Aquatic Sciences Meeting, Albuquerque 2001

SS40 Long-Term Research Programs in the Twenty-first Century (Spatial and Temporal Connections)

Date: Thursday, February 15, 2001, Time: 10:30:00 AM

Location: Ruidoso/Pecos

Soballe, D, M, U.S. Geological Survey, La Crosse, Wisconsin, USA, dave_soballe@usgs.gov

Richardson, W, B, U.S. Geological Survey, La Crosse, Wisconsin, USA, william_richardson@usgs.gov

Holland-Bartels, L, , U.S. Geological Survey, La Crosse, Wisconsin, USA, leslie_holland-bartels@usgs.gov

LARGE AND SMALL-SCALE HYDROLOGIC INFLUENCES ON SEDIMENT AND NUTRIENT DYNAMICS IN THE UPPER MISSISSIPPI RIVER: THE NEED FOR A MULTI-SCALE APPROACH

Studies on the Upper Mississippi River are coupling long-term monitoring with short-term, process-oriented investigations to understand the nutrient and sediment dynamics of this complicated system. The monitoring data show that long-term (e.g., decadal) oscillations in the flow regime strongly influence the delivery of sediment and nutrients to the river from the watershed. Large-scale phenomena influence the nutrient and sediment processing potential of the system by establishing the overall nutrient and sediment regime and by controlling the spatial-temporal distribution of sediments and aquatic macrophytes. We have found at smaller scales (hours to days) that the delivery of nitrate nitrogen to processing sites (e.g., areas of intense microbial denitrification) is controlled by short-term water level changes. Events at these same scales produce an alteration of oxicanoxic conditions and this allows coupling between nitrification and denitrification at these sites.

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Aquatic Sciences Meeting, Albuquerque 2001

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