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<br />I <br />I <br />I <br />I <br />. <br />. <br />I <br />I <br />I <br />I <br />I <br />- <br />I <br />~ <br />. <br />I <br />, <br />I <br />, <br /> <br />EXECUTIVE SUMMARY <br /> <br />INTRODUCTION <br /> <br />This report presents the results of a process to develop flow recommendations for the native fish <br />community, including the endangered Colorado pikeminnow (Prychocheilus /ucius) and razorback <br />sucker (Xyrauchen texanus), in the San Juan River of New Mexico, Colorado, and Utah. Flow <br />recommendations are a major milestone of the San Juan River Basin Recovery Implementation <br />Program (SJRIP), which was initiated in 1992 with the following two goals: . <br /> <br />I. To conserve populations of Colorado squawfish and razorback sucker in the <br />basin, consistent with the recovery goals established under the Endangered <br />Species Act, 16 U.S.c. 1531 et seq. <br /> <br />. <br /> <br />2. To proceed with water development in the basin in compliance with federal <br />and state laws, interstate compacts, Supreme Court decrees. and federal trust <br />responsibilities to the Southern Utes, Ute Mountain Utes. Jicari II as , and the <br />Navajos. <br /> <br />Mimicry of the natural hydrograph is the foundation of the flow recommendation process for the San <br />Juan River. Scientists have recently recognized that temporal (intra- and interannual) flow <br />variability is necessary to create and maintain habitat and to maintain a healthy biological community <br />in the long term. Restoring a more-natural hydrograph by mimicking the variability in flow that <br />existed before human intervention provides the best conditions to protect natural biological <br />variability and health. The linkages between hydrology, geomorphology, habitat, and biology were <br />used to define mimicry in terms of flow magnitude, duration, and frequency for the runoff and base- <br />flow periods. The flow characteristics of these linkages were compared with the statistics of the pre- <br />Navajo Dam hydrology to assist in fine-tuning the flow recommendations. The flow <br />recommendations require mimicry of statistical parameters of flow. based on the linkages developed <br />and the statistical variability of the pre-dam hydrology rather than mimicry of each annual <br />hydrograph. A 65-year-long period of record (1929 to 1993) was used to assess the relationship <br />between water development scenarios and the ability to meet the flow recommendations. <br /> <br />. <br /> <br />Data were gathered and analyzed during a 7 -year research period (1991 to 1997) to determine fish <br />population and habitat responses to reregulation, of Navajo Dam to mimic a natural hydrograph. The <br />research involved quantification of several relationships, including flow/geomorphology. <br />geomorphologylfish habitat, and flowlhabitat availability relationships. <br /> <br />The SJRIP will use an adaptive management process, along with monitoring and continued research, <br />to adjust the flow recommendations in the future. The ability to adaptively manage the system is <br /> <br />SJRIP Biology Committee <br />May 1999 <br /> <br />S -1 <br /> <br />Executive Summary <br />Flow Report <br />