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<br />and fill were also observed by Andrews (1982) on the East Fork river in <br />Wyaning. This river was in its natural state, undisturbed by human activi- <br />ties. River channel changes were induced by the variation in discharge. <br /> <br />In 1906, the Associated Press filed a well-written report which seemed <br />to end one of the world's most spectacular stor ies. In the story, the AP <br />reported that the Colorado River flooded; the water moved fran the All <br />l\merican Canal to the New River and poured down to the Salton Sea. The sea <br />rose seven inches per day. The water became a cascade and its force cut <br />back the banks. Soon the bank was receding faster and faster, moving <br />upstream into the valley at a pace of 4,000 feet a day and widening the New <br />River channel to a gorge of more than 1,000 feet. This example also <br />illustrates the dramatic widening of river channel associated with a rising <br />bed elevation. <br /> <br />A field study by the U. S. Bureau of Reclamation (1963) upstream of <br />Milburn Diversion Dam on the Middle Loup River, Central Nebraska also <br />exanplifies the aggradation of a channel and associated channel widening. <br /> <br />The construction of Milburn Diversion Dam was completed in <br />May, 1956... By May 1957, two months after the reservoir was <br />impounded for the first irrigation season, the channel had aggraded <br />an average of 1.6 feet, with a rise in the channel thalweg eleva- <br />tion of 2.2 feet; and by October of the same year, the total rise <br />in the streambed averaged 2.2 feet. The cross section obtained in <br />December 1957, shows a continued rise in the thalweg elevation. <br />During the same period, the width of the channel had increased by <br />70 feet, fran 475 feet in 1951 to 545 feet in 1957. One-third of <br />thi s increase occurred during the June, 1956 - December, 1957 <br />period . <br /> <br />For these two case histories, both alluvial rivers entered reservoirs <br />with a rising base level. The transient changes are characterized by rising <br />channel bed and increasing channel width. Although measurements of the dis- <br />charge and other parameters are not available, it is possible to describe, <br />at least in trend, the nature of power transformation in the river channel. <br />8 <br />