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- -- ----~--"- --......:.:.:-,~.........-__.._~--~~--- 16 3,261 ft3/s (21). The Mineral Bottom site had substantially fewer and smaller backwaters than all other sites. Backwaters per mile ranged from 2.1 at 2,748 ft3/s to 3.1 at 3,261 ft3/s. Backwater area per mile ranged from only 250 m2 at 2,748 ft3/.s to 481 m2 at 3,261 ft3/s. Average backwater size varied from 109 to 154 m2. Linear Regression Regression of flow versus backwater area indicated two different ~~~ \L~~ relationshiPs... Significant (P = 0.05), negative re ressio s occurred~'he c.q,"::" \,a.. Island Park [r = -0.87; regression equatlon: ackwater area = 31,200 + 0' j (=10.2) flow] and Jensen [r = -0.91; regression equation: backwater area = l,~. ~r 30,500 + (-9.97) flow] sites. Regressions at the Ouray [r = +0.29; t.<-~\..- ",Q.."" regression equation: backwater area = 34,600 + (4.95) flow] ~ Sand Wash [r = -0.39; regression equation: backwater area = 11,300+ (-.890) flow] sites indicated there was no relationship between flow and area. Comparability of riverflow to backwater area relationships within the four upper sites was analyzed. The hypothesis that relationships were equal at each site was rejected (P = 0.10). Furthermore, when Island Park and Jensen were paired and Ouray and Sand Wash were paired, it was apparent that the regression relationships between flow and backwater area within each pair were more alike than expected by chance. The pooled regression for the Island Park and Jensen pair was -0.88 (P <0.01), and +0.17 (NS) for the Ouray and Sand Wash pair. The statistical difference between the two pairs was highly significant (P <0.02), indicating the relationship between flow and backwater area for the Island Park and Jensen pair was statistically \ different from the Ouray and Sand Wash pair. Consequently, based on these ~a~~~~~T data, backwater area ca . bl be redi ted from flow between 2,423 and~~~)~. 1 10 t s f r the Island Park and Jensen sites but cannot e re lC e \~,1 0 j,-,,~.., Jlr Olfray aM Sand Was .. )I,....t "":~ t l. .,.. ~\y\. l~\1- . Regression analyses of flow vs. backwater number indicated there was no c~5t !i9~ificant relationship-at any site (P = .05). However, at a lower -- probability level (P = .10) the negative regression at Island Park site was significant. 1988 Study Considerable variation occurred in backwater area and number per rm during 1988. Table 14 presents backwater area and number/rm and the average backwater size for 20-mile segments of the Green River. The 20-mile river segments are shown on figure 1. In general, backwater area and number/mile were greatest in the upper portions of the river. Backwater area/mile ranged from 1,193 to 3,880 m2 from Island Park to about Sand Wash (rm segments 331 to 176). Backwater area/mile from about Desolation Canyon to the Colorado River confluence (rm segments 1 to 195) ranged from only 185 to 766 m2. Backwater number/mile was also greater in the upper portions of the river, ranging from 5.2 to 4.2/mile for rm segments 331-236; however, upper rm segments 235 to 196 had somewhat lower backwater number/mile, ranging from 2.2 to 2.8/mile. The mean backwater size for these rm segments was the largest for the entire river, ranging from 542 to 520 m2. RM segment