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.--, c::> ,,~ ~.u EXECUTIVE SUMMARY ;-... ..... INTRODUCTION This report presents the results of a process to develop flow recommendations for the native fish community, including the endangered Colorado pikeminnow (PI.VcllOchei!lIs !lIciIlS) and razorback sucker (XvrGllchen teXG/llls), in the San Juan River of New Mexico" Colorado, and Utah. Flow recommendations are a major milestone of the San Juan River Basin Recovery Implementation Program (SJRIP), which was initiated in 1992 with the following two goals: l. To conserve populations of Colorado squawfish and razorback sucker in the basin, consistent with the recovery goals established under the Endangered Species Act. 16 U.s.e. 1531 et seq, ~ To proceed with water development in the basin in compliance with federal and state laws. interstate compacts. Supreme Court decrees. and federal trust responsibilities to the Southern Utes, Ute Mountain Utes, Jicarillas. and the Navajos. Mimicry of the natural hydrograph is the foundation of the flow recommendation process for the San Juan River. Scientists have recently recognized. that temporal (intra- and interannual) flow variability is necessary to create and maintain habitat and to maintain a healthy biological community in the long term, Restoring a more-natural hydrog'raph by mimicking the variability in flow that existed before human intervention provides the best conditions to protect natural biological variability and health, The linkages between hydrology. geomorphology, habitat. and biology were used to define mimicry in terms offlow magnitude, dUriltion, and frequency for the runoff and base- Ilow periods, The f10wcharacteristics of these linkages were compared with the statistics of the pre- Navajo Dam hydrology to assist in fine-tuning the flow recommendations, The flow recommendations require mimicry of statistical parameters of flow. based on the linkages developed and the statistical variability of the pre-dam hydrology rather than mimicry of each annual hydrograph, A 65-year-long period of record (1929 to 1993) was used to assess the'relationship between water development scenarios and the ability to meet the flow recommendations. Data were gathered and analyzed during a 7-year research period (199 I to 1997) to determine fish population and habitat responses to reregulation of Navajo Dam to mimic a natural hydrograph, The research 'Involved quantification of several relationships, including flow/geomorphology. geomorphology/fish habitat, and f10wlhabitat availability relationships, The SJRfP will use an adaptive management process. along with monitoring and continued resea"rch" to adjust the flow recommendations in the future, The ability to adaptively manage the system is SJRIP Biology Committee February 1999 S - 1 Execulive Summary Flow Report