江の川の塩水楔 : 塩水遡上の長期連続観測システムの開発(予報)

We have developed a long-term observation system for the study of saline wedge at the mouth of river. The observation were carried out at the lower stream of River Gonokawa of Shimane Prefecture during December 14, 1997 and January 24, 1998. The following instruments were used for observation: (1) Underwater acoustic profiler for survey of saline wedge (SC-1 of Senbon Denki Co., Ltd.), (2) On-line type, underwater acoustlc observation system for detecting of halocline (SC-2 of Senbon Denki Co., Ltd.), (3) Off-line type, underwater acoustic observation for detecting of halocline (CL-1 of Clover Tech Inc.), (4) Thermometry system using optical fiber distributed temperature sensor (DTS-80 of Y.O. systems Inc.), (5) CT multi-sensor cable remodeled by XCTD probes for measurement of salinity and temperature (Tsurumi-Seiki Co., Ltd.), (5) Electoromagnetic current meter (Alec Electronics Co., Ltd.) and (6) Compact water temperature recorder (T.S. WaDaR of Tsurumi-Seiki Co., Ltd.). On the basis of acoustic profiling survey by ship, the front of saline wedge at River Gonokawa was observed to be located at 7.0km point from the river mouth on Dec. 14, 1997 and at 4.0 km point on Jan. 14, 1998, respectively. All instruments were arranged on the said date at the area between 5.4 km and 6.0 km from the river mouth. It was successfully observed that saline water had invaded at least twice to this area. This newly developed system has indicated to be very useful for long-term observation of saline-wedge.