32 
COLORADO EXPERIMENT STATION. 
16. The amount of evaporation increases with the temperature 
of the water, with the wind, and diminishes with increased moisture 
in the air. 
17. From the standard evaporation tank at the Experiment 
Station, the average evaporation for 11 years, has been 41 inches. 
18. Evaporation proceeds when the water is frozen, but at a 
diminished rate, averaging about 1 to 1 J inches per month. 
19. The evaporation at night is the same as during the day, 
the difference being less with the increase of the size of the bodies of 
water. 
20. The loss by evaporation from several lakes exceeded that 
from the standard tank. 
21. The loss from the lakes was about 60 inches per year. 
22. The increase is due to higher temperature ot the water, 
and to freer exposure to the wind. 
23. In some of the summer months, the lakes lost twice as 
much as the standard tank. 
24. The lower temperature of water at high elevations, and 
the lower dew points, tend to decrease the evaporation. 
25. The diminished barometric pressure tends to increase the 
evaporation, amounting to 14 per cent at 8,000 feet, and to 18 per 
cent at 10,000 feet, over the evaporation at 5,000 feet. 
26. Every mile of wind movement in 24 hours increases the 
evaporation by from 1 to 2 per cent over the evaporation if calm. 
27. The winter period is longer at the high elevations. 
28. For the whole year, the evaporation in all probability is 
considerably less at the high elevations than at the low ones. 
29. Evaporation is lessened by any influence which diminishes 
the wind or decreases the temperature of the water. 
30. Protection of lakes by wind breaks is in many cases prac- 
ticable, and in small lakes sometimes desirable. In the large lakes 
the benefit is by reducing the wind velocity ; in small lakes both 
from effect on wind and by lessening action of sun. 
31. The deeper the lake the cooler the water as a whole, the 
cooler the surface, consequently the less evaporation. 
32. Assuming a loss of 5 feet in depth per annum, an area of 
100 acres would require f cubic feet per second for the whole year 
to make good the losses from evaporation ; one of 500 acres would 
require 3| cubic feet per second, considerably more than would be 
used to irrigate an equal area. 
33. The net loss to the reservoir would be the sum of the above 
losses from seepage and from evaporation, diminished by the rain- 
fall, a combined loss which may be considered as a depth of 6 feet 
in one year. 
34. As irrigation reservoirs are usually full for a few months 
only, the loss is much less than this for the high water area. 
