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SPDSS Memorandum <br />Final <br />To: Ray Alvarado and Ray Bennett <br />From: LRE -Mark Mitisek and Erin Wilson <br />Subject: Task 3 Summary -Key Diversion Structures <br />Date: Apri 1 5, 2008 <br />Introduction <br />The objective of this Task 3 memorandum is as follows: <br />Identify key diversion structures accounting for approximately 85 percent of the net <br />absolute decreed surface water rights in Water Division 1. Include additional structures, <br />as appropriate, based on water rights and location and other structures that should be <br />considered key based on interviews with Water Commissioners and Division Engineers. <br />Background <br />Key diversion structures were initially identified as diversion structures representing the <br />approximately 85 percent of net absolute decreed water rights within each Water District in the <br />SPDSS study area. The preliminary list of key diversion structures was then revised during <br />subsequent phases of the SPDSS effort based on interviews with Water Commissioners and <br />Division 1 personnel. These interviews discussed diversion structures and/or diversion systems <br />that should be included in potential future modeling efforts due to their impact on basin <br />operations. Diversion systems are defined as a group of diversion structures on the same <br />tributary and operated in a similar fashion to satisfy a common demand. <br />During Phases 1 and 2, fourteen meetings were held with Water Commissioners, Division <br />Engineers, and Division of Water Resources personnel to discuss administrative practices in each <br />Water District, particularly with regard to key diversion structures (SPDSS Task 3), transbasin <br />diversions (SPDSS Task 4), and key storage structures (SPDSS Task 5). Meeting notes were <br />prepared for each of the Task 3 meetings that summarize available information related to stream <br />gages, diversion and storage structures, and the use of transbasin water in the Water Districts. <br />Normal year river call sequences were discussed and summarized in the meeting notes along <br />with information related to dry-up points on the river, return flow locations, and specific <br />administrative practices. <br />During Phase 3, the key structure list was again reviewed and revised based on acreage <br />assignments in the final SPDSS 2001 and historical irrigated acreage coverages as well as the <br />availability of diversion records. <br />The approach and results associated with development of the initial and final list of key diversion <br />structures are summarized below. The key structure list provided in this memorandum will be <br />Page 1 of 38 <br />