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Climatic Data: Rainfall versus Evapotranspiration <br /> NLS§3.2. It is generally and scientifically accepted that when precipitation exceeds <br /> evapotranspiration(Eto), deep percolation of surface rainwater may occur. Evapotranspiration <br /> refers to water evaporation that takes place both at the soil surface and transpiration by plants. <br /> The following Table illustrates rainfall and evapotranspiration for the Tracy area. Precipitation <br /> data was obtained from the Soil Survey of San Joaquin County. The conservative "2 years in 10" <br /> data was used and not the "average rainfall"data. Evapotranspiration data was obtained from the <br /> California Irrigation Management Information System (CIMIS): <br /> TABLE 3 <br /> PRECIPITATION AND Eto DATA FOR TRACY, CA <br /> Month 2 Years in 10 will have more Eto Average Potential Deep <br /> precipitation than: (in/mo) (in/ma) (in/day) Percolation(in/mo) <br /> January 2.93 1.55 0.05 1.38 <br /> February 2.21 2.24 0.08 -- <br /> March 2.38 3.72 0.12 <br /> April 1.51 5.10 0.17 <br /> May 0.71 6.82 0.22 <br /> June 2.09 7.80 0.26 <br /> July 0.28 8.68 0.28 <br /> August 1.05 7.75 0.25 <br /> September 0.84 5.70 0.19 <br /> October 1.06 4.03 0.13 <br /> November 2.10 2.10 0.07 -- <br /> December 2.38 1.55 0.05 0.83 <br /> TOTALS(in.) 13.18 57.0 ------ 2.21 <br /> The Table illustrates that evapotranspiration far exceeds precipitation, even when using higher <br /> rainfall data that exceeds normal rainfall data by 28% (10.33 in. vs. 13.18 in.). Only in the <br /> months of December and January, and possibly November and February would deep percolation <br /> potentially occur. This data illustrates a relatively high potential for there to be significant <br /> evapotranspiration(or bare soil surface evaporation). <br /> Page -5- <br />