# Impact of High Water Levels in Lake Baikal on Rare Plant Species in the Coastal Zone
## 3 Results and Discussion  
The issue of regulating the level of Lake Baikal has been discussed since the construction of the Irkutsk hydropower plant (HPP) in the late 50 s. After its completion, the level of Lake Baikal has become dependent on the discharge through the HPP dam, in addition to surface and underground inflow. The amplitude of annual water-level fluctuations increased from 82 cm in the natural state to 94 cm following the regulation of the reservoir [40]. In subsequent years, the water level of Lake Baikal repeatedly exceeded the standard storage level of 457.00 m within the Pacific system (the optimal level of a reservoir that can be maintained by a dam over an extended period). Again, this led to negative consequences on the eastern coast [27]. The causes of this water-level surcharge were multifaceted, including natural water inflow fluctuations and the strategic accumulation of water resources to ensure safety at new construction sites along the lower pool in Irkutsk [24]. The ecosystem of the Baikal coast is also impacted by low water levels. Therefore, the decrease in the water level to 455.30 m between 1980 and 1982 led to the drying and wind erosion of the shores, which contributed to the intensive development of abrasion processes. This was particularly evident with the subsequent rise in the water level to the normal storage level and above,especially on the shores formed from loose sediments (most of the southeastern and eastern shores of the lake and some parts of its western coast) [27]. In order to prevent similar situations, on 26 March 2001, the Government of the Russian Federation issued Resolution No. 234 \"On Limit Values of Lake Baikal Water Level in the Course of Economic and Other Activities\", which established minimum and maximum levels at 456.00 and 457.00 m, respectively. From 2001 to 2014, the level of Lake Baikal remained within the established range. However, from 2015 to 2018, the level of the lake dropped below 456 m four times. This was due to incorrect inflow prediction in the previous year, excessive water mass drawdown, and a subsequent low water period in the lake basin [23] (Figure 3). Following the transition from a low-water period to a high-water period, the water level exhibited an upward trend, surpassing 457.00 m in 2020, 2021, and 2023 [41]. This was facilitated by the impossibility of discharging large amounts of water downstream (more than 4000 m\({}^{3}\)/s) due to the threat of the inundation of a part of Irkutsk. Each time, the Government of the Russian Federation was forced to introduce special Resolutions that allowed the regulation of the water level of Lake Baikal in the range of 455.54-457.85 m. The recent water-level elevations have expectedly led to the inundation of coastal areas, the intensification of abrasion, and the disruption of infrastructure in the upper pool (Lake Baikal). Therefore, there is a need for scientific substantiation of the optimal use of Baikal water resources in order to minimize damage to the environment and technosphere in the water-level fluctuation zone of the lake. Water-level regulation should be based on a comprehensive assessment of potential damages to economic and natural objects at high and low water levels [42] (Figure 3). Figure 3: Plot of the water-level changes of Lake Baikal. Compiled by the authors based on data on the long-term monitoring of Lake Baikal water levels conducted by Rosvodresurs ([[https://voda.gov.ru](https://voda.gov.ru)]([https://voda.gov.ru](https://voda.gov.ru)), accessed on 16 October 2024). Field studies of rare plant species vulnerable to fluctuations in water levels were conducted during the growing season of 2022 on the southern and eastern coast of Lake Baikal. The selection of areas with the location of rare species was conducted according to the Red Data Book of the Republic of Buryatia [30].