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15 distance along the cross section. These measurements were made whenever one of the variables changed noticeably. All measure- ments were made along the transect line, and differences up and downstream from the transect line were not measured. After a cross section was completed, three velocity measure- ments were made for each pl ant bed on the tran sec t 1 i ne. Two velocity readings were made at a reference point located halfway across the plant bed, measuring along the transect line. One reading was made on the river bottom at this reference point and a second at the maximum height of the plant stalks at this refer- ence point. The third velocity reading was made on the river bottom at the upstream edge of the plant bed, located directly upstream from-the reference point. Invertebrate sampl es Benthic samples were collected to determine invertebrate density for five substrate types: nonvegetated silt, macrophyte beds on silt, gravel, rubble, and from rock with Cladophora at-. .. tached. Samples were taken from within the intensive study site located below Pipe Creek. Samples were taken only from greater water depths (1.4-5.8 m) than were sampled during earlier studies on the Green River (Holden and Crist 1981) in order to provide a more compl ete picture of i nvertebra te popul a ti ons. A special enclosed sampler was used which allowed samples to I be taken by a diver and returned to the surface without loss of -invertebrates. The orginal prototype sampled an area of 0.07 m2 while a later model had an opening of 0.1 m2. ,. .~'~'_-_'" ""rll._""...,-<,,,,,<.v,~,_,,,__.. ,,~._.._~____._,_,