232 



Journal of Agricultural Research 



Vol. X, No. s 



pan was installed in November, 191 5, emptied for the winter, refilled in 

 March, 1916, and used throughout the year ending in November, 1916. 

 Table X presents figures from this pan in comparison with the evaporation 

 with tank 7. Based upon the totals during the time of use of the pan, 

 evaporation from it was exactly i % times that from the large pan sit- 

 ting in the ground. In extension to large water surfaces this figure would 

 be safe to use under conditions similar to those at Denver. However, 

 since the pan departs so greatly from the reservoir, in that its whole 

 water body is above the ground and is subjected to effects of radiation 

 and heat concentration, no statement can be made regarding the appli- 

 cation of the figure {1%) to other locations. Temperature records show 

 a very much higher day temperature, a somewhat lower night tempera- 

 ture, and a lower mean temperature for this tank than any set in the 

 ground. It follows more closely the variations in air temperature than 

 any of the other tanks used except the very shallow ones. 



Table X. — Relation between evaporation from tank 7 {12 feet in diameter by 3fee4 in 

 depth, set in ground 2.'/jfeet) and a Weather Bureau standard pan (tank 8) for class A 

 station, under same conditions 



Week ending- 



1915 

 Nov. 22 



29 



Dec. 6 



i3«.... 



1916 

 Mar. 6 



13 



20 



27 



Apr. 3 



10 



17 



24 



May I 



8 



15 



22 



29 



June 5 



12 



19 



26 



Week ending- 



1916. 



July 3 



10 



17 



24 



31 



Aug. 7 



14 



21 



28 



Sept. 4 



II 



18 



25 



Oct. 2 



9 



16 



23 



30 



Nov. 6 



13...... 



Total & 



Evai> 



oration 



from 



tank 7. 



In. 

 2. 18 

 2. 18 

 1.58 

 1.83 

 1.76 

 I. 40 



1-43 

 I. 70 



1.47 

 ^•57 

 1.82 

 .98 

 1.03 



I- 15 

 I. II 



.63 



.24 



.90 

 .38 



47- 95 



Evap- 

 oration 



from 

 tank 8. 



In. 



.89 



.04 



.64 



2.71 

 2.66 

 1.97 

 2. 09 



2-37 



1. 92 



2. 24 

 2-45 

 ^■■32, 

 1.80 



i^54 



1.63 



I. 09 



.36 



•50 



1.30 



.60 



71^95 



Evap- 

 orfttion 



from 

 tank 8, 



ex- / 

 pressed 

 as per- 

 centage 

 of that 



from 

 tank 7. 



a. 



178 

 140 

 167 

 148 



157 

 141 

 146 

 139 

 131 

 143 

 135 

 136 



175 

 133 

 147 

 174 

 150 



145 



o Record broken. No. 8 was emptied on December 14 because of ice, and filled on February 29. 

 b Total evaporation from tank 8 expressed in percentage of that from tank 7, 150.0. Mean weekly per- 

 centage, 151.8. 



