3 54 



FORESTRY AND IRRIGATION. 



April, 



about 46 miles. This is good bottom land 

 -and in large part above high water. 



At the Needles the mountains rise to 

 several thousand feet on either side at 

 distances of 10 miles from the river, 

 offering no opportunities for extensive 

 diversions The river at the Needles 

 bridge, at Mellin, Arizona, was exam- 

 ined for a gaging station. At its present 

 low-water stage the channels are irreg- 

 ular and diagonal. The bridge is 80 

 feet above the water and would make a 

 poor station. Two miles below the 

 bridge the river enters the Blue Canyon, 

 at which point it is contracted to a width 

 of 400 feet. If a dam 100 feet high 

 could be placed here it would flood the 

 large flat above the Needles. The Santa 

 Fe railroad crosses the river at Mellin 

 with an imposing cantilever bridge 

 80 feet above the surface of the .stream. 

 Boats passing up and down the river 

 clear the bridge. A dam 100 feet high 

 at Blue Canyon would raise the water 

 above the floor of the bridge ; the town 

 of Needles also would be inundated. 

 Spillway opportunities exist on the left 

 bank 100 feet above the present level of 

 the river. A great reservoir would be 

 created by the construction of such a 



dam. No surve}'s were made of this 

 site, but it is probable that a dam 100 

 feet high would give a reserv'oir capac- 

 ity of over 3,000,000 acre-feet. A dam 

 40 feet high would probably create a 

 reservoir some 20 miles long, flooding 

 45,000 acres of land and impounding 

 500,000 acre-feet of water. The flood 

 stages of the river coming in May and 

 June and filling this reservoir by the 

 first of July, the water would not neces- 

 saril}' be retained therein over four 

 months, and the loss by evaporation 

 should not exceed four feet in depth. 

 When this 40- foot reservoir became 

 filled with silt, by raising the height 

 of the dam 10 feet, 500,000 acre-feet 

 additional capacity would be obtained. 

 By repeating this operation the reservoir 

 could be maintained for many years. 

 The gates of such a reservoir should be 

 kept open subsequent to October, when 

 it should have been emptied, and remain 

 open until June, so as to avoid silting 

 above the flow line in the reservoir and 

 permit of the scouring out of channel. 

 In view of the exi.stence of several reser- 

 voir sites below and of the damage 

 which would occur from the construc- 

 tion of a dam at the Blue Canyon, it is 



DAM SITE ON THK L0WP:R C0I,0RAD0 RIVER TWO MILES BEIvOW NEEDLES BRIDGE. 



