SECTION II 

 INTRODUCTION 



This report describes the nutrient monitoring Investigations 

 conducted over a period of ten yesirs, from 1959 through 

 1969, the greatest emphasis being placed on the more Inten- 

 sive Investigations conducted recently. 



Intensive Investigations of nutrients In San Joaquin Valley 

 agricultural subsurface (tile) drainage were undertaken from 

 May 1959 through June 19d9, as part of the San Joaquin 

 Valley Drainage Investigation (l). 



Area of Investigation 



Drainage problems have existed for some time In many areas 

 within the trough of the San Joaquin River Basin and the 

 Tulare Lake Basin. However, during the last two decades 

 severe high water table conditions have increased in many 

 areas where subsoil permeability is restricted and irriga- 

 tion has been intensive. Existing high salt concentrations 

 in subsurface water have caused extensive damage to crops 

 and rendered large acreages nonproductive. The use of sub- 

 surface drains as a practical means of alleviating high 

 water table conditions was initiated in the San Joaquin 

 Valley 20 years ago, following many years of successful 

 operation in the Imperial Valley . 



Now more than 34,000 acres are directly subjected to tile 

 drainage within the San Joaquin Valley; a much larger acre- 

 age may actually be benefited because tile systems intercept 

 lateral movement of subsurface waters from adjacent and 

 upslope areas. Installation figures obtained from the U. S. 

 Department of Agriculture indicate that new tile systems 

 have been installed at an average rate of about 200,000 

 linear feet per year in the valley areas. In addition, a 

 massive network of tile drains covering 300,000 acres has 

 been planned by the Westlands Water District for the Federal 

 San Luis Unit Service Area in western Fresno and Kings 

 Counties . Although drainage problems exist to some extent 

 in every county on the valley floor, tile installation has 

 progressed most rapidly in portions of San Joaquin, Stanis- 

 laus, Merced, Fresno, and Kings Counties. Tile drains in 

 San Joaquin County are situated along the west side, between 

 the towns of Byron and Westley; in Stanislaus County, 

 between Westley and the town of Gustine; in Merced County 

 and northwest Fresno County, between the towns of Gustine 

 and Mendota; and in Kings County, west of the City of 

 Corcoran, on the northeastern shore of the old Tulare lakebed, 



