Around 70% of the drinking water produced by De Watergroep (a Belgian public water company) is extracted from 83 groundwater pumping sites. To control the risks that endanger the drinking water supply and for the groundwater extracted to be as pure as possible, a risk-based approach for the protection of the catchment areas is developed, as part of the water safety plans. The approach consists of three steps: first, the compilation of a site-specific source file, second, the performance of a risk analysis for every catchment area, and third, the development of a monitoring strategy and action plans. The general goals are to lower the level of purification and to enhance the sustainability of groundwater extraction. The listed benefits make it worthwhile to implement this approach, despite the uncertainties.

THE NEED FOR A PROTECTION PLAN

De Watergroep is a major water company in Flanders (the northern part of Belgium), producing around 140 million m3 of high quality drinking water every year for around 2.8 million inhabitants. Around 70% of the produced drinking water comes from pumped groundwater. The groundwater is extracted at 83 sites throughout Flanders from more or less vulnerable aquifers (Figure 1). The current legislation for the protection of groundwater (e.g. restrictions on farming activities, ground works and building foundations) dates from the mid-eighties and is not yet adapted to the current developments. This legislation will be adapted in the near future. To ensure a safe drinking water supply in such a highly dynamic environment and densely populated, cultivated and industrialized region as Flanders, the water companies recently started to implement a risk analysis and risk management strategy. This strategy was made official in Flemish legislation by the act on ‘Public Service Obligations’ of 2013 (Belgian Statute Book 2013).

Figure 1

Location of the groundwater pumping sites of De Watergroep in Flanders, classified by vulnerability to pollution.

Figure 1

Location of the groundwater pumping sites of De Watergroep in Flanders, classified by vulnerability to pollution.

According to the World Health Organization (WHO 2011), the most effective means of ensuring safe drinking water is through the use of comprehensive risk assessment and risk management. In the first place this risk management should focus on the groundwater catchment as this is the first subsystem in the water supply chain (Rosén et al. 2008).

Based on the guidelines of the WHO and IWA (Davison et al. 2005; Howard & Schmoll 2006; WHO 2011), on the experience and proposed approach of the European project Techneau (Beuken et al. 2008; Rosén et al. 2008), and on the experience of other drinking water companies (see e.g. Kozisek et al. 2009; Kirch 2011; Schmoll et al. 2011) a workable approach for risk analysis and risk management was developed in close cooperation with the Flemish Environmental Agency (VMM – Figure 2) and with the business organization of Flemish water companies, Aquaflanders (Aquaflanders 2014).

Figure 2

General approach for the risk management of hazards in groundwater catchments.

Figure 2

General approach for the risk management of hazards in groundwater catchments.

The approach consists of three steps:

  1. The compilation of a site-specific source file.

  2. The performance of a risk analysis and risk ranking.

  3. Derivation and implementation of a risk reduction program.

To implement this approach in the De Watergroep company, the goals, its integration in its daily activities and organization, document management, timing, the costs and the benefits were written into a management plan. The main content of this management plan is presented below.

DEVELOPMENT OF A RISK-BASED PLAN

As a first step, information concerning the catchment sites, the groundwater extraction infrastructure and the land use is collected (Table 1). This information is gathered in close cooperation with the Flemish Environmental Agency VMM and stored as a digital site-specific source file. This source file consists of location maps, technical information on the wells, evaluation reports on water availability in the wells and in the aquifer (source: database containing all available water level data and pumped quantities) and on groundwater quality (source: Laboratory Information Management System, i.e. the water quality database). Further on, descriptions and maps of other known activities with a possible impact on groundwater quality or quantity are added (Table 1). These data originate from several databases available at different governmental institutions. An intensive cooperation with these governmental institutions is necessary in order to cover the risks that fall outside the jurisdiction of the water companies. The EU Water Framework Directive 2000/60/EC assigns the government responsible for quality and quantity of the water bodies. In Table 1, the chapters and the content of the site-specific source file are presented.

