Graduate School of
Science and Engineering

In the fluid mechanics laboratory, we are building a “nowcast system” to track the 3D distribution of temperature and water currents in Lake Biwa, which is the largest lake in Japan and supplies water for 14M.  The system, one of the first “Operational Forecast Systems” of a lake or coastal sea in Japan, will combine available observations of the lake with computer simulations in the same way as Numerical Weather Forecasting, thus exemplifying Data Assimilation, the “Fifth Paradigm of Science”.  A feature of this effort is the world’s first application of Acoustic Tomography to a lake, wherein we have obtained strong evidence of currents in the lake’s deep waters, based on small differences in the reciprocal acoustic travel times between pairs of SONAR-type transponders separated about 10 km.   We also study basic processes of sand particle motion on river beds, developing and experimentally verifying highly detailed computer simulations of erosion and deposition (see figure).