Don't get lost in detail
From REFORM wiki
Diurnal, seasonal and inter-annual natural variations in aquatic communities are well recognized. They are especially pronounced at the smallest spatial scale of microhabitats and less variable at the larger scale of river reaches and river segments. Accordingly, the impacts of human pressures are best separated from natural variations at large spatial scales. Thus, monitoring and assessment should be designed for large spatial scales, using indicators representative for whole river reaches.
Find more information in How can we improve? and How does my river work?
