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SPDSS Memorandum <br />Final <br />To: Ray Bennett and Ray Alvarado <br />From: LRE, Erin Wilson and Mark Mitisek <br />Subject: Task 56 -Conveyance and Application Efficiencies <br />Date: August 25, 2006, revised March 2008 (to represent finalized structure list) <br />Introduction <br />This memorandum describes the approach and results obtained under Task 56 - <br />Conveyance and Application Efficiencies. This task includes an estimation of both ditch <br />system conveyance and maximum application (on-farm) efficiencies likely to be <br />experienced in the South Platte basin, plus a recommendation on efficiencies to use for <br />the historic consumptive use analyses. The conveyance loss estimates are to be used for <br />ditches of variable size including key structures identified in Task 3 and medium and <br />small ditch systems throughout the basin. All estimates are based on available data or <br />developed from sources using adata-centered approach. <br />Conveyance Efficiencies <br />The StateCU model uses estimated conveyance efficiencies to determine the quantity of <br />river diversions delivered to the farm for application on the crops. <br />Factors that affect conveyance efficiencies typically include: <br />• Frequency and duration of diversions (i.e., the beginning of diversion season <br />versus late summer diversions) <br />• Soil properties such as hydraulic conductivity and permeability <br />• Canal geometry (e.g. wetted perimeter) <br />• Canal length <br />• Location of water table relative to the depth of flow in the canal <br />• Flow rate in the canal <br />Approach-Conveyance System Efficiencies <br />In an effort to acquire the best available information regarding conveyance efficiencies <br />for irrigation ditches in the South Platte basin, the following steps were performed: <br />• A literature search of published studies on conveyance losses in the South <br />Platte basin was completed, <br />• Summaries of water rights decrees and published loss estimates were <br />reviewed (most notably, summaries of decreed ditch losses and application <br />efficiencies compiled by LRE, Martin & Wood Water Consultants, Inc., and <br />Bishop-Brogden Associates, Inc., and Water Resources Investigation reports <br />developed for the Colorado Division of Water Resources), <br />Page 1 of 5 <br />