Exploring the hydrologic relationships in a swamp-dominated watershed—A network-environ-analysis based approach

Wetlands are complex habitats with complex hydrologic connections all around. The protection and restoration of wetlands require the information on processes of interactions among different hydrological units inside and outside wetlands. An important but difficult step is to explore their hydrologic relationships from a holistic perspective. In this study, we developed an assessment framework in which the network environ analysis (NEA) was employed to solve the above difficulty. The swamp-dominated Okefenokee watershed in the USA was taken as an example and we explored the hydrologic relationships among four subsystems (swamp surface, swamp subsurface, upland surface and upland groundwater) in the watershed. Three functional analyses, including utility analysis, control analysis and unit environ analysis in NEA, were used to explore their independencies. Results indicate that hydrologic connections among subsystems are extremely important for maintaining integrity of the current system. Direct hydrologic relationships differed from integral one with indirect interactions considered. An interesting finding is that hydrologic relationship between swamp subsurface and upland surface changed from direct neutralism to integral mutualism, indicating the above two subsystems benefited from each others from indirect hydrologic transactions. It is concluded that the proposed method can provide effective ways to examine the hydrologic interdependencies inside and outside a wetland ecosystem and contribute to basin-wide wetland protection and water resources management.