Water Pollution Continuous Monitoring Technology in Japan
 Plan of Water Pollution Monitoring

1. Plan of Water Pollution Continuous Monitoring

1.3 Precautions for Water Pollution Monitoring

(1) Rivers, lakes and reservoirs, and coastal waters

(a) Rivers

-Items to be recorded include: date and time of the sample collection; surface area of the water; distance of the sampling point from the right and left banks of the river; water depth, flow rate, flow direction; rain condition, land profile and water use in the area near the sampling point; and main pollution sources.

-Certain samples are subject to oxygen fixation. The water temperature, ambient temperature, color phase, transparency, turbidity, smell and biological phase of all the samples should be measured or observed.

-Measuring method of flow rate: Flow rate is indispensable for the calculation of pollution load. Therefore, the flow rate must be measured precisely by avoiding a time difference between measurements of flow rate and other water quality items. Generally, a flow rate should be measured by: properly dividing the horizontal section area into several zones; measuring the average flow rate of each zone; and then calculating the sum of the values obtained by multiplying the flow rate of each section area and the section area measured. Other methods, such as curve related with water level and flow rate, may also be applied.

Water surface

A number of methods are available to obtain average flow rate. An example is shown below. If the river is extremely shallow and measurement cannot be made with a flow-rate meter, measurement should be made with a floated piece of wood.

• Rivers more than 1 meter deep:
-Two-point method, using a flow-rate meter
-Mean value of the flow rates, measured at depths equal to 20% and 80% of the total water depth

• Rivers less than 1 meter deep:
-One-point method, using a flow-rate meter
-Flow rates, measured at depths equal to 60% of the total water depth

(b) Lakes and reservoirs
-Items to be recorded include: date and time of sample collection; surface area of the water; distance of the sampling point from the right and left banks of the river; water depth, flow rate, flow direction; rain condition, land profile and water use in the area close to the sampling point; and main pollution sources.

-Certain samples are subject to oxygen fixation. Water temperature, ambient temperature, color phase, transparency, turbidity, smell and biological phase of all the samples should be measured or observed.

(c) Coastal waters
-Parameters to be recorded include: date and time, location and water depth of the sample collection; time of low tide, tide level and tidal current; rain condition, direction and velocity of wind; water use near the sampling point; and main pollution sources.

-Certain samples are subject to oxygen identification. Water temperature, ambient temperature, color phase, transparency, turbidity, smell and salt content of all the samples should be measured or observed.

(2) Underground water
Overall conditions such as the existence of wells, water use and underground water flow in the target area should be surveyed properly to understand overall requirements for an effective survey of water pollution

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