JOMAL OF AGRiaiTim ffiSEARCH 



Vol. X Washington, D. C, July 30, 191 7 No. 5 



EVAPORATION FROM THE SURFACES OF WATER AND 

 RIVER-BED MATERIALS 



By R. B. Slhight, 



Assistant Irrigation Engineer, Office of Public Roads and Rural Engineering, United 



States Department of Agriculture 



INTRODUCTION 



The Irrigation Field Laboratory at Denver, Colo., where the following 

 experiments were made, was established for the purpose of studying from 

 an engineering standpoint problems connected with the utilization of 

 water in irrigation. It is a laboratory of such size and kind that natural 

 phenomena may be observed under conditions somewhat less artificial 

 than are usual in laboratory work. An examination of figure i will show 

 the general exposure and topography of the laboratory tract. This field 

 (22),^ though it has the conveniences and facilities of a city location, is 

 as open to the elements as the prairie homestead. 



A maximum elevation of 5,346.4 feet above sea level is reached at one 

 point of the tract. The surrounding country, except to the east, is lower. 

 The grade to the east is very slight and the country is open prairie. All 

 buildings in the immediate section of Denver are shown; these are gen- 

 erally of the one-story or bungalow type, and offer no interference with 

 experiments that may be in progress, since the nearest is some 200 feet 

 from the laboratory. Figure 2, which shows the layout of the laboratory 

 for the season of 191 6, indicates the location of such facilities as electric 

 power, water supply, etc. The hillside provides a 20 per cent slope for 

 the flow of water and furrow work. The panorama (PI. 33) supplements 

 the information given by figures i and 2. Surrounded by a 6-foot 3-inch 

 mesh woven wire fence, with top and bottom barbed wires, the field has 

 been free from animals. A rule that has been rigidly enforced is that 

 visitors are not permitted except when accompanied by some member 

 of the organization. 



At the beginning plans v/ere started for a study of duty of water and 

 movement of water through soils. Evaporation has a large part in the 

 apparent efficiency of the use of irrigation water. Evaporation measure- 

 ments and data available were not considered sufficient for the require- 

 ments of the proposed work. It was therefore necessary at first to carry 



Reference is made by number to "Literature cited," p. 259-261. 



Journal of Agricultural Research, Vol. X, No. 5 



Washington, D. C. July 30, 1917 



ja Key No. D — 11 



(209) 



