Groundwater protection strategy Troels Kærgaard Bjerre Odense Water GroPro International Conference ATV JORD OG GRUNDVAND KLARSKOVGAARD september 2008

Agenda Odense Water Background Groundwater protection strategy of Odense Water Conclusions Perspectives

Odense

Facts and figures about Odense Water Approximately 2600 common water utilities in Denmark with total abstraction of approximately 400 mill. m³/year. Odense Water is one of the biggest water utility with a abstraction permission of 13,8 mill. m³/year. Groundwater abstraction on 7 wellfields. 42 abstraction wells (25 to 100 m deep). Geological setting: Glacial deposits on a basement of paleocene chalk and marl. Aquifers: Glacial sand- and graveldeposits and to a small extend paleocene chalk.

Quantitative threats Urbanization Environmental targets Climate change Qualitative threats Pesticides Chlorinated solvents Other org. haz. subst. Nitrate Chloride Hardness (Ca and Mg) Arsenic Major threats towards the wellfields of Odense Water

Why is groundwater protection a hot issue in Denmark? 99% of the drinking water in Denmark comes from groundwater! The National Groundwater Policy of Denmark! Action plans for groundwater protection!

The National Ground Water Policy of Denmark Objectives Production of drinking water should be based on a decentralized abstraction structure. Protection against exploitation of groundwater. Production of drinking water should be based on clean ground water – no advanced treatment. Protection against ground water pollution. Water abstraction should be balanced against nature and surface water objectives.

Action plans for groundwater protection State authorities carry out a detailed hydrogeological investigation of the ground water ressources in Denmark. The investigations are financed by tax on abstraction permissions From : mill. kr. (140 mill. Euro). The results are used by local authorities as the foundation of action plans for ground water protection.

Ground water protection at the wellfields of Odense Water At present a detailed hydrogeological investigation are being carried out by the state authority in cooporation with Odense Water The results of the investigation is expected by 2009 and forth The first groundwater protection plan is expected in 2010 Meanwhile we are getting prepared for the effort……..

Groundwater protection strategy of Odense Water Proactive role in ground water protection Basis for cooporation with authorities Framework for our future investments in ground water protection The aim is cost-effective investments in ground water protection for the benefit of our consumers and their descendants

Groundwater protection strategy of Odense Water: Headlines General actions (geographically unspecific) coorporation with environmental authorities communicating the need for groundwater protection protection of interests through The Danish Water and Wastewater Association education etc. Specific actions (geographically specific) based on an detailed hydrological investigation detailed zonation of catchments (areas of interest) program of measures !

Premises for specific actions Centralized wellfields - considerable ground water abstraction help to ensure cost-effectiveness in ground water protection. Sustainable ground water abstraction - minimizes deterioration of the ground water quality due to exploitation. Consideration of vulnerable nature. Optimized abstraction strategy - minimizes human and natural threats towards groundwater quality on the wellfields. Up to date waterworks - high technical standard minimizes the risks of polluting the drinking water from source to consumer.

Areas of interest Measures Bnbo1Bnbo2Zone1Zone2Zone3Zone4Zone5Zone6 Partly financing of municipal and state afforestation Support for private afforestation Buing arable land for afforestation Agricultural land use agreements (pesticides) Agricultural land use agreements (nitrate) Sludge from wastewater treatment plants Plugging of old unused wells Plugging of sewage infiltration plants and renewal of sewers Handling of pesticides Groundwater related environmental inspection of industry and agriculture Campaigns focused on better practice in agricultural land use Extraordinary information effort Coorporation with local authorities about planning etc.

Subdevision of the catchments: Focus Ground water recharge Ground water vulnerability (nitrate) Travel time (based on numerical modelling and particle tracking)

Subdivision of the catchments: Terminology Travel time (< 25 years) Groundwater recharge Groundwater vulnerability Terminology Yes Zone1 Yes NoZone2 YesNo Zone3 NoYes Zone4 NoYesNoZone5 No Zone6

Travel time Negative correlation between transportation time and risk of contamination. Transportation time separates the near from the distant catchment. Near catchment: Zone 1-3 Distant catchment: Zone 4-6 Why use ”travel time” in the aquifer instead of ”total travel time”? Why 25 years? Life expectancy map *

Why 25 years? Inspired by Dutch and Canadian practice. Exclusion of ”particles” trapped in aquitards and inclusion of the hydrologically active parts of the saturated zone. General assumptions and experiences with degradation, dispersion, diffusion and dilution of organic hazardous substances in groundwater. But………it is a rather pragmatic solution that works quite well in the hydrogeological setting of Denmark. It is certainly a big step in the right direction towards cost-effective investments in groundwater protection, but it is not rocket science.

Wellhead protection zones (BNBO) BNBO1: Travel time less than 1 year. BNBO2: Travel time between 1 and 2 years. Differentiation of groundwater protection near abstraction wells. Why? Not all threats in the proximity of the wellfields are equal.

Wellhead protection zones (BNBO) 1 year 2 years 25 years

Conclusions The measures are well known and well tested in Denmark. But the combination of measures and areas of interest calls for attention. A detailed subdivision of the catchments based on knowledge about groundwater recharge, aquifer vulnerability and travel time. The use of travel time through introduction of differentiated wellhead protection and the “25 year boundary” distinguish the strategy from common practice in Denmark. The use of travel time in the groundwater protection strategy gives more attention to the threats towards the wellfields.

Perspectives “Well Vulnerability: A Quantitative Approach for Source Water Protection”, Ground Water, vol. 44, nr. 5, p. 732 – 742 by Frind, E.O., Molson, J.W. and Rudolph, D.L. Integration of travel time in the vulnerability assessment. ”Aquifer vulnerability” = 3D groundwater protection. ”Well vulnerability” = 4D groundwater protection. This knowledge is of great importance when…….. prioritizing the groundwater protecting actions in a cost-effective manner. planning hydrogeological surveys.

It is time the thoughts behind the concept “well vulnerability” gains more attention in Denmark like the well established concept “aquifer vulnerability”. Because……..at the end of the day a drinking water producer shall be more concerned about the consumers than the aquifers.

Thank you for your attention!