Oguta Lake is a lean 'finger lake' formed by the damming of the lower Njaba River with alluvium. it is the largest natural lake in Imo State, Southeastern Nigeria; within the equatorial rainforest region of Niger Delta. Oguta Lake's catchment area comprises the drainage area of the Njaba River and a part of the River Niger floodplain in the region south of Onitsha.

Njaba River, in the Niger Delta Basin is a major tributary of Oguta Lake in Nigeria's South East Imo State. With 4.5m mean depth, the river has a total stream length of 78.2 km, basin area of 145.63 square kilometers and an average specific discharge of about 1700 m3/hour.