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

Abstract

Conservation practices, such as buffers, are often installed to mitigate the effects of nutrients and sediment runofffrom agricultural practices. The Riparian Ecosystem Management Model (REMM) was developed as process-based modelto evaluate the fate of nutrients and sediment through a riparian buffer up to the edge of a stream. A one-at-a-time sensitivityanalysis was performed on REMM to evaluate the effects that changing herbaceous buffer scenarios have on N, P, andsediment in surface and ground water. Vegetation characteristics such as rooting depth, LAI, and plant height, along with somephysical buffer characteristics were varied within their typical range and compared to a base case scenario. Modeloutputs were not sensitive to plant height or LAI, but moderately sensitive to changes in SLA. Model outputs were onlysensitive to rooting depth as roots became shallower in the soil profile. Sediment yield and dissolved nitrate in surface waterwere the most sensitive to changes in Mannings n, while other soil physical characteristics such as surface roughness, surfacecondition, and % bare soil had little to no effect on model outcomes. Dissolved surface nitrate, organic P, and dissolvedsubsurface 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 transportof nutrients and sediment in surface and subsurface water; therefore, utilizing REMM to evaluate effects of specificherbaceous plant types may have limited value unless specific leaf area or rooting depth are considered. It would be possibleto model and perhaps achieve specific load reductions by modifying slope and other physical characteristics or by consideringforest versus grass buffers.