Representative periods are readily apparent when both the monitor and operations data are
incorporated (Figure 6). Data falling outside the "window" that defines representative periods,
generally resulting from changes in project operations, are not included in final reporting as they
are not reflective of the parameters of concern.
a. May 31-June 30, 1995
b. June 18-19, 1995
Figure 6. Hartwell Dam operation and release temperatures
A large equilibration period (longer than 20 minutes) may be required by some instruments before
accurate measurements are possible. This is especially true for gas measuring instruments such as
DO or total dissolved gas sensors. Instrument and design limitations such as these should be
considered during the final analysis, particularly in situations where rapid changes are experienced.
Case Studies
Continuous, automated monitors are presently being used by the Corps to monitor the release
water quality of the hydropower projects on the Savannah River forming the Georgia/South
Carolina border, the tailwater conditions during periods of no release at St. Stephen Dam on the
Cooper River in South Carolina, the effectiveness of turbine venting procedures at Bull Shoals
Dam on the White River in Arkansas, the total dissolved gas concentrations at various projects
throughout the Columbia and Snake River systems, and at other projects throughout the United
States. The monitoring goals, parameters of concern, and available funding vary significantly
from project to project; however, the overall goal--to collect representative data--is common to
all. The case studies discussed below demonstrate some of the techniques that have been used to
ensure sample reflectiveness at various projects.
Richard B. Russell Dam
Richard B. Russell Dam is a Corps generation/pumped storage project located on the
Savannah River between the Corps reservoirs of Hartwell and J. S. Thurmond (Figure 4). The
Russell monitor measures release water quality for the purpose of maintaining a release DO
concentration of 6.0 mg/L. The Corps operates an oxygen injection system in Russell forebay to
maintain this concentration during the summer months when hypolimnetic DO concentrations
approach anoxia. The 6.0 mg/L DO concentration requirement applies to the release and not to
the tailrace or tailwater conditions; therefore, the sampled water must reflect the Russell release
and not the conditions of the Thurmond headwater.
8
Water Quality Technical Note AM-02 (January 1998)
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