dsd-int 2015 - identification of mixing zones in the eu – a tiered approach - dju bijstra,...
TRANSCRIPT
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Experiences with mixing zones in the Netherlands
Dju Bijstra (RWS)
Frank Kleissen (Deltares)
Christophe Thiange (Deltares)
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Rijkswaterstaat
2 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Contents
• Context
• Discharge test
• Tiered approach
• developments of the discharge test
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Rijkswaterstaat
3 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Why using the discharge test?
• WFD objectives
- Good ecological status (2027)
- Good chemical status (2027)
• Insight in relation (point)sources and waterquality is necessary
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Rijkswaterstaat
4 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Mixing zones: why used and restricted?
• 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
C > EQS
Mixing zones are inevitable
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Rijkswaterstaat
5 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
x L
MAC-mixing zone:
(acute effects)
EQS-mixing zone:
(chronic effects)
Because of the ecological significance
of (river)banks concentration at the
bank is calculated and used as a starting
point for the assessment
LengthMAC-mixing zone (Xmac) :
0,25*Width (max 25 m)
LengthEQS-mixing zone (XL):
10*Width (max 1000 m)
Mixing zone
For calculating the dimensions of a mixing zone an application “the
discharge test” has been develloped.
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Rijkswaterstaat
6 Experiences in with mixing zones in the Netherlands
RWS UNCLASS November 20, 2015
Starting points: discharge test
Fast and easy
Little info needed
EXPERT DETAILED RESEARCH Time consuming
Lots of data needed
sieve
Worst case (low flow) conditions:
Q90 and max. load
Inert behaviour substances
Non problems
Potential problems Complex modelling
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Rijkswaterstaat
7 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Experiences with the discharge test in the Netherlands
• The discharge test has been developed in the Netherlands in 2000
• Assessment with discharge test is required for a permit
• Most discharges can the meet the criteria
• In 2011 the EU-guidance on mixing zones was adopted
• In 2011 the NL-discharge test has been adapted to this guidance
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Rijkswaterstaat
8 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Tiered Approach (1)
• TIER 0: Are (prioritary) substances present in the discharge in concentrations >EQS? NO Stop
• TIER 1: is the discharge significant? NO Stop
Yes
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Rijkswaterstaat
9 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Tier 1: Significancetest
Stop Yes
Is Ccomplete mixing significant?
Attention!:
For discharges at sea and lakes with a width
> 2000 m and harbours the siginifance test can NOT
be applied!
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Rijkswaterstaat
10 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
watersystem width [m] Allowed (trivial) increase in concentration (% EQS)
(after complete mixing)
fresh waters and tidal rivers*)
Small ≤ 100 1
Middle 100 < width ≤ 400 0,75
large > 400 0,1
Canals
all all 1
Can criteria in
table be met?
Stop Yes
Is Ccomplete mixing significant?
Tier 1: Significancetest
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Rijkswaterstaat
11 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Tiered Approach (2)
• TIER 0: Are (prioritary) substances present in the discharge in concentrations >EQS? NO Stop
• TIER 1: is the discharge significant? NO Stop
• TIER 2: determination of mixing-zone whith the discharge-test:
are dimensions of MAC-MZ and/or EQS-MZ
bigger than criteria proposed? NO Stop
Yes
Yes
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Rijkswaterstaat
12 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Tiered Approach (2)
• TIER 0: Are (prioritary) substances present in the discharge in concentrations >EQS? NO Stop
• TIER 1: is the discharge significant? NO Stop
• TIER 2: determination of mixing-zone whith the discharge-test:
are dimensions of MAC-MZ and/or EQS-MZ
bigger than criteria proposed? NO Stop
• TIER 3: Complex modelling: Is MZ a problem? NO Stop
• TIER 4: Local (effect)assessment (i.e. bioassays) (optional):
Is MZ a problem? NO Stop
Yes
Yes
Yes
Yes
measures or
or measures
measures Yes If necessary new complex modelling
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Rijkswaterstaat
13 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Modeling tools for Tier 2
• Excell discharge test (fresh (streaming) waters) (simple and the amount of input data needed is limited)
• Web-based application (fresh waters; harbours; tidal waters) (more input data are needed)
• http://apps.helpdeskwater.nl/prog/extra/immissietoets/sources/#version=nl-nl
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Rijkswaterstaat
14 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Developments of the discharge test
Discharge test 2000 (spreadsheet)
New tools 2011:
Webbased application and spreadsheet
WFD and guidance on mixing zones
Complexity of tidal waters
Database with Water-
system parameters
User experiences
New tools 2015:
New environment for Webbased application
Database with water quality data
Database with water quality standards
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Rijkswaterstaat
15 Experiences in with mixing zones in the Netherlands
RWS UNCLASS April 2011
How it works
• Based on a combination of mixing factors:
– Backgroundmixing
– Additional plume/jet mixing:
• Substances not affected by processes other than mixing
• The calculations depend on the type of receiving water
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Rijkswaterstaat
16 Experiences in with mixing zones in the Netherlands
RWS UNCLASS April 2011
Rivers/Canals
No density difference: plume calculation using Fisher’s description
With density difference: jet calculations using jet3D (3-dimensional)
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Rijkswaterstaat
17 Experiences in with mixing zones in the Netherlands
RWS UNCLASS April 2011
Harbours
Concentration resulting from:
Exchange harbour and main water body and plume/jet
Exchange of water
between harbour and
main waterbody due to:
• Tidal exchange,
• eddies,
• density difference.
In addition optional other
discharge
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Rijkswaterstaat
18 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Tracer simulations
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Rijkswaterstaat
19 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Waterbody properties from database
20 november 2015
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Rijkswaterstaat
20 Experiences in with mixing zones in the Netherlands
RWS UNCLASS
Questions?
• Thank you for your attention!
Workshop 4 pm in Room Ambition.
Questions ?