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Groundwater Data & Monitoring

South Central Region
Groundwater Quality Monitoring

Shallow Groundwater and Electrical Conductivity

To help identify and monitor areas of shallow, poor quality groundwater, the District collects elevation and water quality data from a network of observation wells. Two parameters commonly collected in this work are depth to groundwater and electrical conductivity.

Shallow groundwater is characterized as an area where the water table is within 20 feet of the ground surface at any time during the year. Because inadequate drainage accumulates salts within a rising groundwater table, the San Joaquin Valley Drainage Program identifies and separates shallow groundwater into two problem areas, 1) a "present problem area" is defined as a location where the water table is within 5 feet of the ground surface and, 2) a "potential problem area" indicates the water table is between 5 and 20 feet below the ground surface. See shallow groundwater study area map:

   Water Agencies within the San Joaquin Valley Shallow Groundwater Study Area (PDF, 8.23MB)

Electrical Conductivity is a measure of the ability to conduct an electrical current through a given solution and is used to indicate the total salt content, or Total Dissolved Solids, for a given water at a specific site. The more salts in the water, the better conductor it becomes. The strength of the electrical current is dependent upon the temperature of the solution and type and concentration of ion within the solution. EC and TDS, in conjunction with other parameters such as SAR, and total hardness, are used to determine the suitability of water for agriculture.

Available Shallow Groundwater & Electrical Conductivity contour maps for the San Joaquin Valley drainage area:

   2002 Shallow Groundwater Map with close up plates (PDF, 2.8MB)
   2005 Electrical Conductivity Map (PDF, 3.0MB)
   2001 Electrical Conductivity Map (PDF, 2.0MB)

The table below lists shallow groundwater and electrical conductivity contour maps for the five study areas in the San Joaquin Valley. In addition, a map illustrating the change in elevation of shallow groundwater from 1991 to 1997 is also available below. See our base map for an overview of the study areas.

Subarea
Shallow Groundwater
Electrical Conductivity
Kesterson 1991 / 1997 / 1998 / 1991-97 change
1999 / 2000
Dos Palos/Mendota 1991 / 1997 / 1998 / 1991-97 change
1999 / 2000
Lemoore/Corcoran 1991 / 1997 / 1998 / 1991-97 change
1999 / 2000
Lost Hills/Semitropic 1991 / 1997 / 1998 / 1991-97 change
1999 / 2000
Kern Lakebed 1991 / 1997 / 1998 / 1991-97 change
1999 / 2000

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