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WATER RESOURCES RESEARCH,
VOL. 35, NO. 12,
PAGES 3747–3759,
1999
Influence of Various Water Quality Sampling Strategies on Load Estimates for Small Streams
Dale M. Robertson
Water Resources Division, USGS, Middleton, Wisconsin
Eric D. Roerish
Water Resources Division, USGS, Middleton, Wisconsin
Abstract
Extensive streamflow and water quality data from eight small streams were systematically subsampled to represent various
water-quality sampling strategies. The subsampled data were then used to determine the accuracy and precision of annual
load estimates generated by means of a regression approach (typically used for big rivers) and to determine the most
effective sampling strategy for small streams. Estimation of annual loads by regression was imprecise regardless of the
sampling strategy used; for the most effective strategy, median absolute errors were ∼30% based on the load estimated
with an integration method and all available data, if a regression approach is used with daily average streamflow. The
most effective sampling strategy depends on the length of the study. For 1-year studies, fixed-period monthly sampling
supplemented by storm chasing was the most effective strategy. For studies of 2 or more years, fixed-period semimonthly
sampling resulted in not only the least biased but also the most precise loads. Additional high-flow samples, typically
collected to help define the relation between high streamflow and high loads, result in imprecise, overestimated annual
loads if these samples are consistently collected early in high-flow events.
Received 2
February
1999;
accepted 7
September
1999.
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Citation: Robertson, D. M., and E. D. Roerish
(1999),
Influence of Various Water Quality Sampling Strategies on Load Estimates for Small Streams,
Water Resour. Res.,
35(12),
3747–3759.
This paper is not subject to U.S. copyright. Published in 1999 by the
American Geophysical Union.
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