Shorebirds of the Yellow Sea
Importance, threats and conservation status
Wetlands International, 2002
ISBN 90 5882 009 2
2. The Yellow Sea
The Yellow Sea is a semi-enclosed shallow sea, with extensive intertidal areas, located between the Korean Peninsula in the east and China to the west (Figure 2). The southern boundary of the Sea is a line drawn from the northern side of the Chang Jiang (Yangtze River) Estuary eastwards to the island of Cheju and then northwards to the south-west coast of South Korea (UNDP 2000a).
The Yellow Sea is situated between longitudes 117º 35' E and 126º 50' E and latitudes 31º 40' N and 41º 00' N, is about 1 000 km from north to south and 700 km from east to west and has an area of 458 000 km2. The average depth is 46 m, but is only 26 m in the Bo Hai (Yuan et al. 2001).
For the purposes of this report, shorebird data from the Chang Jiang Estuary, and its islands, and from the south coast of South Korea have been included in the analysis.
The Yellow Sea: location, national boundaries, constituent parts, major cities and rivers
The Yellow Sea climate varies from cold temperate in the north to warm temperate in the south, being controlled by cold, dry northerly winds in the northern winter and warm, moist southerlies in the northern summer.
Most rain falls in the May-September period, with total precipitation varying from 600-900 mm in the north to 1 100-1 300 mm in the south (PRC CDB; Park et al. 2000).
Mean air temperatures on the north coast of the Yellow Sea are about -8º C in January, increasing to 1º C in March, 16º C in May and 24º C in July, whilst in Shanghai mean temperatures in the same months are 4º C, 8º C, 19º C and 28º C (PRC CDB). Mean temperatures in Seoul are -4º C in January and 25º C in July (Park et al. 2000).
Average sea surface temperatures in the north are between -2 ºC and 0 ºC in January and February, 2 ºC in March and 4 ºC in April (Meteorological Office 1947; Moores et al. 2001). Normally, Liaodong Wan, Bohai Wan and the region around the Yalu Jiang mouth freeze for 2-4 months during winter, with thawing occurring in mid- to late March. Drift ice up to 35 cm in thickness is found throughout the Bo Hai, in north Korea Bay and around the Changshan Peninsula (Lanzhou Institute of Glaciology and Geocryology 1988; UNDP 2000a; ADB 2000b; Yuan et al. 2001).
Information on important rivers flowing into the Yellow Sea is given in Table 1 (UNDP 2000a; ADB 2000b; Yuan et al. 2001; Moores et al. 2001). All have peak run off in the northern summer and minimum discharge in the northern winter (UNDP 2000a).
The Huang He (Yellow River), which is the second longest river in China, has the highest sediment loading of any river in the world (Li 1995), but the annual water volume is relatively low, especially when compared with the Chang Jiang (Yangtze River) which has by far the highest flow of any Chinese river.
The Huang He and Chang Jiang account for almost all of the annual input from Chinese rivers of 1.6 x 109 tonnes of sediment into the Yellow Sea. Silt discharge from the Huang He can reach Laoshan Bay, north of Qingdao, whilst the plume from the Chang Jiang significantly affects the southern Yellow Sea (UNDP 2000a). It has been suggested that the great majority of silt forming the extensive intertidal areas of the west coast of South Korea has come from the Huang He (Koh 1997), but there is evidence from South Korean work that these sediments are derived from Korean rivers (N. Moores in litt.).
The Chinese coast consists of extensive stretches of tidal flats separated by the rocky regions of the Shandong and Liaoning Peninsulas and north-west Liaodong Wan. Deltas occur at the mouths of the Chang Jiang, Huang He, Luan He and Liao He. The west coast of South Korea consists of extensive tidal flats, which are contained in broad estuaries in the north and surround islands in the south-west. The south coast has deep bays with large mudflats. The main tidal flat distribution, with regional areas in km2 and average tidal ranges for a number of coastal areas, is shown in Figure 3 (Moores et al. 2001; Yuan et al. 2001). The total area of intertidal flats in the Yellow Sea, including the Chang Jiang Estuary and the south coast of South Korea, is about 20 000 km2, which also includes 1 350 km2 in numerous bays and estuaries around the Shandong Peninsula (Wilson & Barter 1998; Yuan et al. 2001; Moores et al. 2001; Scott 1989). The tidal ranges of the central west coast of the Korean peninsula are amongst the highest in the world.
(109 m3 y-1)
(106 t y-1)
|Huang He||4 845||745 100||36.01||911.02|
|Chang Jiang||6 300||1 808 500||921.0||500.0|
|Liao He||1 430||219 000||17.0||35.0|
|Daling He||379||17 687||4.9||35.0|
|Luan He||877||44 900||4.5||27.0|
|Huai He||1 000||269 150||26.0||13.0|
|Yalu Jiang||790||61 889||29.0||2.0|
|Nakdong River||450||240 000||15.0||1.0|
|Hun He||415||7 944||2.0||0.9|
|Wulong He||124||2 653||0.6||0.8|
|Dagu He||179||4 631||0.7||0.6|
|Geum River||396||99 000||7.0||0.6|
The intertidal areas of the northern Yellow Sea are frozen during winter and are unlikely to support shorebirds at this time of the year (Melville & Li 1998). However, air and water temperatures rise quickly from March onwards (see above) and the mudflats then become available to shorebirds during the northward migration period.
Main intertidal areas (km2) and selected average tidal ranges in the Yellow Sea