Groundwater chemical status in Denmark

Klaus Hinsby, GEUS

Climate change and adaptive water management in EU and beyond: Themeday at ATV winter meeting 9.3.2009 – including relaunch of Danish IAH national chapter.

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WFD & GWD stipulate that:

• EU MS have to achieve good groundwater status in 2015 based on environmental standards and good status objectives for:

• 1) Legitimate uses (drinking water, etc.)• 2) Associated aquatic ecosystems• 3) Dependent terrestrial ecosystems

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Good chemical status:

• A body or a group of bodies of groundwater shall be considered to be of good chemical status when:…..

….. relevant threshold values established ….are not exceeded

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Example of groundwater chemical status assessment based on good status objectives for associated aquatic ecosystems:

Harmful Algal Blooms/ HABs (Cyanobacteria)

Baltic Sea between Denmark and Germany – 25.8.2006

Photo: NERI – Univ. Aarhus / Peter Bondo Christensen

Foto: Klaus Hinsby, GEUS

Sea Floor Anoxia (Horsens Fjord Estuary,

Denmark)

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GW TV for nitrate based on good status objectives for associated aquatic

ecosystems:

Courtesy GRAS A/S

University of Copenhagen / DHI Water and Environment

Photo of Cyanobacteria

Photo of Seafloor Anoxia

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Odense PRB

Global review of hypoxia in coastal marine waters

Diaz and Rosenberg, 2008. Science, 321, 926-929

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N fertilizer application and groundwater concentrations as a function of time 1950 -

2000

From Hinsby et al. Groundwater quality and age. In P. Quevauviller (ed.) Groundwater Science and Policy. RSC Publishing, London, 2008.

Natural background level in gw

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Threshold value for nitrate in oxic groundwater in the Odense Pilot River Basin

~1/3 x N to Odense Fjord estuary to achieve good status <=

~1/3 x N to Odense river <=

~1/3 x N to oxic groundwater

Conceptuel model of Odense Pilot River Basin: After Dahl et al., J. Hydrol, 2007& Hinsby et al. Sci Tot Env, 2008

Nielsen et al. 2003 =>

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Derivation of groundwater TV for N based on sustainable load to Odense river and Fjord:

Substance Ref_dischargeto river (mg/L)

DF1) AF 2) Derived Groundwater

threshold value for total N (mg/L)

N (aver.) 2.3 1 0.53) 4.6P (aver.) 0.08 1 1 0.08N (OZD)

P (OZD)

N (RZD)

P (RZD)

3) Average of previous estimates (Windolf et al. 2003, Hansen, 2006 and Hinsby et al. 2008 (~ 18 mg/l NO3

-, assuming 90 % of N is in nitrate

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Nitrate in the unsaturated zone and groundwater at different depths –

data from the LOOP and GRUMO monitoring programmes

Average nitrate concentrations in different depths. Data from LOOP (Grant, 2007) and GRUMO (Thorling, 2007) monitoring databases and reports.

DWS = 50 mg/l

TV = 18 mg/l for oxic groundwater

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Average nitrate concentrations in oxic groundwater and streams in

Danmark, 1990 - 2004

Data from (Thorling, 2007) and (Kronvang et al., 2008). Modified from Hinsby and Jørgensen, in press.

TV = 18 mg/l for oxic groundwater

Oxic groundwaterStreams

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Nitrate concentrations in the Åkær stream catchment, december 2008

Red color indicate nitrate above DWS = 50 mg/l

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Nitrate concentrations in the Åkær stream catchment, december 2008

Åkær stream: 30 mg/l

Highest value: 101 mg/l in drainage tile Lowest value: 0 mg/l in forest spring

Red color indicate nitrate above TV = 18 mg/l

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NO3 (mg/l)

Cumulative frequency plot of nitrate in Danish GRUMO wells 2006-2007 (n = 426)

~40 % > DWS of 50 mg/l

~70 % > TV of 18 mg/l i.e. ~70 % of oxic

groundwater in Denmark has a poor quality when based on groundwater TVs for nitrate derived from good status objectives for aquatic ecosystems

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Foto: Klaus Hinsby

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Climate change, Eutrophication and sea floor

anoxia/hypoxiaClimate models predict increasing winter precipitation, hence increasing river discharge and nutrient export (~ 8% in the A2 scenario according to Andersen et al., Sci. Tot Environ, 365, 2006)

Relative change in river discharge at station 55.01 (Zealand) for the A2 and B2 emission scenarios compared to present. Modified from van Roosmalen et al., Vadose Zone Journal, 2007.

Simulated T in the Baltic Sea in the A2 and B1 scenarios, Shaffer et al. Nature Geoscience, 2009

As well as increasing Baltic Sea temperatures

Simulated dissolved O2 in the Baltic Sea in the A2 and B1 scenarios, Shaffer et al. Nature Geoscience, 2009

and oxygen depletion (=> increased risk of algal blooms and Sea floor anoxia)

Conclusions and perspectives:• The major part of the shallow oxic Danish

groundwater has a poor quality according to status assessments based on EU directives and guidelines

• A major part of shallow oxic Danish groundwater will most probably not comply with good status objectives in 2015

• Climate change will most probably work against the effect of measures to reduce nutrient loads

• There’s a strong need for developing new agricultural practices safe guarding water resources, human and environmental health

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HAB (cyanobacteria) in the Baltic Sea between Denmark and Germany – 25.8.2006

Thank You ☺

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Foto: Klaus Hinsby