In this chapter, we discuss hydrology as an input in modeling pedogenesis by comparing the advantages and limitations of different modeling approaches. Water is the main driving force of pedogenesis, as it is responsible for the transfer of solutes and particles and for most of the geochemical and biological reactions occurring in soils. It is thus indirectly responsible for soil texture and structure evolution that influences water transfer and residence time in soils. Two example models that combine geochemistry, hydrology, and plant growth modules are presented: SoilGen and WITCH. These two models simulate the evolution of some soil characteristics on the pedologic time scale reasonably well. However, in their present states of development, these models are not able to simulate any type of soil evolution; therefore, further improvements are needed to implement soil processes and the feedbacks among them. Parametrization and validation, on pedologic time scale, also remain a challenge.