Oil Spill Modelling using Water Forecast Models.doc/NHP-2008-02-14 1 Oil Spill Modelling using Water Forecast Models By Niels Hvam Pedersen DHI Water & Environment, Agern Allé 5, DK-2970 Hørsholm, Denmark, Tel.: +45 4516 9200, Fax: +45 4516 9292, E-mail: [email protected]ABSTRACT The paper discusses the principles of assessing and controlling oil spills in surface waters using Water Forecast models. The primary goals of such a system is to forecast the movement and spreading of oil spills in order to make decisions on how to decrease the impact of the oil spill in the affected area. The system can also be used to detect from where the oil spill originates by backward tracing the observed oil spill. 1. INTRODUCTION Oil spills are serious threats to the marine environment, and place enormous demands on the national authorities responsible for the response and clean-up operations. In many cases, the resources required are beyond the means of a single country. In the last 30 years, around 5 million tonnes of oil have been spilled in the world's seas as a result of nearly 10,000 accidents. The majority of the spills are small (less than 700 tonnes), and it is the large spills that account for most of the amount spilled. Thus, in the period 1988-1997, 70% of the oil spilled came from just 10 incidents. However, the history of oil spills has shown that in general the amount of impact on the environment has rarely been correlated with the amount of oil spilled. Many ecosystems potentially suffer from deterioration due to oil spills. Accidental spills together with leaching of oil originating from oil production and transport activities may result in contaminated water constituting a severe risk for the water environment, fish, birds or coral reefs etc. The impact depends on a number of factors, such as the ecological sensitivity of the impacted site, type of oil and meteorological conditions (water temperature and weather). Once the spilling incident has taken place, natural processes including weathering, evaporation, oxidation, biodegradation and emulsification, will start taking place. They can reduce the severity of the oil spill and accelerate the recovery of the affected area The environmental impact of a given oil spill, however, will be influenced by many factors. The topography of the system, evaporation, run-off events and tidal variations will determine the magnitude and direction of flow. The position, duration and amount of oil spilled to the river/bay, the transport/spread of the oil as well as self-purification processes in the waters will determine the position of the oil slick and the concentration of oil constituents in the water phase.
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Oil Spill Modelling using Water Forecast Models.doc/NHP-2008-02-14 1
Oil Spill Modelling using Water Forecast Models
By
Niels Hvam Pedersen
DHI Water & Environment, Agern Allé 5, DK-2970 Hørsholm, Denmark,