RGDSS_Task7-1_HistoricMonthlyModel_AggregateWaterRightsIrrigatedLands

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RGDSS Memorandum Final TO: Ray Bennett FROM: Ed Armbruster, Hydrosphere SUBJECT: RGDSS Surface Water, Task 7.1 -Aggregate Water Rights /Irrigated Lands Not Explicitly Modeled in Phase 1a DATE: March 13, 2000 CC: Randy Seaholm Introduction This memorandum represents delivery associated with Task 7.1, Aggregate Water Rights / Irrigated Lands Not Explicitly Modeled in Phase la.. The objective of this task is as follows: Aggregate those direct flow diversion structures not explicitly modeled in Phase 1 a model development. Combine these structures into approximately 30 aggregation groups. Use information on swing water rights to identify 8 water right classes to be used by aggregate direct flow diversion structures. The determination key direct flow diversion structures represented in the Rio Grande Surface Water model was accomplished during Phase la model development and is described in a memorandum documenting Task 6.2 ("Finalize Key Structures"). Those structures not meeting the defining criteria for key structures were considered during Task 7.1 for Phase lb model inclusion as aggregated structures. This memo describes the process used to evaluate and group individual direct flow structures into aggregates. Aggregation Process A sub-set of all direct flow diversion structures in Division 3 was reviewed to identify which structures to represent in the surface water model in an aggregated fashion. The structures examined were those that were not explicitly represented (key structures) in Phase la modeling efforts. By definition, these structures include those: • that have decreed rights for less than 5 cfs • that irrigate less than 250 acres • that were not represented in previous surface water modeling studies; and • that were not identified as important structures in river administration by Water District Commissioners • that are located on smaller or less tightly administered rivers and streams This subset was comprised of roughly 865 diversion structures. This list of structures was then evaluated as to the appropriateness of including them in the model as part of an aggregated structure. Examined were whether irrigated lands could be identified by the Consumptive Use Contractor and whether these ditches had diverted water in recent years. Several structures divert from seepage or drainage ditches rather than directly from the river, and no irrigated acreage is C:Acdss\Task7-l.doc Water Right Aggregation March 13, 2000 -Page 1 of 6