1904 



FORESTRY AND IRRIGATION 



judicious thinning, and remove all of 

 lie, leaving II<2 and b for a ground 

 cover. These latter are too small to 

 take out profitably, and yet, by allow- 

 ing them to remain for cover, more o'f 

 the paying sizes in la and b can be re- 

 moved. The accompanying diagram 

 represents a trifle more than foursquare 

 rods of twenty-seven-year old white pine 

 which has been thinned by this method. 

 The selected trees are from 12 to 15 

 feet apart. It is expected that the final 



stand will be recruited from these, but if 

 anything happens to some of them other 

 members left from Class I will take their 

 places. A similar but less radical method 

 can be applied to a pole thinning which 

 has been thinned in the sapling stage. 

 Thinning has little effect after the 

 period of most vigorous growth. If the 

 stand has become mature without thin- 

 ning it will probably be best to make a 

 light increment cutting or successive 

 cuttings for reproduction. 



LITTLE COLORADO RIVER. 



WITH ITS TRIBUTARIES MAY BE USED 

 TO RECLAIM ARIZONA ARID LANDS. 



AFIELD party consisting of mem- 

 bers of the U. S. Geological 

 Survey, under the direction of Assist- 

 ant Engineer James G. Camp, has made 

 an investigation of the possibilities of 

 irrigation on the Little Colorado River, 

 in Arizona. 



The Little Colorado River drains 

 nearly 9,000 square miles in northeast- 

 ern Arizona and 6,000 square miles of 

 territory in northwestern New Mexico, 

 making a total drainage area of 15,000 

 square miles tributary to the river above 

 Winslow, Arizona. This drainage basin 

 extends from the Mogollon Mountains 



on the south to the Salahkai Mesa on 

 the north, and eastward to the Conti- 

 nental Divide. There are two flood 

 seasons the spring flood, due to the 

 melting of snow on the mountain slopes, 

 and the fall flood from the late summer 

 rains. 



The surface of most of this area is 

 either red or blue clay on the lower 

 slopes and a solid sand or lava rock 

 partially covered with sod. The latter 

 covers 50 per cent of the mountain and 

 foothill slopes. As no measurements 

 of the flow of the Little Colorado nor 

 its tributaries have been made during 



WESTERN PI.AIN COVERED WITH SAGE BRUSH, BEFORE IRRIGATION. 



