The Huai He River Basin is one of the seven major river systems in China (Zhai et al. 2014). It lies about midway between the Yangtze and Yellow Rivers and flows in a west-east direction through Henan, Anhui and Jiangsu Provinces (He et al. 2010). It discharges into the Yangtze River after passing southwards through Hongze Hu and Gaoyou Hu (He et al. 2010). The river is 1,078 km long and has a catchment area of 174,000 km² (He et al. 2010).

The Huai He River Basin is one of the most densely populated and heavily developed regions in China, characterised by an extensive network of water-related projects (Zhai et al. 2014). It also suffers from severe pollution. As the first large-scale initiative for pollution control in China, the Huai He River Pollution Control Project was launched in 1994, setting the ambitious goal of restoring the river’s water quality by the end of the 20^th century (Zhai et al. 2014). Although some progress was made, such as shutting down heavily polluting factories and upgrading sewage treatment infrastructure, the overall objective was not achieved by 2000 (Zhai et al. 2014). The situation further deteriorated with several acute pollution incidents in 2004, which drew international attention and highlighted the ineffectiveness of earlier efforts (Zhai et al. 2014). Due to the Basin's complex natural characteristics and intense human activity, pollution control remains an enormous challenge (Zhai et al. 2014). Water pollution in the region is exceptionally severe, leading to devastating impacts on the aquatic environment and local ecosystems (Zhai et al. 2014). Until 2013-2019, the water quality did not seem to be improving (Wang et al. 2023).

Historically, the Huai He River Basin has supported a large number of waterbirds (Cao et al. 2010). Its significance has diminished, likely because widespread control of water levels restricts habitat availability for Anatidae. In addition, pollution has severely degraded water quality, rendering it unsuitable for irrigation, industrial use or as waterbird habitat (Cao et al. 2010). Despite the presence of expansive wetlands, only a small portion – approximately 3% – of the Huai He River floodplain provided suitable habitat for Anatidae in 2005 (Cao et al. 2010).

Here, we present winter survey data collected in 2005 and 2006. The Anatidae data were reported as part of east China Anatidae population estimates and the Huai He River was not considered separately (Cao et al. 2008, Cao et al. 2010). More recent studies have reported on the entire Huai He River Basin (from December 2023 to February 2024; Li et al. (2025)) and for the Anhui section of the basin during January 2023 (Liu et al. 2024). Although the absence of detailed distribution and abundance data limits more nuanced comparisons, the overall quick comparison suggests that, while the number of species has increased, total abundance has remained stable (Liu et al. 2024). We hope that making these detailed public data available will support long-term, standardised monitoring of waterbirds in the Huai He River Basin and serve as a historical baseline for future research and comparative studies.

We gratefully acknowledge the contribution of field survey teams for the fieldwork, especially Mark Barter and Xin Wang. The work was supported by the Ministry of Science and Technology of China, The National Key Research and Development Program [grant number 2022YFF1301401] and the China Biodiversity Observation Networks (Sino BON).