actually drained. Contributions of subsurface drainage from 

 outside Influence were Impossible to quantify. Therefore, 

 any attempt to use the foregoing data to predict drainage 

 from a small area would be erroneous. However, discharges 

 representing several tile systems within a given soil series 

 (Table 17) might be used for predicting drainage from an 

 extensive area where soil conditions aire slmllair. For 

 instance, tile systems in the Tulare Lake aj?ea discharge low 

 volumes of effluent. Further installations in this area can 

 reasonably be expected to do the same. Accordingly, other 

 discharge values given for specific soils under similar soil 

 conditions might be applicable. 



Nutrients 



When drainage from tile systems occupying similar soil series 

 and physiographic positions was composited, the highest 

 nitrogen concentration was shown to occur in the drainage 

 from the Lost Hills soil series (older alluvial fan). 

 Drainage from related Panoche and Panhill soils (recent fans) 

 was the next highest in nitrogen concentration. These three 

 soils represent large alluvial fans along the west side from 

 Mendota to south of Bakersfield. Tile drainage from tile 

 systems located in Sorrento and Rlncon soils was found to be 

 low in nitrogen. These soils also represent substantial 

 acreages of recent and older alluvial fans, respectively, 

 within the northern etrea. 



Drainage composited from tile systems situated in Oxalls and 

 Tuleire soils, which comprise the largest acreage of the basin 

 rim and basin positions, respectively, was rather low in 

 nitrogen. The lowest nitrogen level (4.0 mg/l) was found in 

 drainage from a single tile system in the Willows soil 

 series . 



Relatively high concentrations of phosphorus were observed 

 in the drainage from all of the soil series near Tulare Lake. 

 Foster and Hacienda were slightly higher in phosphorus than 

 was the Tulare series. 



From these comparisons, high nitrogen concentrations in 

 drainage composited from San Joaquin Valley tile systems were 

 found to be associated mainly with Panoche and related soil 

 series located in the Gustine-Mendota area. Tile drains in 

 this area are expected to contribute approximately 36 percent 

 of the total drainage from the Valley by the year 2020, and 

 because nitrogen concentrations are significantly higher in 

 the drainage from this area compared to other major tiled 

 areas, the seasonal Impact upon a drainage facility becomes 

 important . 



64 



