Beavers are ecosystem engineers that are currently expanding their range northward from Alaska’s boreal region into tundra ecosystems. Beaver pond formation alters hydrologic flowpaths and increases soil inundation, accelerating permafrost thaw and liberation of previously stored organic matter, nutrients, and heavy metals that can then be mobilized to rivers. This can change water chemistry and quality, impacting stream biota including fish, which has implications for Alaskan communities. It remains unclear whether the effects of Arctic beaver ponds on stream chemistry are local, or if they propagate to the entire watershed. Here, we aim to understand how beaver ponds in permafrost catchments influence stream chemistry at the watershed scale. We look at how chemistry (especially nitrate and phosphate) varies from early to late thaw season across three catchments with different levels of beaver influence, compare the chemistry of beaver ponds to the mainstem, and evaluate the influence of subcatchments with beaver ponds on chemistry at the catchment outlet. This study takes place in Cape Krusenstern National Monument and Noatak National Preserve, Alaska. Stream chemistry data were collected via synoptic sampling of ~31 sites within each catchment in June (early thaw season) and August (late thaw season) 2022. Water samples were collected directly from beaver ponds in two catchments. We found that all catchments had similar nitrate concentrations in June. Nitrate increased across the thaw season most in the catchment with the least beaver influence (mean=0.18mg/L in June to 0.24mg/L in August). In the most beaver-influenced catchment, phosphate was higher in June (mean=0.02mg/L) compared to the other catchments (mean=0.009mg/L) but decreased in August (mean=0.008mg/L). Both nutrients showed high spatial stability in the most beaver-influenced catchment, suggesting subcatchments acting as sources versus sinks remain the same from the early to late sampling. Overall, the northward expansion of beavers into vulnerable permafrost landscapes necessitates study of their impact on water quality and aquatic ecosystems.