MACRO 5.2

Examples of applications:

• Simulations of water flow and pesticide leaching from tile drained agricultural fields.
• Estimations of contaminant concentrations in groundwater.
• Reactive and non-reactive solute transport in soil lysimeters.

MACRO is a one-dimensional, process oriented, dual-permeability model for water flow and reactive solute transport in soil. The soil pore space is divided into a micropore and a macropore domain characterized by different flow rates and solute concentrations. For the micropore domain water flow is governed by Richards’ equation and solute transport by the convection-dispersion equation.

For the macropore domain water flow is gravity driven and the solute transport assumed to be solely convective. The lateral exchange of water and solutes between pore domains is calculated using approximate, physically-based, first-order expressions. Additional model assumptions include first-order kinetics for degradation in each of four `pools' of pesticide in the soil (micro- and macropores, solid and liquid phases), together with instantaneous or kinetic sorption.