TABLE 2.
Estimated Coefficients for the SPARROW Total Nitrogen Models for Northeastern U.S. NHD Streams.
| Estimated model* |
|||
|---|---|---|---|
| Predictor Variables | Coefficient | Units | Standard Eror |
| Sources | |||
| Municipal wastewater | 1.42 | Dimensionless | 0.39 |
| Atmospheric deposition | 0.412 | Dimensionless | 0.058 |
| Cultivated agricultural land | 678 | kg/km2/year | 260 |
| Developed urban and suburban land | 726 | kg/km2/year | 232 |
| Land-to-water delivery | |||
| Soil permeability | 0.387 | Dimensionless | 0.154 |
| Instream loss | |||
| θS1 | 0.0513 | m−1 day−1 | 0.0084 |
| θS2 | -1.319 | dimensionless | 0.076 |
| Reservoir/lake loss | 9.9 | m/year | 1.6 |
| Number of observations | 113 | ||
| R2 | 0.95 | ||
| RMSE (root mean square error in %) | 44.2 | ||
*
The model as defined by Equations (1)-(5) is estimated using load data for the 65 stream monitoring sites and additional literature measurements of the nitrogen loss rate in streams (N = 12) and lakes (N = 36) in New Zealand, North America, and Europe (data are from Seitzinger et al., 2002; Böhlke et al., 2004;Mulholland et al., 2004).