A Review of the Trophic Status of the Milford Haven Waterway

1. A Review of the Trophic Status of the
Milford Haven Waterway
An overview of the available evidence for
designation as a Polluted Water (Eutrophic) under
the provisions of the Nitrates Directive
Lucie Haines, NRW

2. Aims:
• Provide an overview of the process and assessment
methodology
• Outline the evidence used
• Summarise the conclusions and outputs

3. The Nitrates Directive
(91/676/EC)…
All waters which are eutrophic due to nitrates derived from agricultural
sources, or are at risk of becoming so unless preventative action is taken,
must be identified as a Polluted Water (eutrophic) and areas of land
draining into those waters, must be designated as Vulnerable Zones.
Eutrophication is defined as “the enrichment of water by nitrogen
compounds, causing an accelerated growth of algae and higher forms of
plant life to produce an undesirable disturbance to the balance of
organisms present in the water and to the quality of the water concerned”.
3

4. Assessment methodology:
Overview
The approach adopted in England and Wales since 1993 has
been to collate and assess evidence according to the following
criteria:
• Category I –Causative parameters –elevated nutrients
• Category II –Response parameters – evidence of algal
growth – opportunistic macroalgae/phytoplankton
• Category III – Secondary and other effects – evidence of
undesirable ecological disturbance/ evidence of impact to
the quality of water

5. Elevated nutrients +accelerated plant
growth + undesirable disturbance

6. A case for designation?
A case for designation is considered to exist where it is
found
(i) that the Category I criteria are exceeded and
(ii) some (or all) of the Category II and III criteria are
exceeded, or may be exceeded, taking into account the
influence of relevant environmental factors and
considering the overall weight of evidence

7. Eutrophication in a wider
Policy Context
EU directives
• Nitrates Directive / Urban Waste Water Treatment Directive
• Bathing Waters Directive
• Water Framework Directive
• Marine Strategy Framework Directive
International Agreements
• OSPAR Convention for the Protection of the Marine
Environment of the North-East Atlantic
• HELCOM

8. Water Framework Directive (WFD)
Status Classes
Meets WFD
Standards
Fails WFD
Standards

9. WFD status classes in relation to
trophic status

10. WFD Water Bodies

11. DIN data used with WFD status
class boundaries
0
50
100
150
200
250
0 5 10 15 20 25 30 35 40
DIN(umol)
Salinity (ppt)
Poor
Moderate
Good
High

12. DIN loads to the Milford Haven
Waterway
E.Cleddau
19%
W.Cleddau
32%
Cartlett Brook
4%
River Cresswell
2%
Other catchments
37%
Direct
STWs
4%
EPR-installation discharges
2%
DIN load kg/day
E.Cleddau
W.Cleddau
Cartlett Brook
River Cresswell
Other catchments
Direct STWs

13. Summary of nutrient trends and
source apportionment
Dissolved inorganic nitrogen
(DIN)
Dissolved inorganic phosphorus
(DIP)
Overall temporal trend None None
5 largest STW discharges Downward trend Downward trend
Total EPR permitted water discharge 800 kg/day
(292,000 kg/yr)
Not specified
Actual EPR discharge ≈ 100 kg/day
(≈ 36,500 kg/yr)
No data
Estimated load from aerial emissions (kg/yr) 9,736 No data
Direct STW discharges (kg/yr) 101,222 13,653
Losses from agricultural land (kg/yr)* 2,017,000 No data
Total load to waterway (kg/yr)** 2,207,000 39,000

14. Phytoplankton
Chlorophyll
Elevated cell counts
Seasonal succession
Spatial extent
Cover
Biomass
Entrainment
Opportunistic
Macroalgae
Response Parameters - What do we
measure?

15. The extent of opportunistic
macroalgae in Milford Haven
waterway

16. Opportunistic macroalgae at
Cosheston Pill

17. WFD Opportunistic Macroalgae
Classifications - Inner
Year Method Opp Mac Extent
(hectares)
% cover of AIH Average algal
cover (%)
Classification
2009 True Colour Aerial
Photography
147.36 16.4 81.46 Moderate
2011 True Colour Aerial
Photography
114.24 12.7 61.56 Good
2012 Compact Airborne
Spectral Imager
(CASI)
219.47 40.8* 61.61 Moderate
2014 True Colour Aerial
Photography
140.5 12.4 75.57 Moderate

18. WFD Opportunistic Macroalgae
Classifications - Outer
Year Method Opp mac Extent
(hectares)
% cover of AIH Average algal
cover (%)
Classification
2009 True Colour Aerial
Photography
49.42 16.14 42.9 Good
2011 True Colour Aerial
Photography
59.44 19.40 63.58 Good
2012 Compact Airborne
Spectral Imager
(CASI)
56.56 18.47 54.57 Good
2014 True Colour Aerial
Photography
96.4 25 76.07 Good

19. Effects on other flora and fauna
Salicornia spp. Zostera noltii
Anoxia in surface
sediments

20. Impacts on water use
• Reports of detached rafts of opportunistic
macroalgae getting entangled in propellers of
boats and interfering with boating activities
• Reports of detached rafts of opportunistic
macroalgae interfering with fishing – fishermen
have complained about net clogging
• Reported occurrences of opportunistic
macroalgae rafts accumulating on slipways in
the Inner Haven
• Reports of algal ingress at the cooling water
intake of Pembroke Power Station

21. Weight Of Evidence Tool
• No single piece of evidence provides enough
confidence that eutrophication is a problem
• Combine evidence on nutrient pressure, primary
production, & secondary adverse effects

22. To Conclude -
• A case for designation was made for the
Milford Haven Inner water body and
catchment area
• This is supported by evidence in all three
of the categories the assessment was
based on, however Category III evidence
is limited
• For the Outer water body there is also
evidence to suggest the waters are
hypernutrified (it is failing for DIN)
however the Category II evidence did not
support a case for designation as
macroalgal growth is more localised in the
Outer water body

23. The Bigger Picture -
• Contributes to improving the water quality of Milford
Haven
• Informed Welsh Government’s decision to implement a
“Whole Territory” approach to protecting waters from
agricultural pollution in Wales
• The methodology is being used as a template for
trophic status assessments in other areas

24. Diolch am wrando
Thank you for listening