Water Quality

Nearly all of the surface water entering the District is conveyed through the California Aqueduct. The District provides raw, untreated water for agricultural purposes and there is no regular program for sampling District water as there would be for a potable water supply. It can be assumed, however, that District-supplied water will tend to be similar to Aqueduct water in terms of chemical quality and bacteria content. A good history of Aqueduct water quality can be found in the California State Department of Water Resources (DWR) Water Quality Data Library.


About once per month, the DWR collects grab samples from various points on the Aqueduct. These are analyzed by Bryte Chemical Laboratory for general minerals, general physical characteristics and metals. The closest sampling point and the one most reflective of District water quality is located at DWR’s Teerink Pumping Plant. The Teerink Pumping Plant is located roughly 4.5 miles downstream from Maricopa Highway and 2 miles upstream from the WRM 10 Pumping Plant. Note that water quality can vary significantly from month to month and year to year. For example, electrical conductivity (EC) which is related to salt content, is lower in spring than in the fall and lower in wet water years than dry water years.

Follow the directions below to search for historical Aqueduct grab sample water quality within a selected data range. The Engineering Department can provide assistance upon request.

  1. Click this link
  2. Change the “Search By” to “Station Group”
  3. Go to the Station Group drop down, choose “O&M CA Aqueduct Grab Sample Data”
  4. Click the “Search” button
  5. Put in your desired data range and check the box next to Teerink Pumping Plant (Station Number KA02783)
  6. Click the “Get Data” button


Once per week, the District collects a water sample at its headquarters on Highway 166 to help provide an indication of the amount of coliform bacteria in the California Aqueduct. These samples are only representative of one arbitrary point in the District’s WRM 8 system and are neither intended to suggest fitness for human consumption nor to represent bacterial levels at all points in the Districts 300-mile piped system. Customers that need to know bacteria levels in their process water, wash water, or irrigation water for compliance purposes should collect their own samples downstream from their meter.

Click here for: District Headquarters bacteriological