Forest Water Quality: What's the Baseline for Evaluation?

Water quality in streams draining commercial forest lands is far better than that draining all other commercial land uses.  Furthermore, due to continued improvement and refinement of regulatory and voluntary best management practices (BMPs), it is far better now than at any time since timber harvest began.   BMPs for road construction, road runoff management, road surface management, riparian buffers, and steep slope protections have produced high quality stream habitat in forest streams.  However, many salmonid populations throughout the PNW are depressed below historical and desirable levels, and this situation fuels continued concern over forest water quality since commercial forest lands comprise a large portion of the salmonid habitat in the PNW.  Furthermore, there will always be some hydrologic effects of silviculture, some sediment transport from roads to streams, and some landsliding to which silvicultural activities have contributed.  In other words, commercial forestry will never meet a zero-impact standard.  This situation begs the question, how good is good enough for forest water quality?  If the answer is, “not good enough until salmonid escapement is in the desired range,” then commercial forestry will face continued tightening of water quality protection requirements with the possible unintended consequence of hastening the conversion of forest lands to other uses, with far greater negative water quality effects.  The question for forest operations is how much water quality (flows, woody debris, sediment, temperature, etc.) change can occur without noticeably altering stream ecosystems?   More research is needed in developing and testing quantifiable and repeatable watershed-scale aquatic ecosystem health metrics and in quantifying the temporal and spatial variability of such metrics in undisturbed watersheds.