The mass balance in a caldera lake and new ponds, produced by a volcanic eruption

2001年7月至10月和2002年3月至8月对托雅湖进行了流速、浊度、水温监测和悬浮物截流。结果表明，在2000年4月至10月期间，我们没有发现由泥石流产生并保留的高度浑浊的湖底层。浑浊层的耗竭是由于悬浮泥沙的重力沉降。2001年7月至11月和2002年4月至2003年2月，分别对2000年乌苏火山喷发产生的火山口池（N-12或N-19）和新池（泉池）进行了水文检查。池内水量收支估算结果表明，lzumi池和N-19池的地下水净产量分别为0.003 ~ 0.004m^3/s和0.005 m^3/s。这表明在火山口池中主要是蒸发出水量而不是地下水出水量。

We monitored flow velocity, water turbidity and water temperature and trapped suspended sediment in Lake Toya for July to October 2001 and for March to August 2002. As a result, we did not find the highly, turbid bottom layer in the lake, which was produced and retained by the mudflows for April to October 2000. The depletion of the turbid layer is due to the gravitational settling of suspended sediment.A crater pond (N-12 or N-19) and a new pond (Izumi Pond), produced by the 2000 eruption of Usu Volcano, were hydrologically examined for July to November 2001 and for April 2002 to February 2003, respectively. An estimate of water budget in the ponds gave the net groundwater output at 0.003 to 0.004m^3/s in lzumi Pond and 0.00005m^3/s in N-19 Pond. This indicates that the water output by evaporation rather than the groundwater output prevails in the crater pond.