Accurate Throughfall Measurement with a Bottle Using a Digital Hanging Scale and Graduated Cylinder

Abstract

　For Japanese forest hillslopes, the water volume of a rain bottle gauge is measured in many cases using a handheld graduated cylinder or digital hanging scale. No reported study has verified the error produced when using these measuring instruments. For this study, to verify the measurement accuracy of water amounts in bottles on forest hill slopes, we conducted a measurement experiment using a handheld graduated cylinder and a digital hanging scale. Results of measurement experiments conducted with a handheld graduated cylinder demonstrated tendencies to tilt the upper part forward by 2° to 3°, with reading of more than the actual amount of water. The horizontal state must be maintained to reduce these errors. Results of a measurement experiment using a digital hanging scale indicated that the generated error is less than that of a handheld graduated cylinder for weight of 5 kg or more. However, the water surface must be kept stable. A suitable instrument must be devised depending on conditions such as the measurer and the water contained in the bottle.