ESTIMATION OF BOD LOADS CONSIDERING WATER TEMPERATURE IN THE YAMATO RIVER CATCHMENTS

Calculated Pollutant load per unit production and actual pollutant load of Yamato River were estimated. The actual pollutant load was determined from measured flow rates and concentrations. As a result, actual BOD load showed seasonal changes with low values of summer and high values of winter. The change depended on temperature because a rate of decomposition of organic compound depends on temperature. The actual BOD loads between two pints along the Yamato River with no branch river and no drainage were measured and a rate of decomposition between them was calculated. The calculated seasonal BOD load from pollutant load unit production method including rate of decomposition showed the same pattern of the actual BOD load. The total BOD load value by unit production including decomposition calculated method was 4 times of the actual load. As BOD was not measured at flood condition, the actual BOD did not include floating material at the condition of high flow rate and then was smaller than the calculated load per unit production.