RMA4 is part of the TABS-MD suite of programs and is used for tracking constituent flow in 2D models. RMA4 can be applied to represent the transport of a contaminant, salinity intrusion, or tracking DO and BOD in a system. RMA4 can only be run after having initially run a hydrodynamic solution. Currently, SMS only interfaces RMA4 with a solution file from RMA2. Because RMA4 is tracking the transport or a constituent, it is by its nature a dynamic model.. RMA4 uses the flow solutions to compute the constituent concentration as it flows through the mesh. The initial hydrodynamic solution computed by RMA2 can be either steady state or dynamic. RMA4 will utilize a steady state solution repetitively, or can loop through a portion of a dynamic solution repeately to simulate the transport over time.