Groundwater governing equations

In the simplest cases of reactive transport, a species sorbs according to a linear isotherm (Chapter 9), or reacts kinetically by a zero-order or first-order rate law. There is a single reacting species, and only one reaction is considered. In these cases, the governing equation (Eqn. 21.1 or 21.2) can be solved analytically or numerically, using methods parallel to those established to solve the groundwater transport problem, as described in the previous chapter (Chapter 20). 

To analyze the transport and retention of chemical contaminants in groundwater flowing through soils, experimental and theoretical studies generated several reliable models. Diverse numerical methods have been applied to solve the governing equations efficiently. Some computer models include the simulation of physical and chemical processes. 

The two-dimensional governing equation used in most simulations of groundwater flow is ... 

On the other hand, the coupled processes in the far field are described in this chapter based on the results of the near field analysis. Assuming that mechanical behavior and unsaturated flow are negligible for regional groundwater flow system, only coupled thermal and hydraulic processes in saturated zone are considered. Governing equation... 

A governing equation for three-dimensional transient groundwater flow through a saturated anisotropic porous sedimentary material can be expressed in a Cartesian coordinate system as (McDonald Harbaugh, 1988) ... 

Numerical methods allow one to obtain a solution to the groundwater contaminant transport equation even when the equation is nonlinear (for example, when sorption is described by either a Freundlich or Langmuir isotherm). These numerical methods also permit solution of the governing partial differential equation when parameter values and initial and boundary conditions vary in space and time. 

The two-dimensional, transient transport of solute-humic substances in water saturated, homogeneous porous media under uniform interstitial groundwater is governed by the following partial differential equation ... 

---