The area of the Netherlands is about 42,000 km2 including 3,000 km2 large freshwater reservoirs (eg. the IJsselmeer). The Netherlands is a densely populated country with 15 million inhabitants. The main river systems of The Netherlands are those of the river Rhine and the river Meuse. The Rhine has a large impact on The Dutch water management, as approximately two thirds of the water influx is delivered by the Rhine. The main transboundary rivers, the Rhine, the Meuse, and the Scheldt, contribute substantially to the water quality in Dutch surface waters and in the North Sea.

Involved institutions

In the Netherlands the Ministry of Transport and Public Works has the responsibility for the national surface waters. Water management is delegated to the operational organization of the Ministry, the Rijkswaterstaat, daily management of surface water being undertaken by operational regional directorates. Expert knowledge and know-how about water quality issues is available at the expert institutes RIZA (Institute for Inland Water Management and Waste Water Treatment) and RIKZ (Institute for Coast and Sea).

RIZA and RIKZ are to: (1) give advice on policy and management; (2) gather information at the national level; surface water quality is monitored, partially analyzed at the RIZA laboratories, and the data is stored in information systems and used in reports on water quality trends and for policy development; (3) coordinate water quality issues at a local level of government, through the CUWVO-coordination commission.

Organizationally Dutch surface waters are divided into national surface waters, for which RIZA and RIKZ are responsible, and regional waters, for which several local waterboards are responsible. National surface waters are the main water (transport) system and include the rivers Rhine and Meuse (including sub-systems), Lake IJssel, estuaries, the Wadden Sea and the North Sea. All other surface waters are part of the regional water systems.

Inland surface waters

The monitoring activities of inland surface waters are coordinated by RIZA (Table 3.10).

National Surface Water Monitoring Programme (R1)

The major part of Dutch monitoring is encompassed by the yearly MWTL (National Surface Water Monitoring Program). The goal of this network, consisting of a physical, chemical and biological part, is to test and detect trends in water quality.

In 1955 chemical monitoring of inland waters was initiated at 4 locations. During the 1970s the number of locations increased by 100 per cent, during the 1980s, however, the number of locations decreased to about 130. In 1992 the monitoring network was evaluated and as a consequence of statistical relations between locations the number of locations was reduced to 26 and frequency increased. In addition to this re-design of the chemical monitoring, the biological monitoring network was started in 1992.

The chemical monitoring network consists of 26 sampling sites in inland waters. Approximately 120 variables are measured and the water concentration of some is analyzed. Since (apolar) organic micropollutants and metals are partially attached to suspended matter, some of these variables are (also) measured in suspended solids.

The biological monitoring network in inland waters consists of the following groups: fish, birds, macroinvertebrates, zooplankton, phytoplankton, vegetation (water plants), and ecotoxicological variables. Some of the variables are measured yearly, as for other variables a four year monitoring cycle is set up according to which each year a water system is subject to detailed study.

Aqualarm (R2)

The purpose of the Aqualarm monitoring network is early warning. Based on information on calamities, action can be taken and users of water warned. This network was initiated in 1974 and in the beginning of the 1990s (semi)continuous measurement of water quality was made at 7 on-line stations along the Rhine and the Meuse rivers. Since 1994 three stations remain (at the borders to Germany and Belgium along the rivers the Rhine and the Meuse and at Keizersveer). The instruments used are automated and work continuously in order not to miss incidents during night-time and weekends. Since the start of the network when only the classic variables (dissolved oxygen, temperature, conductivity, turbidity, pH) were measured and ionselective electrodes (for chloride, fluoride and cyanide) were used the number of measured variables have increased along with the introduction of instrumentation for on-line metal measurement (polarographic measurement of Cd, Cu, Pb, Zn), instrumentation for measurement of organic micropollutants and bioalarm systems. At present instrumentation for apolar organic variables (based on preconcentration, GC-FID), volatile organic variables (purge-and-trap GC-FID) and polar organic variables (based on preconcentration, LC-DAD) is installed. Bioalarm systems based on fish and daphnia systems are used and algal and a bacterial systems are planned to be introduced in the future.

