QUANTIFYING THE SENSITIVITY OF THE RIPARIAN ECOSYSTEM MANAGEMENT MODEL (REMM) TO CHANGES IN CLIMATE AND BUFFER CHARACTERISTICS COMMON TO CONSERVATION PRACTICES

Conservation practices, such as buffers, are often installed to mitigate the effects of nutrients and sediment runoff from agricultural practices. The Riparian Ecosystem Management Model (REMM) was developed as process-based model to evaluate the fate of nutrients and sediment through a riparian buffer up to the edge of a stream. A one-at-a-time sensitivity analysis was performed on REMM to evaluate the effects that changing herbaceous buffer scenarios have on N, P, and sediment in surface and ground water. Vegetation characteristics such as rooting depth, LAI, and plant height, along with some physical buffer characteristics were varied within their “typical” range and compared to a “base case” scenario. Model outputs were not sensitive to plant height or LAI, but moderately sensitive to changes in SLA. Model outputs were only sensitive to rooting depth as roots became shallower in the soil profile. Sediment yield and dissolved nitrate in surface water were the most sensitive to changes in Manning’s n, while other soil physical characteristics such as surface roughness, surface condition, and % bare soil had little to no effect on model outcomes. Dissolved surface nitrate, organic P, and dissolved subsurface nitrate were all moderately sensitive to changes in saturated hydraulic conductivity and the slope of the buffer. Results indicate that within the model, many vegetation characteristics do not directly play a role in the physical transport of nutrients and sediment in surface and subsurface water; therefore, utilizing REMM to evaluate effects of specific herbaceous plant types may have limited value unless specific leaf area or rooting depth are considered. It would be possible to model and perhaps achieve specific load reductions by modifying slope and other physical characteristics or by considering forest versus grass buffers.