Chain-2d model is a computer program used to simulate two-dimensional variation of saturated water flow, heat transfer, and solute motion related to sequential first-order decay reactions. This equation solves Richards' equation of saturated unsaturated water flow and convection dispersion equation of hot melt movement numerically. The flow equation is used to explain the method of water absorption by plant roots. The flow part of the model can deal with the given head, gradient and flux boundary, as well as the boundary controlled by atmospheric conditions.