and transpiration (evapotranspiration) to the actual levels for the particular crop, which was assumed to be entirely bluegrass turf for simplifying this analysis. Bluegrass is more of a water consumer than other common grass varieties and the seasonal water requirement for bluegrass also compares favorably with most shrub bed plantings. Therefore, a bluegrass assumption, for purposes of this analysis, is somewhat conservative. The seasonal irrigation requirement for turf is 30 inches. However, it can range from 28 inches to 36 inches depending on the desired appearance and use of the area. For instance, some cities apply 32 inches annually for their heavily used parks. Some golf courses in the vicinity may use 36 inches, or more, to maintain the desired aesthetic appearance in areas of high traffic. Aqua Engineering, Inc, June 2004 Canal Modernization Feasibility Study - 6 -