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<br />, <br /> <br />8 <br /> <br />GIS Results <br /> <br />. <br /> <br />1937 -1986 <br /> <br />, <br /> <br />Summaries of the 1937 versus 1986 analysis showed that there was a <br />negligible change in instream water area, but decreases in island area and <br />side channel/backwater area. Area measurements for the 32 mile reach of <br />river showed a 1 % increase in water area between 1937 and 1986, a 20% <br />decrease in island area, and an 18% decrease in side channel/backwater area <br /> <br />tt <br /> <br />(fable 1). Figure 4 shows that although there was a net decrease in most <br />measurements, some areas showed an increase in potential habitat. Some <br />of the areas of increased island and side channel/backwater area are due to <br />the river filling abandoned gravel pits. Approximate error estimates are <br />::1:2% for the water and island area measurements and I10% for the side <br /> <br />, <br /> <br />channel/backwater area measurements. <br /> <br />. <br /> <br />Table 1. Percent change of instream water, island, and side <br />channe1/ backwater area for the 15 and 18 mile reach of the Colorado River <br /> <br />Year Instream Water Area Island Area Side Channel/Backwater Area <br /> <br />. <br /> <br />1937-86 <br /> <br />+1% <br /> <br />-20% <br /> <br />-18% <br /> <br />1954-68 <br /> <br />-12% <br /> <br />-16% <br /> <br />-27% <br /> <br />. <br /> <br />Table 2. Percent of river miles experiencing a decrease in instream water, <br />island, and side channel/ backwater area for the 15 and 18 mile reach of the <br />Colorado River. <br /> <br />. <br /> <br />Year <br /> <br />Instream Water Area Island Area Side Channel/Backwater Area <br /> <br />1937-86 <br /> <br />63% <br /> <br />69% <br /> <br />81% <br /> <br />. <br /> <br />1954-68 <br /> <br />78% <br /> <br />56% <br /> <br />66% <br /> <br />. <br />