large swampy lake in southeastern Iraq, south of the junction of the Tigris and Euphrates rivers. Fed by distributaries of the Euphrates, the lake (70 miles 【110 km】 long; 750 square miles 【1,950 square km】 in area) drains via a short channel into the Shatt al-Arab near Basra. It was once only a reed-filled marshland but was later utilized as a natural irrigation reservoir for the fertile soils of the delta region, where dates, rice, and cotton were grown. The lake and surrounding marshlands are the traditional home of the Maʿdan, a tribe of seminomadic marsh dwellers who are sometimes referred to as Marsh Arabs. Their distinctive culture is based on the herding of water buffalo, the hunting of wildfowl and pigs from reed canoes, and the building of elaborate houses of woven reeds (Arabic: mudhīf). The structures have Gothic-appearing arches made of bundles of reeds fastened together at the top; the walls are woven in intricate patterns of reeds. A 4th-millennium-BC plaque from the Sumerian city of Uruk on the western edge of the marshes depicts such a structure, showing the longevity of the style.

In 1992 the Iraqi government began draining the country's southern marshlands in an attempt to drive out Shīʿite guerrillas who had taken refuge there. By 1993 one-third of Lake Ḥammār was dry and many thousands of the marshlands' residents had moved deeper into the marshes or fled to Iran.