from 1977 to 2021
Biqing Tian1 Gao Peng12 Mu Xingmin12 Zhao Guangju12
1 Institute of Soil and Water Conservation, Northwest A&F University, Yangling 712100, Shaanxi, China
2 Institute of Soil and Water Conservation, Chinese Academy of Science and Ministry of Water Resources, Yangling 712100, Shaanxi, China
Corresponding Author : Institute of Soil and Water Conservation, Northwest A&F University, Yangling 712100, Shaanxi, China
E-mail address:gaopeng@ms.iswc.ac.cn(Gao Peng)
Abstract:
Lake has an essential role in Earth’s hydrologic cycle. The changing of lake water areas shows the ecological health of lakes by instant feedback. Remote sensing monitoring reflects the changes in lake water intuitively. This study, based on remote sensing, combined with the hydrological data, meteorological data, and land use survey, investigated the Poyang lake water area changes from 1977 to 2021. Examined the relationship between the lake water area and the impact factor and analyzed the influence of river lake interaction on the lake water area. The results showed that: (1) From 1977 to 2017, the water area of Poyang Lake in flood season (June to September) and dry season (November to Next February) showed a significant downward trend by years. (2) In flood season, runoff, sediment, and precipitation significantly correlate with a water area. In the dry season, sediment significantly correlated with a water area. (3) The Three Gorges Dam water impoundment at the upper reaches of the Yangtze River weakened and eliminated the block and reverse flow of the Yangtze River on Poyang lake, causing the water area to decrease in advance at the end of the flood season after 2005, and decrease rapidly in the dry season after 2003. (4) The change in lakebed elevation caused by sedimentation and human activities also accelerated the shrinkage of the water area. Results demonstrated that the variation of river lake interaction is the primary cause of the Poyang Lake water area’s dramatic change.
Keywords: Poyang Lake remote sensing image, climate change, human influence, river lake interaction
1. INTRODUCTION
Lake is the natural reservoir of water formed by stagnant water in the depressions of the Earth and has a broad expanse of water and slow current, which is an essential role in Earth’s hydrologic cycle (Qi et al. 2020). Lake provides water to the surrounding area and influences river flow regulation and groundwater levels. The ecosystem formed by the lake also provides an essential living habitat for the creature. The stable state of the lake is essential for the overall ecological balance.(Vaheddoost and Aksoy 2018; Rosenberry et al. 2015; Y. Li et al. 2017). In recent years, the average global temperature has climbed sharply, accompanied by the influence of human activities, which has changed the major lakes in the world to different degrees. The Changes in the lake have led to cascading changes in the surrounding environment. Some scholars use big data to analyze the characteristics of global lake changes and confirm that the changes in lake area affect the overlying atmosphere and lake-air interactions, thus causing the changes in lake temperatures(Huang et al. 2022). In ecologically sensitive areas, these cascading changes are more prominent. Lakes on the Qinghai-Tibet Plateau (QTP) have notably expanded over the past 20 years, which degrades the permafrost occurring beneath the bottom and surrounding the lake. That leads to the release of organic carbon into lakes, affecting the water environment, and further discharged into the atmosphere affecting regional climate changes(G. Zhang et al. 2020; Y. Zhang et al. 2022). Hence, Mastering Lake Changes is significant for controlling the regional ecological balance.
Lake water areas will visually show the changes in the lake morphology. Variations of lake morphology are affected by many factors, such as the runoff exchange, climate, or topography of the lake basin. Keeping a grip on changes in the lake morphology will help us better understand the actual state of the lake. In particular, the large lakes are more complex and variable. Therefore, comprehensive, actual, and detailed research will master the hydrological processes of large lakes. Remote sensing obtains lake water areas easily, quickly, and dynamically monitors the changes in the lake water areas, which is an excellent way to master the actual change characteristics of the lake. Some scholars combining multiple remote sensing data retrieve Lake Chad, Africa’s second-largest Shallow endorheic Lake, available surface water area series. They showed that from the 1960s to 2020, Lake Chad experienced a change from shrinking to gradually expanding. It truthfully reflects the response process of the lake to climate and anthropogenic events in the basin. (Mahmood and Jia 2019; H. Li et al. 2021).
Lake Poyang, the largest freshwater fluvial lake in China, is located in China’s most important economic development region-The Middle-lower Yangtze Plain. (Fig.1) As the largest lake connected to the Yangtze River, Poyang Lake is an alternately inflow-outflow lake with complex hydrological relationships and unique rhythmic changes. Poyang Lake appears as a lake landscape in flood season and a river landscape in the dry season. These unique lake water area changes in the Poyang Lake were jointly affected by the Poyang basin and Yangtze River runoff, which has important implications. (F. Li et al. 2014). After the 21st century, Hydrological monitoring finds the interval between the flood and dry season is getting shorter; seasonal drought events aggravate; meanwhile, floods often occur during the flood season (Wu and Zhan 2020; Z. Zhang et al. 2015). Some scholars suggest that building a dam at the estuary of Poyang Lake and artificially regulating the interaction between the Yangtze River and Poyang Lake will effectively avoid disaster events. Therefore, having a comprehensive grasp of the hydrologic process of Poyang Lake is necessary. This study uses 40 years of Poyang lake historical images to extract the lake water area data of flood and dry seasons and combine it with the basin hydrology, meteorology, and land use data. Use statistical methods to analyze the influence process of climate change and human activities on the hydrological relationship of Poyang Lake. Moreover, providing the theoretical basis for Poyang Lake water resources regulation.