Gravity currents encountered in both natural environment and engineering applications have important influence on industrial production and life. In this paper, two high-speed digital cameras (one is from the top view and the other one is from the side view) were employed to obtain the three-dimensional motions of lock-exchange gravity current through a large number of repetitive experiments, i.e. these experiments were carried out under the same conditions. The front location, speed, height, and angles of the gravity current and their uncertainties were analyzed, and the effects of three-dimensional current motions on these uncertainties were investigated. The images from the top-view show that the density current head positions across the flume are different, indicating the presence of the three-dimensional motions in gravity current. The results show that the gravity current is composed of lobes and clefs, and the three-dimensional patterns of current motions from the lateral diffusion and the friction from the wall may be the cause of the uncertainty for current motions. The front location, speed, height, and angles of gravity current follow normal distributions at the selected time. The uncertainties of these parameters were measured by the coefficient of variation (COV). For the front locations, theCOVvalues decreases rapidly in the initial stage, and decreases below 6% slowly in the subsequent stage. TheCOVvalues for the front speed also rapidly reduces and then maintains a near constant value, approximately equal to 5%. Based upon the experimental results, the uncertainty for the front location or speed of gravity currents due to the three-dimensional gravity current motions will be approximately 5%~6% of the averaged front location or current speed, which can be used as a reference value for future individual measurement.
