13 Jun 2024
 | 13 Jun 2024
Status: this preprint is open for discussion.

Novel Statistical Analysis Illustrates Importance of Flow Source for Extreme Variation in Dissolved Organic Carbon in a Eutrophic Reservoir in the Great Plains

Anthony A. P. Baron, Helen M. Baulch, Ali Nazemi, and Colin J. Whitfield

Abstract. Long-term dissolved organic carbon (DOC) trends have been observed across many regions of the Northern Hemisphere, yet the drivers of these trends are not universal. Elevated DOC concentrations are a major concern for drinking water treatment plants that draw from freshwaters, owing to effects on disinfection byproduct formation, risks of bacterial regrowth in water distribution systems, and increasing treatment costs. Using a unique 30-year data set encompassing both extreme wet and dry conditions in a eutrophic drinking water reservoir in the Great Plains of North America, we investigate the effects of changing source water and in-lake water chemistry on DOC. Using wavelet coherence analyses and generalized additive models of DOC, we find DOC concentration was significantly coherent with flow from a large upstream mesotrophic reservoir. DOC was also coherent with sulfate, total phosphorus, ammonium, and chlorophyll a concentrations across the 30-year record. These variables accounted for 56 % of the deviance in DOC from 1990 to 2019, suggesting that water source and in-lake nutrient and solute chemistry are effective predictors of DOC concentration. Clearly, climate and changes in water and catchment management will influence source water quality in this already water-scarce region. Our results highlight the importance of flow management to shallow eutrophic reservoirs. They also highlight a key challenge where wet periods can exacerbate water quality issues and these effects can be compounded by reducing inflows from systems with lower DOC. These flow management decisions address water level and flood risk concerns but have important impacts on drinking water treatability.

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Anthony A. P. Baron, Helen M. Baulch, Ali Nazemi, and Colin J. Whitfield

Status: open (until 08 Aug 2024)

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  • RC1: 'Comment on egusphere-2024-1503', Anonymous Referee #1, 18 Jun 2024 reply
  • RC2: 'Comment on egusphere-2024-1503', Anonymous Referee #2, 12 Jul 2024 reply
Anthony A. P. Baron, Helen M. Baulch, Ali Nazemi, and Colin J. Whitfield
Anthony A. P. Baron, Helen M. Baulch, Ali Nazemi, and Colin J. Whitfield


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Short summary
We worked to understand how climate variability and flow management affected water quality in a key drinking water source. Our focus was on dissolved organic carbon, or DOC, and our work demonstrates that DOC can change rapidly, reaching high concentrations in wet periods, when flow sources are dominated by the local catchment. Results indicate that the impacts of high local flow, and low inflows from managed sources are compounding water quality challenges, creating issues for water treatment.