Lake Hāmūn (Persian: Daryācheh-ye Hāmūn) or Hamoun Oasis is a term applied to wetlands in endorheic Sīstān Basin on the Irano-Afghan border. Hāmūn is generic term which refers to shallow lakes (or lagoons), usually seasonal, that occur in deserts of southeast Iran and adjacent areas of Afghanistan and Pakistan as product of snowmelt in nearby mountains in spring. The term Hāmūn Lake (or Lake Hāmūn) is equally applied to Hāmūn-e Helmand (entirely in Iran), as well to shallow lakes Hāmūn-e Sabari and Hāmūn-e Puzak, which extend into territory of present-day Afghanistan with latter being almost entirely inside Afghanistan. The Hamun is fed by numerous seasonal water tributaries; the main tributary is the perennial Helmand River, which originates in Afghanistan Hindu Kush mountains. In modern times, and prior to the existence of the dams for agricultural irrigation, spring floods would bring into existence much larger lakes.
In Iran term Daryācheh-ye Sīstān (“Lake Sīstān”) is also used, with similar meanings, for lake Hāmūn-e Helmand.
It is located in Afghanistan which forms on the Sīstān marshes west of the Dasht-e Mārgow desert where the Helmand River forms a dendritic delta. Water flows in a circular fashion through a string of lakes starting with Hāmūn-e Puzak in the northeast, sweeping into Hāmūn-e Sabari and finally overflows into Hāmūn-e Helmand in the southwest.
It used to cover an area of about 4,000 km2 (1,500 mi2) with dense reed beds and tamarisk thicket fringing on the edges of the upper lakes. Area was thriving with wildlife animals and migratory birds.
A trapezoid shaped basalt outcropping, known as Mount Khajeh,rises up as an island in the middle of which used to be Hāmūn Lake and the northeastern edge of Hāmūn-e Helmand. Its flat-topped peak rises up 609 meters above sea level with a diameter 2-2.5 km, being the only remaining natural uplift in the Sīstān flatlands.
The area has important archeological remains. The ruins of an ancient Achaemenid city Dahan-e Gholaman (“Gate of Slaves”) are near the Hāmūn Lake.
In 1975 the Hāmūn-e Helmand, together with Hāmūn-e Sabari, was designated a Ramsar site.
In the past five millennia, people around Hamoun Oasis for the most part lived in harmony with the wetlands and their wildlife. Specific culture formed around the Hamoun with a way of life suited to the desert wetlands. They fashioned long reed boats to navigate the shallow waters and erected squat, red clay houses to withstand the heat of the desert. Their livelihood was based almost entirely on hunting, fishing, and farming.
Until the late 20th century, irrigation waxed and waned in the Sīstān Basin for over 4,000 years without destroying the wetlands, but then population rapidly increased and new more efficient water management technologies were brought to the region. Soon irrigation schemes began to snake their way throughout the basin. Farther west, revolving Afghan governments constructed large dams (Arghandab Dam, Kajaki Dam) that diverted water from the upper reaches of the river.
Devastation by extreme droughts in 1999-2001
Precipitation variability in the Hindu Kush results in alternating periods of flooding in the Helmand and droughts, which may cause entire lagoons to dry up. This occurred several times in the 20th century, when only the uppermost of the lakes remained flooded. Landsat satellite imagery show how dramatic decrease in precipitation resulted in decrease of snow-covered area in the Helmand Basin, from 41,000 km2 in 1998 to 26,000 km2 in 2000. By 2001, Iran and Afghanistan were experienced for the third consecutive year an extreme drought that was so severe that the Hamoun dried out completely.
Sīstān’s population, swelled by refugees from war-torn Afghanistan, has been severely affected by water shortages. Irrigation channels have run dry and agriculture has come to a standstill, which has resulted in the abandonment of many villages as people migrate in search of water.
Combination of drought and the massive irrigation proved to be a shock to the wetlands. Within five years period (1998-2002) once fertile wetlands rapidly deteriorated. We could reasonably presume that transformation of Hamoun into arid country, like their surrounding areas, was mainly caused by irrigated agriculture expansion since the 1970s (represent as bright red patches on satellite images, mainly wheat and barley), coupled with one of the worst droughts ever witnessed in Central Asia in 1999-2001 period.
The wetlands have been replaced mostly by lifeless salt flats and decaying reed stands. The wildlife, the towns, the fisheries, and the agriculture that once surrounded the Hamoun have all fallen away, giving rise to a wasteland.
Winds that were once cooled by the waters of the wetlands now drifting dust, sand, and salt from the dried lakebeds onto the surrounding villages, and these sand drifts have submerged nearly 100 villages beneath dunes in a landscape reminiscent of the Aral Sea disaster. Most of the crops have been reduced to dustbowl conditions, livestock herds have been decimated, and thriving fishery with an annual catch of around 12,000 tons has been wiped out. Many who had lived around the Hamoun for generations either moved away or lost everything.
Local bird population disappeared and migratory birds no longer stop for lack of refuge, and wildlife that could not sustain themselves in the desert or make the long journey to another oasis died. The rest of the wetlands now give off the harsh glare of dried salt flats. The only relatively large bodies of standing water are Chāh-Nīmeh IV reservoir maintained for drinking water.