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<br />Draft Preliminary Flow Recommendations <br />Conditions considered at 2/24/98 Biology Committee Meeting <br /> <br />/lHc<chfTl en f- I <br /> <br />.. <br /> <br />Q <br />a <br />'=' <br />....'f <br />c.n <br />00 <br /> <br />The following conditions of the hydrograph have been determined to be required to maintain suitable conditions for recovery <br />of the Colorado squawfish and razortiack sucker in the San Juan River. These conditions are used to assess river operation <br />model results based on the attached Navajo Dam Operating criteria. The attached table presents the values associated with <br />the 1929-1993 model runs for the various configurations tested to date. Funher work is required to refine these conditions. <br /> <br />A. <br /> <br />Category: <br />Duration: <br />Frequency: <br />Purpose : <br /> <br />Flows> 10,OOD cfs during runoff period <br />5 days minimum, Natural variation - criteria set after cmalyzing statistics <br />20% on sverage, marimum period without condition met to be determined <br />To provide new cobble sources, generate new channels, provide for diversity <br /> <br />B. Category: Flow> 8,000 cfs during runoff period <br />Duration: 5-10 di1ys minimum, Natural variation- criteria sel after analyzing statistics <br />Frequency: 33% on average, marimum period without condition met to be determined <br />Purpose: To build bars, maintain channel, provide conditions to suppon measured response ofnativc species to <br />duration abovc 8,ODO cfs, provide spawning and nursery conditions for raz;orback sucker. <br /> <br />C. Category: Flow> 5,000 cfs during runoff period <br />Duration: 21 dayl, Natural variation - cri/eria set after analyzing slatistics <br />Frequency: 40% -50% on average, maximum period wilhout condition met to be determined <br />Purpose: Clean backwaters in reach 3, maintain secondary channels <br /> <br />D. Category: Flow >2,500 cfs during runoff period <br />Dumtion: 10 days, Natural variation - criteria set after cmalyzing statistics <br />Frequency: 80% on average, maximum period without condition met to be determined <br />Purpose: Clean spawning bars <br /> <br />E.. Category: Peak timing similar to historic conditions, including variability <br />Timing: Mecm peak with re-operation to be wi/hin 5 di1ys '" of mecmfor historic period <br />Variability: Slandard deviation of date of peak to be 14-25 days <br />Purpose: mimic natural hydrograph <br /> <br />F. Category: Target Base Flow (mean weekly non-spring runoff flow) <br />Level: 500 cfs at Farmington to Lske PoweD with 250 cfs minimum from Nsvajo <br />Purpose: This level balances provision ofnear-ma'<imum low velocity habitat and near-optimum flows in <br />secondaries while allowing water to be available for maintaining required frequency, magnitude and <br />duration of peak flows. <br /> <br />G. Category: Flood Control Releases (incorporated in operating rule) <br />Control: Maintain mecm weekly base flows below 900 cfs by releasing water in a peak hydrograph during <br />falH.inter as needed for flushing & non-nalive control. High magnitude (up 10 5.000 cfs), shari dura/ioll <br />release to be usedfor mee/ingflood control levels in the dam. (Rules on hydrograph shape 10 be defined) <br /> <br />H. <br /> <br />Category: <br />Measure: <br /> <br />Provide cobble for Razorback spawning on ascending limb <br />This condition provided by meeting Conditions A-F <br /> <br />I. <br /> <br />Category: <br />Measure: <br /> <br />Provide cobble for Squawfish spawning on descending limb <br />This condition provided by meeting Conditions A-F <br /> <br />Key: Bold = items agreed to on 2/24/98 ~ ~(3. <br />italics = items requiring funher infonnation and discussion before agreement is reached. <br /> <br />r <br />