Presented here is a mathematical model study of a prototype solar still built at Jug Island near Gunsan City. A pair of ODE was solved numerically with auxiliary equations to demonstrate that the predicted water productivity was in good agreement with experimental values. Monthly average water absorptance was the major factor that influenced the solar still performance. It was also found that the initial water depth, the degree of insulation and the ambient temperature had significant influence upon the water productivity, wherease the wind velocity, the cover slope and the still orientation exhibited negligible effects.