Long-term decreases in phosphorus and suspended solids, but not nitrogen, in six upper Mississippi River tributaries, 1991–2014

Environmental Monitoring and Assessment
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Abstract

Long-term trends in tributaries provide valuable information about temporal changes in inputs of nutrients and sediments to large rivers. Data collected from 1991 to 2014 were used to investigate trends in total nitrogen (TN), total phosphorus (TP), nitrate (NO3–N), soluble-reactive P (SRP), and total suspended solids (TSS) in the following six tributaries of the upper Mississippi River: Cannon (CaR; Minnesota (MN)), Maquoketa (MR; Iowa (IA)), Wapsipinicon (WR; IA), Cuivre (CuR; Missouri (MO)), Chippewa (ChR; Wisconsin (WI)), and Black (BR; WI) rivers. Weighted regression on time discharge and season was used to statistically remove effects of random variation in discharge from estimated trends in flow-normalized concentrations and flux. Concentration and flux of TSS declined in all six rivers. Concentration of P declined in four of the rivers, and P flux declined in five rivers. Concentration and flux of N exhibited small changes relative to TP. TN concentration and flux did not change substantially in four of the rivers and decreased in two (ChR, CuR). Nitrate concentration and flux increased in three rivers (ChR, BR, CaR) and remained relatively constant in the other three rivers. General declines in P and TSS suggest that improvements in agricultural land management, such as the adoption of conservation tillage and enrollment of vulnerable acreage into the Conservation Reserve Program, may have reduced surface runoff; similar reductions in N were not observed.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Long-term decreases in phosphorus and suspended solids, but not nitrogen, in six upper Mississippi River tributaries, 1991–2014
Series title Environmental Monitoring and Assessment
DOI 10.1007/s10661-016-5464-3
Volume 188
Year Published 2016
Language English
Publisher Springer
Contributing office(s) Upper Midwest Environmental Sciences Center
Description Article 454; 19 p.
Country United States
State Illinois, Iowa, Minnesota, Missouri, Wisconsin
Other Geospatial Upper Mississippi River Watershed
Online Only (Y/N) N
Additional Online Files (Y/N) N