 In Bely, it turns northwest and crosses into Zharkovsky District.The mouth of the Obsha is located by the village of Ustye.The drainage basin of the Obsha includes almost the whole area of Belsky District, as well as minor areas in the west of Sychyovsky District, in the south of Oleninsky District, in the northeast of Zharkovsky District, and in the north of Kholm-Zhirkovsky District of Smolensk Oblast.