irrigated pasture mixes and in native mountain meadows. The pas- 

 ture was grazed nearly continuously by cattle, and was usually short 

 but fully covered the ground. Typical percentages of green growin-: 

 leaf surfaces were as follows: In April, 40 percent, increasing to 

 100 percent by the end of the month; May through September, 100 per- 

 cent; October, 100 percent, decreasing to 50 percent by the end of 

 the month. Cover of green foliage varies between zero and 40 per- 

 cent during the winter, depending to a large extent upon the severit 

 of the winter. In milder v/inters, some green live shoots survive, 

 while in severe winters the foliage is completely Inactive, and the 

 green color is gone. 



The evapotranspirometer site v;a5 enclosed by a barbed- 

 wire fence forming a 25- by 75- foot rectangle. Inside the fenced 

 area the grass was mowed several times during the season to main- 

 tain approximately a 5-inch height. Two cylind-^ical steel evapo- 

 transplrometers, 36 Inches in diameter and 30 Inches deep, were 

 installed in the soil within a fenced area, one at each end. Also, 

 inside the plot were a hygrothermograph and evaporation pan, at- 

 mometers, phyheliometer, and a precipitation gage. 



V/ater was supplied to the evapotranspirometers by means 

 of a steady, small flow, at a rate calculated to exceed evapotran- 

 spiratlon. It took approximately one week to utilize the water from 

 a cylindrical supply tank 5 feet deep and l8 Inches in diameter. A 

 discharge tube was attached to the evapotranspirometer 6 inches be- 

 low the ground surface, and the excess water not consumed in the 

 transpirometer spilled into a buried sump tank, where it was measurei 



The numerous mechanical problems encountered during the 

 first 2.5 years rendered the collected data of questionable validity 



-38- 



