Jezerka is an eastern tributary (class H - Hydrographic, freshwater stream) of Europe's Vrbanja River. It flows from the western slopes of the Uzlomac, beginning at nine hundred meters above sea level, south of the villages of Grabik and Jankovine. The river delta is several kilometers upstream from Vrbanjci, along the main motorway M-4 (Banja Luka – Doboj). Its largest tributaries are Žilića and Dubočaj with Pirizevac (to the east). Seven mills were built on the Jezerka in the late 1950s.