DRAINAGE LOAD-FLOW RELATIONSHIPS IN ARID IRRIGATED AREAS

The load-flow relationship of salt in drainage water was studied using drainage water flow and salinity data from an irrigation district on the west side of the San Joaquin Valley of California. Flow and salini ty data were collected from the main district drain, individual draina ge sumps, and two field sites. Linear regression was used to describe the salt load-flow relationship at each drainage site. The slope of th e regression line for the salt flow in the main drain was different co mpared to the subsurface drainage sites because of the inclusion of su rface runoff from irrigation in the main drain. The EC in the water fr om the subsurface drains was not correlated with the flow rate. Cluste r analysis of the load-flow relationships of 45 individual drainage su mps indicated that the load-flow relationship for flow from the distri ct could be characterized by one of three relationships.