The General Constituent Simulation Module (GCSM) computes simple kinetics of general constituents in the water column. A conservative tracer, coliform bacteria, and reactive particles are some of the general constituents that can be modeled with GCSM. The four processes are simulated in GCSM for any user-defined general constituents: zero-order decay, first-order decay, sediment release, and/or net settling loss. GCSM does not simulate interactions among constituents.