Total Phosphorus trends in Mississippi and Atchafalaya River Basin Watersheds: Exploring the roles of streamflow and watershed features 2000-2020
Posted by Keenan Ganz
Score:
Importance – 4
Strength of Evidence – 4
Clarity – 4
Overall summary: High phosphorus (P) concentration in streams contributes to hypoxia in downstream waterbodies. This problem is especially pronounced in the Mississippi-Atchafalaya River Basin. Various management strategies have been deployed in the basin, but determining their effectiveness is difficult because P load is driven by both year-to-year variation in streamflow and watershed conditions. To disentangle these factors, the authors used the modeling technique WRTDS on a harmonized dataset of streamflow and P load in the MARB over a 20-year period. They found that most sites had decreasing P concentration, but increasing P yield. P yield was highest in urban and cultivated sites. Trends were dominated by non-streamflow factors, especially in the center of the basin.
Critique: The paper demonstrates that management strategies have had little overall effect on P load in the MARB. Although P concentration decreased in some places, P yield has actually increased in most places. Correlation analysis revealed that P load was related to landcover type as would be expected based on past research. These findings are discussed in isolation from specific policies that may explain some of the geographic variation identified with cluster analysis. Without this connection, the paper cannot recommend a course of action for improved management of the MARB.
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