Dabaeva D.B., Tsydypov B.Z., Garmaev E.Z.
Baik al Institute of Nature Management SB RAS, Ulan-Ude, Russia E-mail: dabaevadarima@gmail.com
The history and problems of regulating of the level of Lake Baikal were considered. The analysis of changes of water level, fluctuation range and useful inflow over the observation period (1898-2015) were carried out. In this study the main causes and effects of extreme water shortage in the basin of the lake in the 2014-2015 biennium are discussed.
After the building of the Irkutsk hydroelectric power station (1956) Lake Baikal has become an artificia l water reservoir, as its level is determined mostly rather the interests of hydroenergetics than natural factors. It should be noted that since 1996 Lake Baikal is the site of World Natural Heritage by UNESCO. Due to the fact that the Baikal is an artificial reservoir, it can lose this honorary status, this may lead to statement of the inclusion of Lake Baikal to the list of World Heritage in Danger.
The factual water levels in natural conditions (1903-1959) ranged from 454.93 m (historical minimum rec- orded in 1904) to 457.10 m (maximu m recorded in 1869). In regulated conditions (1960-2015) minimal mark was registered in 1982 (455.27 m), the maximu m was registered in 1988 (457.42 m). Hereinafter Pacific system of heights is used.
Average annual useful inflow into the lake during the observation period (1900-2015) is 1872 m3/s, in the natural conditions (1900-1956) – 1916 m3/s, the minimum average annual inflow to the lake was observed in 1903 – 1106 m3/s, the maximu m in 1932 – 3251 m3/s, in over-regulated period 1960-2015 – 1824 m3/s, the min imu m inflow was recorded in 1979 – 1244 m3/s, the maximu m in 1973 – 2848 m3/s [2].
At controlled outflow of Lake Baikal it may gradually lose its uniqueness and over time this can lead to the loss of biodiversity up to the complete disappearance of many species. Exceeding the level of 457.0 m, during the high-water years in the middle of 90th years of the last century, low-lying coastlines of east coast were destroyed (coastal forests, recreation zones, beaches and coastal constructions), widespread environmental damage through- out the natural and biological complex of lake system was caused. Apart it should be noted the real threat of complete destruction of the island ridge Yarki that separates the open Baikal from Verkhneangarsky shallows.
When approaching the lake level to the mark 457.0 m and a corresponding wave of activity for 3-5 days Yarki island group would be flooded as a result Lake Baikal would increase to the north up to 40-50 km and Verkhnean - garsky sor and delta of the Kichera river, the Upper Angara river will completely disappear. Cold Baikal water will destroy all unique ecosystem of shallow waters in the delta of the Upper Angara and the Kichera including Verkhneangarsky omul race. At the same time all the parameters of the lake water bowl and consequently the level regime will change [1].
The results of extremely low level of Lake Baikal are following:
regime changes of groundwater and groundwater lowering;
violation of the existing mechanisms of Baikal water purification;
reduction in water exchange sor system with open Baikal;
the increase in average temperatures and heavy overgrowth of shallow water;
the death of aquatic organisms on the shore of the lake and the coastal system as a result of drying and supercooling of habitats, which are responsible for the processing of organic matter;
peat fires in the delta of Selenga river.
The warm period in 2015 was characterized by big defeat of forests from fires in the Republic of Buryatia.
The dynamics of forest fires on the lands of the State Forest Fund of the Republic for the period from 1936 to 2015 was analyzed. According to the Federal Forestry Agency of the Republic of Buryatia from April to October of 2015 the territory of the State Forest fires were exposed area of 750,500 hectares, that exceeds the "norm" by 12 times! The total damage caused by forest fires was 20.46 billion rubles (according to minimum rates of payment for standing timber) and 203.36 billion rubles (according to the auction prices of standing timber). Be appreciated that the calculations do not include the basic costs of firefighting.
