Groundwater chemical status in Denmark Klaus Hinsby, GEUS Climate change and adaptive water management in EU and beyond: Themeday at ATV winter meeting – including relaunch of Danish IAH national chapter. 1/18

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 2/18

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 3/18

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 – Photo: NERI – Univ. Aarhus / Peter Bondo Christensen Foto: Klaus Hinsby, GEUS Sea Floor Anoxia (Horsens Fjord Estuary, Denmark) 4/18

5/18

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 6/18 Odense PRB

Global review of hypoxia in coastal marine waters Diaz and Rosenberg, Science, 321, /18

N fertilizer application and groundwater concentrations as a function of time From Hinsby et al. Groundwater quality and age. In P. Quevauviller (ed.) Groundwater Science and Policy. RSC Publishing, London, Natural background level in gw 8/18

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 => 9/18

Derivation of groundwater TV for N based on sustainable load to Odense river and Fjord: SubstanceRef_discharge to river (mg/L) DF 1) AF 2) Derived Groundwater threshold value for total N (mg/L) N (aver.) ) 4.6 P (aver.) N (OZD) P (OZD) N (RZD) P (RZD) 3) Average of previous estimates (Windolf et al. 2003, Hansen, 2006 and Hinsby et al (~ 18 mg/l NO 3 -, assuming 90 % of N is in nitrate 10/18

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 11/18

Average nitrate concentrations in oxic groundwater and streams in Danmark, Data from (Thorling, 2007) and (Kronvang et al., 2008). Modified from Hinsby and Jørgensen, in press. TV = 18 mg/l for oxic groundwater Oxic groundwater Streams 12/18

Nitrate concentrations in the Åkær stream catchment, december 2008 Red color indicate nitrate above DWS = 50 mg/l 13/18

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 14/18

NO 3 (mg/l) Cumulative frequency plot of nitrate in Danish GRUMO wells (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 15/18

Foto: Klaus Hinsby 16/18 Climate change, Eutrophication and sea floor anoxia/hypoxia Climate 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 (Zealand) for the A2 and B2 emission scenarios compared to present. Modified from van Roosmalen et al., Vadose Zone Journal, 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 17/18

HAB (cyanobacteria) in the Baltic Sea between Denmark and Germany – Thank You ☺ 18/18 Foto: Klaus Hinsby