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<br />. <br /> <br />. <br /> <br />estimated number of KAS lost by 40% (Kanab Ambersnaillnteragency Work Group <br />1997a), <br /> <br />Before another habitat-building flow, Reclamation agreed to enter into informal <br />consultation with the Service to evaluate prior test flow studies, the establishment or <br />discovery of a second population of Kanab ambersnail in Arizona, and reinitiate formal <br />consultation with the Service if incidental take will exceed the 10 percent of occupied <br />habitat, as established in the 1994 B.O, Also, the 1996 B,O. indicated that the impacts <br />of all flows above ROD levels (25,000 cfs) should be evaluated prior to, within one <br />month after, and 6 months after exceptional high flows. <br /> <br />In October 1997 the Service followed the 1996 8.0. recommendations regarding <br />consultation and mitigation on a proposed November 1997 Habitat Maintenance Flow <br />(HMF). HMFs are annual or biennial flows of variable duration at near-powerplant- <br />maximum discharge (33,200 cfs) that may rejuvenate riverine habitats. The Service <br />agreed with Reclamation's Finding of No Significant Impact (FONSI), allowing the HMF <br />to proceed provided that monitoring was conducted immediately before, within one <br />month after, and 6 months after the HMF. <br /> <br />The November 1997 HMF lasted 2 days, and inundated 29.79 m2 of existing habitat <br />(3,5% of the estimated existing total primary habitat at Vaseys Paradise), scouring 4.3 <br />m2 of habitat (0.5% of the estimated total primary habitat), That HMF eliminated no <br />more than an estimated 181 KAS, which was 1.4% of the estimated KAS population <br />existing downslope from the approximate 70,000 cfs stage, and 0,5% of the estimated <br />total KAS population at Vaseys Paradise (Kanab Ambersnaillnteragency Work Group <br />1997b), <br /> <br />Natural winter mortality may reduce the KAS population by nearly an order of <br />magnitude: the lowest KAS populations observed from 1995 through 1997 occurred <br />during emergence in March, indicating winter mortality rates of 43.5% to 84.7%. March <br />floods may result in a lower total take of KAS because there are fewer total KAS prior to <br />reproduction, but the proportional take is probably approximately equivalent in any <br />month from January through July. <br /> <br />Additional factors to consider regarding differences in take between months are (1) that <br />a BHBF when watercress is abundant and in the middle of its growth phase may result <br />in increased proportional take, and (2) a BHBF from mid-May through July is likely to <br />result in take of reproductively active snails, potentially affecting annual reproductive <br />output Therefore, although BHBF's later in the growing season may take an equal <br />proportion of KAS, later high flows may exert relatively greater impacts on KAS <br />reproduction. <br /> <br />If the estimated total primary habitat upslope from the approximate 70,000 cfs stage in <br />March 1998 is 416,3 m2 (77.2% of that mapped in 1994 by Stevens et al. 1997b), then <br />101,22 m2 (14.0%) of the estimated total habitat will be lost due to inundation or scour <br /> <br />1998 GeD Beach/Habitat Building Flow 10 <br /> <br />Biological Assessment <br />