Temporal Variability of Phosphorus Concentration in the Stream to Squam Lake, New Hampshire During Storm Events

Phosphorus (P) enrichment to most rivers and lakes degrades the water quality, particularly by stimulating the growth of aquatic plants and algae. To determine the relative importance of precipitation events to the nutrient inputs to lakes, P input was estimated at Livermore Cove Brook, tributary of Squam Lake, NH during 3 storm events in summer 2016. Water samples were collected hourly during the events using ISCO samplers and analyzed for specific conductivity, turbidity, total P (TP), total dissolved P (TDP), total particulate P (TPP), soluble reactive P (SRP), dissolved organic P (DOP) and deuterium isotope (2H). 2H was used in two-component mixing analysis to calculate the % of new-water as a proxy for direct runoff. TP concentrations peaked with stream flow (up to 453.7 ppb) with much higher concentration in rising limb than on falling limb resulted in clockwise hysteresis. We believe this is due to the changing contribution of different water sources to the streams and variable mobility of sediment P during runoff. The SRP was minor component during event but was more significant during baseflow periods. We also found that DOP was most dominant form of P except during strong runoff periods where TPP was an important component