Conclusions and recommendations regarding nutrient emissions

1. Ensemble modelling of diffuse nutrient loads and sources in EUROHARP catchments:Uncertainty in applying different models and the problem with retention Brian KronvangNational Environmental Research Institute, Dept. Freshwater Ecology, University of Aarhus, Silkeborg, DenmarkBKR@DMU.DK U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

2. No ‘European best model’ was nominated by the EUROHARP project (2001-2006) but we learned a lot about models and the EUROHARP Toolbox is a potential ‘money saver tool’ for catchment managers U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

3. Conclusions and recommendations regarding nutrient emissions • Net nutrient loads should always be quantified using monitoring/modelled results – the net load is the most accurate estimate as shown in EH. • Gross nutrient emissions from background or non-anthropogenic sources should be quantified independently using monitoring data or models. • Nutrient retention in surface waters should be quantified independently using model estimates at water body or river basin scale (EUROHARP NUTRET tool). • EUROHARP has shown that ensemble modelling is a possible way forward to ensure that an estimate of the uncertainty involved in especially nutrient load partitioning can be given. • Application of more than one model will be useful in the future emission reportings as e.g. one simple pan-European method (statistical model), one load apportionment method and one country specific method (source oriented). U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

4. Continued • Agricultural emissions should always be reported using three indicators: • Nutrient surplus • Leaching from root zone (1 m) (gross emission to groundwater and surface water). • Gross emission to surface water – edge of surface waters • HYDROLOGICAL DATA IS CRUCIAL BEFORE EVERYTHING ELSE. • OSPAR HARP-NUT has developed several guidelines concerning nutrient losses also an updated guideline 6 on diffuse nutrient losses and guideline 9 on nutrient retention both based on EUROHARP results is to be prepared by Denmark. • EUROHARP has created a tool box to assist catchment managers in chosing the best model(s) for a given river basin. U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

5. WFD sets new standards and requirements for calculation of nutrient sources, emissions and retention in catchments with the purpose of achieving a concentration in surface waters below the level required for obtaining a good ecological quality Nutrients Diffuse Sources Nutrient Retention Ecology of water body types Nutrients Point Sources Nutrients Reference Conditions U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

6. Background concentrations of nitrate-N in Danish surface waters – large regional differences U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

7. Nutrient losses from fields to surface waters – the problem of retention Catchment export Surplus surface water retention (c) Surface runoff buffer zone retention (e) Root Zone root zone retention (a) wetland retention (d) Leaching subsurface retention (b) Subsurface emission Point sources, background, atm. deposition Total retention = a+b+c+d+e U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

8. Estimated Nitrogen retention in groundwater and surface waters for different Danish catchments used for WFD River BasinManagement plans U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

9. EUROHARP model tools Data oriented (empirical) Annual predictions based on export coefficient approach Low SA NOPOLU REALTA Level of complexity Methods differ profoundly in their complexity, level of process representation and data requirements Model type NLES-CAT MONERIS EVENFLOWTRK Process oriented (deterministic) High Daily simulations of flow and solute concentrations NL-CAT SWAT U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

10. Nutrient emissions – the EUROHARP definitions U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

11. Location of the EUROHARP river catchments and diffuse gross N-losses to surface waters U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

12. Large differences in the bias involved when modelling net N export from European catchments U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

13. The mean deviation between the P-loads calculated by linear interpolation or by the OSPAR method is ~22%. • Higher deviations occur also for Southern European catchments. • More than 1/3 of the deviation between the model results for P-loads are due the uncer-tainty of the “observed” P-load • Precision of loads depends on substance, observation frequency and catchment size. U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

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16. Mean deviation when modelling nitrogen (N=66) and phosphorus (N=50) in 17 EUROHARP catchments Mean deviation N P Net load (export from catchment): 27% 41% Gross loss from agricultural land: 37% 67% Gross loss from other diffuse sources:67% 75% U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

17. Nutrient retention in surface waters was the factor experiencing the largest variation between models. U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

18. EUROHARP Nutrient Retention Software - NUTRET Offer nutrient retention calculations in different Tiers Tier 1: Simple - Tier 5: Advanced U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

19. In future more emphasis has to be drawn on delivering nutrient modelling results from modellers to managers with some measure of the uncertainty involved U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology

20. Water Framework Directive General information about the EUROHARP project, partners and modelled European catchments Tools and models used in project, search in model capabilities, add new tools Educational pages related to diffuse pollution from European catchments, guidelines Policy instruments; European and international, relating to diffuse pollution U N I V E R S I T Y O F A A R H U S Danish Environmental Research Institute Department of Freshwater Ecology