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(-;) <br />Task 3 -Identify Key Diversion Structures, Review Diversion Data, Aggregate Remaining <br />Agricultural Diversions, and Fill Missing Data <br />Backgroaand: <br />The goal of the historic crop consumptive use analysis is to account for 100 percent of the crop <br />consumptive use in the basin by representing 100 percent of the irrigated acreage from 1950 to <br />present. There are over 8,000 individual irrigation structures in the basin. Therefore, larger <br />diversion structures and structures of administrative importance are represented "explicitly" as <br />key structures, while smaller diversion structures can be aggregated and modeled together <br />without significantly reducing the accuracy of the results. Parcels irrigated with ground water <br />only (ground water only structures) will also be aggregated based on location and modeled as an <br />aggregate. <br />Supply-limited consumptive use is the actual amount of irrigation water consumed by crops, <br />based on available surface water and ground water. Measured or estimated surface water and <br />ground water diversions are required in water-short systems to determine actual consumptive use. <br />Therefore, surface water diversion records for key structures and structures grouped in aggregates <br />will be extracted from HydroBase and filled, as necessary, for use in the historic crop <br />consumptive use analysis. <br />During phases 1 and 2 of the SPDSS efforts, key diversion structures were identified for use in <br />future modeling efforts. Therefore task 3.1 below is not included in the Phase 3 budget. <br />Objective: <br />Perform abig-picture QA/QC of diversion data associated with the key diversion structures, <br />identified in years 1 and 2, to identify large discrepancies in monthly diversions compared to <br />water rights and monthly diversions compared to irrigated acreage. Aggregate remaining <br />structures to represent 100 percent of the basin consumptive use. Fill missing monthly diversion <br />records for the recommended study period for use iri the consumptive use analysis. <br />Approach.• <br />3.1 Identify initial key diversion structures. Note that this task was completed in Phases 1 <br />and 2. <br />3.2 Perform a review to identify potential problems with key structure diversion records. <br />Note the State performs QC/QA of diversion records when they are loaded into <br />HydroBase, therefore major problems are not expected. Key structure diversion records <br />will be reviewed to identify potential problems such arun-on of one diversion record for <br />_ _ the entire season or over the winter months, diversion records exceeding water rights, <br />diversion records exceeding structure capacity, and discrepancies between irrigated <br />acreage and diversions. The results of this analysis will be documented in a memorandum <br />and provided to the State's SPDSS project and Hydrobase data managers. <br />3.3 Aggregate non-key agricultural diversions structures. to represent 100 percent of the <br />irrigated acreage in the historic consumptive use analysis. Aggregations will be based on <br />the GIS location of irrigated acreage, streamflow gage locations, critical administrative <br />reaches,- and on an objective that aggregations be similar in total acreage. It is .anticipated <br />that the new GIS DMI being .developed in Task 18 of this Scope will be used. Non-key <br />irrigation structures with diversion records but no associated .irrigated .lands (if any) will <br />be investigated through discussions, with water commissioners and resolved. It is <br />Exhibit A-1Page 4 <br />