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Sources of Nitrate <br /> Septic systems and dairies have been found to be the most significant sources of nitrate <br /> in ground water. Orchards that require fertilization in sandy soils are also a significant <br /> source of nitrate contamination in shallow or sandy aquifers in San Joaquin County. <br /> Contribution of Rainfall <br /> An estimate of the quantity and quality of rainfall was required for the nitrate loading <br /> analysis. An estimate of the deep percolation of rain was based a calculation using <br /> average monthly precipitation of rainfall and evapotranspiration rates for the area. The <br /> calculation first determines whether the average monthly precipitation exceeds average <br /> monthly potential evapotranspiration. If so, then the difference is potential deep <br /> percolation. This method does not consider runoff. Based on the calculation shown in <br /> the following table, the deep percolation of rain (recharge) for the Lodi, California area is <br /> found to be 6.58 inches per year. <br /> 3 z- <br /> Table 3. Estimate of Deep Percolation of Rainfall for Lodi, CA. <br /> Average Rain- Average Potential Annual Potential Deep <br /> Month Fall inches Eva Percolation of Rain <br /> (inches) Evapotranspiration (inches) (inches) <br /> January 3.43 0.79 2.64 <br /> February 2.94 1.55 1.39 <br /> March 2.71 3.28 None <br /> April 1.30 5.17 None <br /> May 0.61 6.58 None <br /> June 0.15 7.51 None <br /> July 0.03 7.87 None <br /> August 0.04 6.85 None <br /> September 0.27 5.11 None <br /> October 0.93 3.29 None <br /> November 1.93 1.54 0.39 <br /> December 2.92 0.76 2.16 <br /> Totals 17.23 50.3 6.58 <br /> Notes: CIMIS evapotranapkation information at wwwcimis.water.ca.gov/canis/for station 166 Lodi,CA. Rainfall <br /> average from station 045032(Lodi,CA)at www.wrcc.dri.edu.Closest available stations to Site were selected. <br /> �' LOGE 1301 Page 9 <br />