Use of Nonlinear Regression for Estimating Emission of Nitrogen to Estonian Rivers

A statistical model, MESAW, was modified to estimate non-linear diffuse source emission coefficients. This model uses regression for estimation of source emission coefficients for different land use or soil categories and retention coefficients for pollutants in a river basin or lakes. In this study, the emission coefficients were calculated based on a non-linear dependency between the emission and the land cover percentage in sub-basins. Results show that exponent of non-linear emission coefficients for different land covers vary from 2 to 6 times between single years. Maximal unit area loads gained in this study coincide well with results obtained in previous similar investigations indicating that the new approach on defining the emission coefficients is reliable.