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the four study reaches and divided by the total water area of the four reaches to arrive at a density estimate for each flow level. As before, the four study sites were treated as one composite reach. For habitat units per mile of river, we summed the total number of polygons and divided by the summed miles of river in the four study sites. For habitat units per hectare, there was an inverse relationship: as flow increased, habitat density declined (Fig. 22). When density and discharge were graphed, the overall trend was apparent but an anomaly existed: the trend was inconsistent at the lower discharge levels. Density declined sharply between flows of 557 and 810 cfs, and increased again at 1,240 cfs before declining again. In an attempt to understand this inconsistency, we partitioned the data by year of mapping. What emerged were two lines that were relatively consistent (Fig. 22). The difference between the two lines was that flows at the lower end of the spectrum resulted in higher densities in 1991 than in 1990. One possible explanation for this is that the experience of the individual performing the on- the-ground mapping increased as the project progressed and slightly more detailed maps were produced toward the later part of the study. Regardless of the cause, there appears to be a consistent pattern in which density decreases only slightly between lower and mid-range flows and declines more at higher flows. In 1990, density dropped sharply between flows of 1,530 and 2,870 cfs; in 1991, between flows of 1,240 and 1,630 cfs. Thus, habitat density was highest at 557 cfs, and 98% of maximum at 1,240 cfs. Habitat units per hectare at 1,630 cfs, the recommended summer and winter flow, was 76% of that at 557 cfs. The highest total number of discrete habitats, and therefore the highest number per mile, occurred at 1,240 cfs. Number per mile did not vary as much with discharge as number per hectare (Fig. 22). At the recommended flow of 1,630 cfs, habitats per mile was 82% that at 1,240 cfs. Final Considerations for Summer and Winter Flow Recommendations (Objective No. 4) In developing the final summer and winter flow recommendations, our primary consideration was to maximize the area of preferred habitat while minimizing potential depth limitations. Analysis of effects of discharge on habitat area resulted in 1,630 cfs as the best flow level for both seasons. A secondary consideration was to retain a reasonably high degree of interspersion of individual habitat units. Interspersion (density), was highest at 557 cfs (per unit area) and 1,240 cfs (per linear mile of river). We conclude that 1,630 cfs remains the best flow of those studied for the following reasons: 1) a flow of 2,870 cfs would provide less preferred habitat and a lower density of habitats than at 1,630 cfs; 3) a flow less than 1,630 cfs would provide less preferred habitat area while depth could become limiting in more locations; 4) though interspersion was not maximized at 1,630 cfs, it remained reasonably high; (5) for winter, flows less than 1,630 cfs are outside the range of flows within which winter preference could be tested and the next highest flow studied, 2,870 cfs, is considerably higher than the mean flow of either the recent or historic winter periods; and (6) when summing weighted area of preferred habitat, backwaters made up a large contribution (24-41 %) to total area, yet stage and bed profile monitoring indicated that adequate depth in backwaters is far from assured; a large proportion of backwaters may often be unsuitable due to insufficient depth. 47