Home – Home – Jornals – Geography and Natural Resources 2022 number 5S

The problem of regulation of the lake level, the operating modes of the Irkutsk hydroelectric power station and its impact on the Baikal ecosystem is a subject of active discussion at various public and scientific levels in Russia and internationally. By the decision of the Presidium of the Russian Academy of Sciences No. 115 of June 22, 2021, the Scientific Council of the Siberian Branch of the Russian Academy of Sciences (SB RAS) on the problems of Lake Baikal was tasked to consider scientific problems, the results of research as well as draft regulations on Lake Baikal conservation on the basis of open, uncompromising and professional discussion, pursuing the goals of Lake Baikal conservation in conditions of ensuring the rights of the region’s residents. Presented is an overview of the efforts made by SB RAS and the Scientific Council of SB RAS on Lake Baikal Problems in 2021, the norm formation procedure as regards the permissible impact on the lake ecosystem and the achievement of coordinated positions of scientists concerning the issues of joint definition of requirements for discharges into Baikal and presumption of danger of anthropogenic impact on the ecosystem. In the work on studying the influence of the Lake Baikal level regulation modes on the condition of its ecosystem, SB RAS performs the functions of the leading organization in relation to scientific institutes under the scientific and methodological guidance of SB RAS, educational institutions and research institutes of federal departments. Measures are suggested in this paper to further develop the powers of SB RAS to carry out integrated scientific research, and the use of the “only supplier” institute represented by SB RAS is substantiated to provide scientific support of the measures for the conservation of Lake Baikal.

The problems of Lake Baikal level regulation, hydrological conditions and characteristics of changes in the level regime of the lake in recent years, including the low-water (2014-2017) and high-water (2020-2021) periods, and also the changes in the legislative framework caused by them are considered. A historical overview of the development of the water resource management rules of the Irkutsk reservoir (Lake Baikal) for the period from the end of the construction of the Irkutsk HPP to the present is given. The main problems that arise in the regulation of the lake level in different periods of water level in the Baikal basin, and the contradictions of the existing WRMRs are analyzed. The reasons and prerequisites for the adoption of Decree No. 234 and temporary Decrees of the Government of the Russian Federation on the regulation of the lake level are pointed out. The results of individual, previously performed studies on this issue are presented. Particular attention is paid to the analysis of the proposed “environmental requirements” that must be taken into account when regulating the level of the lake. The reasons that do not allow their practical application are noted. The ideas that have developed in recent years about the causes of emerging problems and ways to solve them are considered. The most urgent and still unresolved issues related to the level regulation are highlighted. To form scientifically based and practicable principles for regulating the level of Lake Baikal in different water level conditions, taking into account modern environmental, socio-economic and water management requirements and restrictions, it is reasonable to carry out a comprehensive research work. The purpose, main tasks and expected results of research work on the topic “The impact of changes in the water level in Lake Baikal on the state of the lake ecosystem, the determination of damage to economic facilities and infrastructure of the coastal territory of the Republic of Buryatia and Irkutsk oblast, depending on the levels of the lake and discharges from the Irkutsk HPP” are outlined. The work has been carried out within the framework of the national project “Ecology” (“Preservation of Lake Baikal” subproject) by the institutes of the Siberian Branch of the Russian Academy of Sciences, the Ministry of Science and Higher Education of the Russian Federation, the Federal Service for Hydrometeorology and Environmental Monitoring, and the Federal Agency for Fishery.

An analysis is made and methodological approaches are suggested to assess the economic, social and environmental consequences of flooding and waterlogging of territories confined to the water area of Lake Baikal. The concept of economic assessment of the impact of the level regime of a water body on natural and economic complexes and the population is generalized. The factors influencing the valuation of damage are identified, and the main characteristics of the consequences of the negative impact of water are presented. The necessity of updating the methodology for assessing the likely damage from the negative impact of water and assessing the effectiveness of the implementation of preventive water management measures in terms of certain categories of damage is shown. A technique for geoinformation mapping of the negative impact of the level regime of Lake Baikal on natural and socio-economic sites is suggested. The cartographic database contains a vector layer of land boundaries and an attribute table. On the basis of direct counting methods, local damages are calculated by taking into account actual losses based on standard specific indicators and prevailing market prices for products, lost profits, and valuation of ecosystem services. The methods of transport and recreational costs are used, which assess the willingness to pay for environmental benefits in accordance with information on time and cost expenditures when visiting a recreational facility. An analysis of the regulatory framework for assessing socio-economic risks in case of changes in the water level in Lake Baikal is made by using the territory of Buryatia as an example. A grouping of socio-economic systems of coastal territories was carried out according to vulnerability criteria.

