Health assessment of the water-level-fluctuation zone (WLFZ) in the Three Gorges area based on spatial information technology

The WLFZ in the Three Gorges area is alternately controlled and influenced by both water ecosystem and terrestrial ecosystem. Its ecological vulnerability and instability are significant. Taking small watershed as a unit of assessment, we select population density, urbanization intensity, temperature, precipitation, and humidity and vegetation coverage to construct the fluctuating zone wetland ecosystem assessment index system. The comprehensive health index is calculated after extracting the main information of the six variables using principal component analysis. It is ranged into three levels: good, medium and poor. The results show that the health state of the entire Three Gorges area is at medium and poor levels. Regions at medium health state account for 58% of the entire area, and the remaining regions are at poor health. Taking Wanzhou District as the boundary, the health state of the southwest region is better than the northeast region.