Satellite-Based Mapping of the Negative Impact of Gold Mining Enterprises on the Natural Environment of the Cryolithozone (Using the Example of Magadan Oblast)

Gold mining at ore and alluvial deposits substantially negatively impacts the natural environment, in particular, by land degradation and the contamination of watercourses with suspended solids. In this study, we consider a methodology for identifying and mapping the negative impact of gold mining enterprises on the natural environment based on a long-term series of free-available Landsat and Sentinel-2 satellite images. This study is carried out using the example of Tenkinsky, Susumansky, and Yagodninsky districts in Magadan oblast, where the largest gold deposits are located. Identifying features of active mining areas, as well as abandoned ones (on which vegetation began to recover), have been found in satellite images. Based on the expert interpretation of the images and NDVI analysis, it is found that about 2% of the study area has been affected by gold mining. The processes of vegetation recovery are identified only on 10% of the degraded lands. In the Tenkinsky district, the area of disturbed lands for the period 2001–2021 increased more than seven times, which is associated with a substantial increase in gold mining. Using the C2RCC processor (module of the SNAP software package), the content of suspended solids in the water of the most impacted rivers, the Berelekh, Ayan-Yuryakh, and Kolyma, has been estimated in comparison with natural values (typical for noncontaminated water). We have found that the main source of suspended matter in the rivers is the alluvial gold deposits located in the floodplain of the Berelekh River. At the same time, the seasonal variability of water contamination is determined by the hydrological situation. In particular, water turbidity decreases during low water periods and increases during high-flow periods.