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<br />390 <br /> <br />J, KORMAN, S, M, W1ELE AND M, TORIZZO <br /> <br />0) <br /> <br />1800 T <br /> <br />1~1 <br /> <br />1<00 <br /> <br />o Pre-Dam <br />. Post.Dam <br /> <br />U 1200 <br />. <br />!- <br />5 <br /> <br />1000 <br /> <br /> <br />! =] <br />~ l~+~_~ <br /> <br /> <br />~1l~ <br /> <br />2345678 <br /> <br />9 10 11 12 <br /> <br />Month <br /> <br />b) <br /> <br />100 I <br />I <br />I <br />eo <br /> <br />'0 <br /> <br /> <br />-Pre <br />-Post <br /> <br />. <br />. <br />(:. <br />. <br />3 <br />. <br />E <br />;:: <br />C <br />. <br />~ <br />. <br />a. <br /> <br />50, <br />I <br />I <br /> <br />20 <br /> <br />o ,~.. <br />o <br /> <br />. -..,----.---. ------, <br /> <br />500 <br /> <br />1000 <br /> <br />1500 <br /> <br />OIKhlrge (m)/sec) <br /> <br />Figure 5. Mean monrhly discharge and 95% confidence limils for pre- and post-dam periods (a) and flow exceed:::mce curves (b) measured al [he <br />Lees Ferry gauge. Oa..hed vertical lines highlight discharges of 226 and 566 mJ/s <br /> <br />Historical changes in dam operations have influenced seasonal patterns in suitable shoreline habitat (Figure 7), <br />Differences in ill1i\y average suitable shorel'me habitat area across operating regimes were greatest at the sensitive <br />sites (ALC, RI, R4), The modified low fluctuating flow (MLFF) alternative restricted the diurnal range of dis- <br />charge from GCD (Table Ill, Figure 8), This in turn reduced both the frequency of low flows and the monthly <br />variation in low~flow frequency relative to the 'no action' alternative, resulting in lower but consistent suitable <br />shoreline habitat availability, Greater suitable shoreline habitat availability under the 'no action' alternative rela-. <br />tive to MLFF could also be caused by higher discharge in the years used to assess the latter regime (1996-1999), A <br />comparison of the two regimes in months with similar average discharges (e,g. January), however, still showed that <br />the 'no action' alternative produced more suitable shoreline habitat. The effects of the LSSF experimental steady <br />flow in lbe spring and summer of 2000 (May-September) on suitable shoreline habitat availability is evident at the <br />sensitive sites, The reduced flow resulted in a large improvement in suitable shoreline habitat availability in June, <br />July, and August relative to other operating regimes and the pre-dam period, The LSSF experiment did not produce <br />a 'natural' seasonal pa\lern in suitable shoreline hab"tat availability lbat mimicked the pre-dam era, Instead. it gen- <br />erated high suitable shoreline habitat availability in June and July, which, in the pre-dam period, were months <br />when suitable shoreline habitat availability was lowest <br /> <br />Copyright :0 2004 John Wiley & Sons, Ltd. <br /> <br />River Res. Applic. 20: 379-400 (2004) <br />