Survey of harmful substances

In the preparation of the last policy documents RIZA and RIKZ selected the lists of variables to be measured on the basis of toxicity, production and transport information. Since information on the occurrence of many of the harmful (organic) micropollutants is insufficient, the list of variables is divided into a M-(Monitoring)-list and an I-(Inventory)-list. For M-list variables regular monitoring is obligatory, but studies, surveys and analytical methods will have to be developed for I-list variables. The intention is to evaluate the I-list variables before initiating regular monitoring. So monitoring as well as assessment are incorporated into the policy document.

Assessment of the water quality is part of the policy documents and a survey study is undertaken. This study, called I-list-investigation, was started in 1991 and will be evaluated in 1995. It concentrates especially on the measurement of new organic micropollutants, such as pesticides, and rare heavy metals at selected locations.

At a national level polluted sediments constitute a major problem. For this reason (locally gathered) data on sediment pollution are reported by the CUWVO-coordination to RIZA and stored in an information system. On the basis of this information detailed studies are carried out, policy plans suggested and a clean up is initiated.

Table 3.10: Dutch national surface water monitoring programmes.

No. Name Responsible institution Variables Period of operation &
Sampling Frequency (SF)
Data &
Inland surface waters
R1 National Surface Water Monitoring Programme (MWTL)
Monitoring of Inland Waters
RIZA 120 chemical, physical and biological variables Since 1955
SF: Chemical & physical variables 6-52/yr, biological variables
Presently 26 sites
throughout the country
Data storage and yearly reporting by RIZA
R2 Aqualarm
Early warning network
RIZA Chemical & physical variables Since 1974
(semi-) continuous
7 online stations along the rivers Rhine & Meuse No reporting
Coastal and marine areas
M1 National Surface Water Monitoring Programme (MWTL)

Monitoring of Marine Waters

RIKZ Chemical, physical and biological variables Since 1972
SF: chemical & physical variables 1-13/yr,
biological variables
95 sites along the coast Data storage and yearly reporting by RIKZ

RIZA: Institute for Inland Water Management and Waste Water Treatment; RIKZ: Institute for Coast and Sea

Marine waters

The monitoring activities in marine waters are coordinated by RIKZ (Table 3.10).

National Surface Water Monitoring Programme (M1)

The chemical monitoring programme of marine waters was started in 1972. The present monitoring network consists of approximately 95 locations, of which 21 are used for assessment of bathing water quality, and six for assessment of organic combinations in yacht havens. Sampling frequency varies from once to 13 times annually. The following variables are measured: general variables (oxygen, acidity, BOD, visibility), nutrients and eutrophication variables, inorganic and organic micropollutants, radioactivity variables, bacteriological variables and several sum variables.

Joint Monitoring Programme

Under the authority of the Oslo and Paris Commissions the condition of the seas covered by the Convention is being continuously reviewed. For this purpose a Joint Monitoring Programme (JMP) has been in operation since 1979. For the Netherlands the programme comprises (a) estimation of the level of pollutants in edible fish, (b) biological and biological effect monitoring, (c) assessment of spatial distribution of pollution, and (d) assessment of temporal trends in pollution within the Convention Area. The Dutch part of the JMP is closely related to the national programme (M1). Every year the results of the JMP monitoring activities of the preceding year are supplied to the ICES data bank.

Local monitoring

The monitoring network of local waterboards operates at a regional level and is therefore not incorporated into the national programme. The regional monitoring network covers several thousands of locations. Network design and operation is coordinated by the CUWVO-commission (RIZA being the coordinator). To make an annual report on Dutch water quality, a nation-wide inventory on water quality data of representative locations has been set up by CUWVO. For the next policy cycle this information will be incorporated into the policy information system called Aquatic Outlook. With this information it is possible to calculate and predict the results of different policy scenarios.


Geographic coverage


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Filed under: surface water
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