Ultimate subsidence along Outside Canal in the San Joaquin Valley, California

A 30-mi-long upstream reach of the unlined irrigation Outside Canal in the San Joaquin Valley, California, is affected by subsidence caused by irrigation overdraft of the confined aquifer system. This subsidence interferes with normal operation and maintenance of the canal. Ratios between past subsidence along the Outside Canal and the nearby, better-surveyed Federal Delta-Mendota Canal were graphically obtained for five pairs of points along the canals using: 1) past Federal levelings along the Delta-Mendota Canal and irrigation district levelings along the Outside Canal, and 2) selected subsidence contour maps.--Modified journal abstract.