Brackish groundwater is a largely untapped water resource that is available in much of the arid US. The low salinity of brackish water (1000–10 000 mg/L TDS) makes it a viable alternative water supply for municipal, industrial, and agricultural applications. Improvements in desalination technologies are required to fully utilize these waters. Electrodialysis (ED), capacitive deionization (CDI), and membrane capacitive deionization (MCDI) are tunable techniques with low energy requirements and operational costs and have advantages over conventional reverse osmosis (RO) in many applications. The aim of the current effort is identifying the conditions under which these technologies may be applicable and developing models of these processes for the purposes of optimization and design. A steady-state 2D ion transport model for ED and a 2D transient ion transport-adsorption model for (M)CDI are presented. The models are capable of successfully describing the concentrations and potential distributions in the processes during brackish water desalination. The models are used to describe the effects of thermodynamics, hydrodynamics, and operating conditions on ion transport in these systems.