U.S. Salinity Laboratory
450 West Big Springs Road
Riverside, CA 92507-4716
TETrans is a functional, layer-equilibrium model of one-dimensional solute transport through the vadose zone under transient-state conditions. This type of model is often referred to as a "tipping-bucket model".
TETrans is a capacity model that defines changes in amounts of solute and water content rather than rates of change. As such, it is driven by the amounts of rainfall, irrigation, or evapotranspiration and only considers time indirectly by using the time from one irrigation or precipitation event to another.
TETrans predicts the average concentration of a solute within each defined soil layer or depth increment. Transport through the soil profile is modeled as a series of events or processes for a finite collection of discrete depth intervals. These sequential events or processes include: (i) infiltration and drainage to field capacity, (ii) instantaneous chemical equilibration for reactive solutes, (iii) water uptake by the plant root resulting from transpiration and evaporative losses from the soil surface, and (iv) instantaneous chemical reequilibration. Each process is assumed to occur in sequence within a given depth interval as opposed to reality where transport is a collection of simultaneous processes.
TETrans accounts for the hydraulic and physicochemical processes of water flow including preferential flow, evapotranspiration with a root growth and water uptake distribution function, adsorption-desorption, and drainage. The model determines the vertical profile distributions of total, soluble and adsorbed concentrations of a solute within and beyond the root zone; soil water content profile distribution; total drainage; total solute loading beyond the root zone; plant water uptake distribution; and leaching efficiency.