To clarify water quality and pollutant loads in the Edo, Ara and Tama Rivers, we examine the temporal changes of water pollution using monitoring data obtained by local governments and continuous monitoring data for COD. We also evaluate yearly-averaged SS, COD, T-N and T-P fluxes in these rivers by conducting the field measurements under several hydrologic events. The trend analysis for COD continuously monitored in the Edo River indicates that the changes of COD under low flow conditions are not similar to those under flood conditions. The estimated COD, T-N and T-P fluxes in these rivers reveal that non-point sources are comparable to point sources. These facts demonstrate that previous data and analysis methods for pollutant loads into Tokyo Bay should be examined carefully.
