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v Groundwater dilution effects can only be truly discerned with complicated groundwater monitoring and modeling. According to a scientific paper authored by Shaw and Turyk (1994), reduction of nitrate concentrations in groundwater can occur primarily through dispersion, or by percolating rainwater recharge. Climatic Data: Rainfall versus Evapotranspiration NLS§ 3.2. It is generally and scientifically accepted that when precipitation exceeds evapotrans- piration (Eta), deep percolation of surface rainwater may occur. Evapotranspiration refers to water evaporation that takes place both at the soil surface and transpiration by plants. The following chart illustrates rainfall and evapotranspiration for the Lodi area. Precipitation data was obtained from the Soil Survey of San Joaquin County. The conservative "2 years in 10" data was used and not the "average rainfall" data. Evapotranspiration data was obtained from the California Irrigation Management Information System (CIMIS): TABLE 4 PRECIPITATION AND Eto DATA FOR LODI, CA Month 2 Years in 10 will have more Eto Average Potential Deep precipitation than: (in/mo) (in/mo) (in/day) Percolation (in/mo) January 5.04 1.04 0.03 4.00 February 3.98 1.66 0.06 2.32 March 4.03 2.88 0.09 1.15 April 2.34 4.36 O.14 May 0.72 5.63 0.18 -- June 0.35 6.76 0.22 -- July 0.32 7.91 0.26 -- August 0.34 7.09 0.23 -- September 0.92 5.20 0.17 -- October 1.66 3.56 0.11 -- November 3.98 1.69 0.13 2.29 December 4.43 1.00 0.14 3.43 TOTALS(in.) 23.00 48.78 13.19 8.67 The chart above illustrates that monthly evapotranspiration far exceeds precipitation, even when using higher rainfall data that substantially exceeds normal rainfall data. Only in the months of January, February, March, November and December would deep percolation potentially occur. 6 Chesney Consulting