89 



An examination of the data suggests that caution be used 

 in extending certain measured losses to wider areas. All tanks 

 were grouped at a central station, but it is extremely doubtful 

 that consumptive use as determined represents field consumptive 

 use of all crops. Crop overhang of vegetation spreading beyond 

 the tank area, as in the sweetclover tanks, without doubt induces 

 the drawing of erroneous conclusions. Likewise, the vertical 

 intercept of insolation varies, and consumptive use is increased 

 for those plants which normally protect themselves by dense growth. 



Studies of Upper Rio Grande Basin — ' 



At the request of the National Resources Committee, the 

 Division of Irrigation in 1936 undertook investigations in the 

 upper Rio Grande Basin in Colorado, New Mexico, and western Texas 

 to determine, among other things, the quantity of water consumed 

 by various species of native vegetation (5). The Division began 

 investigations at Parma, 6 miles east of Monte Vista in San Luis 

 Valley, Colo.; at Isleta, 13 miles below Albuquerque, in Middle 

 Rio Grande Basin; and at Mesilla Dam, 5 miles below State College 

 in Mesilla Valley. Investigations at Mesilla Dam are being con- 

 tinued in cooperation with New Mexico Agricultural Experiment 

 Station. 



San Luis Valley, Colorado 



Tules and grasses . --The general arrangement of the Parma 

 station is shown in Figure 10. Tules and native meadow grasses 

 were transplanted into ground tanks, each being surrounded by 

 areas of similar growth. Tules in tank No. 1 and meadow grass in 

 tank No. 2 stood in shallow water above the soil surface. Tank 

 No. 3 was equipped with a Mariotte supply bottle to maintain a 

 water table 8 inches below the soil level, but this was not always 

 possible because of rains. 



1/ This investigation was conducted by Harry F. Blaney, Irri^ 

 tion Engineer, Division of Irrigation. 



