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

Gold mining at ore and alluvial deposits causes a substantial negative impact on the natural environment, in particular land degradation and 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. The study was carried out on the example of Tenkinsky, Susumansky and Yagodninsky districts of the Magadan region, where the largest gold deposits are located. Identification features of active mining areas, as well as abandoned ones (on which vegetation began to recover), have been found on satellite images. Based on expert interpretation of the images and NDVI analysis, it was found that about 2% of the study area was affected by gold mining. The processes of vegetation recovery were identified only on 10% of the degraded lands. In the Tenkinsky district, the area of disturbed lands for the period 2001–2021 increased by more than 7 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 Berelekh, Ayan-Yuryakh and Kolyma, was estimated in comparison with natural values (typical for non-contaminated water). We 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 hydrological situation. In particular, water turbidity decreases during low water periods and increases during high-flow periods.