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Show Record concerned, represent conditions through Grand Canyon below the mouth of the San Juan. 4156 Plate 8 represents the relation between the mean velocity in the cross- section and the gage heights. This plate, as I see it, is of little value in the case. Plate 12, which is a cross- section of the river at Lees Ferry, is based on observations made May 31, 1924, which shows to what extent the velocities and the cross- section vary at any particular time. When that measurement was made the velocities varied from a maximum of 8.86 mile an hour to less than 1 mile; that is 8.86 miles per hour in the thread of the stream to less than 1 mile an hour at the banks, and to less 4157 than 5 miles an hour at the bottom in the center of the stream. When the measurement was made the discharge was 59,400 second feet. The average flow at Lees Ferry is, I think, 20,000 second feet. 4158 Plate 9 indicates the mean depth of the river at the 4159 gaging stations. Taking a depth of 5 feet as an example, which is at Lees Ferry, a depth of 5 feet or greater is expected for 280 days. At Green River, Wyoming, a mean depth of 5 feet for 140 days. At Greenriver, Utah, a depth of 5 feet for over 120 days. For the Colorado River at Cisco a depth of over 5 feet for 110 days. For the San Juan River at Bluff a mean depth of over 5 feet for 80 days. In general, as to mean depths, there is no portion of the year when the Colorado River, at Lees Ferry has a mean depth of less than 3 7/ 2 feet; or at Green River, Wyoming, of 3.2 feet. There is no day in the year when the mean depth at Cisco is less than 3 feet. There is no day in the year when the mean depth at Green River, Wyoming, is less than 3 1/ 2 feet. There is no day in the year when the mean depth is less than 2 feet at Greenriver, Utah. On the San Juan River at Bluff there is no day when the mean depth is less than a foot. There are 200 days in the year when the mean depth at Bluff is more than 2 feet. 4160 Plates 1- A, 2- A, 3- A, 4- A, and 5- A show the cross- sections of the river. An examination of those cross- sections will show that' 596 |