THE RISK CAUSED BY HYDROCARBON SPILLS IN THE EASTERN REGION OF THE CANARY ISLANDS WATERS: TESEO MODEL AND SIROCO SYSTEM RIESGO DERIVADO POR VERTIDOS DE HIDROCARBUROS EN LA REGIÓN ORIENTAL DE LAS AGUAS CANARIAS: MODELO TESEO

In view of the increasing oil interest shown by Spain and Morocco, the aim of this project is to test the risk of hypothetical spills of hydrocarbons in the eastern region of the Canary Islands waters and their surroundings through the Simulation Model of Hydrocarbon Transport (TESEO) and the Island Response and Operations System against Ocean Pollutants, in Spanish Sistemas Insulares de Respuesta y Operaciones Ante Contaminantes Oceánicos (SIROCO). Palabras clave: Oil Spill; SIROCO; TESEO RESUMEN En este trabajo se analizan a través del Modelo de Simulación de Transporte de Hidrocarburos (TESEO) y los Sistemas Insulares de Respuestas y Operaciones ante Contaminantes Oceánicos (SIROCO) el riesgo derivado de hipotéticos vertidos de hidrocarburos en la región oriental de las aguas canarias y sus proximidades ante el reciente interés petrolífero en la zona por parte de España y Marruecos.

The core of the oceanic operational system consists of two elements: observing services and dynamic models with data assimilation. The appliances of this system are countless and they have prompt scientific, technological and socio-economic benefits. Optimal strategies against marine pollution (LCC) are set out to trace and analyse the progression of spills through the oceanographic operational system, at both regional and local level. The developed appliances are equally useful to predict floating objects and shipwrecks. The integrated systems are also useful for the integrated management at coastal zones, maritime transport, port engineering and the management of fish resources, through physical variables predictions, both meteorological and oceanographic, that are the basis of chemical-biological models.
The ESEOO Project (Establishment of an Oceanographic Operational Spanish System) provides essential information to respond to emergency situations by accidental polluting spills and allows addressing these critical situations in the best possible way. The oceanographic operational system consists of a range of services based on numerical modelling and oceanographic data analysis, both historical and live data. The Simulation Model of Hydrocarbon Transport (TESEO) can simulate the transport and degradation of hydrocarbons. The structure of the TESEO operational system is as shown in Figure 1. The drifting model is a two-dimensional Lagrangian Model, which simulates the movement and degradation of a hydrocarbon, considering the spill as the sum of particles that move separately, due to strengths such as wind, waves, current and turbulent diffusion.
The model has been calibrated using the algorithm SCE-UA (Shuffled Complex Evolution Method -University of Arizona) and adapted for its application in Oceanography (ABASCAL, 2008).
The calibration using drifting oceanographic buoys enables to optimize the algorithm ( Figure 2) and obtain ratios which reduce the differences between the real movement of the spill and the numerical prediction. The optimization method pursues the calibration of the predictive Lagrangian Transport Model. The objective of the calibration is to find the value of the coefficients that minimize the objective function.  The application has two operating modes called operational and re-test mode. The re-test mode can manage the forcing files and control the parameters of implementation of the model. The system consists of three modules: the input module, the Oil Spill Transport and Fates module and the Graphical Output module. Each module is integrated in a simple graphical user interface (GUI), which provides efficient information on the ability to manage oil spills and respond to them (ABASCAL, 2008).

Input Model
The relevant event data, the forcing data and the selection of the type of spill are entered in the TESEO System input module. The interface allows remote control (FTP) to different operational predictive systems and the data can be introduced in NETCDF format ( Figure 4).  The transport model takes into consideration the influence of weathering processes on the evolution of the spill. The drift processes are described by approaching to a multiparticle system, based on the PICHI model developed by the University of Cantabria after the Prestige oil spill (2002).The Table 1 shows the equations used in TESEO model [Fay (1969[Fay ( , 1971); Lehr et al. (1984); Stiver and MacKay (1984); MacKay (1980)]. Advective velocity Where: ⃗ advection velocity; ⃗ diffusion velocity; ⃗ current velocity; ⃗ wind velocity; ⃗ Stokes drift; A Spill Area; Volume; T Tempreature; , son las constantes de destilación; wind velocity (10 m); maximum water content in oil.

Graphical Output Module
The results of the numerical simulation are shown in this section and they are represented in five different types of graphics: the positions of the centre of gravity, distribution of particles, probability maps, mass balance and evolution of the hydrocarbon characteristics. The results obtained can be taken into consideration for the implementation of contingency plans and cleaning operations, both at sea and throughout the coast.
TESEO has been successfully tested as an operational tool at emergency actions in different oil spill simulation exercises carried out by Maritime Rescue (SASEMAR), in the Atlantic and the Mediterranean Sea. These experiences were the first attempt made in Spain to include operational systems to respond to hydrocarbon spills. The capacity of TESEO to use live data for the decision-making process was proved during the performance of the simulation. Comparing the predictions of the system with the track of the buoys, the results showed a high level of coincidence with the model behaviour (ABASCAL, 2008).
In order to get the best results from the path of the various spills, as well as to estimate the aging process of crude petroleum once it has been spilled into the water, a number of simulations have been carried out using the TESEO Model.
By comparing the results obtained from the simulations with any of the applied models, you can estimate the most likely path of a certain spill and how will its properties vary as it moves on the water surface and until it hits the coast. Besides that, you can obtain an average value of the quantity of hydrocarbon that has remained on the coast, where it hit.

RESULTS AND DISCUSSIONS
Several deterministic and stochastic cases have been analyzed .The following lines show the results obtained in a deterministic case from a hypothetical hydrocarbon spill in a region which has received significant interest from the oil industry. To conclude, a chart synthesizing various scenarios is attached.
3.1 Region "Canarias-6" (TESEO) The project starts by analysing the region "Canarias-6". The input parameters to carry out the simulation are detailed in Table 2. On the present simulation TESEO splits the path into three different sections. It is possible to observe date and time of the spill from each of them, as well as the moment when it hits the coast. Figure 5 shows the predicted path and the evolution this spill will take until it hits the coast of Fuerteventura.      The location of the spill after 72 hours is shown in Figure 9.
Source: Authors.                      Table 3 shows as an overview the results of the evolution of the spill by each of the scenarios tested with the TESEO Model.

CONCLUSIONS
We have analyzed the results of deterministic and stochastic simulations for a possible accidental oil spill during underwater oil exploration in the eastern region of the Canary Islands waters.
The potential spill trajectories have been analyzed using TESEO model to evaluate the impact on the coast. Real data from National Meteorological Agency and Puertos del Estado was used to accomplish the description of wind, water flows and waves in the area.