The Bighorn River below the Yellowtail Dam is a world-renowned blue ribbon public trout fishery that serves as an important economic and recreational resource to the state of Montana. It is also the largest cold water fishery in the state that lacks a conclusive water quality monitoring program. The majority of its cold water fishery (defined as waters below Yellowtail to the city of Hardin) occurs within the boundaries of the Crow Indian Reservation. However, the forty miles of river length that occur within Crow Reservation boundaries are deemed as “public” and are estimated at having an annual economic value of $51 million dollars. As per EPA policy and approval language for the state of Montana water quality standards, “Montana water quality laws do not apply on tribal reservations,” and it is up to “tribal governments to establish EPA approved water quality standards .”
The Bighorn River Alliance (BHRA) recognizes the importance of the Bighorn wild trout fishery to the angling community and the local economy, and is concerned about water quality conditions below the Yellowtail Dam and throughout the Crow Reservation. Over the years, observations reported by anglers and outfitters have prompted growing concerns about the health of the Bighorn between Yellowtail Dam and the city of Hardin. Rapid and unpredictable flow releases from the Bighorn Reservoir during the spring and summer months may cause disturbances to the biotic productivity of the river and its species causing perturbations in temperature, water depth, dissolved oxygen, and delivery of sediments. Studies have shown that rapid fluctuation in river flows can adversely affect Rainbow and Brown trout, both of which are adapted to a limited narrow range of conditions, while also reducing species abundance, diversity and productivity of aquatic communities. In recent trout population surveys, Montana Fish Wildlife and Parks have noted a decrease in side channel diversity on the Bighorn River, as well as decreased channel stability. Gas super saturation in upper river reaches is also a reoccurring problem as well as increased algae/macrophyte growth.
Importantly, the current absence of water quality monitoring on the Bighorn River through the Crow Reservation makes it impossible to quantitatively measure and explain observed river water quality changes. Water quality testing needs to occur to develop conservation strategies that work to benefit the wild trout fishery of the Bighorn River. Specifically, this monitoring is necessary to 1) determine the current health of the river, 2) identify sources of pollutants into the system, which may be delivered through reservoir flow management, or the surrounding land use/irrigation practices, and 3) provide data that can be used by BHRA, the Crow Tribe and the EPA to establish water quality standards on the Bighorn River below the Yellowtail Dam and the city of Hardin. With oversight provided by Montana’s DEQ, the BHRA will collect baseline data pertaining to temperature, dissolved oxygen, PH, total phosphorus (TP), total persulfate nitrogen (TN), Nitrate + Nitrite as N, total Ammonia as N and Biochemical Oxygen Demand (BOD). These data will provide a quantitative analysis of current river conditions that will be used to design conservation improvement programs that benefit wild trout and promote healthy waters.
The objective of this project is to collect water quality data on a currently unmonitored section of the Bighorn River below the Yellowtail Dam to establish a baseline of current river conditions. These data will aid the BHRA and agency partners in the development of conservation strategies and management practices that sustain, and even improve, the angling opportunities and wild trout populations in this region. Information will be shared with the general public, local state and federal agency partners and the Crow Tribe Reservation, to help develop a general framework for future for monitoring.
 Mohr, Jason. A Guide to Montana Water Quality Regulation. DEQ Publication. Page 14.  Montana DEQ. 2010 Detailed Assessment Report. http://deq.mt.gov/WQinfo/CWAIC/Reports/2010/MT43R001_20.pdf  Bullock, Steve and Tracy Stone-Manning. Montana Final Water Quality Integrated Report. Department of Environmental Quality document. (2014) Section 7, Page 4.  Cushman, Robert M. Review of Ecological Effects of Varying Flows Downstream of Hydroelectric Facilities. Fisheries Management. (2012) Pages 330-339.