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. ~~ ,- ,... .....\ ~\ \; ~ ~-' River.' As a result of this action, the Bureau of Reclamation was requested by the State to resume studies on the dam on the 10wer South Platte River Valley .in 1958. In 1960, the Bureau started site selection studies based on the alternate cost of reservoirs at the Weld COWlty and Narrows Dam sites. These studies were completed in 1961. Upon review by the State of Colorado, the Bureau of Reclamation was requested to provide additional information regarding the hydro- logic benefits of both sites. As a result of this request, the Bureau completed hydrologic site selection studies in February of 1963 and investigations were started for the feasibility report. By January of 1964 all work that could be accomplished prior to site selection was complete and studies were suspended pending support from the State of Colorado on the Narrows Site Selection. In Septem- ber 1964, the State of Colorado officially requested that a dam be constructed in the lower South Platte River Basin at the Narrows site. With the official support of the State of Colorado for the Narrows Site, the feasibility studies were resumed and carried through to completion. PHYSICAL GEOGRAPHY .,: While the main stem of the South Platte River has a northeast trend, the basin spreads northwesterly as a consequence of large tributaries entering the river from the north and weGt. The course of the South Platte River \olithin the basin measures 450 miles. The Narrows Dam site is toward the mid part of the river's course. Downstream from the damsite the basin narrows to a width of 15 to 20 miles. The Narrows Dam will control runoff from about 13,450 of the 2l+,030 square miles within the basin. The South Platte River drains portions of four physiographic areas--the Colorado Piedmont, the High Plains, the Front Range, and South Park. The Colorado Piedmont and the High Plains are sections of the Great Plains Province; the front range and South Park are sections of the Southern Rocky MOWltain Province. Of these four areas, the Colorado Piedmont, an undulating plain which slopes east- ward from the foothills to the escarpments forming the boundary between the Piedmont and the High Plains, is of greatest importance to the Narrows Unit because a large portion of the plains drainage area of the South Platte Basin lies within this area. The South Platte River and its tributaries have cut broad, terraced valleys in the Piedmont Plain. . The foothills of the front range lie at elevations between 5,000 and 5,500 feet. From the foothills the land has an eastward slope with an elevation of 3,467 feet at Julesburg near the Colorado- Nebraska state line and 2,775 feet at the confluence of the South and North Platte Rivers. The highlands on either side of the South Platte River rise 300 to 400 feet above the valley floor. The main stem has 16