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I I I I I I I I I I I I I I I I I I I The seasonal irrigation requirement for turf is approximately 28 inches. However, it can range from 28 inches to 32 inches depending on the desired appearance and use of the area. For instance, some cities apply approximately 32 inches annually for their heavily used parks to maintain the desired aesthetic appearance in areas of high traffic. In order to develop the secondary supply conceptual plan and cost estimates, the above assumptions were made to represent the "average" requirements within the service area. Although some parks may need to be irrigated in a shorter watering window, say 8- hours, there are also areas such as streetscapes that can be irrigated in a longer watering window, say 16 hours. Drip irrigation, because of low evaporative losses, is generally acceptable outside of an otherwise assumed or imposed water window. Therefore, applying a watering window of 12 hours to the entire area allows for anticipated variations from site to site. Additionally, some turf areas will require more than 28 inches of water and some areas will require less, so an average of 28 inches per year was applied to the overall irrigated area. Table 3 summarizes the assumptions made to determine water requirements for the irrigated areas served by this system. Table 3. Water Use Assumptions DESCRIPTION OF ASSUMPTION UNITS VALUE % 80 % 25 in 12 % 80 in/day 0.29 % 80 in 28 Proposed Irrigation System Application Efficiency Effective Precipitation Ratio Seasonal Precipitation Tap Utilization Efficiency Peak Season Reference ET Crop Coefficient For Bluegrass Seasonal Irrigation Requirement For Bluegrass LANDSCAPE AREAS BLUEGRASS ft2 acre 190,575,000 4,375 Table 4 shows the water use calculations for the total irrigated area within the Highland Ditch secondary supply service area. The total required flow rate to irrigate 4,375 acres within a 12-hour watering window is approximately 59,820 GPM during peak season (typically in July). Aqua Engineering, Inc. November 8, 2004 Canal Modernization Feasibility Study - 9-