The Belly River is a significant watershed in southwestern Alberta, flowing approximately 181 kilometers from the US/Canada international boundary northward to its confluence with the Oldman River. This river passes through some of Alberta's most dramatic landscapes, including portions of Waterton Lakes National Park, where it offers anglers a chance to pursue a diverse mix of cold and cool-water species in a stunning mountain and foothills setting. Historically regarded as a cold-water river supporting trout and whitefish, the Belly River's character shifts considerably from its headwater reaches — where cold-water species remain the primary draw — to its lower sections, where warmer temperatures and agricultural influences have altered the fish community. The river's upper reaches retain the clearest cold-water character, while the lower mainstem reflects the cumulative effects of water withdrawals and upstream land use.