Towards the development of an operational tool for oil spills management in the Algarve coast
Portugal is strongly vulnerable to sea hazards due to intense vessel traffic and sea conditions. The southwest region off the Iberian Peninsula lies in the main route from the Mediterranean and Southern Hemisphere to the Northern Europe, causing a ship concentration in a narrow band off Cape São Vicente. Tankers represent a significant part of the vessel traffic and the occurrence of oil spills cannot be disregarded. Cape São Vicente region is part of a Natural Park with 110 Km of coastline, integrated in the European Natura 2000 network and its socio-economic context is closely related with sea resources exploitation, particularly fishing and tourism. Recognizing the importance of accurate information systems for the decision making process in an oil spill situation, this work presents the development of an integrated tool to support the process in the Algarve coast. The system relies in a regional operational mathematical model based on the MOHID modelling system. The system core is composed by three models (3D hydrodynamics, wave and Lagrangian transport) all linked in the same system and exchanging information in real time. Oil advection and weathering processes are coupled to the Lagragian transport model. The overall operational system includes external operational data products as inputs, to ensure a successful validation of the results. The system is linked to stakeholders and response authorities using a geographic referenced database based on Mapserver technology that will include relevant information for oil spill management.
KeywordsOil spills Emergency response Operational modelling Decision-making tool
The increase of human occupation in the world coastlines makes oil spill impacts more harmful today than 40 years ago. Nowadays, impacts in industries like tourism, aquaculture and energy must be added to the impacts on the environment and fishing. If we also add the growing environmental awareness among the general public and media coverage, the response decision to oil spills becomes a politically sensitive task.
The processes that govern both the transport and weathering processes of oil in water are complex and depend not only from oil characteristics, but also from the hydrodynamic and atmospheric conditions at the spill site (Mackay and McAuliffe 1988). To deal with this complexity and transform it in a predictable solution, operational modelling systems assimilating observed sea state an atmospheric data, coupled with models that can simulate the oil weathering processes are required.
In fact, monitoring and forecasting the fate of marine pollution, including oil spill, is one of the focus applications in operational oceanography with most coastal nations supporting monitoring and response services for oil spill response. Although prediction services can play an important role in decision-making during incidents, their use can be extended for designing the response services (Hacket et al. 2008).
A good link between the operational results and stakeholders is another key element in these types of operational instruments. Due to the vast array of different environmental and socio-economic impacts of a spill, a multitude of stakeholder groups with diverging interests are expected and should be address during the development/planning phase of the system.
The aim of this work is to present a new approach towards an integrated tool for decision making and emergency response for the Algarve coast, that addresses not only authorities directly involved on the pollution accident, but also regional and local stakeholders that might be affected.
The regional socio-economic system is closed linked to the sea. The economy of the region relies 46.0 % on the tourism, mainly in the coastal area, that represent directly 44.7 % of the regional Gross Domestic Product (GDP) and 37.1 % of the employment. Fisheries represent 3.7 % of the regional employment against 0.7 % at national level (INE—Instituto Nacional de Estatística 2008).
The maximum amount available for compensation under the 1992 Civil Liability Convention and the 1992 Fund Convention in respect of the Prestige incident is €171.5 million while the figures given in May 2003 by the Governments of the three States affected by the incident (Spain, France and Portugal) as to the damage caused, indicated that the total amount of the damage could be as high as €1 050 million (IOPCF 2009).
State of the art
In Europe operational oceanography and data assimilation systems have been growing in importance for the last few years. All these systems use different operational capacities, data streams and expertise. They aim to support a wide range of scientific and operational services and applications including oil spill monitoring, marine safety as well as offshore oil industry (Daniel and Dandin 2005).
Funded by the Financial Mechanism of the European Economic Area (EFTA) and the Hellenic Ministry of National Economy, the POSEIDON system has been developed and operated by the Hellenic Center for Marine Research (HCMR). It is based on OCEANOR's Sea-watch System, (Hansen and Stel 1997), consisting of separate yet interrelated components. The spine of POSEIDON is an integrated network of ten oceanographic buoys and ten wave buoys deployed in several locations in Greece, equipped with a variety of sensors for monitoring the sea environment. Properties like wind speed and direction, air pressure and temperature, surface water temperature, sea-surface current speed and direction, wave height and direction, water temperature and salinity, dissolved oxygen, chlorophyll-a and nitrates are measured, quality controlled, stored and pre-processed in a automated way through a computing system and software present in all sensors and are near real-time remotely transmitted to the Operational Centre of HCMR by a two-way telecommunication. The control and surveillance of the POSEIDON system is made through the Operational Centre located at HCMR's installations. POSEIDON forecast ability comes from the Aegean Operational Forecasting System (AOFOS), which consists of a set of separated but interacting numerical simulation/forecast models adapted to the Greek seas environment. They consist of a weather prediction model, an open sea wave forecast model, a 3D hydrodynamic model, a shallow water wave prediction model and a buoyant pollutant transport model. A detailed description of the system and a preliminary evaluation of its forecasting skill are included in Nittis et al. (2001).
