Soil carbon lives in every element of the environment (atmosphere, plants and soils), although this same statement has also been coined for water. As such, the linkage of soil organic carbon with the water cycle is elementary to function and form of soils from the minute scale of soil pores to the broad scale of modeling. The establishment of specific points of contact among soil variables and the variability due to environmental and soil conditions is now of the essence to enumerate soil organic carbon on global scales. Whereas the initial modelling of carbon suggested a categorical system of carbon pools, recent literature provides evidence that optimum conditions for microbial life are also related to optimum soil carbon increase and at specific soil conditions with balance of soil, water and surface area. If soil organic carbon can be represented as a continuum in relation to other soil variables (e.g. soil water, groundwater flow rates), the prediction and mapping of soil carbon can be developed with greater precision. This presentation will capture the relationship of soil organic carbon to soil water content from an agricultural context, and develop a range of aspects where this relationship could be beneficial to solve environmental problems, most specifically to improve modelling and parameter estimation in hydrology.