Monitoring and assessment of river basin water quality

With a focus on the Danube, Dr Igor Liska and Dr Benedikt Mandl give an overview of the key elements of international monitoring and assessment of water quality in river basin management.


The International Commission for the Protection of the Danube River (ICPDR) coordinates the efforts of the European Union (EU) as well as 14 countries that have a share in the Danube’s 2,000km2 catchment area to improve water quality. Two bodies of public international law underlie this: the Danube River Protection Convention (DRPC) and the EU Water Framework Directive (WFD).

The EU WFD came into force in December 2000. It established a legal framework to protect and enhance the status of aquatic ecosystems, prevent their deterioration and ensure the long term, sustainable use of water resources. The WFD requires all EU transitional, coastal and surface inland waters to achieve “good chemical status and ecological status or potential.” Starting in 2009, the WFD will also require countries to develop river basin management plans with six-year implementation cycles.

The WFD calls for the creation of international districts for river basins that cover the territory of more than one EU member state, such as the Danube River Basin (DRB). Therefore, it is the catchment area and not just national borders that defines a relevant geographic region for water management. In this context, it is worth noting that all countries cooperating through the DRPC committed themselves to implement the WFD, i.e. even non-EU member states that are ICPDR contracting parties.

Both development and implementation of the Danube River Basin Management Plan (DRBMP) are linked to water quality monitoring and analysis activities.

The six-year implementation cycles rotate, in simplified terms, from: • Analysis and pressure identification • Drawing up measures in response to these pressures • Implementation of these measures

Following the implementation, the cycle starts for a second time, evaluating the impacts of the first. Currently, the second DRBMP is under preparation, where it will stay until December 2015. Water quality monitoring and assessment can be seen as a basis for the management plans, the Danube Basin Analysis (DBA), prepared in accordance with article 5 of EU WFD, as the analytical starting point.

The overall aim of the DBA is the identification or estimation of surface water bodies, such as rivers, lakes, transitional waters and coastal waters, being at risk or not at risk of failing the WFD objectives in relation to four main pressures: organic pollution, hazardous substances, nutrient pollution and hydromorphological alterations. These four pressures are considered Significant Water Management Issues (SWMIs), which represent cornerstones for the management plan.

The DRBMP is based mainly on national data, as well as two major analytical efforts: the Transnational Monitoring Network (TNMN) and research expeditions called Joint Danube Surveys. In the following, a more detailed account of both is given.

Transnational monitoring network

The TNMN has been in operation since 1996, although the first steps towards its creation were taken about ten years earlier. It was revised between 2000 and 2007 to align it with the objectives of the WFD. Since then, the major objective of the TNMN has been to provide an overview of the overall status and long-term changes of surface water, and where necessary the groundwater status, in a basin-wide context with particular attention paid to the transboundary pollution load.

In view of the link between the nutrient loads of the Danube and the eutrophication of the Black Sea, it is necessary to monitor the sources and pathways of nutrients in the DRB district and the effects of measures taken to reduce the nutrient loads into the Black Sea.

The TNMN for surface waters consists of the following elements: • Surveillance monitoring I – monitoring of surface water status • Surveillance monitoring II – monitoring of specific pressures • Operational monitoring • Investigative monitoring

Surveillance monitoring I and operational monitoring are based on the collection of data on the status of surface water and groundwater bodies to be published in the DRBM plan once every six years. Surveillance monitoring II is a joint monitoring activity of all ICPDR contracting parties, which produces annual data on concentrations and loads of selected parameters in the Danube and major tributaries.

Investigative monitoring is primarily a national task, but at the basin-wide level joint Danube surveys were pursued, e.g. for the harmonisation of existing monitoring methodologies, filling the information gaps of the monitoring networks operating in the DRB, testing new methods or checking the impact of chemical substances not assessed so far in different matrices. Joint Danube surveys are described in more detail below.

The TNMN is based on national monitoring networks and the operating conditions are harmonised between the national and basin-wide levels. The selection of monitoring sites is based on the following criteria.

Monitoring sites that have been monitored in the past and are therefore suitable for long-term trend analysis, including sites: • Located just upstream or downstream of an international border • Located upstream of confluences between Danube and main tributaries or main tributaries and larger sub-tributaries, to enable estimation of mass balances • Located downstream of the major point sources • Located to control important water uses • Sites required to estimate pollutant loads, e.g. of nutrients or priority pollutants, which are transferred across boundaries of contracting parties, and which are transferred into the marine environment

The sites are located in particular on the Danube and its major tributaries near crossing boundaries of the contracting parties.

TNMN parameters

Surveillance monitoring I covers all parameters required by WFD and by the Directive 2008/105/EC, amended by the Directive 2013/39/EU.

The selection of parameters for the operational monitoring is unique to each sampling site that represents an affected water body. The parameters are selected according to the relevant pressures.

To cover pressures such as organic pollution, nutrient pollution and the general degradation of the river, the following biological quality elements have been agreed for surveillance monitoring II: • Phytoplankton (chlorophyll-a) • Benthic invertebrates (mandatory parameters: saprobic index and number of families once yearly) • Phytobenthos (benthic diatoms – an optional parameter)

Priority substances and parameters indicative of general physico-chemical quality elements and for the assessment of trends and loads, as well as monitoring frequencies, are given in Table 1.

Loads are calculated for BOD5, inorganic nitrogen, ortho-phosphate-phosphorus, dissolved phosphorus, total phosphorus, suspended solids and – on a voluntary basis – chlorides. Silicates have been measured at the Romanian load assessment sites since 2004.

TNMN quality control, data management and publication

The analytical quality control scheme involves the annual distribution of surface water samples to be analysed for general parameters, nutrients, metals and organic pollutants.

