Technical note: Analytical sensitivity coefficients for the GAML infiltration model

Sensitivity coefficients are important in the selection and use of hydrologic/water quality models. The Green-Ampt-Mein-Larson model is increasingly being used to predict infiltration. Sensitivity coefficients for this model are derived for the soil parameters of effective conductivity, initial saturation, and field saturated moisture content and the Brooks-and-Corey parameters. They are shown to be a function of cumulative infiltration depth. Relative sensitivity coefficients for effective conductivity vary between zero at ponding and an asymptotic value of one as the cumulative infiltration depth approaches infinity. Relative sensitivity coefficients for initial saturation have a modal shape with values of zero at both ponding and as cumulative depth approaches infinity. The maximum value lies between these two limits and is dependent on the initial saturation. Infiltration depth is generally more sensitive to the effective conductivity than the initial saturation.