Effective and Critical Placement of Tile Drain 



Whenever possible, tile drainage systems are strategically 

 placed within a field or airea to alleviate high water table 

 conditions and to prevent their recurrence. At times, 

 subsurface water moving laterally through an aquifer can be 

 Intercepted by critical placement of the conduit. Instead 

 of by tiling an entire field (total relief). The choice of 

 method Is usually decided by farm operators who are guided 

 by advice from drainage specialists. Several tile drainage 

 systems In the northern area have been strategically located 

 to Intercept lateral water movement through former submerged 

 streambeds. Many tile systems In the Gustlne-Mendota area 

 have been placed to Intercept lateral movement from canals. 



Physiographic Positions 



The drains located along the west side of the San Joaquin 

 Valley are found associated with soils occupying three 

 commonly recognized physiographic positions (6). Those 

 positions are the "alluvial fan", which extends from the 

 base of the surrounding foothills nearly to the edge of the 

 valley floor; the "basin rim", a relatively narrow band of 

 alluvial, saline soils which lie between the more recent 

 alluvial soils and the soils of the basin; and the "basin" 

 or lowest central part of the valley floor. The alluvial 

 fan Is often divided Into the "recent fan deposits", usually 

 occurring In low-lying sites subject to fairly recent stream 

 overflow, and "older alluvial fans" occurring at higher 

 elevations. The manner of soil formation causes soil charac- 

 teristics to differ widely from one physiographic position 

 to another. 



Recent Alluvial Fan 



Soils In recent alluvial fans have been deposited by recent 

 flooding of Intermittent streams from older alluvium and 

 parent materials at higher elevations. They are derived 

 from out-wash materials, mostly sandstone and shale rock, 

 and generally owe their characteristics to the character of 

 the stratified parent material. Time has not permitted the 

 formation of well -developed horizons within the solum. 

 (Developed soils are those which exhibit clay movement from 

 the surface horizon and clay accumulation In the lower 

 horizon. ) 



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