Presented are the results from investigating changes in the water balance components of Lake Baikal for the operation period of the Irkutsk HPP (1960-2020) on the basis of analyzing the long-term dynamics, including the surface inflow, discharge through the Irkutsk HPP, precipitation on the lake surface, and evaporation from the lake surface in monthly, quarterly and yearly resolutions. The surface inflow constitutes the main component of the inflow portion of the water balance and is determined from observational data obtained at 32 posts on the rivers flowing into the lake and from calculated values of the inflow from the part of the catchment which is not covered by hydrometric observations. It is pointed out that the share of the large rivers (Selenga, Upper Angara, and Barguzin) accounts for about two-thirds of the total surface (river) inflow. Over the last several decades, the proportion of the inflow via the Selenga river has decreased by 20 % against the preceding period. An analysis of the long-term changes in the river and useful inflows showed the existence of two periods with low water: 1976-1981 and 1996-2017 as well as two periods with abundance of water: 1960-1975 and 1982-1995, and an increase in the inflow since 2018. A comparison is made of the water balance components for two periods of equal duration: 1971-1995 and 1996-2020. A disturbance of the uniformity is observed for the discharges through the Irkutsk HPP. The study revealed an increase in mean annual temperature by 1-2 °C and a decrease in atmospheric precipitation almost throughout the lake drainage basin. The annual values of precipitation after 1996, compared with the preceding period, decreased throughout the territory of the lake drainage basin by 30-60 mm. Using two extreme periods of low water (2014-2017 and 1976-1981) we consider the role of the Irkutsk HPP in the regulation of the level regime of the lake.

Based on regular observations of the water-level regime of Lake Baikal, we studied the characteristics of interannual fluctuations in the level of the water body under natural conditions and in the period of the regulated lake. There were differences in the onset of the seasonal water level extremes, the range of its fluctuations and the rate of its increase/decrease in different months. The main differences in the characteristics of the water-level regime of the lake were associated with forcing and anomalous periods in terms of water content. In the forcing years, the interannual range of fluctuations in the water level increased by 20-25 %, and the dates of autumn water filling of the lake delayed up to 30-40 days. The intensity of increase in the water level after the regulation of the lake remained within 6-7 mm/day but reached 18 mm/day in August 1973. The restructuring of interannual fluctuations in the surface water inflow to the lake caused by climate change could also affect the changes in individual indicators of the water-level regime of Lake Baikal. The assumption about the adaptability of Baikal organisms to the water-level regime of the lake, which existed under natural conditions, included concerns about the need to preserve its main parameters in the years after regulation of the lake. Some problems are pointed out regarding the compliance with the rules for the use of the Baikal water resources and maintenance the optimal water-level regime of the lake for its aquatic biological resources. The major problems are the new restrictions of the discharge through the Irkutsk Hydroelectric Power Station both in terms of non-flooding of economic facilities in the downstream of the hydroelectric complex and in terms of ensuring uninterrupted water and heat supply to the cities located there. Also, there are restrictions of the upper limit water level of Lake Baikal in the zone of variable backwater. Moreover, the existing legislation concerning regulation of the lake runoff and its water level needs to be improved.

In conditions of extremely low- and high-water years, the boundary conditions for the level regime of Lake Baikal as established by resolution of the RF Government No. 234 of 3.26.2001 (within 456-457 m according to the Pacific Elevation System, PES) cannot be complied with objectively for a number of reasons. An objective assessment of the influence of the water level on the socio-economic and ecological state of the coastal territories requires a modeling of the position of the shoreline with its different levels. On the basis of an analytical overview of publications, we compiled a list of settlements located along the eastern coast of Lake Baikal which are experiencing the negative influence of water level fluctuations. Information regarding the existence of unique natural sites and a well-developed touristic-recreational infrastructure was also included. Field and laboratory work was made on modeling the characteristics of the topography of model territories involving high-precision aerial photographic imaging from an unmanned aerial vehicle, and the creation of orthophotomaps and digital elevation models. Flood zones of the coastal areas of Lake Baikal were constructed for extremely high levels of water surface (457.25, 457.50, and 457.85 m PES). We compiled the list of natural sites within the flood zone: nesting sites of rare species of the avifauna and rare and endangered plant species included in the Red Data Books of the Republic of Buryatia and Russia. The possible negative effect on the ichthyofauna of the aquatic ecosystem of the Posol’skii Sor Bay is pointed out. The negative consequences of the high water level in Lake Baikal also imply coastal forest dieback due to abrasion processes affecting the shores. The results obtained by modeling efforts can serve as a basis for calculating the potential damage to economic and ecological systems of model territories.

