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actual ET. The actual ET is almost always less than the potential evapotranspiration. <br />potential evapotranspiration was estimated by using both the Turc's method and the <br />FAO -24 pan method. The Turc's method was rated second over 20 different methods for <br />humid locations (Committee on Irrigation Water Requirements of the Irrigation and Drainage <br />Division of the ASCE 1990). The FAO -24 pan method was rated 17th, but it was the highest <br />rated pan evaporation method. When the Turc's method is expressed on a daily basis in <br />mm•d 1 of evaporated water the equation is: <br />T (50 - RH) (3) <br />PET = 0.013 - (RS + 50) 1 + <br />(T + 15) 1 70 <br />where T is the average temperature in °C, R. is the solar radiation in cal- cm2•d-', and RH is <br />the relative humidity for values < 50 % or set equal to 50 % for RH values ? 50 %. For our <br />analysis T was converted to OF and PET was converted to inches per day. <br />The equation for the FAO -24 pan method is: <br />PET = k • E (4) <br />p pan <br />where Epan is the daily pan evaporation in inches, and the pan coefficient kp is calculated from <br />the following formula when the upwind area had green vegetation: <br />k = 0.108 - 0.000331•U2 + 0.0422•ln(Fetch) + 0.1434•ln(RHm =) <br />- 0.000631 • [ln(Fetch)]2• [ln(RHm�)] <br />The limits for equation 5 are: <br />30 <_ RHmean < 84 % <br />84 < U2 <_ 700 km•d71, where U2 = wind at 2 m above soil <br />1 <_ Fetch <_ 1000 m <br />The above limits were set to their respective limit if the value exceeded its bounds. <br />Evapotranspiration from the water table was estimated with a method described by <br />Gerla (1992). This method uses the daily cycle of water table drawdown and recoveries <br />caused by ET and groundwater flow to obtain an estimate of the ETwT rate (qET), and the <br />ground - and soil-water flow rate near the well (%v). The following matrix equation describes <br />22 <br />