The Cyprus Ocean Model (CYCOM), described in detail in Zodiatis et al. (2003a, b, c) is the high resolution model in CYCOFOS, with a spatial step of 1.5 km. Its boundary conditions are supplied from ALERMO 5 day’s forecasts and high frequency (hourly) meteorological forecasts from SKIRON.
For offshore wave forecasts, CYCOFOS uses WAM model (WAMDI Group 1988) in a three level nested domain. The intermediate level, the Levantine basin, is nested with the Mediterranean wave forecast model (first level) and forced with wave height and direction, together with SKIRON wind velocity, every 3 h. Waves around Cyprus (third level) are simulated with a high-resolution SWAN model (Holthuijsen et al. 1997), forced by the wave conditions obtained from the second level domain, and by hourly SKIRON winds (Zodiatis et al. 2005).
CYCOFOS components are all integrated within a network of near real time data from observations. The MFS assimilates two satellite altimeters along track data, satellite daily sea surface temperature, and vertical hydrological profiles of Temperature (T) and Salinity (S) from XBT and ARGO profilers as described in Dobricic et al. (2005, 2006). Levantine Basin is being monitored through an ocean observation station, MedGOOS-3, that measures conductivity and temperature and pressure and communicates with CYCOFOS by satellite.
A coastal station, MedGloss, located in Paphos (Cyprus) supplies the operational system with coastal levels, water temperature and air pressure. A satellite ground receiving station, operational since 2001 collects sea surface temperature images from NOAA AVHRR satellites, and clorophyll-a images using NASA MODIS AQUA (Zodiatis et al. 2003a, b, c).
In Portugal a national contingency plan - “Plano Mar Limpo” (Clean Sea Plan) - was approved in April 1993. This plan gives overall responsibility for spill response to the National Maritime Authority (Autoridade Marítima Nacional) and, in particular, to its coordinating body, the Maritime Authority Directorate General (Direcção-Geral da Autoridade Marítima), all part of the National Navy. This response however is more related to the containment and recovery at sea, and clean-up operations in shore, the operational models to forecast spill trajectories and to assist field operations are being developed and maintained by the Hydrographic Institute (Instituto Hidrográfico), part of the Portuguese Navy, in charge of supporting the Navy actions in the field of marine science and technology.
Similar to the operational systems described above the Hidrographic Institute (IH) developed the MOCASSIM system. It uses a broad range of observations provided both from IH observational networks (wave buoys, tidal gauges) and programs (hydrographic surveys, moorings) as well as from external sources. The MOCASSIM system integrates a circulation model based on the Harvard Ocean Prediction System (HOPS) and a wave model based on the WaveWatch3 (WW3) model, which provides wave conditions in the North Atlantic basin, and on the SWAN model that is used to improve the wave forecasts on coastal or other specific areas of interest. Meteorological forcing is accomplished in the framework of collaboration with the Portuguese Meteorology Institute using ALADIN model predictions for the entire country (Vitorino et al. 2003).
For the prediction of oil spills the system uses a simple trajectory model, that doesn’t take into account oil weathering processes, instead it relies on a more accurate characterization of the sea and wind state to forecast spill trajectory. Future IH strategy for operational modeling is divided in the implementations of new numeric models, like ROMS and HYCOM, to improved operational forecasts, the deployment of real time data observation systems to support the modeling forecasts and the development of an oil spill module to include in the operational system (Vitorino, J., personal communication, February 1st, 2010).
The MOCASSIM system has already been used in several operational contexts. These included the operational environmental assessment during both national and NATO navy exercises and the monitoring of the oceanographic conditions in the NW Iberian area affected by the oil spill of MV "Prestige". The system is also being used in the framework of national and European funded projects in the ongoing research on the oceanography of the Portuguese continental margin, which is presently being conducted at IH (Vitorino et al. 2003).
