Abstract
Seasonal and spatial changes in water quality in Lake Teganuma were investigated by using the field data and were simulated by a flow, water quality and sediment model. Chlorophyll-a and COD increased, and inorganic nitrogen, phosphate, total nitrogen and total phosphorus decreased toward downstream direction. Chlorophyll-a increased in summer and decreased in winter, and inorganic nitrogen and phosphate decreased in summer and increased in winter at the observation point of Nedo-shita. These observed variations of nutrients were practically reproduced in the simulation of the flow, water quality and sediment. Furthermore, according to the mass balance, 50 percent of total phosphorus in the inflow load was transported to downstream and the rest of 50 percent was accumulated to the bottom of the lake. Moreover, the results of the simulation suggested that 20 percent of total phosphorus in the inflow load is release from sediment.
