1. Experiences in The Netherlands
Mixing Zones
Experiences in The Netherlands

2. Water quality based approach
Sources
Emission based approach
Surface water

3. Observations Focus used to be on emission based approach
Application of BAT/BEP to all sources
Despite progress, levels of substances still exceed standards
Clearer match between water quality objectives and emission reduction is necessary

4. Mixing zones where two watercourses join there is a mixing zone
difference in flow
difference in concentration
as long as Cdischarge > Csurface water there is a mixing zone
as long as Cdischarge > EQS there is an area of exceedance

5. Mixing zone

6. At the monitoring station?
Mixing zones
where should an EQS be met?
Everywhere?
At the monitoring station? X

7. A description of each mixing zone is nonsense
A description of a general approach might make sense

8. Discharge test ( Start )

9. Discharge test No problem to make it very complex
Complex models; a lot of information and resources are needed
Be pragmatic

10. Criteria Discharge test
No significant contribution to exceedance of EQS
No acute effects on the aquatic ecosystem within the mixing zone
No acute effects on sediment dwelling organisms within the mixing zone

11. Discharge test EXPERT DETAILED RESEARCH Fast and easy
Little info needed
EXPERT DETAILED RESEARCH
Time consuming
Lots of data needed

12. Distribution pattern
X- ax C
Y-ax

13. Discharge test

14. Findings large receiving waters, no additional controls above BAT
smaller receiving waters, additional controls

15. Developments Discharge test for thermal discharges
Discharge test for tidal waters
Discharge test for marine waters

16. Thank you for your attention

18. Discharge situation Perpendicular to the flow
In line with the flow near shore
Half of depth
Perpendicular to the flow

19. CE CW
jet
plume
watersurface
bottom

20. TEST AREA
W < 100 m
CIRCA 1/4 W
10 . W
Discharge

21. TEST AREA
5 to 10 % van B
B > 100 m
MAXIMUM 1000 m
Discharge

22. Risk level Quality standard Serious Risk SR Intervention value
Maximum acceptable risk
MAR
MAR
Negligible risk NR
Target value
1/100 of MAR