Drainage model may refer to: a surface drainage model or rainfall-runoff model; see surface runoff, runoff model (reservoir) a subsurface (groundwater), drainage model related to: a spacing equation for subsurface pipe drains and open ditches (horizontal drainage) or wells (vertical drainage); see watertable control a hydrological subsurface drainage model; see soil salinity control for an example of an agro-hydro-salinity subsurface drainage model (SaltMod) groundwater flow in the aquifer; see groundwater model or an example of an agro-hydro-salinity groundwater model: SahysMod Hydrology models