Water Quality Monitoring (1) Continuous Monitoring of Public Waters and Groundwater (Japan)
WEPA Water Environment Partnership in Asia
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(1) Continuous Monitoring of Public Waters and Groundwater

Overview

Water Pollution Control Law requires governors to comply with the following four obligations:

  • To continuously monitor the progress of pollution of public waters and groundwater;
  • To prepare a monitoring plan that requires not both national and local governments to measure the same variables in a uniform manner at sites having the same selection criteria;
  • To have measurement results obtained in accordance with the plan reported to them; and
  • To punish progress of pollution control efficiency.

The water quality survey on public waters covers 26 health parameters under the environmental standards, 10 parameters relating to the living environment and 23 precautionary monitoring parameters. As for the water quality survey on groundwater, it covers 26 health parameters and 23 parameters relating to the living environment.

In fiscal year 2006, the national and local government measured 237,873 samples from 5,487 locations for quality standard variables related to human health. Measurements relating to quality standards for protection of the environment were made on 409,182 samples from 7,155 locations. In fiscal year 2006, groundwater quality was measured at 4,738 general survey well sites, 1,642 survey around contaminated well sites, and 4,895 regular monitoring survey well sites.


Water Quality Monitoring by Local Governments

Water quality survey methods
“Standard Survey Methods of Water Quality” published by the Environment Agency (present Ministry of the Environment) in 1971 provides the standard methods for water quality surveys. They shou1d be followed in all surveys including continuous monitoring of pollution of public water by governors, surveys required for the designation of the types of water areas for quality standards, those to establish local effluent standards that are more stringent than the national ones, those for effluents from the factories and business establishments, and those for bottom sediment in public waters.

Monitoring parameters and frequencies Parameters related to human health
As for health related water quality standards, water samples shou1d be collected and analyzed at least l day a month and 4 times a day on the day of sampling. All heath parameters should be surveyed at least once per month. As for the rest of the days monitored, surveys are implemented only for the parameters that previous surveys have suggested there might be necessary.

Parameters related to living environment
Parameters related to the living environment, at reference stations, or those located in areas monitored for achievement of standards, or at locations of important water uti1ization, water samples should be collected and analyzed at least l day a month, approximately 4 times a day. However, the sampling frequency may be reduced depending on the situation. For example, at locations where water quality fluctuations are minor, such as those in the upstream of rivers and those off the shore monitoring frequency might be reduced.

At locations having major daily water quality fluctuations through a year, water samplings and analyses should be conducted 13 times a day at 2 hour intervals, approximately 2 days a year.

In supplementary surveys at locations other than those mentioned above, water samples should be collected and analyzed at least 4 days a year.

Timing of surveys and sampling locations

Rivers
Survey periods sbou1d cover the time lowest water level and the time of active water use. Sampling should be conducted on days having stable water quality following several days of relatively calm weather.

Sampling locations should be selected based on the following considerations; (1) the location of water use, (2) the location where polluted water is sufficiently diluted after it has been discharged to the river and the location upstream of such discharge, (3) the location where the water from a tributary is sufficiently mixed with water of the main stream, and the locations of the main stream and tributary upstream of their junction, and (4) any other location to be established as required. Reference stations for quality standards must be always included in the ambient water quality monitoring survey.

Lakes and reservoirs
Since water quality differs significantly between stagnation and circulation periods, surveys should be timed so that the water quality in both periods is measured. In addition, the period when water quality adversely affects water use should be included.

Sampling should be conducted on a day with stable water quality conditions following severa1 successive days of relatively calm weather.

Sampling locations should be selected based on the following considerations; (1) the center Of a lake, (2) the location of water use, (3) the location where polluted water is sufficiently diluted after it has entered the lake or pond, (4) the location where water from the river is sufficiently mixed with water of the lake or pond, and the location of the lake or pond upstream to the inflow of the river, and (5) the location where the lake or pond water flows out. Water quality reference sites must always be included in ambient water quality monitoring surveys.

Sea areas
Surveys should cover the period when water quality adversely affects water use. It is desirable to arrange surveys of sea areas during the same period as those for influent rivers. Samples should be collected at spring tides on a day with minor influence from rain and wind.

