Jangan-gu lies in the north of Suwon. It is bordered by Uiwang to the north-west, Yongin to the north and east, Yeongtong-gu to the south-east, Paldal-gu to the south and Gwonseon-gu to the south west.

Most of the streams passing through Suwon originate in Jangan-gu, on Gwanggyosan or other nearby peaks. Since Suwon is bounded to the east by other hills, the streams, chiefly the Suwoncheon, flow southwards through the city, eventually emptying into the Yellow Sea at Asan Bay. The entirety of Suwon is drained in this manner.etc