□ Water level control 　 ● Target water levels for Lake Biwa □ Maintenance and Management of Facilities 　 ● Weeding of lake levees 　 ● Patrols of lake levees 　 ● Inspection of sluice gates 　 ● PInspection of drainage facilities 　 ● Dredge ship route ■ Operation of Facilities 　 ● In drought conditions:internal drainage facilities 　 ● In flood conditions:bypass aqueducts and water supply facilities and gates for water level □ Gathering Environmental Data in the Lake Biwa Basin 　 ● Hydrologic and meteorological data 　 ● Lake Biwa information provided by comprehensive automatic observation stations 　 ● Lake Biwa water environment survey including submerged plant observation ■Operation of Facilities In drought conditions:internal drainage facilities internal drainage facilities Flood-caused water increases exceeding a certain level in Lake Biwa have often resulted in inundation to low lands in the vicinity. They have also caused the rivers usually flowing into the lake to flow backward and flood their estuaries, and this causes damage in the region. Internal drainage facilities can minimize this damage. →An animate cartoon(Japanese) Top▲ In flood conditions:water supply facilities and gates for water level and bypass aqueducts water supply facilities and gates for water level and bypass aqueducts Precise regulation of downstream water discharge rate (flow rate) through Seta River Weir bypass aqueducts Top▲ Retaining the Inner Lake Water Level South Lake's levees and management roads include a zone constructed within the lake. The water remaining between this lake levee zone and the original lakeside formed inner lakes (Tsudae Inner Lake in Kusatsu City and Konohama Inner Lake in Moriyama City). Should the inner lakes be closed by lake levees, there is concern regarding several adverse effects such as: * Deteriorating water quality of the inner lakes * A possibility of the inner lakes drying out due to drought-induced water level drops and this will negatively impact the environment. Tsudae Inner Lake（kusatsu city） Top▲ How to maintain inner lake water level To maintain a satisfactory inner lake water level when Lake Biwa's water level drops, all sluice gates with no weir from among those installed at the midway points of the lake levees are closed first. The weir is then operated while keeping weir-equipped sluice gates open so that the water of the inner lake can accumulate to prevent a drop in level. But just allowing the water to accumulate will result in the water quality gradually deteriorating as the water does not change. In addition, evaporation and agricultural use will impact the inner lake's water level. Handling this situation optimally requires water supply equipment. As shown in the figure, the water supply equipment is installed with a water intake port extended offshore to allow an intake of water even at low water levels. Water from Lake Biwa flowing in through the water intake port is pumped up and sent to the inner lake. As Lake Biwa water is supplied to the inner lake, the inner lake's water level rises, overflowing the weir and running back into Lake Biwa. The inner lake water therefore changes to keep water quality from degrading while maintaining satisfactory water levels. Water supply facility mechanism Top▲   ■Contact us Copyright(c) 2003 Incorporated Administrative Agency Japan Water Agency Lake Biwa Development Integrated Operation & Maintenance Office All Rights Reserved.