Sistan

Sistan is a historical region spanning eastern Iran and southwestern Afghanistan, centered on the Helmand River basin and its endorheic wetlands.

Helmand River: A major river flowing from the Hindu Kush through Afghanistan into the Sistan basin. Its waters sustain Sistan’s settlements and wetlands across national borders.
Sakastan: An ancient region named for the Saka people, whose name later developed into Sistan. The region’s name preserves the memory of Saka settlement.
Sistan Irrigation System: A network of canals and waterworks that distributes Helmand River water across the Sistan plain. Canals turned seasonal river flow into agricultural production.
Sistan drought: A prolonged period of severe water scarcity in the Sistan region, driven by reduced river inflow and high evaporation. Drought exposes the dependence of Sistan’s wetlands and communities on Helmand flows.
Sistan Basin: An endorheic drainage basin in Afghanistan and Iran whose rivers terminate in wetlands and lakes. This basin defines the region’s physical center.
Saka: An ancient Iranian-speaking people associated with nomadic groups across Central Asia and the Iranian plateau. Saka migration and rule gave Sakastan its historical name.
Helmand and Arghandab Valley Authority: An Afghan government agency established to develop water resources and agriculture in the Helmand and Arghandab valleys. Its projects upstream affect flows reaching Sistan’s wetlands.
Dust storm: A windstorm that lifts large quantities of loose dust and sand into the atmosphere. Drying wetlands around Sistan expose sediment that can fuel severe dust storms.
Hamun-e Helmand: A system of shallow lakes and marshes in the Sistan basin, fed mainly by the Helmand River. These wetlands historically supported farming, fishing, and settlement.
Zunbils: A dynasty that ruled parts of Zabulistan and Sistan before the region’s incorporation into the Islamic caliphate. Their rule represents Sistan’s political landscape before Islamic conquest.

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Muslim conquest of PersiaBroader topic: Its frontier campaigns illustrate the conquest's prolonged extension into eastern territories.