Report.

1.5 Water Level of Lake Baikal

In the average long-term water budget of Lake Baikal, the inflow components are:

- surface water inflow (57.77 km³/year – 82.4 %);

- precipitation (9.26 km³/year – 13.2%);

- ground water inflow (3.12 km³/year – 4.4 %) [6].

The outflow components are the following: surface water outflow – the Angara River (60.89 km³ – 86.8 %) (pic. 1.5.1); and evaporation (9.26 км³ – 13.2 %).

Pic. 1.5.1 The Angara River in Irkutsk city

The water level in the lake depends on the operating modes of Irkutsk Hydroelectric Power Station (HEPS), Bratsk HEPS and Ust-Ilimsk HEPS, all working interdependently.  Boguchanskaya HEPS has been in commercial operation since December 1, 2012, and filling of its water reservoir began in summer 2012 and finished in 2014. After construction of the dam of Irkutsk HEPS (44 m high and 2.5 km long) (pic. 1.5.2) 70 km downstream of the Angara River source and filling of Irkutsk Reservoir (1956-1958), the backup water reached Lake Baikal in 1959 and caused its long-term water level to rise by 1.3 m (456.8 m) in 1964.

Pic. 1.5.2  The dam of Irkutsk HEPS

Further, the average long-term regulated water level of the lake (equal to the water level of Irkutsk Reservoir) was maintained at 1 m above the average water level prior to the construction of HEPS. This allowed using a part of the lake volume for controlling outflow by artificially regulating the water level on a seasonal and long-term basis. With its outflow backed up, the annual changes in Lake Baikal water level remained generally close to its natural values. The artificial regulation of the lake level resulted in increased amplitude of level fluctuations (from 80 to 113 cm) and a shift towards delayed in time maximum discharge of water and filling of reservoir. The annual changes in the level of Lake Baikal are characterized by a gradual rise until the levels become close to the normal dammed levels (in May-September), stabilization of maximum levels in October and a decrease during November to April.

As of January 1, 2013, the average water level of Lake Baikal was 456.46 m, which was 0.07 higher than in the previous year and 0.03 m higher than the long-term average (456.43 m) (pic. 1.5.3) [6]. In 2013, during the period when the lake was filled up, the water levels were within the range of long-term values, as a result of smooth regulation of discharge without abrupt fluctuations. The amplitude of level fluctuations was 0.76 m in 2013.

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Pic. 1.5.3 Average monthly water levels of Lake Baikal in 2012 and 2013 compared with the years of the highest (1964) and lowest (1981) levels and long-term values.