This article discusses the main methods for assessing the impact of dynamic changes in hydrological conditions of the lake on the natural environment of its coast. A brief component-wise analysis is made of the current state of the natural conditions of the coastal territory with a focus on the formation of the analytical physical-geographical basis for assessing the ecological consequences under various scenarios of changes of the Lake Baikal level. The territories vulnerable to the occurrence and development of unfavorable natural processes, which are most susceptible to fluctuations of the lake water level, have been identified Baikal. It is shown that the estuarine zones of tributaries and low coastal areas, which are the habitats of endemic and red-book biota species, are most susceptible to the negative influence of fluctuations in the lake level. The study of the natural components of the coast: geomorphological elements, soils, vegetation, animal world and landscapes in general has been carried out on the basis of published data and the results of previous and current research by the authors. It is concluded that the influence of the lake’s hydrological regime on the adjacent territory has not been adequately explored to date.

This article considers the reasons for the intensive destruction of the eastern shore of Lake Baikal during the rise of its level, and gives quantitative characteristics of the wave abrasive activity. It is shown that the most active development of abrasion occurred in 1962, 1964, 1971, 1973, 1983-1985, 1988, and 1990-1994 when the highest rise in the water level in Lake Baikal was observed. Due to the rise of the level in the estuaries of rivers and the coastal part of the lake, the direction and intensity of lateral currents have altered, lateral erosion has intensified, and deposit accumulation conditions have changed. It is shown that sand material washed away from the shores does almost not form beach deposits, because it is moved by currents along the coast. Engineering structures in settlements remain unprotected from the wave impact and continue to collapse. Their operation requires annual repairs. It is shown that when the lake level rises, due to an intensification of flooding, tens of square kilometers of agricultural land will be withdrawn from economic circulation, and motor roads and power transmission lines will be affected. The article highlights the areas of the most intensive development of various negative phenomena during the rise of the water level where additional research is required to determine the damage caused to nature and to engineering structures.

The natural preconditions for the development of various morphogenetic types of estuarine systems of the main tributaries of Baikal are considered. The objective of this study was to examine the estuarine areas and adjacent shores of the lake, the development of which is largely due to fluctuations in the current level of the lake-reservoir. The river mouth systems are represented by a complex of subaerial and subaquatic accumulative-erosive landforms and their sediments formed by a river and the lake within the river mouth at the present stage. Within the estuarine areas, there is a wider range of landforms created during the more ancient stages of interaction in the river - sea system. The main recent factors in the development of the estuarine systems of Baikal include fluctuations in the level of the reservoir, wave activity, alongshore currents, and the associated sediment transport and river runoff. The preconditions for the formation and development of various morphogenetic types of estuarine systems are the geological and tectonic features of the coast, which in turn are predetermined by the positive and negative morphostructural elements of the Baikal rift zone as well as by the layer of loose deposits. In addition, tectonic structures determine the nature of the interaction of river flows at the contact with the waters of the receiving reservoir in conditions of deep or shallow near-shore zone. The relationship between the development of morphogenetic varieties of river mouths and the morphostructural features of the marginal elements of the Baikal rift zone, the geometric pattern of the coasts, the slopes of the seashore, and also the ordinal structure of the river system has been determined. The estuarine systems of Baikal undergo multidirectional changes during periods of different water levels, which correspond to the formation or degradation of coastal landforms and channel deformations in the lower reaches of tributaries. An integrated scheme has been developed, which combines the dynamic and morphogenetic classifications of coasts and the types of mouth for the Baikal tributaries. A schematic map of the morphogenetic types of estuaries and the geological and tectonic preconditions for their formation is presented.

