You are here:
MODEL ANALYSIS OF RIPARIAN BUFFER EFFECTIVENESS FOR REDUCING NUTRIENT INPUTS TO STREAMS IN AGRICULTURAL LANDSCAPES
Citation:
MCKANE, R. B., M. STIEGLITZ, PAN, F., B. L. KWIATKOWSKI, AND E. B. RASTETTER. MODEL ANALYSIS OF RIPARIAN BUFFER EFFECTIVENESS FOR REDUCING NUTRIENT INPUTS TO STREAMS IN AGRICULTURAL LANDSCAPES. Presented at American Geophysical Union fall meeting, San Francisco, CA, December 11 - 15, 2006.
Description:
Federal and state agencies responsible for protecting water quality rely mainly on statistically-based methods to assess and manage risks to the nation's streams, lakes and estuaries. Although statistical approaches provide valuable information on current trends in water quality, process-based simulation models are essential to understanding and forecasting how changes in human activities across complex landscapes impact the transport of nutrients and contaminants to surface waters. To address this need, we developed a broadly applicable, process-based watershed simulator that links a new spatially-explicit hydrologic model and a terrestrial biogeochemistry model (MEL). See Stieglitz et al. and Pan et al., this meeting, for details on the design and verification of this simulator. Here we apply the watershed simulator to a generalized agricultural setting to demonstrate its potential for informing policy and management decisions concerning water quality. This demonstration specifically explores the effectiveness of riparian buffers for reducing the transport of nitrogenous fertilizers from agricultural fields to streams. The interaction of hydrologic and biogeochemical processes represented in our simulator allows several important questions to be addressed. (1) For a range of upland fertilization rates, to what extent do riparian buffers reduce nitrogen inputs to streams? (2) How does buffer effectiveness change over time as the plant-soil system approaches N-saturation? (3) How can buffers be managed to increase their effectiveness, e.g., through periodic harvest and replanting? The model results illustrate that, while the answers to these questions depend to some extent on site factors (climatic regime, soil properties and vegetation type), in all cases riparian buffers have a limited capacity to reduce nitrogen inputs to streams where fertilization rates approach those typically used for intensive agriculture (e.g., 200 kg N per ha per year for corn in the U.S.A. Midwestern states). We also discuss how the insights gained from our approach cannot be achieved with modeling tools that are not both spatially explicit and process-based.