Table 1

Content of the site-specific source file

Content of the site-specific source file 
(1) Information on the water extraction site (3) Water quality in the area of attention 
Map with the location of the extraction site Results of water quality analysis by the water company 
Table with technical information on wells and piezometers Results of water quality analysis by the environmental agency 
Map with monitored piezometers of the drinking water company Report on the evolution of the pumped groundwater quality 
Map with monitored piezometers of the environmental agency (4) Actions and commitments 
Map with legal protection zones around the extraction site Procedure to be followed in case of calamities 
Map with catchment zone and areas of attention Report on the primary groundwater quality and quantity bottlenecks, on the necessary actions and commitments 
Map with supply areas of the extraction site  
Report on the evolution of the groundwater levels  
(2) Land-use impact in the areas of attention  
Map of actual land use  
Map of areas with soil quality research and remediation projects  
Map of areas with the risk of flooding  
Map of wastewater discharge points  
Map with use of fertilizers  
Content of the site-specific source file 
(1) Information on the water extraction site (3) Water quality in the area of attention 
Map with the location of the extraction site Results of water quality analysis by the water company 
Table with technical information on wells and piezometers Results of water quality analysis by the environmental agency 
Map with monitored piezometers of the drinking water company Report on the evolution of the pumped groundwater quality 
Map with monitored piezometers of the environmental agency (4) Actions and commitments 
Map with legal protection zones around the extraction site Procedure to be followed in case of calamities 
Map with catchment zone and areas of attention Report on the primary groundwater quality and quantity bottlenecks, on the necessary actions and commitments 
Map with supply areas of the extraction site  
Report on the evolution of the groundwater levels  
(2) Land-use impact in the areas of attention  
Map of actual land use  
Map of areas with soil quality research and remediation projects  
Map of areas with the risk of flooding  
Map of wastewater discharge points  
Map with use of fertilizers  

An important part of the source file is the delineation of the catchment zone, being the infiltration area of the water wells and so the geographical area to be protected. The determination of the catchment zones is based on a backward particle tracking analysis in a three-dimensional (3D) regional hydrogeological model of Flanders (Lermytte & Thomas 2008). Inside the catchment area four zones of attention are delimited based on the groundwater travel time (Figure 3). Also, the catchment area of the rivers flowing through the well field is delineated and the hazards are determined. Within these zones, the existing hazards are evaluated in order to control their risk for groundwater pollution.

Figure 3

Results of particle tracking, definition of the areas of attention and travel time distribution of the three extraction sites in Heverlee (province of Flemish–Brabant, Flanders, Belgium).

Figure 3

Results of particle tracking, definition of the areas of attention and travel time distribution of the three extraction sites in Heverlee (province of Flemish–Brabant, Flanders, Belgium).

The compilation of the site-specific source files has been adopted by the government in the action program of the second generation river basin management plans in order to respond to article 7 of the European Water Framework Directive. This article requires member states to ensure the necessary protection of water bodies in order to reduce the level of purification required for the production of drinking water (European Commission 2000).

As a second step in the approach, all possible hazards for groundwater quality and quantity are listed, based on the available literature (e.g. Beuken et al. 2008), on the available information in the source files and on brainstorming sessions with colleagues who have differing areas of expertise. In general, 82 possible hazards for groundwater quality and quantity in the catchment areas were identified and listed in 13 thematic groups (Table 2). This list is continually updated when new hazards become relevant.

Table 2

Thirteen thematic groups of hazards for groundwater quality and quantity in the catchment areas

Open energy systems Industrial sites, activities of public services, military sites 
Closed energy systems in the subsoil Parking areas 
Groundwater wells of third parties 10 Infrastructural works 
Transport and transport infrastructure 11 Surface water 
Sewer systems and wastewater discharge 12 Rainwater infiltration infrastructure 
Agricultural activities 13 Other activities with a possible impact on groundwater quality or quantity 
Household activities 
Open energy systems Industrial sites, activities of public services, military sites 
Closed energy systems in the subsoil Parking areas 
Groundwater wells of third parties 10 Infrastructural works 
Transport and transport infrastructure 11 Surface water 
Sewer systems and wastewater discharge 12 Rainwater infiltration infrastructure 
Agricultural activities 13 Other activities with a possible impact on groundwater quality or quantity 
Household activities 

The risk for each hazardous event is determined as a combination of its likelihood and consequence, for each extraction site. A risk matrix, based on Beuken et al. (2008), is used to rank the risks (Figure 4).

Figure 4

Risk matrix used for ranking of the identified hazards (adapted from Rosén et al. 2008).

Figure 4

Risk matrix used for ranking of the identified hazards (adapted from Rosén et al. 2008).

The third step, after classifying the hazardous events according to this matrix, consists of defining action and management plans for hazards with an unacceptable and possibly unacceptable risk. Based on a first general screening of the hazards, several actions have recently been taken (e.g.):

  • In cooperation with the water companies, a reduction in the use of pesticides has been introduced in Flemish legislation.

