Browsing by Author "Jaeschke, Eric"

The pocosins of the North Carolina Atlantic Coastal Plain (ACP) region play a vital role in controlling hydrologic patterns and determine wetland development and ecosystem structure and function. However, these low-lying, shallow water table forested watersheds have received little research attention due to the relative scarcity of long-term monitoring data, watershed delineation challenges and scarcity of unmanaged sites. Without holding anthropogenic activities constant, specific hydrological processes such as runoff generation, are difficult to describe because of drainage network influence on soil water storage. The principal goal of this study was to develop and test a water balance framework for investigating runoff characteristics and the active watershed area contributing to runoff of a managed pocosin watershed in the ACP. Using a water balance approach, the first objective was to calculate monthly and annual water balances with particular emphasis on deriving, mathematically, the area contributing to runoff. The second objective was to explore the concept of variable contributing area by converting discharge measured at the outlet to runoff using a watershed area. The watershed area needed to produce runoff values that result in closure of the water balance equation represents the variable runoff contributing area. The calculation was done for different temporal periods: monthly, seasonal, and annual and runoff contributing area values compared to the topographically defined watershed area. The results of the study indicated that water balance components were generally in good agreement and closure tended to occur at longer time scales, decreasing for shorter periods. Lack of system closure at shorter temporal scales suggested that the contributing area to runoff varied and differed from the topographically defined watershed area. Active contributing area clearly varies temporally but on average is estimated to be approximately 600 hectares. Regression predicted watershed size was smaller than expected which could have been due to the difference between measured and predicted streamflow. The extent at which the active contributing area fluctuates depends on the compounding uncertainty of water balance components.