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

St. Paul District

Big Lake placemat

Big Lake placemat (click to enlarge)

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

Want to stay connected? Email biglakehrep@usace.army.mil to be added to the email list to be informed of upcoming events and meetings related to Lower Pool 4 HREPs.


  • 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.


The Lower Pool 4 study has been separated into three phases: Phase 1 – Big Lake, Phase 2 – Robinson Lake, and Phase 3 – Tank Pond. Phase 1 – Big Lake is currently in the feasibility phase, and it is anticipated that the feasibility study will be complete in 2024. Phase 2 – Robinson Lake will start the feasibility phase in 2023. Phase 3 – Tank Pond does not have an anticipated start date for feasibility at this time.

Phase 1 Big Lake

In Lower Pool 4, the Upper Mississippi River Restoration Program (UMRR) is starting with the Big Lake HREP. The Big Lake study area is from about RM 760 near state Highway 25 (Nelson Dike) near Wabasha, Minnesota, to about RM 757.5 (Figure 1). The site lies within the Upper Mississippi River National Wildlife and Fish Refuge.

Big Lake HREP project objectives

  • Protect and restore or create naturally regenerating, resilient, and diverse bottomland forest habitat
  • Benefit migratory and resident birds and other species
  • Maintain a balance of coverage and relative abundance of native emergent, rooted floating leaved, and submersed aquatic vegetation communities
  • Protect and restore or create flowing channel habitats
  • Protect and restore or create backwater habitats.
    • Flow conditions/sediment dynamics that benefit native fish and mussels

Phase 2 Robinson Lake – Scoping to start in 2023

Quick Facts on the Lower Pool 4 HREP area (all phases)

  • Approximate acres: 9,382
  • States covered: MN, WI
  • Land ownership: Federal
  • Management agency: U.S. Fish and Wildlife Service
  • Management authority: Refuge 

Typical HREP Features

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

Lower Pool 4 HREP Phases 1 and 2 - Big Lake and Robinson Lake

Click to enlarge Lower Pool 4 HREP phases 1 and 2 - Big Lake and Robinson Lake