Water transport may be driven across dense thin-films when contacted with soil to create a non-pressure driven desalination process; however, the roles played by the different soil-water potential components (matric, osmotic, and vapor pressure) in driving water flux are not completely understood. Bench-scale tests were done using a reverse osmosis membrane and three different soils: sand, sandy-loam, and kaolin clay. The diverse physical and chemical characteristics of these soils were used to quantify membrane performance (water flux) and relate it to the magnitudes of the three soil-water potentials. Water flux was highest at initial contact between the soil and membrane, and then declined to reach a steady-state value, irrespective of soil type. The highest steady-state water flux, 1.8 l/m(2)/h, was measured for the pure clay system. Matric and osmotic potential gradients were the primary drivers for water flux, while vapor pressure played a minor role. Membrane orientation (active or support side facing the soil) and internal concentration polarization were also identified as determinants of water flux.