Water and Chemical Budgets for Terrestrial Basins at the Turkey Lakes Watershed

Abstract

Twenty terrestrial basins ranging in area from 2.3 to 62.7 ha were monitored in the 1050-ha Turkey Lakes Watershed (TLW) to measure discharge and ion loss from the terrestrial ecosystem and to estimate terrestrial contributions to the main aquatic system. These basins span 400 m of elevation, beginning at 60 m above Lake Superior (183 m a.s.l.). Annual streamflow represented 28–63% of precipitation; 30–60% of the total occurred during springmelt. Water, H+, and NH4+ output of the small basins increased with basin elevation; conductivity, alkalinity, Ca2+, and NO3− decreased. Losses of Mg2+, K+, Na+, SO42−, and Cl− were not related to basin elevation. Input–output values indicate a net loss of Ca2+, Mg2+, K+, and Na+; Cl− slowly accumulated, N was strongly retained, and SO42− was generally in balance. Alkalinity values indicate that HCO3− was important in balancing cation losses in low-elevation basins but that SO42− dominated in high-elevation basins. Output of H+ was substantially lower than its input through precipitation at ail elevations; however, H+ removal by the terrestrial system was greater in low-elevation than in high-elevation basins within the main watershed. Precipitation quantity and SO42− and NO3− input were measured at the Atmospheric Environment Service APN station southeast of the TLW; other chemical parameters were measured on samples collected near the main outlet on the west side of the TLW.