Dongting Lake

Dongting Lake (Chinese: 洞庭湖) is a large, shallow lake in northeastern Hunan Province, China. It is a flood basin of the Yangtze River, so its volume depends on the season. The provinces of Hubei and Hunan are named after their location relative to the lake: Hubei means "North of the Lake" and Hunan, "South of the Lake".

Dongting Lake is famous in Chinese culture as the place of origin of dragon boat racing and is home to the critically endangered Yangtze finless porpoise.

In the July–September period, flood water from the Yangtze flows into the lake, enlarging it greatly. The lake's area, which normally is 2,820 km² or 1,090 mi² (data before 1998), may increase to 20,000 km² (7,700 mi²) in flood season, when vast amounts of water and sediment from the Chang Jiang flow into the lake. The lake is also fed by four major rivers: the Xiang, Zi, Yuan and Li rivers. Small rivers also flow in, the most famous being the Miluo River, where the loyal official and poet Qu Yuan committed suicide in the early 3rd century BC, according to tradition. In addition, the Xiao River flows into the Xiang near Yongzhou, before the Xiang flows into the lake. Ocean-going vessels can travel through the Xiang to reach Changsha.

The Dongting Lake catchment area is 257,000 km² (99,000 mi²). The lake's only outlet is a natural channel 14 km long and on average 1 km wide.

There are five main rivers in the catchment (excluding the area whose water flows directly into the Yangtze River, the same hereafter):

All of these rivers flow directly into the lake. In addition, some of water of the Yangtze River also flows into the lake through the Sankou distributary channels.

The catchment has highly complex flow regimes featuring strong river-lake interactions. Dongting Lake receives water from the upper Jingjiang reach of the Yangtze River. The water in Dongting Lake finally flows into the lower Jingjiang reach of the Yangtze River at the Chenglingji Station and discharges downstream. The water in Dongting Lake mainly comes from surface runoff and direct rainfall on the lake surface. The Dongting Lake catchment begins to enter the rainy season in April and the rainfall reaches its maximum in June. Then, the rainy area moves to the upper part of the Yangtze River Basin in July and flood water flowing into the lake from upstream increases significantly. The rainy season may continue until the end of September. The flow regime of Dongting Lake maintains the same temporal pattern as the rainfall regime.

The flood season is from April to September. In general, flood water comes mainly from the catchment from April to June and from water diversion of the upper reaches of the Yangtze River from July to September.