Water-quality trends in US rivers: Exploring effects from streamflow trends and changes in watershed management

Science of the Total Environment
By:  and 

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Abstract

We present a conceptual model that explores the relationship of streamflow trends to 15 water-quality parameters at 370 sites across the contiguous United States (US). Our analytical framework uses discrete water-quality data, daily streamflow records, and a statistical model to estimate water-quality trends between 1982 and 2012 and parse these trends into the amount of change attributed to trends in streamflow versus changes in watershed management, such as changes in point or non-point sources related to pollution control efforts. We conceptualize a water-quality trend as an additive function of these two trend components. We found that for most of these records the water-quality trends were more strongly affected by changes in watershed management as opposed to trends in streamflow. However, the importance of these trend components on water quality varied by estimate type (i.e. concentration versus load trends), parameter, and site. Trends in load were more influenced by changes in the streamflow regime than trends in concentration. Trends in major ions, salinity, and sediment were more sensitive to changes in streamflow than nutrients. When results were aggregated by site, 25% of the sites had at least 1 parameter where streamflow trends attributed >7.5% to the water-quality trend for concentrations. For loads, this was the case for 66% of the sites. The findings of this work have important implications for the analysis of water-quality trends. Understanding the relative role of streamflow and management changes can help to isolate the effects of pollution control efforts on water quality and provide clearer understanding of progress, or lack thereof, towards water-quality goals.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Water-quality trends in US rivers: Exploring effects from streamflow trends and changes in watershed management
Series title Science of the Total Environment
DOI 10.1016/j.scitotenv.2018.11.255
Volume 656
Year Published 2019
Language English
Publisher Elsevier
Contributing office(s) Lower Mississippi-Gulf Water Science Center
Description 14 p.
First page 645
Last page 658