Synoptic Surveys

Three synoptic surveys were made of the 60 miles of San Joaquin River in this study:

1. August 22 – September 7, 2007 [ Location , Data ]
2. August 11-21, 2008 [ Location , Data ]
3. September 22-25, 2008 [ Location , Data ]

The first synoptic survey included the collection of data at 30 transects, distributed fairly evenly over the 60 river miles with the exception of a concentration of transects near the Modesto WWTP ponds. At each transect, water quality samples and head differences were collected at 1’ and 3’ depths at the 20% and 80% points across the river. Temperature profiles were collected at about 10 evenly spaced points across the transect at 1’ intervals up to depths of 6’. Field measurements of temperature, pH, DO, and EC were made at the four water quality sample collection points. The water quality samples were analyzed in the laboratory for nutrients, organic carbon, major ions, trace elements, nitrogen gas, and a variety of isotopes.

The second synoptic survey included the collection of data at 30 transects, with 20 transects being evenly distributed over the 60 river miles and 10 transects being clustered upstream and downstream of 5 transects of interest from the first synoptic. At each transect, water quality samples and head differences were collected at 1’ and 6’ depths at the 20%, 50%, and 80% points across the river. Temperature profiles and water quality sampling was done the same as in the first synoptic. In addition, we collected a sediment core of 9” to 24” at the three points in each transect (20%, 50%, and 80%). The cores were evaluated for grain size and color and a composite sample was collected for analysis of percent carbon.

The third synoptic was an evaluation of the longitudinal variability at the 6 fixed in-stream sites with monitoring wells. At the 6 sites, samples were collected at the 50% point at the fixed site and at two sites upstream (0.1 mile and 0.2 mile) and two sites downstream. At the 50% point, all the same measurements were made as during the second synoptic.

Releases were being made to the river from the Delta Mendota Canal via the Newman Wasteway as part of the USBR/DWR DMC Recirculation Study during both the first and second synoptic surveys. During the first survey the release of relatively clean water (about 500 umhos/cm EC) was about 50 cfs and during the second the release was a constant 200 cfs.