This article presents the results of geochemical studies of the main landscape components in the estuarine zones of the tributaries (Goloustnaya, Sarma, Kika, and Barguzin) and the coast of Lake Baikal. An assessment is made of the pollution of snow, soil, vegetation and surface waters. It was established that the most severe pollution is observed in the mouths of the Goloustnaya and Barguzin rivers. In the case of the Goloustnaya river this is due to soil and snow pollution as a result of the atmospheric transfer of emissions from the Irkutsk industrial center. The water in the Barguzin river is heavily polluted, largely as a result of pollutants from overlying catchment areas. In the mouth of the Sarma river, the main pollutants are due to recreational activities and enter soils and river and lake waters. The territory of the mouth of the Kika river is experiencing significant recreational loads but has relatively low levels of soil and water pollution. Accumulation of pollutants occurs on the geochemical barriers of soils and alluvial deposits. A rise of the water level in the lake does not lead to a critical level of permissible content of pollutants, and the quality of drinking water complies with sanitary standards. However, there are local areas with increased levels of toxic elements and substances in the coastal waters of Lake Baikal and in soils near coastal settlements (Sarma, Ust’-Barguzin, and Bol’shoe Goloustnoye).

The estuaries of the rivers are the most vulnerable objects of the lake system, which first of all respond to natural and anthropogenic changes of the river flow and lake level. Results from studying the content of persistent organic pollutants in the estuaries of the Selenga, Barguzin and Upper Angara rivers are presented. The content and profiles of organochlorine pesticides, polychlorinated biphenyls and polyaromatic hydrocarbons were determined in the natural water samples taken during the winter low-water period of 2022. The analysis of the data obtained by gas chromatography with tandem mass spectrometry in the mode of multiple reaction monitoring established the regularities of distribution and pathways of entry of persistent organic pollutants into the main tributaries of Lake Baikal. It was found that the pollution of waters of the main tributaries of the lake by organochlorine pesticides is not high, and the content of polychlorinated biphenyls is “trace” in nature and does not exceed the detection limits. Analysis of polyaromatic hydrocarbons origin in the estuaries is important because, apart from anthropogenic sources, there are also their natural sources. In this connection, we analyzed the ratios of concentrations of individual polyaromatic hydrocarbons, which are markers of the sources of their entry into the environment. Polyaromatic hydrocarbons in the natural water of the estuarine zones of the main tributaries of Lake Baikal have a mixed genesis (pyrogenic and petrogenic), but most of them are of pyrogenic origin. Data obtained for the qualitative and quantitative composition of persistent organic pollutants can be used for regional ecological-geochemical and ecological-hygienic assessments of the natural environment, identification of sources of anthropogenic impact on the natural environment and environmental risk assessment.

This article provides a substantiation for the transformation of the Lake Baikal coast in the area of the Selenga river under the effect of abrasion and accumulation processes associated with the Lake Baikal level rise during the construction of the Irkutsk hydroelectric power plant. It is shown that in the first years after the runoff regulation, an intense erosion of the entire coast occurred. On the basis of processing and comparing cartographic material from different years it was found that there occurred a significant decrease in the length and area of islands, peninsulas and sand bars in the Sor and Cherkalova Sor bays and in the Selenga delta. At present, destruction of sandy islands in the mouths of the rivers and the transport of sandy material along the coast continue during the autumn storms. It is shown that the decrease of the Selenga delta surface is associated with changes in sedimentation conditions. Coarse fraction of the solid runoff began to accumulate in the middle delta, and only fine suspended material enters the lake delta.

An analysis is made of the results from investigating the composition, production indicators and the distribution of macrozoobenthos in the Maloe More Strait of Lake Baikal for different years (1936-1941, 1951-1952, 2008, and 2014) covering a period longer than 70 years. The composition of macrozoobenthos showed the presence of representatives of the following groups: Hydroidea, Turbellaria, Nematoda, Hirudinea, Polychaeta, Oligochaeta, Isopoda, Amphipoda, Gastropoda, Bivalvia, Chironomidae, Trichoptera, Ostracoda, Bathynellidae, and Acariformes. A clearly pronounced azonality of the vertical distribution of benthic invertebrates is described, which is caused by the nature of the deep horizons, bottom sediments, and the development of benthic vegetation. Differences were revealed in the occurrence of macrozoobenthos on the northwestern and southeastern slopes of the bed of the Maloe More Strait. The study revealed a correlation between the biomass indicators of macrozoobenthos and changes in the Lake Baikal level as observed during the period under investigation.

