USGS Water-Quality Information
USGS personnel collect a water-quality sample on the Missouri River. USGS/Photo by Kelly Brady.
Water Quality Data
National Water Information System (NWIS)
NWIS provides current and historical water-quality data.
Today's Water Conditions
Water-Quality Watch provides continuous real-time water-quality measurements.
Water-Quality Web Services
Web services automate the sharing of USGS and USEPA water-quality monitoring data.
For More Data
Additional water-quality data resources are available.
USGS in Your Area
USGS Water Science Centers are located in each state.
6.4 pH, Version 2.0 dated 10/2008
Revised By G.F. Ritz and J.A. Collins
This section of Chapter 6 is available as a pdf file:
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Measurement of pH is critical to the understanding of the viability and vulnerability of environmental waters and is considered a master variable in determining the aqueous geochemistry of an aqueous system. pH is a measure that represents the hydrogen-ion concentration (activity) of a solution. This section of the National Field Manual (NFM) describes U.S. Geological Survey (USGS) guidance and protocols for measurement of pH in ground and surface waters.
6.4 - pH
6.4.1 Equipment and supplies
6.4.2 Maintenance of pH instruments
6.4.3 Calibration of the pH instrument system
6.4.7 Selected References
Section 6.4 Archived versions: