24 
Bulletin 1356, U. S. Department of Agriculture 
f orations in the wall of the still well below the water surface per- 
mitted water to enter and pass out freely, so that the water in the 
still well and that on the plats was always at the same level. 
In determining the quantity and manner of water loss from the 
plats, the losses by evaporation and transpiration were based upon 
the data obtained from three evaporation tanks. These tanks, 6 
feet in diameter and 2 feet deep (figs. 5 and 6), were sunk in the 
ground, their tops projecting about 2 inches above the surface. The 
water level in each tank was kept approximately 4 inches from the 
top of the tank. A brass still well having a diameter of 3 inches 
was attached externally to each tank by a supporting bracket, the 
tank and still well being connected by a half-inch pipe. The quan- 
tit} T of water that was applied and lost by evaporation and transpira- 
tion was measured with a micrometer gauge. 
Tank A had a freely exposed water surface. The water surface in 
tank B was shaded by flat wooden slats half an inch in width and 40 
inches in length. The slats were suspended from fine wires stretched 
across the tank, leaving their ends about 1 inch aboA^e the water. 
They were arranged in rows 8 inches apart and tied together at their 
lower ends to approximate in effect the shade of the rice plants. 
Tank C contained soil in which rice was grown in rows 8 inches 
apart and in water 6 inches deep. 
Table 16. — Average daily loss of water from tanks A, B, and C at the Rice 
Experiment Station, Crowley, La., for July, August, and September and for 
that 3-month period of each year from 1910 to 1922, inclusive 
[Data in inches] 
Year 
Tank not shaded 
Tank shaded by slats 
Tank shaded by 
plants 
rice 
July 
Aug. 
Sept. 
Aver- 
age 
July 
Aug. 
Sept. 
Aver- 
age 
July 
Aug. 
Sept. 
Aver- 
age 
1910 
0.179 
.179 
.164 
0.174 
.175 
.185 
.172 
.143 
.193 
.168 
.182 
.184 
.174 
.178 
.209 
.188 
0.153 
0.169 
0.109 
.111 
.102 
.087 
.121 
.121 
.113 
.128 
0.107 
.093 
.085 
.112 
.097 
.157 
.121 
.115 
0.102 
.078 
.094 
.099 
.129 
.118 
.096 
.109 
0.106 
.094 
.094 
.099 
.116 
.132 
.110 
.117 
0.206 
.230 
.207 
.184 
.2S4 
.260 
.313 
.264 
.238 
.195 
238 
0.281 
.308 
.495 
.293 
.214 
.240 
.424 
.261 
.294 
.316 
.332 
.217 
.269 
0.330 
.239 
.416 
.231 
.294 
.300 
.382 
.228 
.330 
.313 
.346 
.166 
.263 
0.272 
.S59 
.373 
.236 
264 
1911 
. 138 j . 164 
. 139 . 163 
. 126 . 157 
. 171 . 170 
. 162 . 189 
. 169 . 174 
. 161 . . 179 
.176 .193 
. 170 1 . 171 
. 175 . 165 
. 137 . 169 
1912 
1913 
.175 
.197 
.213 
.185 
.194 
.219 
.169 
.141 
.160 
.181 
1914 
1915 - 
267 
1916 
1917 
.373 
.251 
287 
1918 
1919 
275 
1920 
.305 
191 
1921 
.189 
.210 
1922 
.155 
.175 
247 
Average, 1910-1917... 
Average, 1910-1922... 
.186 
.181 
.174 
.179 
.152 
.156 
.171 
.172 
.112 
.111 
.103 
.109 
.244 
.232 
.315 
.303 
.303 
.295 
.2«7 
.277 
Table 16 shows the average daily loss of Avater from the tanks 
shown in Figure 6 for July, August, September, and also for this 
3-month period of each year from 1910 to 1922, inclusive. 
The loss from tank A was by evaporation from a freely exposed 
water surface and is taken to represent the loss of water by evapora- 
tion from reservoirs, canals, large laterals, and small ditches. The 
greatest average daily evaporation occurred in July for the 3-month 
period from 1910 to 1922, inclusive, as shown in Table 16. The 
maximum, minimum, and average monthly and daily evaporation at 
the Rice Experiment Station for the 14-year period from 1910 to 
1923, inclusive, is given in Table 6. 
