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Direct Flow Storage <br />Overview <br />Several decrees were issued since the 1980's allowing direct flow irrigation water rights to be <br />stored in reservoirs and later released to their original decreed points of diversion. This has <br />allowed water users to make better use of their water by matching headgate water supply with <br />their on-farm water demands. <br />Objective <br />Test StateMod's Direct Flow Storage Operating rule that allows a surface diversion structure to <br />store decreed water rights (in excess of their irrigation demand) in a reservoir, and allow release <br />of this water for use by the same structure at a later time. This enhancement was intended to <br />allow representation of current practices by several ditches decreed on the Rio Grande and <br />Conejos River. <br />Test Applications <br />This enhancement to StateMod involved the creation of a new operating rule (Type 16) for <br />implementation in the operating criteria file (rg.opr). Rule Type 16 allows water to be stored in a <br />reservoir under direct flow water rights. Water may then be released from storage using <br />previously existing rule Type 2 (reservoir release to a direct diversion demand or carrier). <br />A test application for this enhancement was provided by the State, Example No. 38, and may be <br />reviewed as found in the StateMod documentation. Hydrosphere ran StateMod with the Example <br />No. 38 input data and reviewed the output. The output indicated that the StateMod enhancement <br />was operating as intended. <br />Direct flow storage operating rules were then added to the operations file for the Rio Grande <br />Model. Type 16 operating rules were specified for three ditches on the Rio Grande to allow <br />storage in three different reservoirs (Rio Grande, Continental and Santa Maria) under direct flow <br />rights. Additional rules were specified to allow direct flow storage by fifteen different ditches on <br />the Conejos River (in Platoro Reservoir). Release of water stored under direct flow rights for <br />these structures was then accomplished using operating rule Type 2. <br />As with the simple test example, application of these rules to the Rio Grande model appeared to <br />produce the desired results. Ditches actively store water under direct flow rights, and this water is <br />later released from storage to specific ditches when their river supply is insufficient to meet <br />demand. <br />Comments <br />Direct flow storage operates within StateMod under rule type 16 when 1.) the water right is in <br />priority, 2.) the structure served by the water right has a demand, 3.) there is an exchange <br />potential between the location of the reservoir and water right, and 4.) there is available space in <br />the reservoir. <br />When applied to the Rio Grande Basin the determination of when a structure may choose to store <br />a direct flow water rather than divert it was implemented by identifying specific, typically junior, <br />decrees based on user interviews. <br />Rule Type 16 allows the user to limit the amount of a direct flow right (variable iopsou(4, k)) that <br />may be stored in a reservoir. The rules specified in the Rio Grande Model limit diversions by <br />Conejos River ditches to 90 percent of water available to a direct flow right. This represents <br />current administrative efforts by Division 3 to prevent injury to other water rights on the river. <br />C:Acdss\TaskS-5.doc StateMod Enhancements August 15, 2000 -Page 2 of 8 <br />