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Combined impact of land cover, precipitation, and catchment area on discharge and phosphorus in the Mississippi basin's sub-catchments.

Phosphorus supplies (concentrations and fluxes) are essential drivers for biological activities in rivers and should be controlled to prevent eutrophication that usually results from urbanization and agricultural expansion. In this paper, data from 26 sub-catchments in the Mississippi Basin, the United States, were compiled for the period from 2013 to 2017 to identify how catchment area, precipitation, and land cover affect discharge and total phosphorus (TP), and how TP yield diverges from a generalized local response mode. Results revealed that area-weighted discharge (Qarea ) is controlled by precipitation and land cover (i.e., increases with precipitation and with both urban and forest land covers, and decreases with both shrub/scrub and pasture/grassland covers). TP concentration increases with agricultural land cover and decreases with both forest and water/wetland covers. TP yield (product of Qarea and concentration) is mainly governed by Qarea as the latter changes by a higher order of magnitude compared to concentration in the current study. Hence TP yield is following the same trends that Qarea exhibits with precipitation and land cover. In all catchments, TP yield varied significantly (p < 0.05) and positively with instantaneous discharge. However, the rate of yield variations with discharge exhibited a significant (p < 0.0001) strong negative (r2 = -0.74) correlation with catchment area. This study provided a robust model that can predict the TP concentration and yield across different catchment scales in the Mississippi Basin by means of discharge readings. This article is protected by copyright. All rights reserved.