Lake Shinji

Lake Shinji is a lagoon located in the eastern part of Shimane Prefecture, in the Shinji lowlands. It has an area of ​​79.1 square kilometers, a circumference of 47 kilometers, and is long from east to west. Its maximum depth is 6.4 meters. It is connected to Lake Nakaumi by the Ohashi River. Mountains and hills are close to the southern and northern shores of the lake, but the shoreline is monotonous. The largest of the rivers that flow into the lake is the Hii River on the west bank, and the largest of the discharge rivers is the Ohashi River, which flows through Matsue City on the east bank and empties into Lake Nakaumi, and the artificial Sada River, which flows out from the north bank and empties into the Sea of ​​Japan. The coastal areas have often been hit by floods since ancient times, so the Sada River was excavated in 1787 (Tenmei 7). Even now, the water level is still 0 meters above sea level, and heavy rains often cause flooding. Seawater can also flow back through Lake Nakaumi and the Ohashi River, causing salt damage. In 1963 (Showa 38), a plan was started to desalinize Lake Shinji and Lake Nakaumi and use the water for agricultural use in reclaimed land and surrounding farmland (Lake Nakaumi Desalination Project) with the aim of increasing rice production. However, rice production was reduced after that, and the deterioration of water quality due to desalinization became an issue, so in 1988 (Showa 63), Tottori and Shimane prefectures asked the national government to postpone the construction, and the project was frozen, and in 2002 (Heisei 14), the desalinization project of Lake Shinji and Lake Nakaumi was canceled. The lake water is brackish, close to freshwater, and is rich in fish and shellfish such as carp, crucian carp, icefish, smelt, mullet, sea bass, and clams. In the eastern part of the lake, there is a small island called Yomegashima, made of basalt rock, and in the north of the lake there is an old sea cliff called Jyurokuhakko. The 138-meter Matsue Ohashi Bridge spans the Ohashi River, which divides the city of Matsue into north and south, and the Shinjiko Ohashi Bridge (310 meters) was built on the west side of the Ohashi River in 1972. Lake Shinji was registered as a Ramsar Convention wetland in 2005.

[Hikari Iida]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

島根県東部、宍道低地帯にある海跡(かいせき)湖。面積79.1平方キロメートル、周囲47キロメートルで、東西に長い。最大深度6.4メートル。大橋川によって中海(なかうみ)に接続する。湖岸の南部と北部には山地や丘陵が迫っているが、湖岸線は単調である。流入する河川のうち西岸の斐伊(ひい)川が最大で、排出河川は東岸の松江市を貫流して中海に注ぐ大橋川と、北岸から流出して日本海に注ぐ人工水路佐陀(さだ)川がある。古来沿岸地域はしばしば洪水にみまわれたため、1787年（天明7）に佐陀川が掘削された。現在も水面標高が0メートルであり、豪雨時には水害を招くことが多い。また、中海、大橋川を通じて海水が逆流して塩害を生じることもある。1963年（昭和38）米の増産を目的に、宍道湖と中海を淡水化し、干拓地や周辺農地への農業用水として利用する計画（中海・宍道湖淡水化事業）が着手された。しかしその後は米の減反が進み、淡水化による水質の悪化なども問題となり、1988年（昭和63）鳥取、島根両県が国に工事の延期を申し入れ、事業は凍結し、2002年（平成14）宍道湖、中海の淡水化事業は中止となった。湖水は淡水に近い汽水(きすい)で、魚貝類もコイ、フナ、シラウオ、ワカサギ、ボラ、スズキ、シジミなど豊富である。湖上東部には玄武(げんぶ)岩からなる小島の嫁(よめ)ヶ島が浮かび、湖北には十六禿とよばれる旧海食崖(がい)がある。水郷松江の市街地を南北に分ける大橋川には全長138メートルの松江大橋が架かり、また、その西側には1972年（昭和47）に宍道湖大橋（310メートル）が架設された。なお、宍道湖は2005年（平成17）に、ラムサール条約登録湿地となった。

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