Fish and Water are integrated conservation issues in the Big Hole River watershed. The fishery is dependent on adequate water quality and quantity, while water quality impairment and need for water quantity is driven by the needs of the fishery. The fishery and water quality and quantity exist in delicate balance with the needs of community drinking water, irrigation, and fishing.

While the Big Hole valley remains undeveloped and open, historic mining, ranching, recreation, logging, development, and introduction of non-native fish have extensively altered the original conditions of fish and water in the Big Hole. Monitoring, planning, agreements, and restoration activity have for decades systematically worked to improve conditions for both water and fish with many millions of dollars invested and yet so much more work to be done.

Often work in the Big Hole has an integrated approach for completing restoration projects by benefitting both fish and water.


The Big Hole River fishery includes the mainstem Big Hole River, a network of tributaries, high mountain lakes, and in some cases irrigation systems such as large ditches and sloughs. Extensive restoration over two decades has vastly improved security for native fish, particularly Westslope Cutthrout Trout and Arctic Grayling.

The Big Hole River watershed is home to a coldwater fishery that includes Native Fish [Arctic Grayling, Westslope Cutthroat Trout, Yellowstone Cutthroat Trout, Mountain Whitefish, Burbot, Dace, Sculpin] and introduced sportfish [Brown Trout, Rainbow Trout, Brook Trout].

Primary concerns for fishery health and production are:

  • Adequate fish habitat, including coldwater refuge, spawning, and rearing;
  • Native fish protection from non-native fish;
  • Water quality, most often high water temperature, sediment and nutrients;
  • Water quantity, particularly during late summer and drought seasons.

Fishery improvement is typically coordinated by Montana Fish, Wildlife and Parks – in the Big Hole that implies the Arctic grayling recovery in the Upper Big Hole or comprehensive fishery improvement through the Big Hole River Fish Biologist.

Water Quality

The Environmental Protection Agency through Montana Department of Environmental Quality identifies water quality needs for Montana. In the Big Hole, water quality primary concern is non-point source pollution, that is say water quality impairments that are not identifiable to one specific source location. Those water quality impairments are largely driven by the needs of the fishery, that is to say that where waters are considered impaired the beneficial use not being met is often the fishery. The fishery health, both on the mainstem and tributaries, is highly dependent on adequate cool, clean water and available habitat to maintain its populations. Remedy of non-point source pollution is voluntary.

Water quality impairment in the Big Hole can be high water temperature, high sediment, high nutrients, and occasionally high metals. Metals are typically present where historic mining occurred. Water temperature can be high where waters lack shade or are shallow. Sediment can enter where river banks are eroding or where uplands are eroding. Nutrient contribution is typically a result of livestock waste concentration.

Water quality in the Big Hole River is assessed and identified for improvement through three steps:

Step 1: Water Quality Assessment

Completed 2009 by Montana Department of Environmental Quality, these documents identify water quality impairments and sources by identifying a Total Maximum Daily Load (TMDL) – an identified threshold for beneficial use.

  • Upper & North Fork Big Hole River Total Maximum Daily Load
  • Middle-Lower Big Hole River Total Maximum Daily Load
Step 2: Water Quality Improvement Plan

The Big Hole Watershed Committee completed Watershed Restoration Plans 2013-2014. The plans use the TMDL’s and several inventories and assessments to assemble a logical plan for meeting water quality needs for the Big Hole River.

  • Upper & North Fork Big Hole River Watershed Restoration Plan
  • Middle-Lower Big Hole River Watershed Restoration Plan
Step 3: Implement Watershed Restoration Plans

The watershed restoration plans layout a plan for improving water quality, and the final step is to implement the plan. This includes identifying next steps with partners, planning the project, securing and managing funding, monitoring for results, and completing the project. Each project can take from a few months to 4-6 years to complete depending on size, scope, and available funding.

Water quality improvement is generally led by Big Hole Watershed Committee and supported by many agencies and partners.

Water Quantity

Water quantity is not regulated, but is managed by the following:

  1. Voluntary Flow Maintenance
    1. The Big Hole River Drought management Plan coordinates shared water quantity goals. Irrigators work together to conserve water in an effort to meet target flows. When flows fall below targets protections are put in place for the fishery by limiting fishing.
  2. Increasing Natural Water Storage and Addressing Climatic Resiliency
    1. Many restoration or conservation projects can maintain or improve natural water storage which can help maintain river flows. This projects can help buffer water quantity needs in years where climatic stress occurs making the watershed more resilient to climatic variation.
  3. Monitoring
    1. USGS and DNRC Real-Time gages report flow and water temperature.
    2. Local flow monitoring through monitoring devices or manual measurement provide a snapshot of current condition.

The greatest stress on water quantity occurs late summer, typically late July through early September and at its worse during drought years. Drought years occur when snowpack is lower than average, spring precipitation is lower than average, or high spring air temperatures cause snowpack to release faster or sooner than average.

Water in the Big Hole River is used by irrigators to provide drinking water for cattle and to water lands for hay or other feed crop production. Water withdrawals are mandated through water rights. In Montana, irrigators own water rights that give them the right to pull water for use identified in their water right. Irrigator participation in water quantity maintenance is a voluntary conservation choice. In general, a reduction in irrigation withdrawals means a reduction of income or higher costs for that rancher. Their participation is very much a financial choice.

Fish & Water Resources

Big Hole River Conditions Page

Big Hole River Conditions & Drought Management Plan Resources