Soil and Water Assessment Tool (SWAT) is a physically based distributed hydrologic model that was designed to assess the impact of changes of land characteristics such as land uses and soil classes. A large amount of input parameters may lead to a high degree of uncertainty in its results when inappropriate estimation of initial values is made. For this reason, personally, I don't like the model. "Small is beauty!" However, there seems no better alternative to this model when it comes to a project involving the assessment of land use change for which the model was designed.
Neitsch, S.L., Arnold, J.G., Kiniry, J.R., Williams, J.R. and King, K.W., 2002. SWAT2000 Theoretical Documentation. Texas Water Resources Institute.