Selection of methods for the detection and estimation of trends in water quality

Journal Article · Wed May 01 04:00:00 EDT 1991 · Water Resources Research; (United States)

DOI:https://doi.org/10.1029/91WR00259· OSTI ID:6030641

Hirsch, R M; Alexander, R B; Smith, R A ^[1]

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1. Geological Survey, Reston, VA (United States)

One result of increased scientific and public interest in water quality over the past few decades has been the gradual accumulation of reliable long-term quality data records and an interest in examining these data for long-term trends. This paper summarizes and examines some of the major issues and choices involved in detecting and estimating the magnitude of temporal trends in measures of stream water quality. The first issue is the type of trend hypothesis to examine: step trends versus monotonic trend. The second relates to the general category of statistical methods to employ: parametric versus nonparametric. The third issue relates to the kind of data to analyze: concentration data versus flux data. The fourth relates to issues of data manipulation to achieve the best results from the trend analysis. These issues include the use of mathematical transformations of the data and the removal of natural sources of variability in water quality due to seasonal and stream discharge variations. The final issue relates to the choice of a trend technique for the analysis of data records with censored or less than values. The authors' experiences during the past decade with the development of several trend detection techniques and application of these techniques to a large number of water quality records provide insight into the issue related to a choice of a statistical test for trend in water quality.

• OSTI ID: 6030641
• Journal Information: Water Resources Research; (United States), Journal Name: Water Resources Research; (United States) Vol. 27:5; ISSN 0043-1397; ISSN WRERA
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540320* -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
DATA ANALYSIS
ENVIRONMENTAL QUALITY
MEASURING METHODS
SEASONAL VARIATIONS
STREAMS
SURFACE WATERS
VARIATIONS
WATER QUALITY