Assessment of Water Quality Trends in the Minnesota River using Non-Parametric and Parametric Methods

Assessment of Water Quality Trends in the Minnesota River using Non-Parametric and Parametric Methods

2009

Excessive loading of sediment and nutrients to rivers is a major problem in many parts of the United States. In this study, we tested the non-parametric Seasonal Kendall (SEAKEN) trend model and the parametric USGS Quality of Water trend program (QWTREND) to quantify trends in water quality of the Minnesota River at Fort Snelling from 1976 to 2003. Both methods indicated decreasing trends in flow-adjusted concentrations of total suspended solids (TSS), total phosphorus (TP), and orthophosphorus (OP) and a generally increasing trend in flow-adjusted nitrate plus nitrite-nitrogen (NO3–N) concentration. The SEAKEN results were strongly influenced by the length of the record as well as extreme years (dry or wet) earlier in the record. The QWTREND results, though influenced somewhat by the same factors, were more stable. The magnitudes of trends between the two methods were somewhat different and appeared to be associated with conceptual differences between the flow-adjustment processes used and with data processing methods. The decreasing trends in TSS, TP, and OP concentrations are likely related to conservation measures implemented in the basin. However, dilution effects from wet climate or additional tile drainage cannot be ruled out. The increasing trend in NO3–N concentrations was likely due to increased drainage in the basin. Since the Minnesota River is the main source of sediments to the Mississippi River, this study also addressed the rapid filling of Lake Pepin on the Mississippi River and found the likely cause to be increased flow due to recent wet climate in the region.

Johnson, Heather O.
Gupta, Satish C.
Vecchia, Aldo V.
Zvomuya, Francis

University of Minnesota St. Paul

University of Minnesota

12

Surface Water
Water Quality & Pollutants
Water Conveyance & Hydraulics
Hydrology

sediment
sediments
sedimentation
total suspended solid
total suspended solids
TSS
water quality
water qualities
water-quality
water-qualities
hydrology
hydrologic
nutrient
nutrients
surface water hydrology
total phosphorus
TP
water monitoring & assessment
water monitoring and assessment

2000-2009

Yes

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