Formation of the sediment yield in areas of mining of placer deposits

An assessment is made of the contribution from different sources supplying sediments to the rivers flowing in areas of open-cast mining of placers in places of their contemporary exploitation (using the Russian Federation and Mongolia as an example). We examine the sediment yield transformation processes in conditions of open-cast gold and platinum mining in the valleys of creeks and small and medium-sized rivers where extraction of mineral resources is an exceptionally important kind of activity (the rivers of the Vyvenka basin, Kamchatka krai) or characteristic for a given territory (Tuul river downstream of the city of Ulaanbaatar, Selenge river basin, Mongolia). We summarized the assessments of the sediment yield transformation downstream of the areas of mining placer deposits along the rivers of Russia, Mongolia, USA, India, Australia, and Surinam. It is shown that stream-channel erosion in anthropogenically modified channels is responsible for up to 90% of technogenic changes in sediment yield. The most significant (by several orders of magnitude) increase in sediment yield has been recorded for small rivers. For large rivers that are characterized by low background values of sediment yield, its change is by a factor of 1.1‒1.2 in the case of single mining operations in the drainage area and reaches a factor of five for large-scale mining operations.