Toassess the condition of a riparian-wetland area, there must be a gauge to measureagainst. The definition of PFC in TR 1737-9 and TR 1737-15 establishes the gaugefor assessing lotic systems. This definition has to be adjusted for lentic systemsbecause they are affected by wind and wave energies or overland flow energiesversus high flow events, and they typically have a restrictive layer (e.g., geologicstructure/soil material/permafrost/manmade restrictive layer) that limits water perco-lation and maintains the site: