The effect of temperature on the surfactant-driven movement of water in wet "unsaturated" sand was investigated and correlated with the equilibrium spreading pressure of the surfactant and the character of the surfactant monolayer at pi(e). The previously determined criteria for surfactant effectiveness were confirmed. An approximately linear relationship between pi(e) and the amount of water moved by effective surfactants was found. Temperature changes affect water movement by influencing the surfactant pi(e), and the monolayer state at pi(e).