This article discusses the joint modeling of surface and groundwater flows by presenting and describing the MC model. The purpose of this deterministic physically based model is to simulate the behavior of available water resources for one or many watersheds. The model integrates surface flow, streamflow, flow in the non-saturated zone, groundwater flow and the interactions between rivers and water tables. Its formulation and its structure, especially its nested square meshes of variable sizes, confer a great deal of flexibility to the model; this facilitates adaptation to variable modeling scales and to a wide range of geological, geographical and climatological conditions.