Lake Hāmūn is fed primarily by water catchments in neighboring Afghanistan, including the Harut River. It is in the Sistan region and it is in the Lash wa Juwayn District of the Farah Province of Afghanistan. The Harut River flows into the lake on the Afghanistan side of the border.In 1976, when rivers in Afghanistan were flowing regularly, the amount of water in the lake was relatively high. Between 1999 and 2001, however, the lake all but dried up and disappeared, as can be seen in the 2001 satellite image.
When droughts occur in Afghanistan, or the water in watersheds that support Lake Hāmūn is drawn down by other natural or human-induced reasons, the end result is a dry lake bed in Iran. In addition, when the lake is dry, seasonal winds blow fine sands off the exposed lake bed. The sand is swirled into huge dunes that may cover a hundred or more fishing villages along the former lake shore. Wildlife around the lake is negatively impacted and fisheries are brought to a halt. Changes in water policies and substantial rains in the region hope to effect a return of much of the water in Lake Hamoun by 2003.