Laserfiche WebLink
<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />2490 <br /> <br />degrees mean temperature to 28 degrees frost. These dates coincide <br /> <br /> <br />fairly well with the assumed May through mid-October growing season. <br /> <br /> <br />Kt values are calculated by: <br /> <br /> <br />Kt =0.0173 t - .314 (18) <br /> <br /> <br />and p values are taken from Table 1 in TR-2l. Seasonal <br /> <br /> <br />consumptive use for alfalfa using this method is 21.6 inches. <br /> <br />FAa MOdified Blaney-Criddle <br /> <br /> <br />Table A-l.6 is a summary of calculation procedures for monthly <br /> <br /> <br />estimates of E:T by the FAO MOdified Blaney-Criddle method using <br /> <br /> <br />equation (12). Mean daily percentage of annual daytime hours (p) is <br /> <br /> <br />taken from Table 1 in FAO-24. "cn values can be taken from Figure 1 <br /> <br /> <br />with a general knowledge of minimum relative humidity, actual and <br /> <br /> <br />maximum possible sunshine hours, and daytime wind conditions. The <br /> <br /> <br />procedure involves graphical interpolation in 3 dimensions and can <br /> <br /> <br />be simplied (and calculated more accurately) through the use of the <br /> <br /> <br />regression polynomial in Appendix A-l.2. <br /> <br />Mean crop factor for alfalfa for all FAO methods is 0.95 based on a <br /> <br /> <br />grass reference crop. This gives a total May through October ET of <br /> <br /> <br />32.4 inches. These figures are increased 10 percent for each lOOO <br /> <br /> <br />meters of elevation above sea level.l/ Elevation of the Fort Lewis <br /> <br /> <br />station is 7600 foot or 2316 meters. An approximate increase of 20% <br /> <br /> <br />is applied to the data to obtain a total seasonal ET of 37.5 inches. <br /> <br />~.. <br /> <br />l- 27 <br />