The effect of external charge oil distribution properties of water molecules confined inside the single-walled carbon nanotube (SWNT) with modified carbon-water interactions is investigated by the molecular dynamics simulations. It is found that when a single external charge (of value +1.0e) is in the middle region of the SWNT, the nanotube is filled by the single-file water chain. Sharp transitions between empty (closed) and filled (open) states occur once the charge moves out the middle region. Simulation results indicate that filling and emptying kinetics depend sensitively on the position of external charge. These findings are helpful to understand the mechanism of charge-dependent gating of hydrophobic nanotubes.