It is established that when making decisions concerning the level management in Lake Baikal which possesses a unique biota and unprecedented hydrological parameters, yet being used in the mode of a reservoir of long-term regulation, it is necessary to take into account the requirements permitting the lake ecosystems to operate sustainably. Such requirements can be defined in the process of developing conceptual scenarios reflecting the impacts of various factors on the biota with due regard for the relationships between them and ecosystem components. We examine the possible factors of the impact of changes in water level on three components (microbial communities, vegetation cover, and fauna) of coastal ecosystems of Baikal and suggest relevant conceptual scenarios. A number of mechanisms of the influence of the water level on microbial communities are highlighted, and direct and indirect impacts on structural and functional characteristics of microbial communities of Baikal in different conditions of water levels are suggested. A two-level framework of factors affecting aquatic and terrestrial coastal vegetation with rising and falling water levels has been developed, and the influence of each factor was qualitatively assessed. Potential threats for the fauna (waterfowl and near-water birds were involved as a case) generated by the water level fluctuations were outlined in connection with biotopic and trophic relationships. In general, the heterogeneity and multidimensional character of the biota responses to the water level fluctuations has been revealed. It is emphasized that environmental integrity of ecosystems of fresh-water lakes, and the character and degree of impact on the biota from changes in water level of lakes still represent a “white gap” for the modern science. This is why the general schemes for ecosystem-based management of lakes have still not been developed.

The influence of long-term and seasonal fluctuations in the water level of Lake Baikal on species diversity of near-water and waterfowl vertebrates, their population density and breeding success is analyzed, the negative impact is revealed as well as a change in forage specificity and behavioral adaptation of species. The animal population of the coastal ecosystems of Baikal is unique and specific in many respects, as a result of which some aspects of its adaptation to long-term fluctuations in the water level are unique. An analysis was also made of data on changes in the abundance and spatial distribution of terrestrial vertebrates depending on the decrease or increase in the water level. The role of the construction of the Irkutsk hydroelectric power station in changing the structure of the population and the dynamics of the number of vertebrates is revealed. It has been established that in the nesting populations of waterfowl inhabiting the Selenga river delta, the rate of water level rise exceeding 1-2 cm/day causes a significant increase in the death of nests and eggs. Prolonged low water, which covered about 20 years, led to a decrease in the number of waterfowl, gulls and waders, which had previously remained numerous. We collected and analyzed information on the distribution and characteristics of the ecology of more than 120 species of vertebrates, permanently or seasonally living on the coast of Lake Baikal and leading an aquatic or semi-aquatic lifestyle. A zoning of the territory of the coast into 10 regions with different lengths, but with similar natural and climatic conditions, was carried out. 46 key areas have been identified, which are most sensitive to water level fluctuations. For these sites, the species composition of background and rare species of animals was established, and the areas of optimal habitat for animals and the zones of flooding of habitats were determined. The cartographic characteristics of two vulnerable territories of the Baikal coast are given.

The features of the influence of seasonal and interannual changes in the level regime of Lake Baikal on the populations of the main commercial fish species inhabiting the littoral zone of the northeastern coast which is the least exposed to the negative anthropogenic impact, are considered. Based on results of monitoring studies conducted during 1984-1990, it was determined that changes in water level of Lake Baikal and its tributaries have only a minor influence on the structure of the fish population in the littoral zone and biological characteristics of the main commercial fish species (black Baikal grayling and lenok) inhabiting this zone. The dominant role of black Baikal grayling in the ichthyocenosis at any water levels has been revealed. Lenok is a subdominant. Other commercial fish species (taimen, lake and river whitefish, pike, roach, dace, perch, and burbot) are not numerous and occur infrequently, mainly in pre-mouth sections of tributaries. It is concluded that one of the mechanisms of fish adaptation to the extreme changing conditions of the lake level regime is, undoubtedly, trophic adaptation aimed at consuming the most numerous and accessible food object. For the black Baikal grayling, they are unarmed small and medium-sized amphipod species and for lenok, they are stone and sand sculpins and large unarmed and armed amphipods. The most numerous food objects, such as imago of the Baikal caddis flies, are intensively consumed by all littoral fishes during their intensive emergence. This significantly reduces competitive relationships and contributes to better adaptation of fish to negative influences.

The water quality in the Listvennichnyi Bay has been investigated in terms of sanitary and microbiological indicators during the period of open water in the years of extreme water level in Lake Baikal (2017-2021). It was shown that the degree of fecal pollution in the Listvennichny Bay didn’t correlate with the water level or temperature, but related to the season and significantly varied on the different sampling stations. The abundance of sanitary-indicatory microorganisms in the summer-autumn period was significantly higher compared to the spring period which could be due to the raising anthropogenic impact through the season. Maximum abundance of thermotolerant coliform bacteria and Enterococci was determined at two sampling stations where raw waste waters reached the lake. At the other sampling stations including the background monitoring station, the water quality was mostly consistent with the SanPiN 1.2.3685-21 requirements. The interannual dynamics showed no significant differences in the thermotolerant coliform bacteria and Enterococci abundance. In the period of extremely low water level in Lake Baikal (2017) the abundance of autochthonous and allochthonous organotrophic microorganisms was significantly higher compared to the high-water years (2018-2021). Also, the abundance of both groups of microorganisms was similar in the autumn period, which can indicate the pollution of the Listvennichny Bay with easily decomposable organic matter and incompleteness of self-purification processes.

