The General Constituent Simulation Module (GCSM) computes the kinetics of general constituents in the water column. It can model various constituents, including conservative tracers, coliform bacteria, and reactive particles. GCSM simulates four processes for any user-defined general constituents: zero-order decay, first-order decay, sediment release, and/or net settling loss. Notably, GCSM does not consider interactions among constituents.