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Draft Preliminary Flow Recommendations Conditions considered at 2/24/98 Biology Committee Meeting /fff"<:.hrn <<.. t- / . The following conditions of the hydrograph have been determined to be required to maintain suitable conditions for recovery of the Colorado squawfish and razorback sucker in the San Juan River. These conditions are used to assess river operation model results based on the attached Navajo Dam Operating criteria. The attached table presents the values associated with the 1929-1993 model runs for the various configurations tested to date. Further work is required to refine these conditions. A. Category: Duration: Frequency: Purpose : Flows> 10,000 cfs during runoff period 5 days minimum, Natural variation - criteria set after analyzing statistics 20% on average, maximum period without condition met to be determined To provide new cobble sources, generate new channels, provide for diversity B. Category: Flow> 8,000 cfs during runoff period Duration; 5-10 days minimum, Natural variation - criteria set after analyzing statistics Frequency: 33% on average, maximum period without condition met to be determined Purpose: To build bars, maintain channe~ provide conditions to suppon measured response of native species to duration above 8,000 cfs, provide spawning and nursery conditions for razorback sucker. C. Category: Flow> 5,000 cfs during runoff period Duration: 21 days, Natural variation - criteria set after analyzing statistics Frequency: 40% -50% on average, maximum period without condition met to be determined Purpose: Clean backwaters in reach 3, maintain secondary channels D. Category: Flow >2,500 cfs during runoff period Duration: 10 days, Natural variation - criteria set after analyzing statistics Frequency: 80% on average, maximum period without condition met to be determined Purpose: Clean spawning bars Eo. Category: Peak timing similar to historic conditions, including variability Timing: Mean peak with re-<Jperation to be within 5 days '" of mean for historic period Variability: Standard deviation of date of peak to be 14-25 days Purpose: mimic natural hydrograph . F. Category: Target Base Flow (mean weekly non-spring runoff flow) Level: 500 crs at Farmington to Lake PoweD with 250 cfs minimum from Navajo Purpose: This level balances provision of near-maximum low velocity habitat and near-optimum flows in secondaries while allowing water to be available for maintaining required frequency, magnitude and duration of peak flows. G. Category:. Flood Control Releases (incorporated in operating rule) Control: Maintain mean weekly base flows below 900 cfs by releasing water in a peak hydrograph during fall/winter as needed for flushing & non-native control. High magnitude (up to 5,000 cfs), short duration release to be usedfor meetingflood control levels in the dam. (Rules on hydrograph shape to be defined) H. Category: Measure: Provide cobble for Razorback spawning on ascending limb This condition provided by meeting Conditions A-F I. Category: Measure: Provide cobble for Squawfish spawning on descending limb This condition provided by meeting Conditions A-F Key: Bold = items agreed to on 2/24/98 4, eGo italics = items requiring funher information and discussion before agreement is reached. .