Locate and mitigate the state of nitrate: Assessing potential sources of nutrients in tributaries to the Nooksack River

Anthropogenic activities greatly increase the amount of nitrogen entering our environment. While this allows for increased agriculture production, excess nitrogen raises health concerns for humans and ecosystems. Understanding the sources of excess nutrients is necessary for effective efforts to reduce them. We aimed to understand nutrient fluxes through tributaries to the Nooksack River, in particular, to what extent are excess nutrients arriving to northern Whatcom County from Canada via both surface and ground water. We collected water samples from three creeks fed by the central portion of the Sumas-Blaine aquifer (Kamm, Fishtrap, and Bertrand), two situated at the southern edge of the aquifer (Tenmile and Deer), and one located outside the aquifer (Schell). In our lab, we analyzed them for concentrations of nitrate, phosphate, and organic phosphorous. Phosphate and organic phosphorous concentrations were relatively low across streams (less than 0.093 mg/L-phosphate and less than 0.079 mg/L- organic phosphorous) while nitrate levels varied more. The highest average concentrations of nitrate occurred in the three creeks closest to the Canada-US border, Kamm Creek (6.05 mg/L), Fishtrap Creek (3.07 mg/L), and Bertrand Creek (1.85 mg/L). Schell Creek’s nitrate concentration was intermediate at 1.36 mg/L while Tenmile and Deer creeks had the lowest concentrations at 0.41 mg/L and 0.47 mg/L, respectively. Based on our results, groundwater contamination flowing southward from Canada may be contributing to the higher levels of nitrate observed in Kamm, Fishtrap, and Bertrand creeks. Comparatively, Tenmile, Deer, and Schell creeks may have lower nutrient concentrations in their stream water as a consequence of their greater distance from Canada. However, other factors such as different land use practices around creeks could impact nutrient concentrations and influence our results. Analyzing nutrient levels in groundwater of the Sumas-Blaine aquifer would help us better understand the relative contributions of local and Canadian nitrate contamination sources