Figure 5 shows diagraminetlcally the functioning of the 

 Alturas-Dorris Ranch and Coleville evapotranspirometers . 



Davis Evapotranspirometer Measurements . In 1958, three 

 sinall evapotransplrometers 2 feet In diameter v;ere installed at 

 Davis in cooperation v/ith the Department of Irrigation of the Uni- 

 versity of California. The purpose v;as to determine how well thej 

 small tanks would compare v;ith a large 20-foot diameter tank, whic 

 was installed "by the university in 1958. Over a 10-month period,, 

 the mean evapotransplration from the 2- foot evapotransplrometers 

 differed less than 5 percent from the 20- foot evapotranspiromete: 

 One reason for this favorable comparison is that both kinds of 

 tanks were located in the same field environment having a con- 

 tinuous, uniform crop height and cover in and around the tanks. 

 The data from the 2-foot evapotransplrometers are presented in thi 

 report. 



Evapotransplration Data Summary 

 Summaries of evapotransplration for measured and esti- 

 mated periods are tabulated in Table 5, v/lth corresponding measure 

 ments of pan and atmometer evaporation. Evapotransplration for 

 missing periods v;as usually estimated as the pix)duct of approprlat 

 pan or atmometer coefficients, and pan or atmometer evaporation 

 data collected during these periods, plus calculated increments fc 

 surface evaporation follov/ing irrigation. Monthly evapotranspirat.d 

 totals have been computed and are also presented in Table 5- A 

 detailed tabulation of evapotransplration and related data are pre- 

 sented in Tables A-6 and A-7 of Appendix A, for the approximatelv 

 v/eekly measurement schedule. Variability of soil moisture values 



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