June 9, 1922] 



SCIENCE 



623 



years, but the report on the first stage has just 

 been published.^ The Forest Service is repre- 

 sented by Carlos G. Bates, silviculturist, and 

 the Weather Bureau by Professor A. J. Henry, 

 meteorologist, the reports representing joint 

 authorship. 



While an effort was made to select water- 

 sheds of similar character, it is obvious that, 

 no matter how good the general agreement of 

 the main features, exact duplication was im- 

 possible. Watersheds A and B at Wagon 

 Wheel Gap, therefore, have certain character- 

 istics in which they are quite different. Through 

 these two small valleys flow tiny streams which 

 descend toward the Eio Grande. The streams 

 are approximately parallel in their lower por- 

 tions and flow, in a general direction, from 

 west to east. The area of the south watershed, 

 A, is 222.5 acres and that of the north water- 

 shed, B, is 200.4 acres. The lower point of A 

 is 9,373 feet and the upper point 11,355 feet 

 above sea-level. Corresponding elevations for 

 B are 9,245 feet and 10,952 feet above sea- 

 level. These facts are not as significant, so 

 far as this study is concerned, as the fact that 

 ■watershed A is relatively long and narrow, 

 while B is short and fan-shaped. These char- 

 acteristics exert considerable influence upon 

 the rate of runoff, for, owing to the short, 

 steep, slopes of A, the flood crest arrives more 

 quickly than in B, but falls sooner, then comes 

 to a secondary maximum of longer duration, 

 because of the greater length of the watershed. 

 The flood at B exhibits no secondai'j- maximum 

 because the water reaches the dam from all 



1 Bates, Carlos G., and Henry, Alfred J.: 

 "Streamflow Experiment at Wagon Wheel Gap, 

 Colo. ' ' Mo. Weather Rev. Supplement No. 17, 

 pp. 55, figs. 41. A very complete paper repre- 

 senting a summary and extracts from the Supple- 

 ment Avas published in the Mo. Weather Eev. for 

 December, 1921, under the same title, pp. 637-650. 

 Believing that separates of this shorter paper 

 will satisfy those who have an academic, rather 

 than a professional, interest in the subject, a lim- 

 ited number of reprints are now available. 

 Application should be made to the Chief of the 

 Weather Bureau, Washington, D. C. Copies of 

 the complete report, Supplement 17, may be ob- 

 tained at 50 cents each from the Superintendent 

 of Documents, Government Printing Office, Wash- 

 ington, D. C. 



parts of the watershed at approximately the 

 same time. Moreover, A and B lying in dif- 

 ferent directions, as explained above, involves 

 a difference in the rate of snow melting owing 

 to the different exposure of the slopes to the 

 sun; this has an effect upon the streamflow. 

 The geological character of the two watersheds 

 has been found to be the same. The trees con- 

 sist largely of Douglass fir, although there is a 

 considerable sprinkling of bristle-cone pine and 

 Englemann spruce, the distribution depending 

 upon the altitude, the exposure of the slope, 

 and the amount of rock in the soil. 



The observing equipment is of two kinds, 

 meteorological and hydrological. Six primary 

 meteorological stations were established at the 

 beginning of the experiment, one at the base 

 and one in the upper reaches of the streams, 

 and two in each of the valleys. The equipment 

 of these stations varies according to the topo- 

 graphic features in the vicinity; but, among 

 them are to be found maximum and minimum 

 thermometers, psychrometers, thermographs, 

 soil thermoscopes, hygrographs, anemometere, 

 raingages, and snow bins. The headquarters 

 station is the most completely equipped, having 

 two standard barometers, and a triple register 

 for recording automatically wind direction and 

 speed, precipitation and sunshine. On A there 

 are 18 snoAvscales — graduated stakes 12 feet 

 high — and on B, 14 scales, the location of each 

 having been carefully selected so as to be rep- 

 resentative of the snowfall on a given acreage. 



The hj'drological equipment consists of a 

 dam in each stream so constructed as to make 

 the surface and subflow of the streams avail- 

 able for measurement. Back of the dams are 

 concrete basins in which continuous automatic 

 record of the waterstages is kept by a Friez 

 recorder. The instrumental record is checked 

 daily by a reading with the hook gage, the 

 latter being so accurate that several observers 

 do not differ more than 0.001 foot on a given 

 reading. , The dams at first had rectangular 

 weirs, but for these triangular weirs were later 

 substituted. 



The following facts are shown by the nine 

 years of meteorological observations: (1) The 

 mean minima for identical periods and times 

 are slightly higher for slopes facing south than 

 for those facing north, but the greatest differ- 



