2018-04-13_HYDROLOGY - M1977436 - Laserfiche WebLink

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Aggregate Industries South Platte Combined SWSP April 13, 2018 Plan IDs 3614, 4773, 3624, 4772, 4616, 3437, 3376, 3650, 3668, and 5475 Page 10 of 20 alfalfa, 26% corn, 15% dry beans, 13% pasture grass, 1% small grains, and 1% sugar beets. A ditch loss of 20% and irrigation efficiency of 65% were utilized for the analysis, which appear reasonable based on review of aerial photos and topography. Based on the above, the historic consumptive use of the 62 Cooley Gravel shares is estimated as 1.87 acre-feet per share. Return flow obligations were allocated as 50% surface return flows and 50% subsurface return flows. The 62 shares to be used for replacement purposes under this SWSP will be delivered through the augmentation station owned by the South Adams County Water & Sanitation District located just downstream of the ditch headgate. The expected consumptive use credit for the 62 Fulton Ditch shares for 2018 has been estimated from a dry-year farm headgate delivery of 2.64 acre-feet per share or approximately 164 acre-feet for all 62 shares. After accounting for return flow obligations, the total consumptive use credit for the 62 shares is projected to equal 120.44 acre-feet in 2018. In the event the Fulton Ditch goes into Sections, the Applicant has sufficient alternative replacement supplies in the form of shares in the Brighton Ditch, as described below, to make up any temporary shortfalls. Brighton Ditch Pursuant to a March 4, 2010 Water Lease with the City of Westminster, Aggregate has the right to use 1.038 shares in the Brighton Ditch Company owned by the City of Westminster for augmentation purposes. The 2016 SWSP request included an updated HCU analysis for the subject shares prepared by Ecological Resource Consultants, Inc. (“ERC”), using a study period of 1950-2001. The total shares include 4/6th (0.667) of a share historically used to irrigate the Wattenberg (aka Broncucci) Property. An average of 42 acres of pasture grass were irrigated by controlled flood irrigation. Using a Blaney-Criddle analysis the crop irrigation requirement for the 42 acres was determined to be 103.38 acre-feet. Assuming a 25% ditch loss and 50% irrigation efficiency the average historic consumptive use for the 0.667 Brighton ditch shares was found to be 100.04 acre- feet. The other 0.371 shares were historically used to irrigate the Haake Property, along with 5.75 shares of the New Brantner Ditch. During the study period, between 10.7 and 11.3 acres of dry beans (prior to 1960) and corn (1960 on) were irrigated by the Brighton Ditch shares only; 20 acres of pasture grass and between 14.2 and 20.1 acres of dry beans (prior to 1960) and corn (1960 on) were irrigated by the New Brantner Ditch shares only; and between 26 and 35 acres of pasture grass and 24 to 35 acres of dry beans (prior to 1960) and corn (1960 on) were irrigated by both the Brighton Ditch and the New Brantner Ditch shares. Using a Blaney-Criddle analysis the crop irrigation requirement was determined to be 17.50 acre-feet for the area irrigated only by the Brighton Ditch shares, 77.18 acre-feet for the area irrigated only by the New Brantner Ditch shares, and 118.63 acre-feet for the area irrigated by the excess water from both the Brighton Ditch and the New Brantner Ditch shares. The amount of Brighton Ditch water used to meet the crop irrigation requirement on the area irrigated by both sources was calculated by multiplying the total crop irrigation requirement by the percentage of Brighton Ditch water in the excess water. Based on a ditch loss of 25% for the Brighton and 20% for the New Branter, and irrigation efficiencies of 65% for the furrow irrigated corn and dry beans and 50% for the flood irrigated pasture grass, the average historic consumptive use for the 0.371 Brighton Ditch shares was found to be 74.19 acre-feet. Aggregate will utilize the entire 1.038 shares for use in this plan. The expected credit for the Brighton Ditch shares has been estimated from a dry-year farm headgate delivery (using a 25% ditch loss) of 334 acre-feet per share, or 347 acre-feet for all 1.038 shares. Return flows consist of surface return flows, which are based on current deliveries, and subsurface return flows which are based on the previous year’s total deliveries. The total consumptive use credit in 2018 is projected to equal 216.03 acre-feet, which is greater than the dry-year yield because of the reduced subsurface return flow obligation requirement resulting from low deliveries in 2017. Aggregate anticipates utilizing the