WATER LOSSES FROM WET AREAS 



123 



2. U. S. Bureau of Agricultural Engineering type, 6 feet in 



diameter bj^ 3 feet deep, set 2.75 feet in the ground. 



3. Los Angeles County Flood Control District type, 2 feet in 



diameter by 3 feet de^p, set 2.75 feet in the ground. 



The standard Weather Bureau pan is the one most commonly used 

 throughout the west and the one from wliich the majority of records 

 are available. In southern California the Bureau of Agricultural 

 Engineering has used this type of pan at each of its experiment stations. 

 The 6-foot tank set in the ground is used in various localities on the 

 valley floor, while the 2-foot tank is used in the mountain watersheds. 

 Other equipment at the Baldwin Park station consists of a Livingston 

 spherical atmometer, maximum and minimum thermometers, a thermo- 

 graph for recording temperatures, a barograph for barometric pressure, 

 an anemometer for wind movement, and both automatic and standard 

 rain gages. 



Monthly evaporation records obtained from the three types of 

 pans at the Baldmn Park station are given in Table 46. 



TABLE 46 



MONTHLY EVAPORATION RECORDS AT COOPERATIVE KEY STATION AT 

 BALDWIN PARK, CALIFORNIA, 1932-1933 



Description of pans: 



Standard AYeather Bureau pan — 48 inches in diameter by 10 inches deep. 



Bureau of .Agricultural Engineering pan — 6 feet in diameter by 3 feet deep, set 2.75 feet in the ground. 



Los .Angeles County Flood Control District pan — 2 feet in diameter by 3 feet deep, set 2.75 feet in the ground. Gage 

 held in center of pan by metal cross bar below water surface. 



Elevation of station: Approximately 400 feet. 



Remarks: This station is operated cooperatively by the following agencies: Bureau of .Agricultural Engineering, 

 U. S. Department of Agriculture; Geological Survey, U. S. Department of the Interior; Los Angeles County Flood 

 Control District; Pasadena Water Department: San Gabriel Valley Protective Association; Division of Water Ilesources, 

 Department of Public Works, State of California. 



It is expected that this investigation will be continued for several 

 years, until sufficient data are available for correlating the evapora- 

 tion records that are being collected by the various agencies. The 

 value of many of these records will be greatly enhanced if the proper 

 coefficients can be determined to reduce the measured los.ses to the 

 equivalent evaporation from a lake surface. It is hoped that eventually 

 every type of pan in common use will be installed at Baldwin Park key 

 station, and that the proper conversion coefficients will be determined. 



