Statistical Evaluation of the Influence of Flow Conditions and Sampling Techniques on Water Quality Data

Abstract

The purpose of this study is to statistically evaluate the influence of various sampling methodologies and flow conditions on the quality and comparability of total phosphorus concentration data collected over the course of 27 months at the South Florida Water Management District (SFWMD) S-65E structure. The data was obtained from the following sampling methodologies: U.S. Geological Survey (USGS) (Reston, Virginia) equal width increment spatially composite grab samples, USGS replicate samples, SFWMD grab samples, and SFWMD autosampler samples. Both significant and insignificant differences were reported from these comparisons. Parametric and nonparametric standard statistical tests for significance were carried out to evaluate the differences between the data. To avoid invalid conclusions of insignificant differences, we conducted tests for equivalence of the means and variances. The results from the data analysis revealed that both flow conditions and sampling methodology affected the water quality data. Water Environ. Res., 79, 147 (2007).

Estimates of sediment and nutrient loads in 10 major catchments draining to the Great Barrier Reef during 2006–2009

“…The representativeness of sampling also has limitations, for instance, grab samples may not be fully representative of the entire cross-section of a stream (Martin et al, 1992;Daas et al, 2007). In addition, errors in flow measurement are acknowledged but not quantified (e.g.…”

Development and Demonstration of a Free Surface Flow‐Dependent Sampling Technology

“…Statistical assessment of water quality data at the S‐65E structure indicated significant differences and inconsistency in nutrient concentrations ( Daas et al, 2007 ). The evaluation showed that currently used water sampling techniques are inadequate because of deficiencies in functionality and sensitivity to flow conditions at the structure.…”