Sampling locations should be selected based on consideration of topography of the area, 1ocal currents and tides, local water uses, locations of major pollution sources and influent rivers, an understanding of the pollution in the water area. Sampling stations shou1d be located at about 500m to l km from each other. Water quality reference sites must be included in ambient water quality monitoring surveys.


Monitoring of groundwater quality

A notice of the “Standard Survey Methods of Groundwater Quality” was issued in 1991, when an amendment of the Water Pollution Control Law introduced a ban on infiltration of water with hazardous substances into underground. This same notice required continuous monitoring of groundwater quality by prefectural governors. A summary of the “Standard Survey Methods” is provided below.

Types of groundwater quality surveys

There are three types of the groundwater quality surveys including, 1) a general survey, 2) a survey of the area around the contaminated well, and 3) a regular monitoring survey.

Their purposes are:

1) General survey
A general survey is a groundwater quality survey to identify the general condition of groundwater in the area. It should be conducted following an annual plan with consideration of local conditions. As a part of this survey, it is desirable to monitor long-term annual changes in groundwater quality at certain representative locations in the area.

2) Survey of the area around contaminated wells
This is a more intensive groundwater quality survey to determine the extent of contamination at sites were pollution was detected during the general survey.

3) Regular monitoring survey
This is groundwater quality monitoring On an annual, or Some Other regular time interval basis to track contamination that was identified during the survey around contaminated wells.

Survey variables and frequencies

1) Survey variables
Groundwater quality should be surveyed for variables specified in the quality standards concerning groundwater contamination. When the contamination is very unlikely, the number of variables to be surveyed may be reduced appropriately. Technical specications of the well to be surveyed should be collected frequently during the survey. Variables other than those specified by the standards should be surveyed for characterization of groundwater quality, when appropriate.

2) Frequencies

i) General survey
When an annual survey plan is prepared, the survey wells should be measured at least once a year. It is desirable to take seasonal variations into consideration.

Surveys of the same wells again should be evaluated after several years to determine possible changes in groundwater flow and/or the need to modify the monitoring variables and frequency.

ii) Survey of the area around the contaminated well
A survey should be conducted as soon as possible after the detection of contamination. It is desirable to complete the survey for each well as quickly as possible to avoid impacts of factors such as precipitation.

iii) Regular monitoring survey
The survey wells should be measured at least once a year during the same season every year. It is desirable to measure seasonal variations and to take them into consideration.

Survey locations

Vertical spreading of the contamination should be considered in surveys. Survey monitoring locations should be selected for each type of survey giving consideration to the following factors.

1) General surveys

  1. Surveys should be designed to identify the general condition of groundwater quality throughout the survey area.
  2. Surveys should concentrate on the areas with significant potential contamination and those with potential impacts of the contamination on local water use. This requires knowledge of factory and business locations relative to the pollution and the use of groundwater.
  3. Priority should be given to monitoring wells that might have significant potential impacts on the health of large populations.
  4. Priority should be given to the wells that might have significant potential contamination suggested by the location of factories and business establishments in the area.

2) Survey of the area around contaminated wells

  1. The survey area should be determined to include all of the predicted contaminated area.
  2. When groundwater flow direction is known, the survey should be conducted in a zone along this gradient.
  3. It is desirable to survey drinking water wells in the area.
  4. When a survey area is large, with many wells to be surveyed, the area should be divided into subareas, and the subareas should be surveyed on a rotating basis.
  5. Although existing wells should be surveyed, consideration shou1d also be given to installation of new wells in areas Where none exist.

3) Regu1ar monitoring survey

  1. Representative locations should be determined to observe annual groundwater quality changes in the area giving consideration to the location of factories and business establishments, as well as the proposed groundwater use. Regular monitoring of contaminated areas shou1d cover locations c1ose to the pollution source as well as uncontaminated locations downstream.
  2. Supplemental observation wells should be established in a manner to promote more effective monitoring, when appropriate.

Reference: Okada M, Peterson SA.(2000): “Water Pollution Control Policy and Management: the Japanese Experience”. Gyosei, Japan, 287pp.


Relevant Information
previous Water Quality Monitoring

previous(2) Monitoring of Effluent Quality
previous(3) Water Quality Monitoring by Local Governments
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