Republic of Yemen is situated in the south of the Arabian Peninsula, bounded to the west by the Red Sea, to the south by the Gulf of Aden, to the east by the Sultanate of Oman, and to the north by Saudi Arabia. The narrow desert plain of the Tihamah bordering the Red Sea rises abruptly to a mountainous interior. These mountains, which are heavily terraced for agriculture, attain heights of between 3,000 and 3,500 m, and include the highest mountain in Arabia, Jabal al-Nabi Shu'ayb, with a peak at 3,666 m. Further east, the mountains fall away in a series of precipitous steps to the fringes of the arid Rub al-Khali (Empty Quarter). In the south, the narrow coastal plain along the coast of the Gulf of Aden is backed by a range of steep mountains rising to almost 2,500 m. North of these mountains, a high plateau falls away gently to the northeast to merge with the Rub al-Khali basin. Numerous large wadis with permanently flowing water in their upper reaches descend from the mountains towards the coastal plains, the most important in terms of surface flow being the Mawr, Surdud, Siham and Zabid in the Red Sea drainage and the Hadramawt in the Gulf of Aden drainage. During the past 20 years, there has been a drastic drop in the water table on the plateau in the central highlands, and this is now of considerable concern to agriculturalists. The fall in water levels has been attributed to excessive pumping of groundwater from boreholes, and reduced water retention because of the widespread collapse of ancient terraces.
Although part of the Republic of Yemen, Socotra Island and its neighbouring islands of Al?Ikhwan (The Brothers) and Abd al-Kuri in the Indian Ocean are geographically a continuation of the Horn of Africa. Socotra lies about 800 km east of Aden and 350 km from the nearest mainland coast of Yemen.
Summary of Wetland Situation
The relatively high annual rainfall in the western and southern highlands feeds a large number of rivers and streams which descend rapidly in steep-sided wadis towards the coastal plains. Many of these have permanently flowing water in their upper reaches, and retain water throughout the year in deep pools along their middle and lower reaches, but in most cases, surface flow only reaches the sea during periods of exceptionally heavy rainfall. In some wadis, this may be as infrequently as once in 50-100 years. The seven most important wadi systems in the western highlands, from north to south, are Wadi Mawr, Wadi Surdud, Wadi Siham, Wadi Rima, Wadi Zabid, Wadi Rasyan and Wadi Mawsa. Scholte (1992) gives details of the major hydrological characteristics of these wadis, all of which drain west into the Red Sea. Major wadi systems draining south into the Gulf of Aden and Arabian Sea include Wadi Warazan, Wadi Jahr, Wadi Hajar and the impressive Wadi Hadramawt. The latter, which is some 240 km in length, is the largest natural permanent river in Arabia, and contains five of the nine indigenous freshwater fishes of the Arabian Peninsula, including three of the six Arabian endemics. There are no natural freshwater lakes in Yemen and few permanent freshwater marshes of any size, due partly to the precipitous terrain and partly to alterations in the landscape by agriculture over many millennia. In a few areas, notably in Wadi al-Malih and Wadi Warazan, sub?surface seepage feeds grassy marshes in valley bottoms. The Wadi al-Malih marshes near Ta'izz are of special interest as they regularly hold small numbers of the critically endangered Northern Bald Ibis Geronticus eremita. The only other significant sites for waterfowl in the interior of Yemen are man?made wetlands, notably Ma'rib Dam, a water storage reservoir on Wadi Ma'rib, and the extensive sewage lagoons near Ta'izz. At the latter site, treated waste water has created a system of small lakes and marshes which regularly support 2,000-3,000 waterfowl in winter. There are also small water storage reservoirs in Wadi Mawr and Wadi Hajar.
Yemen's coastal waters are rich in fish and crustaceans of commercial importance including the lobster Palinurus sp. and the swimming crab Portunus pelagicus, and support an important artisanal fishery (Loulou, 1976). The great productivity of the Arabian Sea, Gulf of Aden and southern Red Sea, caused by upwellings of cold, nutrient-rich waters during the summer monsoon, together with the presence of numerous offshore islands, create ideal feeding and breeding areas for many seabirds, notably Bulweria fallax, Puffinus persicus, Phaethon aethereus, Sula dactylatra, S. leucogaster, Phalacrocorax nigrogularis, Phalaropus lobatus, Larus hemprichii, L. leucophthalmus, Sterna bergii and S. repressa (Evans, 1994).
Preliminary lists of important wetlands in the Republic of Yemen have been given by Al-Safadi (1993) and Scott (1993). A recent inventory of Important Bird Areas in the Middle East, sponsored by BirdLife International, has identified 57 sites as being of special importance for bird conservation in Yemen (Evans, 1994). Sixteen of these sites are primarily wetlands or contain significant tracts of wetland habitat, 12 in the coastal zone and four inland. All of these sites are included in the present inventory, along with two additional inland sites, Al-Hudaydah Sewage Lagoons and Wadi Warazan. Rocky offshore islands and marine areas important for pelagic seabirds have been excluded from the present inventory as they can scarcely be classified as wetlands and have already been well covered in the inventory of Important Bird Areas.