Oil Pollution Monitoring in North Caspian Sea 2011
From February until December 2011, there were 190 sessions of operational radar imagery of the Caspian Sea conducted using RADARSAT-1, RADARSAT-2 and ENVISAT satellites. The average imaging frequency constituted once in two days.
To ensure high imaging frequency and monitoring of the water area condition, multispectral images of SPOT 4/5 satellites (resolutions - 20 and 2.5m respectively) and Landsat 5 (30m) were acquired, as well as high resolution images of EROS B (0.7m). Multispectral images of SPOT and Landsat 5 were used to detect the origin of some oil slicks. In order to assess the maritime environmental condition, generation of three types of products were performed on a daily basis based on MODIS data from Terra and Aqua satellites: chlorophyll and suspended matter concentration map, and map of sea surface temperature. During the freeze-up period, assessment of general ice condition and monitoring of ice cover dynamics was carried out using radar and MODIS images.
National ScanNet technology of multi-satellite monitoring was applied in support of operational and high accuracy detection of oil spills, as well as the geoinformation approach, developed at the Institute of Oceanology of RAS. The principal components of the ScanNet technology, created at ScanEx, are:
- short revisit period (once per day), due to application of three radar satellites data - RADARSAT-1, RADARSAT-2 and ENVISAT;
- direct reception of satellite data in Russia to the network of ScanEx RDC ground stations with automatic processing in near real-time mode, which enables to reduce the cost and to increase the degree of work operability;
- complex application of images, received from optical and radar satellites;
- prompt delivery of results to the customer via web-services and geoportals.
To ensure a high degree of operability, a round-the-clock cycle of radar images reception and processing was organised at the Moscow office of ScanEx RDC. This allowed informing the customer about the facts of detecting oil spills within monitoring area with a minimum time delay. Satellite information after thematic processing, analysis and expertise was submitted in near real-time to the Lukoil-Nizhnevolzhskneft specialists via the web-service Kosmosnimki - Lukoil, which is running on the Russian Web-GISS technology GeoMixer.
Oil spills of human origin were detected on 52 radar images (27.4% of imaging sessions). Analysis of satellite images on the licensed area "Severny", related to production activities on the objects of fuel and energy complex of Lukoil-Nizhnevolzhskneft showed no oil spills. This is the result of the technology of "zero discharge" and of effective measures of ecological and industrial safety on the Korchagin field.
A great portion of detected sea surface spills was spills from vessels as a result of bilge water, engine compartment and other liquid oily wastes dumping. On the satellite images the pollutions were in elongated form and located near shipping routes. Results of the operational modelling using ScanDrifter software revealed that the sources of oil slicks detected within the licensed area were the ships crossing it. A high probability of trans-border transition of oil slicks that appeared in close proximity to the monitoring zone into the licensed area has also been detected.
The largest oil spill of 69 sq km was detected within the Russian sector of the sea at the distance of 115 km to the south of the licensed area. Some satellite images also detected ships, involved in pollutions.
Further geospatial analysis revealed that most oil slicks in Russian and Kazakh sectors of the Caspian Sea grouped near shipping routes, leading to Astrakhan Roads and the Caspian Channel, as well as at the approach ways to the ports of Aktau, Atyrau, Makhachkala, etc.
Origin of some small oil slicks can be related to natural oil seepage. However, identification of such sources needs special monitoring and further studying. Efficiency of ScanNet and GeoMixer technologies was also tested during the operational monitoring of the "Grigory Bugrov" tanker emergency site. The ship had a hole in the hull and grounded in north-western part of the Caspian Sea on 13th October 2011 (37km to the south of the licensed area; ships belonging to Lukoil-Nizhnevolzhskneft were called in for rescue operations). During the rescue ops the imaging frequency of this particular area was reduced to one image per day. The information received enabled to detect that oil spills within the rescue zone had small sizes and were associated with fuel remainder oozing out of the sunken engine compartment of the tanker.
According to satellite monitoring data the environmental situation within the Russian sector of the Caspian Sea in 2011 was stable without serious deviations from average multi-year values. In July a sharp increase in the sea surface temperature was registered that caused changes in the balance of dissolved oxygen and the organic matter in North Caspian. As a result a slight H2S pollution was registered at several places that could have caused adverse environmental impact on the near-shore zone. Human-induced oil slicks on the sea surface, detected during monitoring, did not have much impact on the ecological situation of the North Caspian.