Presented are the results from analyzing a long-term series of observations (1976-2018) of the infection with parasites of the Baikal omul in the Chivyrkuisky Bay of Lake Baikal. Baikal omul (Coregonus migratorius) is one of the most ecologically important and valuable commercial fish species of Lake Baikal, dominating the structure of the ichthyocenosis of the unique reservoir. Parasites observed in each year of research are allocated to the core group; the others are classified as satellite species, and rare species are considered separately among them. There are 31 species of parasites in the Baikal omul in the Chivyrkui Gulf of Lake Baikal, seven species make up the core of its parasitofauna; 24 species are classified as satellite species, including 15 rare species. Among the parasites of the Baikal omul, of the greatest interest to researchers is Diphyllobothrium dendriticum, which has the highest epidemiological significance in Buryatia. The life cycle of the D. dendriticum is complex, proceeding with the change of three hosts: the first intermediate (Cyclopoida), the second intermediate (various fish species), and definitive ones (fish-eating birds and mammals, including humans). The Baikal omul is the dominant second intermediate host of D. dendriticum in Lake Baikal. The level of infection of the Baikal omul with Proteocephalus longicollis and Contracaecum osculatum baicalensis decreases, whereas it increases with D. dendriticum when the water level in Baikal rises. The multidirectional trends in the level of infection of the Baikal omul with mass species of parasites due to changes of the water level in Lake Baikal emphasize the importance of parasitological data for assessing the state of the ecosystem of a unique reservoir.

The issue of water-level regulation of Lake Baikal has been considered since the construction of the Irkutsk hydroelectric power station (1950-1959). Moreover, it remains relevant now, especially during periods of prolonged low water or high water. In this paper, we examine the theoretical, methodological and procedural framework for damage assessment, determine the essence of socio-economic and environmental-economic damage, and review domestic and foreign experience in assessing flood damage, because in the 21^st century the issues of damage due to changes in the level regime of a reservoir have been studied mainly from the standpoint of high water (inundation and waterlogging). It is shown that in Russia there is a certain lack of theoretical and procedural developments on this topic. Particularly acute is the lack of comprehensive economic and geographical work on the assessment of precisely socio-economic and environmental-economic damage. It has been established that one of the gaps in determining the damage from level fluctuations in a reservoir is terminological uncertainty (inconsistencies), which leads to an arbitrary interpretation of basic concepts and, consequently, to a large variation in estimates. We formulated a basic approach to the concept of damage in three main positions: estimated losses for identified economic entities (individual, society, and economic spheres of activity); a cost measure taken when assessing losses in any field of activity, including environmental; accounting for property rights (state, municipal and private), which is significant when considering compensatory measures. We summarized the existing approaches and methods for assessing damages, and identified their features and shortcomings with a view to the possibility for their further practical application.

In this article we consider the results from developing digital elevation models of shallow-water zones and coastal areas which can be potentially damaged due to changes in water level for particular sites on the shores of Lake Baikal, the Irkutsk reservoir and Angara river in the downstream pool of the Irkutsk hydroelectric power plant, which are needed for implementation of the project to assess the impact of regulation of the water level in Lake Baikal. When solving problems that take into account changes in the water level, it is necessary to use a combined relief model that unites surface and underwater relief. We consider the experience gained in the construction of combined relief models for such water bodies as the Irkutsk and Bratsk reservoirs as well as Lake Baikal. When building the combined relief model we tried to use all available data on the relief: topographic and pilot maps, the results of depth measurements using the echo sounder, and coastline contours identified using satellite images. We have developed several algorithms based on the use of Delaunay triangulation to combine data from various sources. A registry of key areas has been compiled for which it is necessary to perform additional data collection in order to update the coastal relief. We also consider techniques for obtaining digital surface models by using unmanned aerial vehicles of various types: quadcopters and aircraft-type drones. Currently we are carrying out digital aerial photography of selected key areas, where it is required to refine their terrain models.