2001 Volume 47 Issue 2 Pages 155-161
The material balance of phosphorus in a semi-closed bay (Omura bay) has been calculated by actuality measurements and data from an observation satellite (LANDSAT 5) over the last eleven years. It appeared that the phosphorus inflows to the bay from the 696 places of business and the twelve rivers were 293 tons/year and 20 tons/year, respectively. About 90% of the phosphorus from the places of business was released into the bay from only six sewage treatment plants. The phosphorus outflows from the bay, which occurred with the tide changes and with the catching of fish, were 219 tons/year and 7 tons/year, respectively. The urban areas inside the watershed that were calculated from the LANDSAT data using the normalized difference vegetation index (NDVI) value showed an increase each year with a wide range of variation. This slope was closer to the one showing the increasing amount of phosphorus in the bay than to the slope of the increase in population inside the watershed.
