Small, recreationally important lakes are economically critical to communities across Canada. Using a ^210^Pb and ^14^C dated sediment core from Alta Lake, Whistler, British Columbia, long-term changes in water quality were reconstructed using C/N stable isotopes, metals, and historical records. Evidence was found for a large-scale influx of terrestrial carbon at 1563±98 AD and channel avulsion on the 21-Mile Creek alluvial fan at 1754±81 AD. Changes in stable isotopes beginning at 1949±17 AD indicated increased productivity in response to nutrient loading from septic-derived nutrients. Increased metal deposition (Cu, As, and Zn) during the same period indicates that watershed disturbance during the construction of the highway was likely a significant contributor of metals to Alta Lake. Previous limnological assessments of Alta Lake concluded that Alta Lake is an oligotrophic, clear-water lake with excellent water quality. This study confirmed these data but indicated that nutrient loading and increased productivity in Alta Lake continue to occur. The application of the paleolimnological method to the assessment of Alta Lake confirmed that the suite of abiotic proxies used was effective in characterizing long-term trends in water quality, and that a long-term perspective on water quality variability is necessary to develop effective management practices for Alta Lake and other small, economically important lakes across Canada.