this lake. The slope reported before the creation of the lake is per . The lake is divided by a barrier into two zones, the upper and the lower. The barrier extends several kilometres southwards. Beyond the barrier, the lake is narrow and long and its outreach is not visible. The Bara Lisa River joins the Niger above Dire. It exits the deltas from the northern shores of Lake Debo and flows east. The Issa Baris, the main arm of the lake, exits from the lake in a westerly direction and turns northeast to join the Bara Lisa. Geological formations recorded at the bed of the lake are "from dense crystalline rock of Precambrian sandstone compacted in the broad Taoudeni Syncline as an alluvial fan and covered by a hard layer of cemented-laterite." The flat slopes and geology of the beds has resulted in creating a meandering and multi-channel flow pattern, which has resulted in the formation of inner delta of the Niger. The inner delta thus has many wide channels, which are shallow and flooded marshes; this delta extends over a length of with a width of . It is inferred from the study of nearly 400 maps that it is the delta which is the origin of the lake and that the lake is the largest in the delta. It is integral to the wide river channel with its size fluctuating with variation of the water level in the lake. It also provides confirmation of the nature of blocked water and also includes the Erg of Bara region. The maximum flood in the lake and the delta occurs during November and December. Below Lake Debo, the Niger valley is marked by a large number of lakes, which are lower than the river level. As part of the central delta, the lake is the largest. As it is a part of the Niger River, its size varies with the fluctuation in the water level. and maximum flood occurs in the river during November and December. The lake has a vast expanse of water extending on all sides. The river that is formed at the outlet of the lake has a width of for a length of downstream, where after it narrows down, gets spilled into many channels; marshy islands are formed and depth of water is in the range of . Foolahs, the nomads who live here, use these