A new approach
As previously mentioned the main goal of this work is to create an operational model for the Algarve coast, with the ability to predict the behavior and evolution of an oil spill in the marine environment and linking it to an online risk assessment/contingency response tool available for stakeholders. The system will include a set of mathematical models to predict the hydrodynamic conditions of the sea surface (wind, waves, currents, temperature, salinity) and to simulate the drift and dispersion of oil spills after pollution events. For this purpose the MOHID water modelling system (Martins et al 2001; Balseiro et al 2003; Leitão et al 2005) will be used. It is a modular system including modules for several processes of the marine environment (physical, chemical and biological). For this study the Hydrodynamic, the Lagrangian transport, and the oil spill modules will be used. This modular system where all the modules are included in the MOHID architecture is the main difference when comparing with the operational systems described before, as it allows the exchange of information in real time between all the modules. As an example, running simultaneously the Langrangean module and the Hydrodynamic model allows the exchange of turbulence information in real time between both modules, with practical results when simulating an oil spill. This type of approach also eliminates the need for data interpolation and increases the uniformity of the data analysis methods used by the model.
To simulate the diversity of processes affecting oil weathering and advection MOHID Oil Spill module will be used for the oil spill simulations (Janeiro et al. 2008). This module is based in a Lagrangian transport model that drives an oil slick evolution model. The Lagrangian transport model was restricted to a single mesh, however modifications have been made to allow several meshes of increasing resolution to be run simultaneously. This has the advantage of having high spatial resolution near the oil spill region without increasing too much the computational needs. The current version of the Oil Spill module already include important processes such as oil density, viscosity, oil spreading, evaporation, dispersion, sedimentation, dissolution, emulsification and interaction with the coast. A review and update of these processes will be done, as well as the inclusion of other important processes such as mechanical spreading, dispersion and sedimentation. The implementation of new algorithms that allow, - based on the actual hydrodynamics, spill time and its physical-chemical properties -, an automatically decision from the module about the best response measure to use on a particular spill will also be implemented.
Data coming from different sources (meteorological, remote sensing, buoys, etc) will be used to prepare the best possible estimate of the true state of the system, to be assimilated by the model and to allow calibration. Adaptation is needed in the control structure of the model to run the system in operational mode. An operational framework to run the model will be constructed in .NET platform in order to execute and monitor all the required operational tasks, such as managing data input to the system, running the model, generate model maps and animations.
To make the bridge between the system and the end-users a web based geographic referenced database using Mapserver technology and including relevant information for oil spill management (bathing beach locations, aquaculture sites, natural sensitive areas, civil protection team’s headquarters, etc) will be created. Methods will also be developed to automate tasks related to management of oil spills, linking the model predictions with the operations on the field.
In parallel with this study a similar operational modeling system is being developed for the Tuscany archipelago (Italy) under the 7th Framework Programme project ARGOMARINE (Automatic oil-spill recognition and Geopositioning integrated in a Marine Monitoring network). The overall objective of the ARGOMARINE project is to develop and test a Marine Information System (MIS) capable of providing precise and punctual pollution control in coastal zone areas with vulnerable or protected habitats, and/or are exposed to risk of accidental or intentional contamination due to their vicinity to industrial or highly densely populated settlements, or crossed by a heavy ship traffic. A Marine Information System (MIS) consisting of a network for data storage, data mining and analysis, decision-support, data warehouse and a web-GIS portal carries out the top control of ARGOMARINE. The communication relies on an Integrated Communication System (ICS), developed to ensure reliable and efficient data transmission from different sensors and models to the MIS. A pre-operational high-resolution mathematical modelling system to forecast hydrodynamic conditions and prediction of oil slick spreading during emergency situations, as part of an early warning system, will be created during the project. The modelling system to be used is the MOHID, and the methodologies followed are the same of those described above allowing and two-way improvement and validation of the methods in use. When fully operational the system will be receiving data from the modeling system and also from Synthetic Aperture Radar (SAR) images, airborne Hyperspectral/Thermal Imaging, AUV/Glider mounted sensors and Electronic Noses. The synergies between the two works will potentiate the results and the validity of the methods proposed.
Despite the encouraging preliminary results showing the potential threat that an oil spill event can represent for the study area, still much work needs to be done. Coupling these high-resolution grids with the PCOM results in order to accomplish reliable 3D hydrodynamic fields for the area, and then use these fields to drive the oil spill module and simulate oil advection and weathering processes are the next steps.
This work is being funded by a Doctoral grant, reference SFRH/BD/44850/2008, from the Fundação para a Ciência e Tecnologia to whom we would like to thank. A special thank to Dr. Francisco Silva and Dr. João Vitorino from Instituto Hidrográfico.
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