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

Abstract

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 tosimulate surface and subsurface riparian buffer hydrology, sediment transport, litter and sediment interactions, vegetationgrowth, and soil carbon, nitrogen, and phosphorus dynamics. For this model to accurately simulate transport and fate ofnutrients in the shallow groundwater beneath a riparian buffer, the subsurface hydrology component must be verified. Twoyears of field data were utilized to evaluate and test the sensitivity of the hydrology component of REMM in the North CarolinaMiddle Coastal Plain. Daily simulated water table depth was compared to observed water table depths across a 15 m widebuffer. The simulated water table depth was sensitive to hydrologic parameters such as groundwater inputs from the uplandinto zone 3, stream depth, and buffer slope. Average absolute errors between simulated and observed water table depth werefound to be 0.35 to 0.36 m, while relative errors ranged from 0.12 to 0.15 m. Simulated evapotranspiration (ET) was higherin zone 3 compared to zones 1 and 2, although all three zones were parameterized alike. Flow into the buffer from the streamis not simulated by REMM, although it occurred frequently during data collection. Estimates of ET should be improved forherbaceous and grass vegetation types to improve water table depth predictions. Also, for conditions where the streamcontributes flow to the groundwater, an additional component in REMM is necessary.