Before the construction of the Irkutsk hydroelectric complex (in natural conditions) the level of the lake varied in the range up to 2.17 m. For exploitation period of the Irkutsk Hydroelectric Power Station (until 2001) the level of the lake was higher than the mark of 457.0 m 17 times and fell below 456 m 18 times. After the adoption of the Russian Federation Government Resolution № 234 in March 26, 2001 "On the limit values of the water level in Lake Baikal in the implementation of economic and other activities" (hereinafter – the Decree № 234) the level fluctuated in the meter range (456.0÷457.0 m), but on February 25, 2015, for the first time since 2001, it dropped below the mark of 456.0 m. This is primarily the result of the low water period, which was established in the middle of 90th years of the last century that was the highest rate ever recorded. The situation with low-water level in Lake Baikal basin escalated in June of 2014, continued throughout the summer and autumn of the last year and will continue in 2016. With a certain degree of probability it can continue in the followin g years.
The minimum mark in the lake – 455.86 m – was observed on 26-28 April 2015. Further with the beginning of the spring flood the filling of Lake Baikal began. The critical minimum level – 456.0 m – was restored on June 5, 2015. The maximu m level of water Lake Baikal was 456.30 m (Fig. 1), which is the lowest value since 2001.
Fig. 1. Average water level of Lake Baikal (2009-2016)
Due to the anomalously high air temperatures and the almost complete absence of rainfall, inflow of water into the lake in the last 2015 was extremely low. The volume of inflows in 2015-2016 aquicultural years expected to be close to a minimum, which observed in the 1903-1904 years and amounted 34.7 km3. In the current aquicul- tural year, inflow is expected to reach 35.3 km3 at long time average annual value of the normal equal to 61.9 km3. Thus, the useful inflow deficit could reach more than 26 km3.
The average level of Lake Baikal and discharge by reservoir for 2015-2016 years was analyzed:
2015 year: 456.0 m with a recession – February 19, 2015, 456.0 m at rise – June 5, 2015 (108 days duration);
2016 year: 456.0 m with a recession – December 26, 2015, if the water drawdown happens at last year's scenario, the forecast duration will be 162 days (up to June 5, 2016 – 456.0 m).
An analysis of the meteorological series of air temperature and precipitation in the whole lake Baikal basin carried out that based on the initial data of meteorological stations and global geospatial meteorological database of Climate Research Unit – CRU (spatial resolution of 0.5×0.5 angle degree). A statistically significant trend of increasing temperature and decreasing rainfall was installed. Two humidification periods were allocated: the pe- riod 1980-1998 years – wet; 1999-2015 years – dry. The wet period is characterized by positive trends of precipi- tation totals for almost the whole lake Baikal basin, with the highest growth rate observed for ridge Khamar-Daba n – 14 mm/yr, and the area of Middle Baikal – 10 mm/yr. There is a negative trend in the number of precipitation
for Lake Baikal basin during the dry season 1998-2015 years. Extreme reduction in moisture is marked for ridge Khamar-Daban and makes -30 mm/yr. The rate of decline in basins of the Upper Angara and the Barguzin rivers reaches -18 mm/yr. At the long-term fluctuations of river flow rather the effects of precipitation than other elements of the water balance affect.
Thus, the average annual precipitation decreased by 41.4 mm, and the mean annual air temperature in the Selenga river basin increased by 2.29 °C (let us note that simultaneously the annual average temperature through- out the world increased by 1.2 °C) over the past 75 years. At the same time, 10 of the warmest and 5 of the 10 driest years in the period 1940-2014 years occurred the period after 1996. The increase in temperature is observed for the whole pool area of Lake Baikal, while areas with low growth of surface temperature rates are interspersed with areas with high growth rates, both in latitudinal and longitudinal directions. Consider the amount of precipi- tation during the summer months at the gauging stations of three main rivers feeding the Baikal. On the Barguzin and Upper Angara rivers rainfall is at the normal range, but there is a decrease in rainfall on the Selenga river.
For the spatial distribution pattern of precipitation on the territory of the study, data from a global base of interpolated WorldClim climatic data with a spatial resolution of 30 arc seconds (approximately 1 kilometer) used.
The data is averaged by months for the period from 1950 to 2000 [3].
