Yan River

Yan River
Native name	延河 (Chinese)
Location
Country	China
Province	Shaanxi
Physical characteristics
Mouth	Yellow River
• coordinates	36°23′53″N 110°28′45″E / 36.3980°N 110.4791°E / 36.3980; 110.4791
Length	286.9 km (178.3 mi)
Basin size	7,725 km2 (2,983 sq mi)

The Yan River (Chinese: 延河; pinyin: Yán Hé) is a river in Shaanxi, China. The river flows from its source, the Xingzi River (Chinese: 杏子河; pinyin: Xìngzi Hé; lit. 'apricot river') in Jingbian County, in the prefecture-level city Yulin,^[1] and then flows through neighboring Yan'an,^[2] finally flowing into the larger Yellow River in Yanchang County, Yan'an.^[3] The Yan River flows a total length of 286.9 kilometres (178.3 mi), and has a total basin area of 7,725 square kilometres (2,983 sq mi).^[4]

The Yan River's source is Zhou Mountain (Chinese: 周山), in the town of Tianciwan [zh] Jingbian County, Yulin.^[1][4] The river then flows to the south into Yan'an, entering by passing through Ansai District.^[5]

The Yan River continues its flow south to Baota District,^[6] the urban center of Yan'an. In Baota District, the river passes through Hezhuangping [zh], Qiaogou Subdistrict, Chuankou [zh], Liqu, Yaodian [zh], and finally, Ganguyi [zh].^[4] The portion of the river which flows through Baota District totals 62 kilometres (39 mi), and has a basin area of 2,203.68 square kilometres (850.85 sq mi).^[4]

From Baota District, the river flows east through Yanchang County, where it merges into the larger Yellow River.^[3]

The Yan River is highly seasonal, due to the large disparities in the region's wet season and dry season.^[4] There is little year-round water flow contributing to the river.^[4]

The Yan River's basin follows a gradient of higher elevations in the northwest, and lower elevations in the southeast, resulting in the river's flow in that direction.^[4] Due to the geology of the Loess Plateau, the Yan River often follows a highly curvy path, and has a high sand content.^[4] Landslides are common in the Yan River's basin.^[4] 34% of the basin is covered in forest.^[4]

The normal flow of the Yan River is about 4 cubic metres (140 cu ft) per second, and the annual average runoff is 220,000,000 cubic metres (290,000,000 cu yd).^[4] The average sediment transport volume is 16 million tons.^[4]

Throughout China's long history, the Yan River has been called a number of different names. During the Warring States period, the river was known as the Qushui (Chinese: 区水; pinyin: Qūshuǐ).^[4] Later, during the Western Han, the river was called the Weishui (Chinese: 洧水; pinyin: Wěishuǐ).^[4] Afterwards, in the Northern and Southern dynasties, and during the Western Wei, the river was known as the Qingshui (Chinese: 清水; pinyin: Qīngshuǐ).^[4] During various points after the Western Wei, the river was called a number of other names, including the Jinshui (Chinese: 筋水; pinyin: Jīnshuǐ) and the Zhuojinshui (Chinese: 濯筋水; pinyin: Zhuójīnshuǐ).^[4] The current name, the Yan River (Chinese: 延河; pinyin: Yán Hé), is only a more recent name for the river.^[4]

The total length of the Yan River's tributaries total 10 kilometres (6.2 mi), and 11 of them have a basin area of over 100 square kilometres (39 sq mi).^[4]

Tributaries along the Yan River's left bank include the Fengfu River (Chinese: 丰富川; pinyin: Fēngfù Chuān), the Panlong River (Chinese: 蟠龙川; pinyin: Pánlóng Chuān), and the Wuyang River (Chinese: 五阳川; pinyin: Wǔyáng Chuān).^[4] Tributaries along the river's right bank include the Xi River (Chinese: 西川; pinyin: Xī Chuān), the Nan River (Chinese: 南川; pinyin: Nán Chuān), and the Masi River (Chinese: 马四川; pinyin: Mǎsì Chuān).^[4]