Prehearing Statement of the Town of Dillon

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Case No. 87CW392 Page 6 a. In order to determine the amount of water diverted and used for different uses pursuant to this plan, Applicant shall estimate the acreage of irrigated areas. The irrigated acreage as of 1991 is estimated to be 25 acres. Applicant sha71 provide a new estimate of irrigated lawn acreage based on actual data such as an aerial photograph every five years or after any calendar year in which the amount of water treated by the Applicant increases twenty percent or more over the previous year for as long as this plan for augmentation and exchange is operated, or more frequently at the option of the Applicant or direction of the Division Engineer. The annual consumptive use due to lawn irrigation shall equal the irrigated acreage times 1.45 acre feet per irrigated acre. An 80% irrigation efficiency sha11 be used to determine the deliveries made for lawn irrigation. Thus, the annual amount of treated water delivered for lawn irrigation use shall be equal to the annual consumptive use due to irrigation divided by 0.80. Computed annual water deliveries for lawn irrigation use shall be distributed according to the following monthly percentages: May, 5%; June, 28%; July, 29%; August, 23%; and September, 15%. These percentages are based on a Modified 8laney-Cridd7e analysis of lawn grass, using data from the Dillon weather station. b. The Applicant shall determine in-house use return flows on the following basis: 1) during the months October through April, actual metered deliveries shall constitute in-house use; 2) for May through September, in-house use sha71 equal actua7 metered deliveries minus irrigation deliveries as determined in qa. above, unless computed irrigation deliveries are greater than actual gross metered deliveries in any given month, in which case in-house use for that month shall equal the minimum actual monthly use during any given month of the preceding year, and irrigation deliveries shall equal the actual metered use minus the in-house uses; 3) 95% of the water delivered for in-house use shall be taken as a credit returning to the Blue River at the Joint Authority Waste- water Treatment Plant. c. Fifteen percent (I5%) of the water delivered for irrigation will return to the Blue River drainage as a result of deep percolation. Using the monthly records compiled in accordance with the above provisions, Applicant will calculate the irrigation deep percolation amount by multiplying the amount of water deiivered for irrigation that month by 0.15. There are delays between the delivery of water for irrigation and return to the Blue River drainage of 15% of that water. The irrigation return flows considered to accrue to the Blue River shall be calculated by applying the following monthly factors to the deep percolation amounts occurring in each month of the irrigation season: Month in Which Lagged Return Flows Occur Starting With Month of Application Factor Month 1 0.6 Month 2 0•2 Month 3 0.1 Month 4 0.1 These factors shall be multiplied by the deep percolation amount occurring in any given month to determine return flows in the month during which the Application occurred (Month 1) and in months following the time of Application (Months 2 through 4). Return flows in any given month shall be equal to the sum of return flo,.,s occurring from deep perco7ation during the month plus return flows