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Transbasin Diversions South Platte River Basin Projects The earliest transbasin diversions were not for agriculture, but for placer mining. In 1860 a ditch was built across Hoosier Pass, taking water from a tributary of the Blue River and using it to work a high placer on the middle Fork of the South Platte River above Alma. Another early ditch constructed by miners was the Ewing Ditch which diverted water from a tributary of the Eagle River across Tennessee Pass to a mining area above Leadville. By the 1880's the rush to secure water rights on the South Platte River and its tributaries had resulted in so many claims that late-comers were often denied water in the latter part of the summer. Because there was relatively little irrigation in the Colorado and North Platte River basins at that time, the appropriation dates for the new trans mountain ditches were relatively senior in the west slope, and the East Slope users could be certain of obtaining dependable water supplies to meet their needs. The Larimer County Ditch Company, known today as the Water Supply and Storage Company, was the first Irrigation Company to construct a transmountain diversion for irrigation. The ditch they constructed was called the Cameron Pass Ditch. It diverted water from Michigan Creek drainage to the Cache la Poudre watershed. The ditch was small, only one-half mile long. This ditch has an appropriation dated July 30, 1882. Next followed many transmountain ditch systems that also diverted water into the Cache La Poudre River Basin. Work began on the creation of a channel to divert water from the Grand River (later renamed the Colorado River) on the west side of the Continental Divide, and to deliver it to farms east of the mountains. Considered an engineering marvel at the time, the channel began sending water eastward in 1890 with 8 miles of ditch across a high mountain pass, dug by hand primarily by Japanese and Mexican laborers. By 1936, with the help of machinery, the ditch extended to 14 miles through the Rocky Mountain National Park. First called the Grand River Ditch, it was renamed the Grand Ditch after the name of the Grand River was changed to the Colorado River in 1921. The ditch is about 20 feet wide and 6 feet deep, although the water is usually no more than 3 feet deep. The ditch starts at an elevation of about 10,300 feet, to where it crosses the La Poudre Pass, at an elevation of 10,179 feet. From the La Poudre Pass, the water flows into a reservoir, Long Draw Reservoir, then into the Cache la Poudre River, and finally to the Larimer Weld Canal near Fort Collins. Farmers in the Cache la Poudre River basin numerous other transmountain diversions. They constructed the Michigan Ditch which also diverted water from the Michigan River Basin. They also constructed 5 transmountain Diversions from the Laramie River Basin the largest of which is the Larimer Poudre Tunnel. In 1904, the newly established United States Reclamation Service (USRS) completed a study which suggested raising the elevation of Grand Lake 20 feet and included the construction of a 12-mile tunnel from Grand Lake to either the Big Thompson River or St. Vrain Creek. This proposed project was heavily supported by water users in the Cache La Poudre Basin. It wasn’t until Dec. 1, 1938, however, that construction of the Colorado Big Thompson Project began with the construction of Green Mountain reservoir. The Green Mountain Reservoir was constructed as a