The water impounded at Indian Creek Reservoir near Lake Tahoe, California is approximately one-third surface runoff and direct precipitation and two-thirds reclaimed water exported from South Tahoe Public Utility District Plant. Discussed are the results of tests which determined the temporal changes and relationships between water quality characteristics of Indian Creek Reservoir and those of the reclaimed water. Initially the reservoir would not support fish life, but as the reservoir matured, ammonia levels declined to less than 4 mg/l and by 1970 it was an excellent trout fishery. Approximately 70% of the ammonia nitrogen was lost to the atmosphere by nitrification-denitrification. Good biological productivity indicated access to other phosphorus sources, probably runoff. Relative to conductivity and chemical components the water is of good irrigation quality. Various parameters showed that the reservoir responds to more complex factors than those measurable in the reclaimed waste water, raising the question of the effectiveness of tertiary treatment for recreational impoundments.