Lower Pool 4, Big Lake, Robinson Lake, and Tank Pond Habitat Rehabilitation and Enhancement Project

St. Paul District

Pool 4, Upper Mississippi River, Miles 760.2-752.8, Wabasha County, Minnesota and Buffalo County, Wisconsin, Congressional Districts: MN-2, WI - 3


  • U.S. Fish and Wildlife Service
  • Minnesota Department of Natural Resources
  • Wisconsin Department of Natural Resources


The overall goal of the Pool 4 HREP is to maintain/enhance/create quality habitat for native and desirable plant, animal, and fish species.

The Lower Pool 4 study area encompasses approximately 9,382 acres of open backwater, meandered side channel, main channel border, and island formations from state Highway 25 (Nelson Dike) at Wabasha, Minnesota, to Lock and Dam 4 near Alma, Wisconsin. It includes the main stem of the Mississippi River and portions of the Buffalo River. The site lies within the Upper Mississippi River National Wildlife and Fish Refuge.

Sedimentation of the backwaters is an ongoing issue in this study area. Big Lake has lost much of its island complex and forest to wind and wave erosion. The barrier islands between the lake and Catfish Slough have been degraded and/or eliminated over the past several years. Tank Pond near the mouth of the Buffalo River has relatively poor water quality due to a lack of water circulation and lower abundance and diversity of underwater vegetation. Overwintering fish habitat in and below Big Lake is limited, in part, by high current velocities. The existing desirable overwintering areas appear to be filling with sediment and are exposed to flows that are more frequent. Without the implementation of forest restoration measures, continued decline.

Quick Facts

  • Approximate Acres: 9,382
  • State(s) Covered: MN, WI
  • Land Ownership: Federal
  • Management Agency: USFWS
  • Management Authority: Refuge 


  • Island construction/enhancement
  • Creation of mudflat and/or terraced habitat
  • Dredging backwater areas and secondary channels
  • Increasing wild celery beds and perennial vegetation