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Scientific Investigations Report 2014–5018

Prepared in cooperation with the U.S. Fish and Wildlife Service

Assessment of Sediments in the Riverine Impoundments of National Wildlife Refuges in the Souris River Basin, North Dakota

By Brian A. Tangen, Murray K. Laubhan, and Robert A. Gleason

Thumbnail of and link to report PDF (32.7 MB)Abstract

Accelerated sedimentation of reservoirs and riverine impoundments is a major concern throughout the United States. Sediments not only fill impoundments and reduce their effective life span, but they can reduce water quality by increasing turbidity and introducing harmful chemical constituents such as heavy metals, toxic elements, and nutrients. U.S. Fish and Wildlife Service national wildlife refuges in the north-central part of the United States have documented high amounts of sediment accretion in some wetlands that could negatively affect important aquatic habitats for migratory birds and other wetland-dependent wildlife. Therefore, information pertaining to sediment accumulation in refuge impoundments potentially is important to guide conservation planning, including future management actions of individual impoundments. Lands comprising Des Lacs, Upper Souris, and J. Clark Salyer National Wildlife Refuges, collectively known as the Souris River Basin refuges, encompass reaches of the Des Lacs and Souris Rivers of northwestern North Dakota. The riverine impoundments of the Souris River Basin refuges are vulnerable to sedimentation because of the construction of in-stream dams that interrupt and slow river flows and because of post-European settlement land-use changes that have increased the potential for soil erosion and transport to rivers. Information regarding sediments does not exist for these refuges, and U.S. Fish and Wildlife Service personnel have expressed interest in assessing refuge impoundments to support refuge management decisions.

Sediment cores and surface sediment samples were collected from impoundments within Des Lacs, Upper Souris, and J. Clark Salyer National Wildlife Refuges during 2004–05. Cores were used to estimate sediment accretion rates using radioisotope (cesium-137 [137Cs], lead-210 [210Pb]) dating techniques. Sediment cores and surface samples were analyzed for a suite of elements and agrichemicals, respectively. Examination of core characteristics along the depth profile suggests that there has been regular sediment mixing and removal, as well as non-uniform sediment deposition with time. Estimated mean accretion rates based on the three methods of determination (two time markers for 137Cs, 210Pb) ranged from 0.22–0.35 centimeters per year, and approximately 70 percent of cores had less 137Cs than expected. Concentrations of sediment-associated elements generally were within reported reference ranges, and all agrichemicals analyzed were below detection limits. Results suggest that there does not appear to be widespread sediment accumulation in impoundments of the Souris River Basin refuges. In addition, there were no identifiable patterns among sedimentation rates from the upstream (Des Lacs, Upper Souris) to the downstream (J. Clark Salyer) refuges. There were, however, apparent upstream to downstream patterns of increased concentrations of some elements (for example, aluminum, boron, and vanadium) that may warrant further exploration. Future related monitoring and research efforts should focus on areas with high potential for sediment accumulation, such as upstream areas adjacent to dams, to identify potential sediment problems before they become too severe. Further, assessments of suspended sediments transported in the Des Lacs and Souris Rivers would augment interpretation of sedimentation data by identifying potential sediment sources and areas with the greatest potential for accumulation.

First posted March 17, 2014

For additional information contact:
Director, Northern Prairie Wildlife Research Center
U.S. Geological Survey
8711 37th Street Southeast
Jamestown, North Dakota 58401

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Suggested citation:

Tangen, B.A., Laubhan, M.K., and Gleason, R.A., 2014, Assessment of sediments in the riverine impoundments of national wildlife refuges in the Souris River Basin, North Dakota: U.S. Geological Survey Scientific Investigations Report 2014–5018, 37 p.,

ISSN 2328-0328 (online)




Study Area

Sample Locations

Soil Core Collection and Analysis

Determination of Sediment Accretion Rates

Assessment of Trace Elements and Agrichemicals

Radioisotopes and Physical Characteristics of Sediment Cores

Sediment Accretion Rates

Trace Elements and Agrichemicals


References Cited

Appendix 1. Radioisotope specific activity, bulk density, particle size, loss on ignition, and water content for each sediment core by depth

Appendix 2. Concentrations of 60 detected elements for each sediment core by depth..

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