Presentation of IWA Groundwater Specialist Conference 8-10 September 2011, Belgrade, Serbia - page 5

 

 

Summary of Papers

On the first day, invited/keynote papers will be presented in a plenary session. These papers addressed groundwater management plans and their implementation. Various global and regional organisations, as well as two countries (Austria and Serbia) presented their agendas in this area. One invited paper each have been prepared under Themes 2 and 3, and presented at the plenary session.

On the second day, papers addressing the four themes were presented at breakout sessions.

Some 60 papers, featuring contributions by scientists and engineers from more than 20 countries, attested to the importance and appeal of this Conference.

Keynote Papers

Dimkić et al. (2011a) discuss implications of oxic conditions in alluvial groundwater. It is estimated that more than 50% of the water supply in the world comes from groundwater; in Europe, this figure is over 60% and in Serbia about 70%, of which more than 50% traces to alluvial aquifers. In Germany, most of the potable water is supplied through bank filtration; more than 300 waterworks use bank filtration and roughly 50 plants are based on artificial groundwater recharge.

The oxicity in an alluvial aquifer is significant, for both the formation of the baseline groundwater quality and its transformation processes. The level of groundwater oxicity in the aquifer in the case of bank filtration depends on the oxygen saturation of river water, the oxidation-reduction processes of organic and inorganic substances, and the level of oxygen renewal in the aquifer.

Under oxic conditions, oxidation takes place through oxygen dissolved in water. Under anoxic conditions, biochemical oxidation is based mainly on nitrates, compounds of ferric iron and tetravalent manganese, as well as sulphates. Oxic environments are generally more favourable for self-purification processes. However, some substances can also degrade in anoxic conditions. Knowledge of the effects that the degree of groundwater oxicity has on the baseline quality of groundwater and understanding of the process of purification of river water to the baseline quality level are fundamental for the design, use and protection of groundwater sources.

The self-purification process of groundwater is of extreme importance for the protection and utilisation of this vital resource; its existence de facto makes groundwater aquifers equivalent to physico-chemical reactors. Of major importance with regard to the quality of baseline flow in rivers, and to the transformation of water quality within an aquifer and along the groundwater flow path to the production well, are the redox conditions in the field and the degree of oxicity of the water within the aquifer. The processes defining the baseline quality and the transformation of groundwater quality are being discussed, such as: oxic conditions, biochemical processes of nitrification and denitrification, reduction and oxidation of iron and manganese, and reduction and oxidation of sulphur. Questions pertaining to the transformation of groundwater quality are extremely important in groundwater use and protection and in the application of bank filtration and artificial recharge methods. Oxic conditions also determine the character and rate of well ageing in alluvial aquifers. Testing of the wells of the Belgrade Groundwater Source (Serbia) indicates that the dominant clogging process is incrustation with iron deposits. Changes in local hydraulic resistance at well screens, which occur as a result of clogging, are linked mainly to the redox potential and the concentration of ferrous iron.

The authors draw a conclusion that long-term operation and the design of wells to be placed in anoxic groundwater are highly dependent on biochemical processes. For wells under high oxic conditions, the seepage stability and maintenance of a laminar flow regime of the groundwater are important factors. The paper also explained the mechanisms that lead to a particular set of oxic conditions in groundwater and the impact of such conditions on the processes that take place in a typical alluvial aquifer. The section of the paper which deals with well clogging correlates the kinetics of the development of hydraulic losses at the well screen to dominant oxic conditions in groundwater and the predetermined indictors of the degree of oxicity. It is shown that biochemical well clogging calls for stricter well design criteria with respect to the entrance velocity at well screens than is the case with traditional design criteria when applied to conditions of highly reduced oxygen concentrations (low degree of oxicity) and low to medium anoxia in alluvial groundwater. Namely, the oxic state in which biochemical processes become dominant is 50 mV ≤ Eh ≤ 200 mV. In this range of oxic conditions the critical well screen entrance velocity depends on biochemical parameters. However, in a highly oxic area, "standard" criteria - seepage stability and laminar flow of groundwater to the well - are the most significant criteria for well screen design and operation.

Weller & Liska (2011) discuss groundwater issues in light of the Water Framework Directive (WFD) in the Danube River Basin (DRB). The EU WFD brings together management and protection aspects and covers both surface and groundwaters. For groundwater, the Member States must ensure that all groundwater bodies are of good status – in terms of water quality as well as quantity.

The Danube countries created a management arrangement to protect and restore the water resources of the Danube by signing of the Danube River Protection Convention (DRPC) in June 1994. DRPC entered into force on 22 October 1998 and it became an overall legal instrument for the cooperation and transboundary water management in the Danube River Basin. One of the major strategic goals of the Convention is to maintain and improve the status of surface and ground water resources, including both quality and quantity, and to prevent, reduce and control water pollution. To implement these goals the Danube countries have established the International Commission for the Protection of the Danube River (ICPDR).

The Commission has created a set of Expert Groups to strengthen the proactive participation of all Contracting Parties. The cooperation and management framework under the ICPDR was strengthened in 2000 when the DRPC signatories decided to make all possible efforts to implement the WFD throughout the entire basin. The Danube countries then agreed to produce a Danube River Basin Management Plan by the end of 2009, including national and basin-wide analysis of the status of Danube surface and groundwaters, and agreed on measures to address the existing problems. The Danube River Basin Management Plan and the Joint Programme of Measures – prepared as an integral part of it - aim for the achievement of environmental objectives of WFD to achieve good status of waters in the whole international basin.

In order to address the issues of groundwater management under WFD the ICPDR created a Groundwater Task Group. The activities of this expert body include identification of transboundary GW-bodies of basin wide importance, development of guidelines for harmonised characterisation of groundwaters in the Danube River Basin, collection of information from groundwater chemical and quantity monitoring networks and preparation of reports to EC as required by the EU legislation including elaboration of Danube River Basin Management Plans. In 2004, 11 transboundary groundwater bodies (GWBs) or groups of large GWBs (>4,000 km2) were identified. Transboundary GW-bodies of basin wide importance (ICPDR GW-bodies) were divided into national parts of ICPDR GW-bodies which can furthermore consist of a number of individual national GWBs. Only ICPDR GW-bodies and national parts of ICPDR GW-bodies are under the focus of the Groundwater Task Group (GW TG) and Transnational Monitoring Network (TNMN) Groundwater.

The paper also outlines pressures on the groundwater quality and describes its current status. Joint Programme of Measures (JPM) builds upon the results of the pressure analysis, the water status assessment and includes, as a consequence, measures of basin-wide importance oriented towards the agreed visions and management objectives for 2015.