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<br />HBC status in the mainstem, may positively influence the overall LCR/HBC <br />population. <br /> <br />. <br /> <br />Initial flow experiments to modify habitat have not shown a strong response in <br />increased HBC abundance. This could be due to a number of factors <br />including both the power of the experiment, the ability of monitoring <br />programs to detect a change, and the short time since the most recent <br />experiment (LSSF) has been conducted. Another possibility is that non-native <br />and native fish interactions (Le., predation and competition) are over-riding <br />any potential positive effects from floWs that improve habitat conditions. The <br />experimental flows described here are intended to test this possibility and <br />produce a measurable affect on non-mitive fish and hence on non-native and <br />native fish interactions. The hope is that this will result in a positive effect on <br />HBC and lead to the designing of experiment;tl flows or other management <br />actions that also can improve habitat for native fish, including HBC that will <br />address Goal 2 of the AMP strategic plan. <br /> <br />Scenarios: -We assume the antecedent and cont4mporilry conditioris for experi!!ll::n~s_ <br />conducted in WY 2002-2003 will be so called 8.23maf or at best average inflow years, <br />thus allowing GCD operations to achieve constant Low-Flows in fall 2002 or lnHd <br />following flows below 10 000 cfs and erha s' . su e . GCMRC is <br />recommen mg three versions of experimental flows for late in WY 2002 and during WY <br />2003. Each is described briefly below and a figure depicting a hydrograph for the <br />particular flow is provided. While these hydtographs show specific daily flow levels, they . <br />.. "-are-int'Cl1ded-t-o-be-eoneeptua}-hydrographs-whqs~recise-nature-(specifieilo(')f&-a11d---' -. <br />ceilings, up-ramp and down-ram rates, and duratjons) will need to be determined. <br /> <br />A) Figure 1. This scenario provides for 1\ set of experimental flows aimed at <br />conserving sediment only. From October 2001 through June 2002 the dam <br />follows normal ROD operations. Followinl! Sediment Inuuts in the Julv - <br />October 2002 period the dam is operated at a constant 8,000 cfs following <br />sediment inputs (or perhaps a low leyel, e.g. 5-9,000 cfs ROD flow) until <br />January 2003. I;l January 2003 a. BHjBF oflimited duration is conducted. <br />Later winter, spring and summer 20Q3 operations would follow monthly <br />volumes under the ROD. This hydro graph could be repeated in WY2003-04. <br /> <br />The BHBF to be released in January 2003 should have a magnitude of at least <br />10,000 cfs above peak powerplant djscharge, or higher depending on lake <br />elevation. A year with significant s~diment inputs would be defined as an <br />Instantaneous discharge of 2,000 cfs or greater from the Paria River or an <br />instantaneous discharge of 10,000 cfs or greater from the LCR during the <br />period August I-October 31. . <br /> <br />~or, <br />- j;j... <br />o <br /> <br />B) Figure 2. This scenario provides for 'experimental flows aimed at both <br />conserving sediment and benefiting native fishes. From October 2001 through <br />June 2002 the dam follows normal ROD operations. Followinl! Sediment <br /> <br />. <br /> <br />Version 1.2 - 2/15/02 <br /> <br />3 i <br />