Publication Summary

In 1996 the volume-weighted mean summer epilimnetic total phosphorus concentration for the Wapato Basin of Lake Chelan was found to be less than 2.6 µg/L. This value is well below the 4.5µg/L TMDL criterion, and is lower than the value of 3.9 µg/L found in summer 1987 and comparable to the summer 1995 value of 2.2 µg/L. All other water quality samples and field measurements show excellent water quality in Lake Chelan. Recommendations include continued monitoring to ensure the TMDL criterion is being met.

In January 1993, the Environmental Protection Agency approved a total maximum daily load (TMDL) for total phosphorus in Lake Chelan. The TMDL was calculated to maintain the summer epilimnetic total phosphorus concentration in the Wapato Basin below a criterion of 4.5 µg/L, the ultra-oligotrophic threshold.

In 1996 the volume-weighted mean summer epilimnetic total phosphorus concentration for the Wapato Basin of Lake Chelan was found to be less than 2.6 µg/L. This value is well below the 4.5µg/L TMDL criterion, and is lower than the value of 3.9 µg/L found in summer 1987 and comparable to the summer 1995 value of 2.2 µg/L. All other water quality samples and field measurements show excellent water quality in Lake Chelan. Recommendations include continued monitoring to ensure the TMDL criterion is being met.