Following the Youden-pair experimental design and evaluation technique, samples are prepared in duplicates, or in other words, two samples of identical matrix and similar concentration are sent out for each determinand.

The TNMN data collection is organised at a national level. The national data managers are responsible for data acquisition from TNMN laboratories as well as for data checking, conversion into an agreed data exchange file format (DEFF) and sending it to the TNMN data management centre in the Slovak Hydrometeorological Institute, Bratislava. This centre performs a secondary check of the data and uploads it to the central TNMN database.

TNMN data is provided via the website, where comprehensive reports based on this data are published annually, the so called TNMN Yearbooks.

Joint surveys

The Joint Danube Survey (JDS) research expeditions are the most significant transboundary activities pursued in the frame of investigative monitoring in the Danube River Basin. Held once every six years (2001, 2007 and 2013), they aim to provide information on parameters not covered by surveillance monitoring, and to provide data from a single source that is readily comparable with no need for further harmonisation.

JDS3 was held in August and September 2013, relying primarily on an international team of about 30 scientists. JDS3 was led by two ships, the Serbian laboratory ship Argus, containing an on-board laboratory with instruments such as a continuous flow centrifuge, sieving machines, microscopes, incubators and refrigerators; and the Romanian Istros, a coastal and river research ship with six cabins, a laboratory and a dining room. For fish surveys, smaller vessels such as the Austrian Wien supported the effort in some river segments.

Over a period of six weeks, a total of 68 sites were sampled with one or two sites sampled daily on average. An effort was made to maintain most of the sampling points, which were monitored during the previous research efforts of the JDS1 (2001), Aquaterra Danube Survey (2004) and JDS2 (2007) in order to ensure comparability with their results.

Unlike the previous Danube surveys with regular and unified sampling patterns, JDS3 followed a target-oriented sampling approach tailored to the in-depth investigation of particular quality elements. This applied primarily to biological quality elements (BQEs), where each parameter was sampled according to an individual plan. A basic set of chemical parameters was assessed at all sites, whereas a number of representative sites were investigated for a wide range of substances.

All sample containers were prepared, labelled and pre-packed before the survey. Sampling at JDS3 stations could include up to five different sample types: water, sediment, biology, suspended particulate matter (SPM) and biota (fish), each with a different list of tests. Many samples were to be tested on board the ships, while others were to be sent to participating laboratories throughout Europe.

JDS3 parameters

Overall, a number of key elements were tested by the JDS3 scientists. Biological quality elements included the following parameters:

• Macro-invertebrates – aquatic insects, worms, clams, snails and other animals without backbones that can be determined without the aid of a microscope and that live in or on sediments

• Fish – the analysis of fish species collected over the whole reach of the Danube aimed to provide a comprehensive picture of fish diversity and species composition. For this, non-lethal electro-fishing was used to stun fish for sampling. The river bottom was also sampled for fish with an electrified bottom trawler net

• Macrophytes – plants, either free-floating or attached to a surface, that can be determined without the need for a microscope

• Phytoplankton – free-floating plants, mainly microscopic, existing in water bodies

• Phytobenthos – microscopic plants such as algae that live attached to surfaces in the bottom layers of the river

• Zooplankton

EU priority and chemical substances are crucial for the assessment of water quality according to the Water Framework Directive. The samples collected during JDS3 were analysed for hundreds of organic substances in combination with ecotoxicological screening to determine substances specific to the DRB.

Physico-chemical parameters included in-situ temperature, pH, conductivity, dissolved oxygen, and the filtration of suspended solids, analysed on board the ships. External laboratory analyses included total nitrogen, dissolved total phosphorus, calcium, magnesium, suspended solids in water, dissolved organic carbon (DOC) and total organic carbon (TOC) in water.

Microbiological monitoring covered the analysis of bacterial abundance and biomass, bacterial secondary production, Escherichia coli, total coliforms, faecal streptococci (enterococci), and DNA determination. DNA based large scale microbial faecal source tracking applied a novel human specific genetic marker system in combination with basic microbiological water quality parameters (E. coli, enterococci), a valuable tool for the characterisation and quantification of sewage input by the tributaries into the main river.

In addition, antibiotic resistance patterns of E. coli, enterococci and metagenomics of bacterial populations based on next generation sequencing were carried out. Radioactive contamination was analysed with attention to the consequences of the Chernobyl accident.

The description and evaluation of hydromorphological characteristics of large rivers is strongly dependent on various background data such as historical, topographical and navigation maps, satellite images, and hydrologic, morphometric (i.e. quantitative analysis of form) and land use data.

For the hydromorphological assessment, JDS3 relied on a number of different approaches such as:

• Continuous longitudinal surveys of stretches 10 rkm-long, including: an inventory of dams and continuum interruptions; bathymetrical data (i.e. measurement of the depth of bodies of water) to understand width and depth variability and channel incision; the degree of degradation of channels and banks; gravel and sand bar occurrence and shape; data on harbours and daily traffic density e.g. wave surge impacts; and ornithological work such as the occurrence of bird colonies adapted to open gravel and sand bars

• Detailed hydromorphological characterisations of each sampling site

• Sediment characterisation, by collecting river bed material at each sampling site

• Flow velocity and discharge measurements at selected sites

• Suspended sediment measurements

• Water level slope and fluctuation data – water level slope helps us to understand channel forming processes, such as erosion and deposition, which are essential for habitat diversity, and can show changes in flow on rivers that have been modified.Water level fluctuation shows change in discharge and flow and can help document the effects of hydropeaking

Published: 21st Aug 2014 in AWE International