HYDROLOGIC EQUILIBRIUM STATUS OF A DISTRIBUTED EASTERN NORTH CAROLINA WATERSHED.

Evaluation of the impacts of artificial drainage systems on wetlands requires an assessment of the hydrologic equilibrium status of the surface hydrologic system. Hydrologic equilibrium is characterized by a high correlation between surplus moisture and stream discharge. A qualitative stability analysis shows that deterioration of artificial drainage channels allows the surface hydrologic system to adjust to the disturbances. The model is tested by examining the correlation between surplus and discharge for a small watershed altered by forestry drainage which is periodically rehabilitated. The original, largely undisturbed watershed is in hydrologic equilibrium. Disequilibrium is induced by artificial drainage-ways, with a return to equilibrium over time. Subsequent renovations of ditches and canals are associated with a recurrence of disequilibrium. The surface hydrologic system is metastable, and cannot be expected to return to previously-existing states following a disturbance. Consistently maintained artificial drainage systems appear to preclude any return to any type of hydrologic equilibrium.