Boundary Reservoir, on the Pend Oreille River, formed by Boundary Dam near the Canadian Border is located in a scenic valley of northeast Washington State. This reservoir is operated by Seattle City Light as a load-following facility for hydropower production. This historically low productivity reservoir is undergoing relicensing efforts and the potential production of periphyton, benthic macroinvertebrates (BMI), and macrophytes was assessed using habitat suitability indices (HSI). Specifically, the daily pool level fluctuation caused by project operations was studied to determine how various operations affected periphyton, BMI, and macrophyte production. This deep, high flow, and low retention time reservoir presented logistical difficulties in collection of data, and analysis of data to formulate HSI relationships. The HSI curves for periphyton, BMI, and macrophytes were developed using a multi-tiered approach. The first step was for provisional HSI curves to be developed from existing literature information and professional judgment. Next, site specific periphyton, BMI, and macrophyte data were collected at various locations and depths within the reservoir. These site-specific field data were used to create suitability values for physical habitat parameters using statistical programs. The final HSI curves were developed using both the provisional and site-specific curves and from input from relicensing participants.