Relationship between NDVI and hydromet factors in grassland area of open-pit coal mine

The groundwater level of an open-pit coal mine in the grassland area of the east Inner Mongolia has been decreasing continuously under the condition of long-term drainage. In order to study whether the growth of vegetation around the mining area was affected by the decline of groundwater level, the NDVI method was used to analyze the change trend of vegetation index in the study area from 2013 to 2019. Based on the joint entropy theory, the mutual information between NDVI and different meteorological and hydrological elements(temperature, rainfall and groundwater depth)were calculated, and the main influencing factors of vegetation growth were obtained. The results show that the vegetation coverage in the study area is getting better year by year; and the vegetation index gradually increases from 0.10 in 2013 to 0.33 in 2019, with an average annual growth of about 0.03. The vegetation growth is closely related to the local temperature and rainfall, with a weak correlation with the buried depth of the groundwater level. The warm and stable rainfall in the study area results in the earlier and longer vegetation rejuvenation period, and the continuous decline of the water level will not cause the death of the surrounding grassland vegetation. The results enrich the research content of the relationship between vegetation growth and groundwater in the eastern grassland area of Inner Mongolia, and provided technical support for such analysis and evaluation.