## 1. Introduction

[2] It is important to understand the behavior of flow of saline fluids in nonisothermal, unsaturated porous media. Understanding the effects of salt in such systems is required in soil science (e.g., arid soils [*Weisbrod et al.*, 2000]), in the design of hazardous waste storage (e.g., the Hanford site), and in drying science (e.g., manufacturing and processing of materials). As early as 1909 [*Müntz and Gaudechon*, 1909], it was noted that water accumulated near salt crystals in soil, and it has long been known that water vapor pressure is reduced above both curved liquid-gas interfaces and above saline fluids [cf. *Edlefsen and Anderson*, 1943]. It is also known that addition of salt will alter the specific volume of water [cf. *Heyrovska*, 1996]. However, to date, understanding of the effects of salinity on water movement in soils has been based on dilute solution assumptions that neglect the effects of changes in specific volume corresponding to changes in salt concentration.

[3] Very general relationships describing salt effects on water vapor pressure and liquid pressure for variably saturated soils have been derived from first principles for isothermal soils where the local equilibrium assumption is valid [*Burns et al.*, 2006]. For simplicity, only isothermal conditions are considered here; but it is noted that the extension of the theory to anisothermal systems only requires that all computations of pressures and any other appropriate variables occur at a range of temperatures, allowing determination of an empirical relationship describing the temperature dependence. This is a common strategy for modeling anisothermal conditions, where the implicit assumption is that concentration and temperature are independent [cf. *Nassar and Horton*, 1989; *Bear and Gilman*, 1995; *Olivella et al.*, 1996].

[4] We now provide an application of this theory. It is of interest to understand when the “standard theory” (defined rigorously by *Burns et al.* [2006]), which is based broadly on the dilute solution assumption, is insufficient. The two goals of this paper are: (1) to show the information required and procedure for application of the theory and (2) to identify the conditions for which it may be necessary to use this more complex general formulation. An example computation is performed for a range of soil textures with sodium chloride (NaCl), to illustrate the effects of different soils on the constitutive relations. Predictions are also compared with the experimental results of *Scotter* [1974].