  • The conditions for the use of ground surface heat pumps have been embedded in Flemish environmental legislation in order to protect groundwater quality and quantity.

  • A procedure where by water companies can advise on soil and groundwater calamities and remediation projects has been introduced at the Flemish Public Waste Company.

  • A dynamic water-quality monitoring strategy has been introduced. According to this strategy, the sampling frequency is increased when a parameter exceeds a threshold. The thresholds are based on the drinking water standards.

  • A drought indicator has been programmed. This indicator classifies automatically the most recent groundwater level of more than 1,500 wells and piezometers as low, medium or high water levels (seven classes) compared to the historical measurements. In this way, upcoming groundwater droughts and also well-clogging are rapidly detected.

A first preliminary assessment for the Heverlee catchment (Figure 3) reveals that for this area the management plans must address at least the following risks:

  • Intensify the monitoring of historical groundwater pollution and the waste dump area.

  • Focus on fuel tanks for heating houses.

  • Update the disaster plan (communication and action).

  • Additional control on the discharges to the river flowing in the catchment zone.

The presented risk-based approach for the catchment areas is simultaneously applied to the other subsystems of the drinking water supply chain, namely water treatment, storage and distribution. The water supply chain ends at the water meter of the consumer.

To prepare and implement the source files and water safety plans, a risk analyst/coordinator is recruited. Small expert groups, composed of experienced employees with technical and operational skills, analyse the different steps in the water supply chain. The coordinator plans and manages the expert groups. Each group is responsible for their part of the source files, risk analysis and water safety plans. The coordinator reports to a newly installed steering committee, composed of the engineering director, the risk manager and the heads of the technical departments. The mission of this committee is to review, approve and audit the plans. Except for the coordinator, no new staff are hired. The organization and the associated tasks are presented in Figure 5.

Figure 5

Organization and tasks for the implementation of water safety plans at De Watergroep.

Figure 5

Organization and tasks for the implementation of water safety plans at De Watergroep.

De Watergroep plans the roll-out of the water safety plans for all water extraction sites (80), treatment plants (62), water towers (82), reservoirs (73) and distribution system (31,000 km) within 6 years, with a review at least every 6 years. This term is also the reviewing term for the river basin management plans.

INITIAL IMPLEMENTATION CHALLENGES

While applying this approach several uncertainties are met:

  • Due to a lack of information on some activities in the catchment zone (e.g. the presence and state of fuel tanks for house heating, leakage of sewer systems), some risks are difficult to assess.

  • Most risks in the catchment zone are based on expert judgment. Little quantitative information is available to assess the risks.

  • The jurisdiction of the water companies in the catchment zones is limited. The governmental organizations and the other stakeholders (e.g. industries, farmers) to be involved in the protection of the groundwater will depend on the identified risks. Their willingness to take action is uncertain.

  • The financial impact of this approach is as yet unknown. Budget restrictions will have an impact on the implementation of the action program.

EXPECTED BENEFITS

Despite these uncertainties, the presented approach for the protection of groundwater offers a long list of benefits:

  • All relevant information concerning the extraction sites is brought together in one site-specific source file.

  • General as well as site-specific risks are identified.

  • Every well site is evaluated according to the same approach.

  • The actions focus on the hazards with the highest risks.

  • The risk analysis and the resulting actions are kept up to date periodically.

  • The approach focuses on groundwater quality as well as groundwater quantity.

  • The approach will lead to an increasing awareness of the importance of groundwater protection.

  • Cooperation with governmental organizations is strengthened.

  • This approach should lead to decreasing treatment costs.

  • New risks for water quality and quantity will be detected at an early stage.

CONCLUSIONS

The approach and implementation of a risk-based protection program for groundwater quality and quantity by the Flemish water company De Watergroep is presented. The first step of the approach consists of the composition of site-specific source files that focus on all available information on the extraction sites and on the present hazards in the catchment zones. In the second step, the risks of the present hazards are estimated by an expert group. For all unacceptable risks, a plan of actions and measures is set up. This approach will lead to better qualitative and quantitative protection of the groundwater that serves as a source for drinking water, and to a more sustainable drinking water supply.

ACKNOWLEDGEMENT

The authors would like to thank the anonymous reviewers for their constructive comments and suggestions to improve the paper.

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