The analysis of the inflow of water into the Baikal is made. The minimum and maximu m water flows, the volume flow of major rivers of Lake Baikal basin were considered. It was found that the runoff of the Upper Angara river and the Barguzin river has remained within the long-term average rate, while the Selenga river re- duces at the moment and now stands at 65 % of normal during the last 20 years. Together these three rivers provide 70 % of the annual inflow of Lake Baikal. It was established that the level of the lake is almost depends on the water content of the Selenga river. A good alignment between the inflow fluctuations in Lake Baikal and runoff of the Selenga river was established, which is confirmed by the high values of correlation coefficients between these variables: for the observation period (1934-2014 years) – 0.85, with the dry periods (1954-1958, 1976-198 2, 1996-2014) – 0.68 [2].
According to gauging stations and dendroclimatic stations, a spatio-temporal reconstruction of river flow parameters in the Selenga river basin has spent. As a result, water flow model reconstruction of Selenga river and its tributaries – rivers Uda, Khilok, Chikoy, Dzida, Orkhon and Kharaa – was obtained. For individual watercourses the time-series until 1666 has been restored. This allowed to reveal regularities of moisture fluctuations in Baika l Asia in retrospect. The obtained statistical model reconstruction of runoff of Selenga river basin represents to 55%
of the average annual flow variations. A detailed chronological comparison of historical chronicles and moisture regime on the basis of the reconstruction of the water regime has conducted. Analysis of historical chronicles is an indirect verification of the received time-series for the reconstruction of water flow in the Selenga river basin.
For the forest-steppe regions of Baikal Asia limiting factor for tree growth is the precipitation, which form the runoff Selenga river basin [4].
The formation of water resources in the catchment area of Mongolia which accounts for 67 % of the water- shed district Selenga was considered. The dynamics of rivers flow of the Selenga and the Orkhon, its main tribu- tary, was studied. High-water period on the Selenga river was observed from 1979 to 1995. In recent years shallow period in the Selenga river basin is observed. Thus for the last 20 years in Mongolia dried up about 700 rivers and 450 lakes, according to the Institute of Meteorology and Hydrology of Mongolia (Ulaanbaatar). The Governmen t of Mongolia intends to start construction of hydroelectric power station "Shuren", designed in the middle reaches of the main riverbed of the Selenga. Furthermore HPS "Shuren" is planned to build hydroelectric power plants on the tributaries of the Selenga – Orkhon, and Delgermuren and Egiin-Gol. Let us note that such actions of Mongolia and the World Bank violate international convention on transboundary waters and a number of other international agreements. When the final decision of Ulaanbaatar on the construction of hydroelectric power station Lake Baika l will be fully controlled, adjustable not only outflow, and the inflow of water.
At March 28, 2016, the level of Lake Baikal is at the mark 455.76 m, which is 16 cm lower than on this date in 2015 and at 24 cm below the minimum limit set by the Russian Federation Government Resolution № 234 dated March 26, 2001.
The minimum flow in dry periods, as well as the annual flow, tends to decrease. It is a continuous series of low flow provided a negative trend of the minimum flow.
Thus, the inflow of water into Lake Baikal in recent years is the minimum record for the whole period of instrumental observations.
References:
1. Arnold K. Tulokhonov, Yendon Zh. Garmaev, Bair Z. Tsydypov. Spatial and temporal dynamics of the Baikal coastal line caused by control of the lake level regime // Geography, environment, sustainability.
2013. N 2 (6). pp. 20-27.
2. Bychkov I.V., Nikitin V.M. Water-level regulation of Lake Baikal: problems and possible solutions // Ge - ography and Natural Resources. 2015. N 3. pp. 5-16. (In Russian).
3. Hijmans R.J., Cameron S.E., Parra J.L., Jones P.G., Jarvis A. Very high resolution interpolated climat e surfaces for global land areas // International Journal of Climatology. 2005. N 25. pp. 1965-1978.
4. Runoff reconstruction of major rivers of the Selenga river basin. Certificate of state registration database
№ 2013621267, Russian Federation. Proposal № 2013620567 / Garmaev E.Zh., Andreev S.G.;
Rightholder: Baikal Institute of Nature Management SB RAS; Receipt date: 06.06.2013; Registered in the Registry Database: 26.09.2013. (In Russian).