Forecasting Productivity of Irrigable Lands

In 1941, Robert L. Lowry, Jr., M. ASCE, and Arthur F. Johnson, Assoc. M. ASCE, working with the United States Bureau of Reclamation, produced a heat-unit method of estimating the consumptive use of water for agriculture.2 The writer considers this a sound and workable method, giving very consistent results from long-term records. Since the only requirement is a United States Weather Bureau record of reasonable length in, or representative of, the area under consideration, the method may be applied anywhere in the western part of the United States. The formula is easily and simply resolved, and the very consistent results, when checked against many determinations by other methods, give an accuracy satisfactory for use in preliminary estimates. As shown by J. L. Burkholder,3 M. ASCE, in his discussion of the Lowry-Johnson paper, the line produced is the median of a band covering the range of divergence of individual years from the average.