9441 - Laserfiche WebLink

Home Browse Search

STUDY AREA Middle Green River section (Duchesne River to Sand Wash) ~ Below the Ouray National Wikllife Refuge, a 20 river mile (RM) area was selected as the middle Green River removal reach. This reach began at RM 248, 200 meters above the confluence with the Duchesne River and ended at RM 228, approximately 11 RM upstream of Sand Wash. This removal reach was arbitrarily divided into five equal, four-mile sections (Figure 1). These divisions served no analytical purpose, but were simply demarcations of where a set of nets would ~ be located each day. River miles are reported with the confluence of the Colorado River set as RM 0. The upper ten river miles of this removal reach is a wide, low gradient, depositional area meandering though a broad flood plain Substrates are primarily sand and silt. Islands and sand ~ bars are numerous. The riparian vegetation is dominated by tamarisk with some cottonwood over story. The lower 10 miles is a transition from the wide, low gradient river above to a more narrow, canyon bound river. This area is still low in gradient and the canyons are broader and less deep than Desolation and Gray canyons. Bottomland topography is still found throughout the lower half of the removal reach. Substrates are dominated by sand, but cobble substrates are ~ encountered more frequently as you move down the reach. Riparian vegetation is limited to sandy shorelines, mouths of canyons, and bottomland areas. In addition to removal efforts in the 20 RM removal reach, monthly electrofishing trips were conducted in sections of the Green River between Jensen, near the inflow of Ashley Creek (RM ~ 299), to Ouray, Utah, near the confluence with the Duchesne River (RM 248). This was the control reach for the middle Green River (Figin~e 1). The sampling occurred in 400 meter sections dispersed throughout the control reach. A total of 17 sites were marked and sampled each month. This sampling was a continuation of a nonnative abundance database started in 1994 by Dr. Todd A. Crowl at Utah State University. However, those data were not included in this report. ~ Lower Green River section (Gray Canyon) In 1997, the section of the Green River between RM 140 and RM 132 was selected as the study area (Figure 1: S2- SS). The entire section was divided into four subsections, alternating two control reaches and two removal reaches. In the control reach, no catfish were sacrificed or ~ removed from the river. During 1998, the removal reach was located between RM 142 and RM 132, in Gray Canyon ~ 1: S1- SS). A five river mile section k-cated between RM 120 and 115, was designated as the lower control reach. The 10-mile removal reach was subdivided into five equal, two-mile ~ sections. The sections were numbered from upstream to downstream. The Gray Canyon removal reach (RM 142-132) is a broader, shallower canyon than Desolation Canyon. Eddies and constrictions below rapids form occasional backwaters. The maul channel is well defined with few islands. Substrates are primarily cobble and bed rock with sand accumulating in eddies and slack waters. Riparian zones are restricted to narrow shorelines and mouths of tnbutary streams. 4 ~