David C. Reutter Jeffrey D. Martin David K. Mueller Melissa L. Riskin 2018 The data-quality objectives for samples collected at surface-water sites in the National Water-Quality Network include estimating the extent to which contamination, matrix effects, and measurement variability affect interpretation of environmental conditions. Quality-control samples provide insight into how well the samples collected at surface-water sites represent the true environmental conditions. Quality-control samples used in this program include field blanks, replicates, and field matrix spikes. This report describes the design for collection of these quality-control samples and the data management needed to properly identify these samples in the U.S. Geological Survey’s national database. application/pdf 10.3133/ofr20181018 en U.S. Geological Survey Quality-control design for surface-water sampling in the National Water-Quality Network reports