We present a simple one-dimensional lattice gas model, which describes very well the equilibrium and kinetic behaviors of water confined in a thin carbon nanotube found in an atomistic molecular dynamics simulation [G. Hummer, J. C. Rasaiah, and J. P. Noworyta, Nature (London), 414, 188 (2001)]. The model parameters correspond to various physical interactions and can be calculated or estimated by using statistical mechanics. Then, the roles of all interactions in the water filling, emptying, and transporting processes are clearly understood. Our results indicate that the interaction from the water molecules outside the nanotube plays a key role in these processes and the interaction can be simply treated as an average effect of the bulk water. (C) 2004 American Institute of Physics.