River Water Level and Droughts in Ado River, An Inlet Stream of Lake Biwa, Central Japan

Droughts have been often observed in the inlet streams of Lake Biwa, central Japan. Water level gauges corresponding to underground flow were laid in the lower reach of Ado River, one of those streams, and the days with drought from (cid:9874)(cid:9872)(cid:9872)(cid:9877) to (cid:9874)(cid:9872)(cid:9872)(cid:9880) were estimated. Droughts occurred in various seasons from May to December. A comparison of river water level during drought, rainfall, agricultural water intake and lake water level revealed that the latter two factors might be possibly concerned with the drought. For the conservation of migratory fishes between Lake Biwa and its tributaries, it is desirable to lay the water level gauges and monitoring cameras those effectively monitor the river flow conditions including low levels and droughts, and have enough discussions on sound water management in rivers and lake in relation to agricultural use and lake level control.