Long-term satellite records of water clarity suggest increasing human activity influence in an inland lake

Water clarity is a key indicator of trophic status and lake health, yet its long-term trends and driving factors remain underexplored due to limited historical data. To fill this gap, we developed a remote sensing algorithm utilizing Landsat imagery to produce water clarity maps in Lake Gaoyou spanning 1984–2023. Our findings reveal a significant inter-annual increase in water clarity, averaging 0.07 meters per decade. The study period was divided into three phases: Phase I (pre-1999), primarily influenced by climatic factors and land use changes; Phase II (2000–2009), marked by decreased riverine material inputs following the diversion of the Huai River; and Phase III (post-2010), shaped by intensified anthropogenic activities. This research underscores the increasing impact of anthropogenic activities on water clarity in an inland lake, offering critical insights for sustainable ecosystem management.