EVALUATING THE IMPACTS OF THE THREE GORGES DAM CONSTRUCTION ON REGIONAL LAND COVER AND VEGETATION CONDITIONS USING SATELLITE DATA

Abstract

Construction of the Three Gorges Dam (TGD), the world’s largest hydroelectric project, has triggered extensive environmental and ecological changes in the surrounding region. This study examines the long-term impacts of the TGD on four sub-basins situated upstream, midstream, and downstream of the Yangtze River Basin (YRB). The analysis focused on land cover and land use (LCLU) changes from 2000 to 2020, as well as trends in the Normalized Difference Vegetation Index (NDVI) from 1990 to 2020. To assess NDVI trends, the study period was divided into pre-impoundment (1990–2002) and post-impoundment (2003–2020). In addition, a precipitation trend analysis was conducted across all regions from 1990 to 2020 to determine whether changes in vegetation were primarily driven by precipitation variability or the effects of the dam. The findings of this study offer valuable insights into the significance of understanding the impact of the TGD on LCLU and vegetation. There are three key findings from this study. First, significant LCLU changes have occurred within the study area, particularly characterized by a marked decrease in vegetation cover by up to 5% and cropland by 6%, and a dramatic increase in built-up areas by as much as 9% across all three regions from 2000 to 2020. Second, the average monthly NDVI increased by 0.01-0.02 post-impoundment, and annual NDVI anomalies rose steadily, with the upstream region exhibiting the strongest greening trend (slope = 0.0016). In contrast, no statistically significant increase in precipitation was observed over time. Third, Pearson correlation analysis revealed weak NDVI-precipitation correlations, except for the upstream post-impoundment period, which showed a significant negative correlation (r = - 0.20, p_value = 0.004), suggesting altered vegetation responses due to water management or land-use changes.