67 



and lower controls differences in flow between these points were 

 computed for 2-hour intervals during a 10-day period when cloudy- 

 weather, with traces of rain, caused periods of minimum evapora- 

 tion and transpiration. On April 19 and again on April 20, 

 evaporation from a Weather Bureau pan at Ontario, approximately 

 20 miles distant, was but 0.04 inch or the equivalent of 0.028 

 inch of lake evaporation. With this low loss from evaporation 

 the consumptive use of water by vegetation in the early morning 

 hours of the same period must have been exceedingly small. With 

 evaporation and transpiration so low as to be negligible the dif- 

 ference in amount of inflow and outflow from the area must neces- 

 sarily be attributed to underflov/ past the lower control, which 

 was thus estimated to be 0.14 cubic foot per second. All remain- 

 ing differences above 0.14 second-foot can be charged to consump- 

 tive use of water by the vegetation. 



A summary of results, given in Table 14, indicates a total 

 loss of 12.9 acre-inches per acre for the 30-day period April 28 

 to May 27, 1929- This was three times the loss from a lake sur- 

 face as indicated by Weather Bureau pan records at Ontario. 

 Figure 8 shows the daily fluctuations in stream flow and the 

 loss of flow due to consumptive use of water by vegetation be- 

 tween the upper and lower controls. The effect of the advancing 

 season in increasing the consumptive use is shown by the diver- 

 gence of the lines representing stream flow at each point of 

 measurement. Comparison of plotted temperature and rate of con- 

 sumptive use by tank vegetation is likewise shown. 



