The Wild and Scenic Rivers Act of 1968 has fifteen management principles that river managers must adhere to; one of the principles is water quality:
Consistent with the Clean Water Act, water quality in wild, scenic and recreational river areas will be maintained or, where necessary, improved to levels which meet Federal criteria or federally approved State standards for aesthetics and fish and wildlife propagation. River managers will work with local authorities to abate activities within the river area which are degrading or would degrade existing water quality.
Part of the reason the Alagnak was designated as a "Wild" river was due to the fact that it was starting off at such a healthy, pristine level. To retain the "Wild" status over time that level of purity will have to be documented and maintained.
Reports on the water quality of the Alagnak are available from the Southwest Alaska Network (SWAN) Inventory & Monitoring Program in PDF format.