We have developed a long-term observation system for the study of saline wedge at the mouth of river. The preliminary survey at the lower stream of River Gonokawa of Shimane Prefecture was done in 1997, and was reported by Tokuoka et al. in 1998. The successive two surveys were done in 1998 fiscal year and the results at a period of water shortage during December 23, 1998 and February 14, 1999 are reported in the present paper. The following instruments of echo-sounders (SC-2 and SC-3 of Senbon-Denki Co. Ltd.), echo-sounder (CL-2 of Clover Tech Co. Ltd.), Optical fiber system of Y.O. System Co. Ltd. and Multi CT Sensor of Tsurumi-Seiki Co. Ltd. with Electro Water Velocity Metor and IC Memory Thermometer were used for observation of saline wedge. The movements of saline wedge were successfully catched by the above instruments, and the present composite long-term observation system has been evidenced to be very useful for analysing salinewedge behaviour.