Methods of discharge compensation as an aid to the evaluation
of water-quality trends
Journal Article
By Douglas A. Harned, C. C. Daniel, III, and J. K. Crawford
Abstract
Two new methods are described for compensating for discharge when evaluating trends in water quality data. One method, discharge normalization, adjusts daily discharges using a central value calculated
for the period of record and recalculates daily specific conductance from the adjusted discharges and discharge versus specific conductance regressions. Normalized concentrations for many constituents can
then be calculated from linear relationships between specific conductance and constituent concentrations.
The second method, discharge-frequency weighting, weights each observed concentration by a fraction
of the total area underneath the discharge-frequency distribution of the period of record. This fraction is
determined using the stream discharge at the time of sampling and the discharge-frequency distribution
for the period of record. The weighted concentrations are summed for each year. Both normalized values
and weighted values can be plotted against time to produce trends essentially independent from discharge effects. Results from the methods are statistically similar to each other and to results from other
trend detection techniques.
Citation:
Harned, D.A., Daniel, C.C., III, and Crawford, J.K., 1981, Methods of discharge compensation as an aid to the evaluation of water-quality trends: Water Resources Research, v. 17, no. 5, p. 1389-1400.
For more information, contact |
To order printed copies, contact |
North Carolina Water Science Center
U.S. Geological Survey
3916 Sunset Ridge Road
Raleigh, North Carolina 27607
(919) 571-4000
E-mail
|
North Carolina Water Science Center
U.S. Geological Survey
3916 Sunset Ridge Road
Raleigh, North Carolina 27607
(919) 571-4037
E-mail
|
U.S. Geological Survey
Information Services
Box 25286, Federal Center
Denver, CO 80225
1-888-ASK USGS
|
|