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<br />------- <br /> <br />------------ <br /> <br />COLORADO UTE - AGRICULTURAL ENGINEERING STUDY <br /> <br />COMPARISON OF EQUATIONS USED FOR ESTIMATING <br />EVAPOTRANSPIRATION, ADAPTED FROM USBR (l983) <br />TABLE A-l.3 <br /> <br />l'\:) <br />~ <br />00 <br />l\;) <br /> <br />Name <br /> <br />SCS Modified <br />Blaney-Cdddle <br /> <br />FAO Blaney- <br />Cdddle <br /> <br />.... <br />I <br />.... <br />lJ:> <br /> <br />Jensen-Haise <br /> <br />Crop <br />Condition <br />Referenced <br /> <br />N/A <br /> <br />Clipped grass <br /> <br />Alfalfa, 30- <br />to 50-cm <br />growth <br /> <br />Odginal <br />Calibration <br /> <br />Field sampling of <br />soil moisture, avg. <br />for a number of sites <br />throughout U.S. <br /> <br />Lysimeter(grass) at <br />Oavis, Calif. <br /> <br />Lysimeter(alfalfa) <br />& field soil moist- <br />ure data, western <br />U.S. <br /> <br />FAO radiation Clipped grass Lysimeter(grass) at <br />Davis, Calif. <br /> <br />FAD Modi fied <br />Penman <br /> <br />Varies from <br />alfalfa to <br />short grass; <br />depends on <br />parameter values <br /> <br />Lysimeters(grass) at <br />Davis, Calif. <br /> <br />Data <br />Required <br /> <br />Monthly avg. <br />temperature <br /> <br />Oaily to monthly <br />avg. temp.y <br /> <br />Daily avg. temp. <br />& daily solar <br />radiation <br /> <br />Daily avg. temp. <br />& daily solar <br />radiationY <br /> <br />Daily: max. & min. <br />temp. ,avg. dewpt., <br />total wind travel, <br />solar radiation <br /> <br />Minimum <br />Usable Time <br />Increment <br />1/ <br />1 month- <br /> <br />Daily to <br />monthly <br /> <br />Daily <br /> <br />Daily <br /> <br />Daily <br /> <br />Minimum <br />Intended Time <br />Increment <br /> <br />1 month <br /> <br />1 month <br /> <br />5- to 10- <br />day sums <br /> <br />10- to 30- <br />day sums <br />10- to 3D-- <br />day sums <br /> <br />1I Originally developed for annual estimates. <br /> <br />Y Additional data such as humidity, percent sunshine, and wind also ~equired although longer <br />time interval is allowed. <br />