WATER LOSSES FRO^I WET AREAS 



47 



Since tanks were protected from rainfall durini>' the first two years 

 and exposed dnrinti- the third year, results from tank studies are not 

 entirely comparable. Greater evaporation occurred from tanks subject 

 to rainfall, both from the soil surface and from moisture intercepted 

 by the grass. On a heavy growth of grass, the latter item might be 

 considerable during an entire season. There was every reason to sup- 

 pose that consumptive use of water by crops grown in tanks exposed 

 ro rainfall during the wet season would exceed that used in tanks 

 protected from rain, and the records show this to be true. 



SOIL ALKALI IN TANKS 



Most western soils contain alkali salts in various amounts and the 

 soil at the Santa Ana station was no exception. As the station was pri- 

 marily for the investigation of consumptive use of water by salt grass, 

 which is tolerant of a considerable concentration of salts, no eifect on 

 the rate of transpiration was expected. Several tanks w'ere used for soil 

 evaporation studies, and it is probable that in a few of these gradual 

 deposition of alkali on the tank surface had some influence in reducing 

 the amount of evaporation. The greatest evaporation from any tanks 

 occurred from those holding disturbed soil, although the most alkali 

 was evident on their surfaces. 



As the processes of evaporation and transpiration continued month 

 after month, the original amount of alkali in the soil was increased 

 by constant addition of water to the soil tanks. This water was obtained 

 at the station from a shallow Avell and chemical analysis showed it to be 

 relatively free from injurious salts and in every waj' suitable for 

 tank use. Water used in the experimental work at the San Bernardino 

 station was supplied from an artesian well and was even better for 

 the purpose than that at Santa Ana. Samples of water from the 

 annular spaces of a number of tanks at both stations also were analyzed 

 and the results of both anatyses are shown in parts per million in 

 Table 8. The carbonates are entirely lacking in both water supplies 

 and bicarbonates and sulphates are the principal salts. No accumula- 

 tion of salts is sho-\ra in the water of the annular space as they are 

 carried into the soil for distribution. Apparently water used at the 

 Santa Ana station is fair and the San Bernardino supply is good for 

 irrigation. 



TABLE 8 



ANALYSES OF STATION WATER SUPPLIES AND WATER FROM ANNULAR SPACES OF 

 SOIL MOISTURE TANKS AT SANTA ANA AND SAN BERNARDINO STATIONS' 



' Samples for analysis were collected during October, 1930, except the second well sample at Santa Ana which was 

 taken in January, 1932. 



