a Weather Bureau pan is of some significance, as both are influ- 

 enced by the same factors of temperature, wind, and hiimidity; and 

 whereas consumptive use determinations are available to represent 

 a strictly limited number of localities, evaporation records are 

 available for many and can be established quite readily for more. 

 When estimates of consumptive use are needed for localities where 

 determinations have not been made, available evaporation results 

 are therefore useful if both evaporation records and consumptive 

 use results are also available from other areas having comparable 

 characteristics. A discussion of such opportunities is found in 

 the chapter headed "Relation of Cons\imptive Use to Evaporation." 



Extensive work in regard to native vegetation has been 

 carried on hy the Division of Irrigation, United States Depart- 

 ment of Agriculture, in cooperation with the Division of Water 

 Resources, Department of Public Works, State of California, and 

 most of the results of the investigations have been published in 

 previous reports of the latter office. In this bulletin these 

 previously published data are assembled and analyzed in associa- 

 tion with the results of similar studies by the Division of Irri- 

 gation — ' in other sections of the West. These studies specifi- 

 cally included those undertaken by the Division of Irrigation in 

 the Upper Rio Grande Basin in cooperation with the States of 

 Colorado, New Mexico, and Texas under an agreement with the 

 National Resources Committee. In Colorado, the Division cooper- 

 ated with the Colorado Agricultural Experiment Station with regard 

 to grasses, sedge, sweetclover, tules, sunflowers, and weeds. 

 Likewise , it cooperated with the Oregon Agricultural Experiment 

 Station in determination of water consumed by grasses and native 

 meadow lands in south-central Oregon. 



The cooperative field work in southern California had been 

 carried on under the general supervision of Harry F. Blaney, by 



17 The Soil Conservation Service on July 1, 1939 took over most 

 of the irrigation investigations formerly conducted by the Bureau 

 of Agricultural Engineering. 



