Potential Ballast Water Movement
within the Fal Estuary
Mr Mark Symons, (Student) Falmouth Marine School (University of
Plymouth) Fdsc Marine Science, Falmouth, Cornwall, United
Kingdom. 58 Manor Way, Helston, Cornwall, TR13 8LJ
Miss Louise Hockley, (Associate Lecturer) Falmouth Marine School,
Falmouth, Cornwall, United Kingdom. MSc Marine Science.
The Fal Estuary a SAC under the E,Us Habitats Directive but home to
a working docks, and invasive species. Its Hydrodynamic traits are
mainly unknown. Measurements of tidal flow in the dockland area
of the Fal are undertaken over an entire tidal cycle of
February/March. This data plotted in vector graphs shows that the
mean movement of water is towards the docklands, and that
statistically there was no significant difference in direction between a
flooding and ebbing tide. Along with this the velocities were so slow
that the maximum any NIS would travel before the tidal current
reversed is 425.52m, thus negating the need to develop any
Transportation of Non Indigenous Species (NIS) through the use of
ballast water in shipping is a well known problem and has been since
the technology was fully established in the 1950s (Griffiths et al;
2009) (other transportation vectors do also exist such as hull fouling).
Though the use of ballast water has a negative effect on the
environment by introducing NIS, it plays a major role in keeping
vessels stable and improving manoeuvrability when free from cargo
(Packard, 1984; Tsolaki, 2009; Zhang and Dickman, 1999). Tsolaki
(2009) states that Shipping moves 80% of the worlds commodities
and transfers approximately 3-5 billion tonnes of ballast water
internationally. This vast movement of ballast water has lead to the
introduction of over 1000 NIS in European coastal waters (Golasch,
2006); though it was the harmful affect to human health and the
economy that attracted the attention of scientists and professionals
to address the issue (Institute for European environmental policy
In 2004 the International Maritime Organisation organised a
convention for the management of ballast water and sediment in
ships. The convention came up with two strategies to combat the
1) They must have and implement a ballast water management
plan approved by the administration.
2) To have aboard a ballast water record book, recording when
ballast water is taken on board and when it is discharged, also
any accidental or exceptional discharges must be recorded
(International Maritime Organisation, 2004).
The two most important regulations are D-1, Ballast water exchange
Ref (Matej, 2008), and D-2 which is a ballast water performance
standard which dictates the acceptable levels of organism allowed
within ballast water. A D-2 table of organisms sizes and quantities
can be found in Tsolakis (2009) review of ballast water treatment.
Regulation D-1 is being phased out and after 2016 only ballast water
treatment systems will be utilised to comply with regulation D-2
(International Maritime Organisation, 2004). Therefore the ballast
water related industry is focused mainly on treatment of ballast
water, this maybe port based or ship based. Even with treatment
systems in place there is not a method which can remove 100% of
NIS (Tsolaki, 2009). The treatment systems do have their place and
should continue to evolve, however there maybe alternative
methods to manage NIS.
This study is to investigate whether simple current modelling can
help to manage NIS within the Fal estuary, Falmouth, Cornwall.
When planktonic NIS is deposited with ballast water in the Fal it is at
the mercy of abiotic factors; Transportation will be controlled by the
estuaries hydrodynamic traits (Becker et al., 2010). The region of the
Fal estuary where the docks are located is macrotidal (Pirrie et al.,
2003) with the largest spring tides of 5.7m. The Fal possess a flood
dominant tidal flow, but low tidal currents (Stapleton and Pethick
1996) this means that settlement of sediment in lower half of the
estuary has been minimal which could have similar implications for
NIS. However geochemical data showing the distribution of
contaminates within the Fal suggests that it follows the dominant
tidal flow (Carrick Roads area) (Pirrie et al., 2003), this could also
have similar implications for NIS.
Apart from the work by Stapleton and Pethic, I am only aware of one
physical study of the Fal performed by Matthew Le Maitre who
undertook a hydrographical survey for the Harbour Commission. The
survey was looking at the accuracy of tidal diamonds on admiralty
charts in comparison with real time data collected from in-situ
buoys. The current flow data was only undertaken for surface layers
and modelled in a programme known as PICES for mapping oil spill
The Fal estuary is a special area of conservation under European
Habitats Directive, which aims to protect the site and stop any
Figure 1. Map showing dominant tidal flow in the Fal. Map A- 3 hours before high water.
Map B 3 hours after high water. Courtesy of Stapleton and Pethic Institute of Estuarine
and Coastal Studies.
degradation and obtain favourable conservation status of the
interest features across their bio- geographical ranges (Langston et al
2006) NIS would conflict with this. The Fal estuary is also a ria
making it one of the deepest natural harbours in the world. This
allows there to be a commercial docks run by A&P Ltd, again
conflicting with the special area of conservation principals. Although
export is low from Falmouth docks ,it still exists. Therefore ballast
water will be released into the estuary; the majority of ballast water
released in the docks is from vessels entering dry docks for repair
(Mike Pereir, A & P Ltd, Pers. Comm., January 14, 2011).
Species that have been recorded in the Fal are:
There is also no management in place by Cornwall council to deal
with invasive species. (Jenny Christie, Maritime Environment officer,
Cornwall Council. Pers. Comm., November 25th 2010). However both
the Environment Agency and Natural England would be responsible
should an outbreak occur that could be contained or eradicated
(Lisa Rennocks, Cornwall Wildlife Trust, Pers. Comm., May 04 2011)
There is a hotline for reporting NIS and each cased is judged on
whether action is needed.
The sampling area is shown in fig 2, the site was not the preferred
location but had to be used to coincide with the working
functionality of the docks. This site is however a good representation
for ballast water transport, as Duchy Wharf is one of the primary
wharfs used by A&P Ltd, thus NIS could potentially be released into
the recorded currents.
The Hydrodynamic traits of this area are unknown, being affected by
natural fluxes and anthropogenic structures. These structures may
be permanent such as the wharfs, or mobile structures such as the
access barge and other vessels using the docks.
Wharf Destroyed in
Figure 2. This GiS Map shows the location of the sampling site, note anthropogenic structures that may
influence hydrodynamic traits. (a) Location was an access barge used for smaller vessels; this was constantly
The sampling was conducted using a Valeport 106 Current Meter. It
was used in self recording mode with the 10-way subconn connector.
Direct operation was not possible due to location. The current meter
was then lowered through the water column stopping at each 1m
interval for a period of two minutes allowing data collection. This
would be done each day over one entire tidal cycle, alternating daily
between flooding and ebbing tides. During spring and neap tides,
both the flooding and ebbing tide would be measured to give a tidal
flow for the extremes of the cycle.
As the 106 current-meter was used in self recording mode, the data
needed to be removed after each daily sample obtained. This is
done using Datalog (software provided by Valeport) and the Y lead to
connect the fish to the computer. Once the data had been removed
it is to be converted into an excel format and filtered (shading
alternative depths for clarity). Each depths flow and heading data
would be copied into a new spreadsheet (Flooding, Ebbing, Spring
Flood, Spring Ebbing, Neap Flooding or Neap Ebbing): Sheets are
then separated into individual depths. Vectors would then be
converted into Cartesian coordinates and then averaged.
( = )
( = )
Once the data is averaged it is changed back to vector (polar)
coordinates using Atan2: