COLORADO STATE UNIVERSITY
Calibration and application of the jensen - haise evapotranspiration equation
TO ESTIMATE THE CONSUMPTION USE OF VARIOUS CROPS USING CLIMATIC DATA, A SUMMARY OF THE PROCEDURE FOR DETERMINING EVAPOTRANSPIRATION AFTER CALIBRATING THE JENSEN-HAISE EQUATION IS AS FOLLOWS: 1) DETERMINE MEAN DAILY TEMPERATURE (T) FROM DAILY MAXIMUM AND MINIMUM TEMPERATURES FOR THE SEASON AND REGION UNDER CONSIDERATION.
Clyma, Wayne; Chaudhary, M. R. · 1970
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Abstract
2) CONVERT THE CORRESPONDING RADIATION VALUES TO EQUIVALENT DEPTH OF EVAPOTRANSPIRATION IN INCHES/DAY (RS USING THE RELATION LANGLEYS/DAY X 0.000673 = INCHES/DAY. 3) SUBSTITUTE THE VALUES OF T AND RS IN THE EQUATION, CALIBRATED FOR THAT REGION AND COMPUTE POTENTIAL EVAPOTRANSPIRATION, E06TP. 4) ACTUAL EVAPOTRANSPIRATION ET CAN BE OBTAINED BY COMBINING ETP WITH KC IN EQUATION. SINCE PLANTS HAVE VERY POOR COVER JUST AFTER PLANTING, ET IS MUCH LESS THAN ETP. HOWEVER THE TWO VALUES TEND TO APPROACH EACH OTHER AS THE CROP GROWS. WHEN PLANTS ARE ASSUMED TO HAVE ATTAINED FULL EFFECTIVE COVER AND KC APPROACHES 1, ET AND ETP ARE NEARLY THE SAME UNTIL MATURATION BEGINS. DURING MATURATION THE TWO CURVES DIVERGE SINCE ET GOES DOWN BECAUSE OF REDUCED PHOTOSYNTHETIC ACTIVITY AND/OR A LIMITED SUPPLY OF WATER.
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