RIPARIAN ECOSYSTEM MANAGEMENT MODEL: HYDROLOGY PERFORMANCE AND SENSITIVITY IN THE NORTH CAROLINA MIDDLE COASTAL PLAIN.

A riparian buffer installed along streams is one alternative that can be used to reduce the delivery of nitrogen, phosphorus, and sediment to the stream. The Riparian Ecosystem Management Model (REMM) has been developed to simulate surface and subsurface riparian buffer hydrology, sediment transport, litter and sediment interactions, vegetation growth, and soil carbon, nitrogen, and phosphorus dynamics. For this model to accurately simulate transport and fate of nutrients in the shallow groundwater beneath a riparian buffer, the subsurface hydrology component must be verified. Two years of field data were utilized to evaluate and test the sensitivity of the hydrology component of REMM in the North Carolina Middle Coastal Plain. Daily simulated water table depth was compared to observed water table depths across a 15 m wide buffer. The simulated water table depth was sensitive to hydrologic parameters such as groundwater inputs from the upland into zone 3, stream depth, and buffer slope. Average absolute errors between simulated and observed water table depth were found to be 0.35 to 0.36 m, while relative errors ranged from 0.12 to 0.15 m. Simulated evapotranspiration (ET) was higher in zone 3 compared to zones 1 and 2, although all three zones were parameterized alike. Flow into the buffer from the stream is not simulated by REMM, although, it occurred frequently during data collection. Estimates of ET should be improved for herbaceous and grass vegetation types to improve water table depth predictions. Also, for conditions where the stream contributes flow to the groundwater, an additional component in REMM is necessary. [ABSTRACT FROM AUTHOR]