BUIUETIN 1155, U. S. DEPARTMENT OF AGRICULTURE. 
The highest daily evaporation was 0.762 inch, in September. 1913, 
and the lowest daily evaporation was 0.006 inch, in October, 1913. 
The average daily evaporation ranged from 0.088 inch, in October, 
1916, to 0.410 inch, in May, 1918. 
Table 6 presents data on the monthly, average monthly, seasonal, 
and average seasonal evaporation from April to October, inclusive, 
for the 9-year period from 1913 to 1921, inclusive. 
Table 6.— Monthly, average monthly, seasonal, and average seasonal evaporation at the 
Biggs Rice Field Station, Biggs, Calif , from April to October during the 9-year period 
from 1913 to 1921. inclusive. 
[Data iu inches.] 
Month. 
1913 
1914 
1915 
1916 
1917 
1918 
1919 
1920 
1921 
Average. 
April 
May 
June 
July 
August 
September 
~'9.'i20' 
11.210 
9.247 
8.767 
6.221 
3.840 
5.789 
7.348 
8.263 
6.775 
5. 760 
3.003 
3.383 
4.996 
8.500 
9.618 
7.825 
5.912 
4.466 
' 7."i6i" 
9.261 
9.270 
8.152 
6.279 
2.713 
4.091 
6.119 
9.448 
10.110 
8.178 
6.158 
4.363 
2 3. 845 
7.160 
7.104 
6.227 
4.691 
2.793 
5. 243 
5.853 
7.052 
9.076 
7.845 
4. 956 
2.879 
i 6. 970 
12.224 
8.679 
7.035 
3.946 
4.480 
"8*991' 
9.692 
7.858 
5.497 
4.256 
8. 789 
9.225 
7.682 
5. 774 
Total: 
June to Octo- 
ber 
May to Octo- 
44. 571 
31. 149 
36. 938 
40. 778 
36. 321 
41.317 
44.700 
35. 675 
42.836 
36.364 
36.294 
27. 975 
31. 808 
37.661 
42.904 
35. 020 
39. 688 
ApriltoOcto- 

42. 794 
i Last 17 davs of May. 
2 Last 18 days of May, 
The highest monthly evaporation recorded during the 9-year 
period was 12.224 inches, in June, 1918; the lowest, 2.713 inches, in 
October, 1916. June, July, and August are the months of highest 
evaporation. The average evaporation for these three months for 
the 9-year period from 1913 to 1921. inclusive, was 25.696 inches. 
The average evaporation from April to October, inclusive, for the 
years 1914, 1915, and 1921 was 42.794 inches; the average evapora- 
tion from May to October, inclusive, for the years 1914, 1915, 1916, 
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8789 
H 9.225 
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Fig. 3.— Average monthly evaporation (in inches) from a free water surface at the Biggs Rice Field sta- 
tion in the four months from June to September during the 9-year period from 1913 to 1921, inclusive. 
and 1921 was 39.688 inches; and the average evaporation from 
June to October, inclusive, for the 9-year period from 1913 to 1921, 
with 1917 omitted, was 35.020 inches. The average monthly evapora- 
tion in inches at the Biggs Rice Field Station from June to Septem- 
ber, inclusive, in the, 9-year period from 1913 to 1921, is shown 
graphically in Figure 3. 
Water measurements show that it requires about 5 acre-feet, or 
60 inches, of water to produce a crop of rice on Stockton clay adobe 
soil. The evaporation records show that at least 40 inches of water 
evaporates from a free water surface during the rice-growing season. 
Assuming that the shading of the water by the rice during the sub- 
