*Article* **Comparison of the Hydrological Dynamics of Poyang Lake in the Wet and Dry Seasons**

**Fangdi Sun <sup>1</sup> , Ronghua Ma <sup>2</sup> , Caixia Liu 3,\* and Bin He 4,5**


**Abstract:** Poyang Lake is the largest freshwater lake connecting the Yangtze River in China. It undergoes dramatic dynamics from the wet to the dry seasons. A comparison of the hydrological changes between the wet and dry seasons may be useful for understanding the water flows between Poyang Lake and Yangtze River or the river system in the watershed. Gauged measurements and remote sensing datasets were combined to reveal lake area, level and volume changes during 2000–2020, and water exchanges between Poyang Lake and Yangtze River were presented based on the water balance equation. The results showed that in the wet seasons, the lake was usually around 1301.85–3840.24 km<sup>2</sup> , with an average value of 2800.79 km<sup>2</sup> . In the dry seasons, the area was around 618.82–2498.70 km<sup>2</sup> , with an average value of 1242.03 km<sup>2</sup> . The inundations in the wet seasons were approximately quadruple those in the dry seasons. In summer months, the lake surface tended to be flat, while in winter months, it was inclined, with the angles at around 1000–1600. The mean water levels of the wet and dry seasons were separately 13.51 m and 9.06 m, with respective deviations of around 0–2.38 m and 0.38–2.15 m. Monthly lake volume changes were about 7.5–22.64 km<sup>3</sup> and 1–5.80 km<sup>3</sup> in the wet and dry seasons, respectively. In the wet seasons, the overall contributions of ground runoff, precipitation on the lake surface and lake evaporation were less than the volume flowing into Yangtze River. In the dry seasons, the three contributions decreased by 50%, 50% and 65.75%, respectively. Therefore, lake storages presented a decrease (−7.42 km3/yr) in the wet seasons and an increase (9.39 km3/yr) in the dry seasons. The monthly exchanges between Poyang Lake and Yangtze River were at around <sup>−</sup>14.22–32.86 km<sup>3</sup> . Water all flowed from the lake to the river in the wet seasons, and the chance of water flowing from Yangtze River in the dry seasons was only 5.26%.

**Keywords:** Poyang Lake; Yangtze River; hydrological changes; water balance
