Arkansas Basin_Water Supply and Needs

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Section 7 Availability of Existing Water Supplies in the Arkansas Basin IJIII that exist elsewhere within the lower South Platte Basin (Camp Creek, Upper Crow Creek). The alluvial aquifer in the Lost Creek, Kiowa-Bijou, and Upper Black Squirrel designated basins has been determined by the State Engineer to be overappropriated and, therefore, no new large capacity well permits will be granted. The remaining aquifers in these designated basins, including the alluvial aquifer in the Upper Big Sandy, Camp Creek, and Upper Crow Creek, the bedrock aquifers within the Denver Basin region (Dawson, Denver, Arapahoe, and Laramie-Fox Hills), plus Camp Creek, and parts of Upper Crow Creek. In these areas, groundwater is subject to appropriation by high capacity wells provided the appropriation does not unreasonably impair existing water rights. The Colorado Groundwater Commission determines whether a proposed new well will cause an unreasonable impairment of existing rights. 7.3 Available Surface Water and Alluvial Groundwater Supply Legally and physically available flows, as well as naturalized flows, are summarized below at select locations for each basin to the extent possible given the available datasets. Calculated naturalized and physically available flows are not available for the Arkansas Basin because it does not have a StateMod data set. Alluvial groundwater supplies that are considered tributary to the major river systems are also summarized. Historical flows at key gages in all river basins are monitored by the State Engineer's Office (SEO). This map, commonly referred to as the "Snake Diagram" is a useful tool for illustrating the volume of flows throughout the state. The snake diagram is shown in Figure 7-5. It is important to note that the snake diagram does not include consideration of Colorado's commitments under compacts and decrees. Therefore, only a portion of the flows that are shown are available to Colorado. There are numerous factors that may affect the physical and/or legal availability of surface water supplies. Some of the factors that are specific to individual basins are listed in the basin subsections below. General factors that must be considered when evaluating the availability of supply are listed in Table 7-1. As can be seen in the table, it is difficult to characterize supply availability without stating which factors have or have not been included in some fashion in the analysis. Table 7.1 Factors that May Affect Future Availability (Legal and/or Physical) of Supplies in the Arkansas Basin 1_"'-;("1' I . r.., '10; l......."": 1":1, Illl'.' " . . . · ''':11'': 'III Ii'.' " . Increases in M&I and Self-Supplied Industrial CUs Reduction in M&I and Self-Supplied Industrial CUs such as reducing lawn areas and industrial process improvements Evaporation from new or enlarged reservoirs Return flows from CU agricultural transfers that cannot be recaptured and reused Increased reuse of existing consumable return flows Unused CU yields from an agricultural transfer that cannot be stored by M&I or SSI users New or increased transbasin diversions out of the basin Increase in transbasin imports Increase in agricultural CU Decrease in agricultural CU . Increase in irrigated lands . Reduction in irrigated lands to lack of supplies for well augmentation . Development of additional supplies to reduce or eliminate agricultural . Transfer of agricultural rights for dedication to in stream flows (increase in shortages availability below the instream flow reach) . Changes in irrigation efficiency such as conversion to sprinklers . Changes to lower CU by crops . Changes to higher CU crops . Changes in crop types . Diversion by downstream agricultural users of increases in M&I return flows Development of irrigated lands resulting in a net increase in CU (increased Development of irrigated lands resulting in a net decrease in CU (decreased depletions per acre) depletions per acre) Additional flow requirements for species protection (e.g., endangered species) Runoff from increase in impervious areas RICDs and instream flow water rights filings (decrease in legal availability Return flows from increased non-tributary groundwater pumping (to the extent above the water right) not reused) Increase in coverage of phreatophytes or change in type of phreatophytes Flow Management Agreements and/or Coordinated Reservoir Operations (increase in environmental or recreational flows for the specific reach at specific times) Additional bypass flow requirements for existing projects Endangered species recovery by means other than flows (stocking, habitat improvements, etc.) Increase in coverage of phreatophytes or change in type of phreatophytes Reduction in coverage of phreatophytes or change in type of phreatophytes Hydrologic variability (e.g., climate change resulting in reduced runoff or Hydrologic variability (e.g., climate change resulting in increased runoff or extended d roug hts) extended wet periods) CDIVI 7-4 O:\SHAWN\ARKANSAS\S7 _ARKANSAS.DOC