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PROCESS TRANSFER FUNCTIONS TO RELATE STREAM ECOLOGICAL CONDITION METRICS TO NITRATE RETENTION
Citation:
FAULKNER, B. R. PROCESS TRANSFER FUNCTIONS TO RELATE STREAM ECOLOGICAL CONDITION METRICS TO NITRATE RETENTION. Presented at 2006 Annual International Meeting of the American Society of Agricultural and Biological Engineers, Portland, OR, July 09 - 12, 2006.
Impact/Purpose:
To inform the public.
Description:
Ecologists have developed hydrological metrics to characterize the nutrient processing capability of streams. In most cases these are used qualitatively to draw inferences on ecological function. In this work, several of these metrics have been integrated in a nonsteady state advection—dispersion equation coupled with reactions among various compartments of the stream system. These include characteristic dead zone and hyporheic residence time distributions, nutrient uptake length, and denitrification rate. With the assumption of linear kinetics, this system was solved in the Laplace domain to yield transfer functions that describe total nitrate retention by moment analysis. The approach can be generalized as a cascade of linear reservoirs for screening level evaluation of stream heterogeneity. The method was verified by quadrature with the outputs of a numerical model (OTIS) for a synthetic heterogeneous stream. Using Monte Carlo analysis with uniform distributions drawn from uniform distributions for the metrics, good agreement was found (F-test: p < 0.0001, N = 1430). This approach yields attenuation factors for stream reaches of interest which can be useful for restoration planning and cost benefit analysis.