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approximately half way in on the north side and two more large, dead cottonwoods formed a horizontal barrier at the back one third of the pool. Again, these subjective designations changed with rising water levels such that the back one third at the beginning of the field season became the middle one third at peak flows. Depths at this site were uniform at lower water. The entire backwater was less than a meter deep at all sampling locations for the first two weeks. The substrate consisted of a 2-7 cm silty flocculent layer overlying a clay base. After river levels rose, the water began to fill the dry wash at the back of the backwater. Here, the substrate was comprised of sand and gravel, likely created by seasonal flash flooding from the Millard Canyon Benches. Towards the latter part of the season, benthic samples were taken in this area where water levels in previous weeks were nonexistent. Even during high water, there were dry, steep banks encircling the backwater on the north and south sides. Mature cottonwood trees provided enough cover so that the backwater was shaded most of the day except for a few hours in early afternoon. Holeman Canyon The most downstream site was a deep, narrow backwater located at RK 28. During the first two weeks of sampling, a submerged point bar extended across the mouth. A deeper channel approximately 2 meters wide allowed access by boat from the north. Holeman was long and narrow, approximately 7 meters wide at the entrance and 40-50 meters long. It had very high, sheer banks on the north side while the south side supported a dense growth of young Salix. Rising river levels caused. Holeman to get deeper but not longer. The backwater was roughly V-shaped underwater with deeper water on the north side and shallower depths on the south. Because of the deep water and thick willow growth, it was often difficult to fmd adequate benthic sample sites in the middle third of the backwater. A silty layer interspersed with pockets of clay and small amounts of sand comprised the substrate. Holeman was the most turbid of the three backwaters, perhaps because there was no side channel, island or other protection at the mouth of the backwater to prevent free mixing with river water. METHODS Sampling Sampling was conducted weekly for seven consecutive weeks from 30 April to 12 June 1997. An additional sample was taken at Millard Canyon only, on 10 July. Five random, vertical zooplankton hauls were taken at each of the three backwater sites during daylight hours. Hauls were made in the middle and back third of the backwater to avoid the more turbid mixing zone at the entrance (front one third). At a sampling site, 3