Chemistry of a Near-Shore Lake Region during Spring Snowmelt

The thermal and chemical characteristics of a spawning area within a base-neutralized lake were monitored through the spring snowmelt of 1989. While the greater part of the lake remained relatively neutral, severe pH (<5.0) and acid neutralizing capacity (ANC; <0 μequiv L^-1) depressions were observed in the upper (1-1.5 m) portion of the water column. Thermal stratification of the near-shore area and a combination of groundwater and surface runoff events controlled the hydrologic response and the changes in water chemistry that occurred during the acid pulse. Dilution of basic cations (SBC) combined with NO₃“ eluted from the snowpack and/or soils resulted in low ANC, low pH runoff affecting the near-shore area. Increases in monomeric Al and H⁺ were coincident with the ANC depression, creating a harmful environment for fish fry emerging from the spawning zone.