Water Quality Monitoring

7.1.1 Types and objectives of water quality assessment

As one of the most important life sustaining resources, water deserves close attention with respect to its quality and suitability both for man and for natural life. According to the UNESCOIWHOIUNEP guide (Water Quality Assessment, 1992), water quality observation programs could be subdivided to monitoring, survey, and surveillance. The surveillance usually is connected with specific operational and management issues. Survey is an intensive study limited in time and serving specific purpose. Monitoring is a long-term observation program reporting status of environment and trends in its development. In practice, the most common case of water quality management is multi-purpose water quality monitoring, which covers various water uses such as drinking water supply, industrial manufacturing, recreation, aquatic life, etc. This necessitates a large set of monitored parameters. Other common water quality assessment practices would be basic surveys, serving the purpose to identi@ major water quality related problems, and operational surveillance (for instance, drinking water supply control).

A special case is the water quality surveying for purposes of understanding the processes affecting the water quality and providing the basis for a policy decision. Usually such assessment is aided with mathematical modeling of water quality. Two such studies were conducted in the Nitra River basin twice, August 1992 and in June 1993, in the course of the reported research project (Chapter 8).

7.1.2 The institutional structure of water quality monitoring in Slovakia and in the Nitra River basin

The Ministry of Forestry and Water Management of the Slovak Republic charged the Slovak Hydrometeorological Institute (abbreviated SHMU in Slovak language) with the task of systematic monitoring of the quality of surface and subsurface waters in Slovakia. The regular monitoring of water quality of the Slovak rivers started in 1963; monitoring of the quality of groundwater started later in 1982. For both flow and quality monitoring, SHMU is in charge of overall supervision and management. In addition, it provides storage of the results in data bases, data processing and evaluation, as well as regular publication them in the form of annual booklets (yearbooks) for reference by any concerned organization.

The surface water sampling and laboratory analyses are carried out by individual watershed authorities. For the Vah and the Nitra river this task is performed by the Vah Authority in Piestany. The SHMU is also responsible for the flow measurements.

The surface water quality evaluation is published by SHMU in annual surveys called "The water quality in the streams of Slovakia" according to the acting Czechoslovak classification scheme (fiom the 1st of July 1990 the valid classification is CSN 75 7221). The evaluation serves mainly for classification purposes and does not have the aim to accomplish standard compliance. For assessment of the groundwater quality, the SHMU applies the drinking water quality standard CSN 75 71 1 1, and this evaluation is also published in annual surveys.

The water quality observation program in the Nitra River basin is a multipurpose monitoring program which reports both the state and trends of the major water quality parameters. As is often the case with multi-purpose programs (Water Quality Assessment, 1992), it exhibits a compromise based upon limited financial resources, the size of the set of parameters, the fiequency of sampling, and distribution of the network over a number of important locations.

As the analysis will show later, the monitoring system is in a need of reshaping. The most important issues are detection of non-traditional (organics, heavy metals) and non-point source pollution, increase of sampling fiequency at important locations (e.g. river mouth), and monitoring the condition of aquatic life. The detailed discussion of the improvement of the monitoring system can be found in Appendix 7.3, and the summary of the recommendations is in Section 7.4.

7.1.3 The monitoring network in the Nitra River basin and its relation to the character and occurrence of the pollution.

The monitoring network in the Vah watershed consists of 63 sampling stations. Of these, 26 sampling stations are located in the Nitra subwatershed (according to the annual survey for season 1989-1990, see Appendix 7.2). Figure 7.1 provides the outlook of the monitoring network in the Nitra River basin with respect to the location of municipal and industrial pollution; the sites where flow measurement are made are also shown.

Figure 7.1 shows that the monitoring points usually have been deployed in pairs, one immediately upstream of municipality and the other downstream, with the purpose to study the effects of the emissions. There are cases when the complete mixing of the effluent with the river water does not occur upstream of the sampling site (see Appendix 7.2). The allocation scheme used in the Nitra River basin would be adequate for checking the overall amount of the effluent material being discharged between the two points. However, in order to receive policy-oriented information, it is necessary to determine the origin of the pollution down to the particular discharge. This is possible only if the emission data are provided by the monitoring scheme, which is not the case at present, or by a specially organized measurement campaign (Chapter 8).

The sampling procedure should take into account high diurnal variability of the pollutant loads (Chapter 6). In order to get an idea about the mean daily average concentration and emission (cf. Figure 6. I), it would be desirable to take composite samples.

Figure 7.1. The surface water quality monitoring network in the Nitra River basin and the point-source pollution.