Assessment of the Impact of Open-Cast Mining on the Vyvenka River Basin (Kamchatka Krai)

Geological exploration and mining operations have been conducted in the Vyvenka River basin on the Seinav-Galmoenan platinum deposit since 1994. The majority of the explored and prospective reserves are located in the valleys of spawning salmon tributaries, raising concerns about the environmental impact of mining activities. Despite the cessation of platinum mining in the 2010s, there has been a continuing impact on the river system in recent years, with extensive sediment plumes forming along the length of the rivers. This research aims to assess the dynamics of disturbed lands and determine the scale of sediment export into the river network from the territory of the ore mining sites of Vetvisty, Penisty, Ledyanoy, Yuzhny, and Levtyrinivayam. Field and satellite data were combined to analyze the suspended sediment discharge regime and the main sediment sources, i.e., the riverbank deformations along the mining sites. As of 2021, the total area of disturbed lands in the Vyvenka basin due to open-cast platinum mining is estimated to be 19.2 km2 corresponding to 0.15 % of the area of the Vyvenka River basin. Up to 75 % of the disturbed area consists of bare lands, making them prone to surface erosion. The largest amounts of sediment influx from the mining-affected river basins were observed in 2018 during the unevenly high freshet. The increased sediment discharge was due to the overflow of sedimentation ponds in certain areas. The study results indicate a prolonged anthropogenic impact on river ecosystems, manifested in the change of hydrological regime, activation of channel deformations, and the increased sediment influx to the river network from ore mining sites.