More properly, the area should be called Nad Ali. Marja is one of the villages with bazaar. Marja has come to be the name given to area of villages near the river. The U. S. built canals to aid farming some years ago.
The map linked here shows the clusters of villages along the Hilmand (Helmand) River and its tributaries in the southeastern part of the district. The population was 105,000 in 2005, nearly all in the small SE part of the district.
Nad Ali map