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The Global Environmental Monitoring System (GEMS) was initiated in 1974 as a means of promoting and coordinating the collection of environmental data nationally, regionally, and globally. While GEMS aims at assisting governments to develop monitoring systems for their own use, its other objectives are to improve the validity and comparability of environmental data globally and to provide for the collection and assessment of environmental data. Within GEMS, major programs were developed for climate-related monitoring, monitoring of natural resources, monitoring of the oceans, and health-related monitoring.
As part of the latter group of projects, the global water quality monitoring project, briefly GEMS/Water, was established in 1976 jointly by WHO, UNESCO, WMO and UNEP. The objectives of the project were:
The global water quality monitoring project is based on the active participation of Member States which routinely monitor the quality of their water resources at selected locations and provide the data for global syntheses and dissemination. Wherever possible, the stations for the global network were selected from existing national or local networks. Where such stations did not exist, new ones were established. Priority was given to water bodies (rivers, lakes and groundwater aquifers) which are major sources of water supply for municipalities, irrigation, livestock, and selected industries. A number of stations were also included to monitor international rivers and lakes, rivers discharging into ocean and seas, and water bodies not yet affected by man's activities (baseline stations).
The target for the first stage of the project (1977-1981) was the establishment of a skeleton network of approximately 300 monitoring stations on rivers, lakes, and in groundwater aquifers. At that time it was estimated that a total of about 1200 stations might ultimately be required to achieve representative global coverage. Measurement of water quality variables at these stations include natural as well as anthropogenic constituents.
The years 1977 to 1979 were used as a preparatory phase during which time guidelines were prepared, specialists were trained in the different regions, and national, regional and global centres were established. National institutions were identified in agreement with the governments and designated as the focal points for GEMS/WATER activities within each country. In addition, laboratories were designated to conduct the routine sampling and analysis at the selected monitoring sites.
GEMS/Water is implemented by UNEP, Nairobi and WHO, Geneva, with the assistance of WHO Regional Offices. Technical support is provided by two WHO regional centres for environmental health. In addition, institutes have been designated as regional reference laboratories for implementing the analytical quality assurance component of the project. The Global Data Centre is located at the Canada Centre for Inland Waters, Burlington, Canada, which was designated both a WHO Collaborating Centre on Surface and Ground Water Quality and a UNEP GEMS Collaborating Centre for Freshwater Monitoring and Assessment. The Danish Institute for the Water Environment (VKI) in Horsholm, Denmark served as the global centre of analytical quality control. UNESCO participated in the field of training and measurement methodology. WMO has concentrated on network design criteria and hydrological monitoring methods.
The initial phase of the project, 1977-81, led to the completion of a basic monitoring network, and routine operations with regard to data flow were established for most stations during 1978 or 1979. The necessary technical procedures were provided through the GEMS/WATER Operational Guide which has been used in all laboratories and institutes as the principal guideline for their monitoring program.
Having achieved a certain level of routine monitoring and data reporting, it was considered timely to compile project results in the form of three publications which appeared in 1983:
The data received from each of the stations listed in the Directory have been summarized for the first operational triennium of the project, 1979-1981, and were presented in a first report. This was followed by the publication of the GEMS/WATER Data Summary 1982-1984, a GEMS/Water Assessment of Freshwater Quality, 1988, the GEMS/Water Data Summary 1985 - 1987, the GEMS/Water Data Summary 1988 - 1990, the GEMS/Water Data Summary 1991 - 1993 and the GEMS/Water Data Summary 1994 - 1996.
This is now followed by the present data summary report which covers the triennium 1997 - 1999. These data summary reports are strictly limited to the presentation of station and monitoring data, including their statistical treatment. The publication of this triennial summary continues the practice of electronic publishing via the INTERNET. This data reporting is part of the ongoing requirements of GEMS/Water to provide country summaries for participating nations.
Based upon the provisions outlined in the GEMS/WATER Operational Guide, a skeleton network of water monitoring stations has been established during the first phase of the project. By June 2002, a total of 865 stations had been formally designated by the responsible national authorities in 76 countries. In terms of waterbodies covered, there are 651 river stations, 95 lake stations, and 119 groundwater aquifers.
All stations filed at the Global Data Centre are briefly described under Station Inventory of this report. The current status of data reporting within the global network is given in section 2, Data Reporting Status. The statistically treated results for the reporting period 1997-1999 are given by station in the section, Statistical Summary of Data, 1997-1999 for all stations where data existed in the 1997-1999 period. .
For the initial project phase, sampling frequencies were suggested for rivers (every two weeks), lakes (every two months) and groundwaters (every three months). Statistical examination of the data would thereafter allow for determination of the optimum sampling frequency at each station. The water quality variables to be measured at each station fall into three categories, namely (i) 13 basic physical, chemical and microbiological variables (ii) globally significant variables comprising such pollutants as heavy metals and pesticides; and (iii) various site-specific optional variables. In addition, hydrological measurements, such as instantaneous discharge are also required. All GEMS/WATER variables and the respective analytical methods are listed in the Code Dictionary (CODES).
All data from the global network are handled at the Canada Centre for Inland Waters where all original country program documentation, Country Fact Sheets and Station Forms, as well as all completed Data Forms are archived. The data are edited visually and by computer methods, thus eliminating obvious errors and identifying anomalies which are referred back to the originating laboratory, together with the periodic data returns.
In addition to the present data summary report, a variety of reports and statistical treatments of the raw data are available to the participating institutions. These include quality control error listings, station and variable inventories, detailed data listings, mass loading computations, and graphical displays. Non-standard data summaries can be produced by the individual stations, types of water bodies, regions or other compilations required for the assessment of water quality.
All water quality data received at the Global Data Centre for the period 1 January 1997 to 31 December 1999 were processed in accordance with the GEMS/Water Operational Guide. The data were statistically treated and summarized for each individual station over the entire three-year period. The results are presented in section 3, Statistical Summary of Data, 1997-1999, in alphabetical sequence by country name.
Each statistical summary by station starts with a brief identification of the major station features. Additional information, including the responsible laboratory, is provided in the GEMS/WATER Directory of Participating Institutions which follows the same sequence of presentation. Detailed explanations, particularly on codified information, are contained in Chapter VI of the GEMS/WATER Operational Guide.
The station data summary tabulations contained in section 3 of this report show the statistical parameters for each of the analytical variables measured at the station. In making comparisons between stations it should be noted that separate variable codes have been assigned in different analytical methods used in the measurement of the same variable. The Dictionary section (CODES) provide the necessary information on methods and codes in an abbreviated form.
The following definitions apply to the statistical parameters used in the data summary tabulations in section 3, Statistical Summary of Data, 1997-1999.
NO. OF G-FLAGGED VALUES provides a count of all values greater than measurement limit (value entered is the maximum measurable value);
NO. OF UNFLAGGED VALUES provides a count of all values that are unflagged.
The statistical summary presentation in this report is limited to the above parameters. For the study of specific water quality problems other forms of data presentation might be used. However, the format chosen allows each participating national/regional centre and all laboratories to rapidly verify the completeness of data reporting and processing. Thus data communication lines could be improved where necessary for the preparation of reliable data summaries in future years.
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