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Climatic Data: Rainfall versus Evapotranspiration <br /> NLS§3.2. It is generally and scientifically accepted that when precipitation exceeds evapotrans- <br /> piration (Eto), deep percolation of surface rainwater may occur. Evapotranspiration refers to water <br /> evaporation that takes place both at the soil surface and transpiration by plants, and is defined as <br /> water loss from a large field of 4-to-7 inch tall, cool-season grass that is not water stressed. <br /> The following Table illustrates rainfall and evapotranspiration for the Stockton 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 5 <br /> PRECIPITATION AND Eto DATA FOR STOCKTON, CA <br /> Month 2 Years in 10 will have more Eto Average Potential Deep <br /> precipitation than: (in/mo) (in/mo) (in/day) Percolation (in/mo) <br /> January 4.42 1.24 0.04 3.18 <br /> February 3.20 1.96 0.07 1.24 <br /> March 3.43 3.41 0.11 <br /> April 1.92 5.10 0.17 <br /> May 0.50 6.82 0.22 <br /> June 0.25 7.80 0.26 <br /> July 0.23 8.06 0.26 <br /> August 0.40 7.13 0.23 <br /> September 0.76 5.40 0.18 <br /> October 1.39 3.72 0.12 <br /> November 3.31 1.80 0.06 1.51 <br /> December 3.67 0.93 0.03 2.74 <br /> TOTALS (in.) 18.92 53.4 ------ 8.67 <br /> Table 5 illustrates that evapotranspiration far exceeds precipitation, even when using higher <br /> i' rainfall data that exceeds normal rainfall data by 28% (10.33 in. vs. 13.18 in.) Only in the months <br /> 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) from the disposal area. <br /> 7 <br />