On the Water Pollution Characteristics of the Yamada River Basin

Basic studies on the management of water quality used for agricultural water (I)

Abstract

The Yamada River flows into the Dondo Dam Reservoir which is under construction in the Toban Agricultural Water Utilization Project. The catchment area of the reservoir is 49.8km². The water will be used for agricultural and domestic uses.
The population in the area has been increasing recently, and reacheed 34, 000 in 1975 increasing from 6, 000 in 1960. This tendency will continue in the future.
We measured and analyzed the discharge and water quality (BOD, COD, nitrogen, phosphorus) at several points along the Yamada River and also at the tributary confluences. In this paper, we dealt with the 'COD and nitrogen which are important in the Agricultural Water Quality Standards.
From the analysis, we get the general view of the water pollution of the basin as follows:
1) The Water pollution of the Yamada River is mainly caused by the inflow of household wastewater.
2) The daily pollutional load production in the basin is estimated to be 450 kg/day for COD and 270 kg/day for total-N.
3) The sum of the load measured at the tributary confluence was 3.27 g/sec (283 kg/day) for COD and 2.04 g/sec (176 kg/day) for total-N.
4) The greater part of the load production is concentrated in three blocks. The load production in these blocks is estimated to correspond to 71% of the total load of COD and 83% of total-N. The load measured at the tributary confluences for the above-mentioned blocks corresponded to 82% of the total load of COD and 90% of total-N.
5) There was a relationship between the COD load and the total-N load at the tributary confluences.