4247 - Laserfiche WebLink

Home Browse Search

17 136-155 had an unusually high number of backwaters{mile (4.2) for the lower Green River, however, the mean size was only 167 m. The remaining lower rm segments ranged from only 1.0 to 2.8 backwaters/mile. Table 15 summarizes backwater characteristics for each of the sampling strata used by Tyus et ale (1987). Strata E and F, which represent the upper nursery area for Colorado squawfish lTyus et ale 1987), contained the most backwater area with 1,737 and 2,340 m/mile. Backwater number/mile was greatest in stratum F (6.7) and was relatively high in stratum E (3.4/mile). The average backwater size in strata E and F was 513 and 350 m2, respectively. Strata A and B represent the lower Green River Colorado squawfish nursery area (Tyus et ale 1987). Although backwater area and number/mile for these strata were similar to those of strata C and 0, the mean backwater size was significantly greater (308 and 348 ml) than for strata C an 0 (155 and 195 m2, respectively). Table 16 shows the comparison of Green River backwater characteristics for Island Park, Jensen, Ouray, and Sand Wash. Flows at Mineral Bottom were not comparable between 1987 and 1988. The Island Park remained relatively stable between the two years, with 52 and 46 backwaters in 1987 and 1988, respectively. Total backwater area was also stable, decreasing slightly from 22,153 ml in 1987 to 20,866 m2 in 1988. While backwater numbers at Jensen remained stable from 1987 to 1988 with 54 and 56, respectively, backwater area decreased significantly from 19,039 m2 in 1987 to only 12,579 m2 in 1988. This was reflected in the average backwater size which decreased from 353 m2 in 1987 to only 225 m2 in 1988. The Ouray site changed most dramatically. Total backwaters decreased from 57 in 1987 to 48 in 1988. Total backwater area decreased by more than 60 percent from 41,177 in 1987 to only 15,108 ml in 1988, respectively. The average backwater size decreased substantially from 722 m2 in 1987 to only 315 m in 1988. Backwater habitat at Sand Wash was somewhat more stable than at Ouray. Total backwaters remained constant at 11 for both years while backwater area increased by approximately 41% from 9,270 ml in 1987 to 13,112 ml in 1988. Average backwater size, which was largest at Sand Wash for both years, increased from 843 m2 in 1987 to 1,192 m2 in 1988. The flow at Mineral Bottom in 1988 was much lower than any flow photographed during 1987, making comparisons between the two years difficult. A total of 12 backwaters were recorded with an area of 1,026 m2 during the 1988 study. These numbers were somewhat less than for any flow photographed during 1987. The average backwater size, which was smallest at Mineral Bottom for both years, was only 86 ml in 1988. Videography Results Results of comparisons indicated that airborne videography equates favorably with aerial photography with respect to backwater area. The August 23, 1988, 1:6,000 scale CIR aerial photography resulted in a total backwater