River Ecosystems

The river network of Sakhalin Oblast comprises 61,178 rivers, most of which are classified as minor rivers and streams, with a combined total length of 93,427 km. The fresh and brackish water bodies (rivers, lakes, and lagoons) are inhabited by 89 species and types of fish and fish-like vertebrates. Migratory fishes, especially Pacific salmon, play an important role in the biodiversity of Sakhalin’s ichthyofauna. The Red Book of Sakhalin Oblast includes seven species of fish, eighteen species of molluscs, and six species of crustaceans. They comprise all the species listed in the International Red Book and the Red Book of the Russian Federation that are found in Sakhalin Oblast, those species that are rare for the Russian Far East, as well as new, recently discovered species, whose distribution and numbers are yet to be confirmed.

The routing of the pipeline system resulted in the crossing of approximately 1,000 freshwater bodies (rivers, streams, lakes, and canals) located on the vast territory stretching from Chayvo Bay in the north to Aniva Bay in the south.

During the preparation and construction stages, Sakhalin Energy conducted baseline studies and environmental monitoring of all water bodies. When moving to the operation stage, the Company developed and implemented a comprehensive monitoring programme for water bodies crossed by the pipelines in order to track any changes, identify critical areas, and propose and apply corrective measures in a timely manner.

The river ecosystem monitoring system covers several areas: quality monitoring of surface waters and bottom sediments, and monitoring of benthos communities and ichthyofauna. River ecosystem quality monitoring primarily reflects the nature and specifics of potential impacts on aquatic ecosystems during the operation of Sakhalin Energy’s pipeline and infrastructure. In addition, monitoring allows for the identification of possible reverse impacts from natural factors on the Sakhalin-2 infrastructure.

The programme of industrial environmental monitoring of river ecosystems includes:

• determination of the hydrological and hydrochemical characteristics of watercourses,
• assessment of the condition of bottom sediments in river beds,
• identification of hydromorphological changes (river bed and bank erosion in areas of pipeline route crossings),
• assessment of the benthos community’s composition and abundance, and
• assessment of ichthyofauna, the area and quality of potential spawning grounds of Pacific salmon.

Monitoring is conducted over three hydrological seasons: spring floods, summer low water, and autumn high water. Samples are taken in two cross sections: an upper, baseline section with no impact from Sakhalin Energy’s assets, and a bottom, control section.

Over the entire monitoring period, on most surveyed river-crossing pipeline sections (from the upper to the bottom cross sections), no significant horizontal or vertical deformations of river beds were detected. The crossings are in satisfactory condition, and no damage to utility lines was found. Additional surveys are carried out in river sections showing signs of bed deformation to ensure timely maintenance and repair.

Quantitative and qualitative analysis of macrozoobenthos and its habitat conditions (such as bed type, current speed, bed soil type, and depth) shows that the variability of the composition, state, and structure of bed communities between the baseline and control cross sections of the water courses under study is caused by the natural heterogeneity of biotopes and hydrologic-hydrochemical indicators at the monitoring stations.

At the operation stage, in addition to the river condition monitoring, the Company completed a long-term programme for studying the ichthyological characteristics of rivers crossed by the pipeline route. The quality of the restored crossings and the condition of spawning areas have shown a lack of impact on the ichthyocomplexes of the watercourses during the operation stage; therefore, the annual programme of environmental monitoring of the ichthyocomplexes at the operation stage includes comprehensive ichthyological surveys of the Goluboy Stream running through the territory of the Prigorodnoye production complex. The scope of surveys includes an assessment of the size and quality of potential Pacific salmon spawning areas. Additionally, Sakhalin Energy monitors juvenile downstream migration and spawning runs of Pacific salmon.