39 



CHAPTER 4 



INVESTIGATIONS OF THE DIVISION OF IRRIGATION 



BASIS AND SCOPE OF STUDIES 



Consumptive use of water by noncrop plants has been the 

 subject of investigations by the Division of Irrigation in cooper- 

 ation with the Division of Water Resources, Department of Public 

 Works, State of California, and other agencies for a number of 

 years. Few native plants have been studied, however, as they are 

 far too numerous for all species to be included in these investi- 

 gations. Grasses, small shrubs, and swamp vegetation may be grown 

 in tanks, but larger shrubs and trees present problems in consump- 

 tive-use measurements that are seldom studied. 



As an adjunct of such investigations, records of tempera- 

 ture, precipitation, evaporation, and wind movement are of value. 

 Such records for the Santa Ana station, Calif. , appear in Table 2. 



Knowledge of consumptive use of water by native growth is 

 most needed for moist areas containing potential water supplies. 

 In closed basins water that may be recoverable amounts to a con- 

 siderable portion of the annual evaporation and transpiration 

 losses. The natural growth of such areas is usually limited to 

 grasses and water-loving shrubs and trees. Saltgrass, found on 

 moist land, has been grown by the Division of Irrigation and 

 other investigators in tanks having both fixed and fluctuating 

 water tables. 



Santa Ana Valley, California — ' 



In 1929, the Division of Irrigation in cooperation with 

 the State Division of Water Resources undertook an investigation 

 in the Santa Ana River Valley to measure the consumptive use of 



17 Field investigations at the Santa Ana, Prado, and San Bernar- 

 dino stations were made by Arthur A. Young, Associate Irrigation 

 Engineer, Division of Irrigation in cooperation with the Division 

 of Water Resources, Department of Public Works, State of Calif or- 

 lia. 



