MetroSouthPlatteInterimBasinWaterSupplyNeedsReport (2)

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Section 4 Legal Framework for Water Use -- has been the principal water supply for the area for at least 15 years and is not adjacent to a naturally flowing stream.55 Designated groundwater exists within designated groundwater basins. The Ground Water Commission establishes designated groundwater basins through a notice and hearing procedure when evidence becomes available that groundwater within a specific geographic area meets the above noted criteria.56 Each designated groundwater basin is administered according to a modified prior appropriation system. Locations of designated groundwater basins are presented in Section 7. 4.2.9 Reuse Colorado law generally provides for one use of water by the original appropriator. The water that is not consumed by an appropriator's first use is returned to the stream system, either as surface run-off or through subsurface infiltration. Junior appropriators, who are entitled to have stream conditions as they exist at the time of their appropriation, rely on these return flows to fulfill their decreed rights. Thus, water that is brought into a watershed from a source unconnected with the receiving system termed "foreign" water may be reused by its owner.57 Foreign water includes non-tributary groundwater introduced into a surface stream as well as water imported from an unconnected stream system ("transmountain water").58 Importers of foreign water enjoy rights of reuse that native water appropriators do not have. Such water is deemed "fully consumable" and can be used and reused to extinction so long as the user maintains dominion and control over the water. Dominion and control in this context refers to the intent to recapture or reuse such water, and is not lost when a municipal provider delivers water to a customer's tap or when consumers use such water to irrigate lawns.59 Dominion over the water is not lost if the importer intends to reuse such water and has some method to track or recapture the water. In addition, agricultural water rights that are changed to municipal use may also generate fully consumable water that can be used to extinction. This is because the 55 S 37 -90-103(6). 56 S 37-90-106. 57 City ofThornton v. Bijou Irr. Co., 926 P.2d 1,66 (Colo. 1996) 58 Id. 59 Public SelVice Co. v. Willows Water Dist., 856 P.2d 829, 834 (Colo. 1993). CONI 4-8 applicant in a change of use proceeding may take credit for, and reuse, the historical CU associated with the prior decreed use. Under this scenario, the amount of water attributable to the historical CU of the senior water right may be used and reused to extinction. Although this is not "foreign water" by definition, it is another source of fully consumable water. In addition, in some circumstances, applicants for new water rights may obtain decrees that allow a new appropriation to carry with it a "fully consumable" designation that allows the diverted water to be used and reused to extinction if the initial appropriator has, from the beginning, a plan to reuse the water. Recently, challenges to these types of applications have focused on whether the claimed use and reuse to extinction is speculative in nature. Any water that is deemed fully consumable may be reused to extinction. In practice, municipal exchanges involving fully consumable water (in most instances municipal effluent or lawn irrigation return flow credits), have been a means to reuse fully consumable water. Recently, municipal entities have also started to operate wastewater reclamation projects where fully consumable water, in the form of effluent, is treated to a high standard and used for outdoor irrigation purposes within the municipality's service area. These projects involve pumping the treated, fully consumable effluent to irrigate portions of a service area and thereby reducing demand for municipal potable supplies for irrigation. Reuse projects involving either pumping or exchanges potentially help increase efficiencies and reduce or postpone the overall demand for new water supplies. 4.2.10 Conservation Activities Conservation practices associated with both municipal and agricultural uses can be an important tool in meeting long-term water supply needs. Demand reduction is an important component of water planning. To the extent that conservation practices are reliable, and/or permanent in nature, such practices can reduce the overall demand for water and thereby reduce any shortfall in supply. Conservation measures can also take the form of increased efficiencies. However, not all water conserved through more efficient uses corresponds to an increase in overall water supply to a water user. For example, a S:\1177\Basin Reports\South Platte\S4_South Platte.doc