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<br />.. . <br /> <br />O,....'n <br />''-' __ U....l. <br /> <br />SUMMARY <br /> <br />Section 3(a)(3) of S. 1029, the Colorado Wilderness Bill of 1991, states that 'while the Piedra <br />Wilderness designated by section 2(a)(10) of this [Bill] is located downstream of numerous <br />State-granted conditional and absolute water rights, the Forest Service can adequately protect <br />the water-related resources of this wilderness area by working in coordination with the <br />Colorado Water Conservation Board through a contractual agreement between the Secretary [of <br />Agriculture] and the Board to protect and enforce instream flow filings established pursuant to <br />the provisions of section 37-92-102(3) of the Colorado Revised Statutes by the Colorado Water <br />Court for Division 7. . <br /> <br />The instream flow claim in this report is recommended within the context of the State of <br />Colorado's priority system for water rights and would therefore be junior to all existing <br />absolute and conditional rights. <br /> <br />The recommended claim results from an assessment of the water related resources and values <br />of the Piedra River and its tributaries within the proposed Piedra Wilderness. The instream <br />flow requirements of these resources include both low and high flow components. Based upon <br />current knowledge of physical and biological systems, the recommended claim is the minimum <br />amount of water necessary to adequately protect the water related wilderness resources and <br />values and to maintain the interaction of processes which have shaped the Piedra River and its <br />ecosystems. <br /> <br />The known, physical and biological requirements of riparian vegetation, fish, and aquatic <br />insects were used to identify requirements for flows associated with both the subsistence and <br />long term maintenance of biological functions within the aquatic and terrestrial ecosystems and <br />the occurrence of required hydrologic processes. Four flow levels or ranges of flow will be <br />necessary to meet these requirements. Two of the flow levels are related to winter, early <br />spring, and fall low flows and are based primarily upon biological function and survival needs: <br />* Qu ' subsistence flow; <br />* Qu' biological maintenance flow; <br />The remaining two flow levels are related to the higher ranges of flow typically occurring <br />during the spring, summer, and fall and are based primarily upon the biological needs of both <br />terrestrial and aquatic species and on the maintenance of physical habitat features: <br />* the range of flows between QA> average annual flow and Q1.5' flow with a return period of <br />1.5 years; and <br />* the range of flows exceeding Qu. <br />The Qu flow occurs an average of two out of every three years. It closely approximates the <br />level of flow needed to just fill the active channel. <br /> <br />The recommended instream flow claim is a dynamic claim which would vary from year to year <br />and would work in the following manner: <br />* when actual streamflow is less than Qw the actual streamflow would be claimed; <br />* when actual streamflow equals or exceeds Qu but is less than Qu, Qu would be claimed; <br />* when actual streamflow equals or exceeds Qu but is less than QA> Qu would be claimed; <br />* when actual streamflow equals or exceeds QA but is less than Qu, a percentage of the <br />streamflow would be claimed; and <br />* when actual stream flow equals or exceeds QI.5' the actual streamflow would be claimed. <br /> <br />Page ii <br />