324 



EEPOET UNITED STATES GEOLOGICAL SURVEY. 



Platte leaves the Park near its southeast corner, cutting a caQon several 

 miles long through the Puma Hills, which form the eastern wall at this 

 place. Its course in this cauon is nearly northeast, changing to a course 

 slightly east of north, which it holds not only until it clears the mount- 

 ains, but as far as Greeley, at the mouth of the Cache la Poudre, in the 

 plains. From the head of its canon, where it leaves the South Park, 

 to its emergence on the plains is a distance of 50 miles. In this part of 

 its course it cuts diagonally across the whole breadth of the Pront 

 Eange, here very broad, but broken up into a confusion of spurs and 

 ridges that defy classification. Its course is alternately in caSon and 

 narrow valley, the former predominating. In this part of its course it 

 receives several good-sized branches — Tarryall Creek, which drains the 

 northeastern part of South Park, Lost Park Creek, which collects the 

 waters of a high, isolated mountain valley, and the l!^orth Fork of the 

 South Platte, which flows through a long,"* narrow caiion-valley. These 

 streams come in from the westward. From the other side the principal 

 affluent is Trout Creek, which collects the drainage of Bergen and Hay- 

 den Parks, interior valleys of the Front Range. Its principal affluents, 

 which head in the Front Eange and enter it in the plains, are as follows: 

 Bear Creek, with its branch, Turkey Creek ; Clear Creek, of which Rals- 

 ton Creek is a tributary; Saint Vrain's Creek, which, in the mountains, 

 divides into Coal, North and South Boulder, Left Hand, Jim, and the 

 North and South Saint Vrain's Creeks ; the Thompsons, Big and Little, 

 ami the Cache la Poudre. 



At the mouth of the Cache la Poudre the South Platte turns abruptly 

 to the east, and, after holding this course to longitude 103° 30', it turns 

 nearly east-northeast, which course it holds to its junction with the 

 North Platte. 



The valley of the South Platte, from the foot of its canon to the north- 

 eastern corner of the State, is 214 miles in length, with an estimated 

 average width of 2 miles, or an area of bottom-land of about 400 square 

 miles. Besides this bottom-land, the bench-land can easily be irrigated 

 at no great expense. There is much more land within reach of irriga- 

 tion than the river can supply with water. I have several measurements 

 of the volume of water carried by this stream, none, however, made at 

 the end of the irrigating season, and therefore they are poor indices ot 

 its irrigating capacity. They are as follows : 



Where gauged. 



Date. 



Cubic feet 

 per second. 



Authority. 





July 3 ... 

 June 29 . . . 



June 23 ... 

 Sept. 8 . . . 

 December 



388 

 367 



1,015 



1,400 



492 



204 



Pearson. 



Hartzell's Itancli, South Park (above mouth Little Platte) 



Link's Kanch, where the road from Colorado Springs first crosses 

 the Platte 



Do. 

 Do. 



root of Canon . 



Ebert. 





Fisher. 





Holbrook. 









At a short distance below the foot of the caSon the Great Platte Canal 

 is taken out. The amount of water abstracted by this ditch should be 

 added to the two last measurements to make them at all comparable 

 with the others. 



Judging by these measurements and the levels which its waters reach 

 at flood and other times, I should say that near the end of July this 

 stream carries about double the volume given by this measurement on 

 September 8, or 2,800 cubic feet per second. Using the rule adopted for 

 the sub-Himalayan districts, ^. e., that one cubic foot per second will 



