The design of sampling transects for characterizing water quality in estuaries

Estuarine, Coastal and Shelf Science
By: , and 



The high spatial variability of estuaries poses a challenge for characterizing estuarine water quality. This problem was examined by conducting monthly high-resolution transects for several water quality variables (chlorophyll a, suspended particulate matter and salinity) in San Francisco Bay (California, U.S.A.). Using these data, six different ways of choosing station locations along a transect, in order to estimate mean conditions, were compared. In addition, 11 approaches to estimating the variance of the transect mean when stations are equally spaced were compared, and the relationship between variance of the estimated transect mean and number of stations was determined. The results provide guidelines for sampling along the axis of an estuary: (1) choose as many equally-spaced stations as practical; (2) estimate the variance of the meanyby var (y)=(1/10n2nj=2(yjyj−1)2, wherey1, . . .,ynare the measurements at thenstations; and (3) attain the desired precision by adjusting the number of stations according to var(y)α1/n2. The inverse power of 2 in the last step is a consequence of the underlying spatial correlation structure in San Francisco Bay; more studies of spatial structure at other estuaries are needed to determine the generality of this relationship.

Publication type Article
Publication Subtype Journal Article
Title The design of sampling transects for characterizing water quality in estuaries
Series title Estuarine, Coastal and Shelf Science
DOI 10.1006/ecss.1996.0199
Volume 45
Issue 3
Year Published 1997
Language English
Publisher Elsevier
Contributing office(s) California Water Science Center, San Francisco Bay-Delta, Toxic Substances Hydrology Program, Pacific Regional Director's Office
Description 18 p.
First page 285
Last page 302
Online Only (Y/N) N
Additional Online Files (Y/N) N
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