Abstract: Despite the growing global concern surrounding the havoc caused by wildfires, there are still prominent gaps in knowledge regarding fire effects on nearby waterways. An agnostic CE-QUAL-W2 model was developed to look at the impact of wildfires on reservoir water quality, with a focus on harmful algal blooms. The model was informed using ten years of meteorological data from sites in the Pacific Northwest, United States. Wildfire scenarios were generated (one each for May, June, July, August, and September) using changes in temperature, total suspended solids, nutrients, dissolved oxygen, organic matter, and solar radiation typical of wildfires, informed via literature review. Harmful algal blooms showed the most sensitivity to fires that occurred prior to the growing season, likely due to the influx of phosphate accumulating in the system prior to growth. However, accumulation of nutrients for fires after the growing season showed impacts on blooms the following year. Increases in total dissolved solids during the fire could potentially lead to delays in initial bloom timing due to temporary light limitation. Results from the model runs indicate that wildfires can impact reservoir water quality and bloom dynamics not only immediately, but for months to years following a wildfire.