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<br />Allocation of Transbasin County Population <br /> <br />Among Basins <br /> <br />The land area of some counties in Colorado are physically in more than one <br />river basin. Therefore, the populations of these transbasin counties must be <br />appropriately allocated among basins. This allocation allowed the <br />formulation of basin level populations. <br /> <br />For many of these transbasin counties the allocations were straightforward <br />due to areas of the counties being uninhabited. Thus, the total population could <br />be allocated to one basin. For example, 85 percent of the land area in Garfield <br />County is in the Colorado River basin and 15 percent of the land area is in <br />the Yampa River basin. However, the 15 percent of the county in the Yampa <br />basin is not populated. Thus, the entire county population is attributed to the <br />Colorado basin. This applied to Archuleta, El Paso, Garfield, Gunnison, <br />Hinsdale, Larimer, Mineral, Park, Routt, Saguache and San Juan counties. <br /> <br />Populations for the remaining six counties with populated areas in more than <br />one basin were allocated to basins using one of two methods. Both methods <br />required identifying towns, cities and other populated areas using an atlas <br />and GIS software. Once populated areas were identified, the names were <br />used to search for population values. Many identified places did not have <br />population data available. For example, Elbert County has a population of <br />19,872 but only 2,858 could be accounted for in identified areas. Thus, leaving <br />a remainder population of 17,014 unaccounted for. <br /> <br />One approach was to allocate the remainder population using the percent of <br />land area in each basin. This method was determined to be the most suitable <br />after visually assessing county information using an atlas and GIS software. <br />For example, the land area of Elbert County is 68 percent in the South Platte <br />basin and 32 percent in the Arkansas basin. After accounting for identified <br />population areas the remaining unaccounted population was allocated <br />among the South Platte and Arkansas basins using the land area percentages. <br />This method assumes that the unidentified population is equally dispersed <br />throughout the county. The allocated remainder population was added to the <br />identified population by basin in order to derive the total county population <br />allocation by basin. For example, in Elbert County the total population was <br />estimated to be 69 percent in the South Platte basin and 31 percent in the <br />Arkansas basin. This approach was applied to the populations of Cheyenne, <br />Elbert and Lincoln Counties. <br /> <br />For three counties the remaining population was allocated using the <br />percentage of identified population in each basin. This method was used for <br />counties in which one basin appeared to be more populated than the other, <br />thus negating the assumption that the remaining population was equally <br />dispersed throughout the county. For example, in Montrose County the <br />identified population was about 90 percent in the Gunnison basin and 10 <br />percent in the San Juan/Dolores basin. It was assumed that the remaining <br />unaccounted population would follow these same percentages, thus the <br />entire county population was allocated 90 percent and 10 percent, <br /> <br />II. Population Projections <br /> <br />5 <br />