Geological Formations and the Quagmire of Stream Extinction in Southern Nigeria

Geology plays a key role in determining the behavior of the ecosystem including its streams network and a better understanding of this concept is the first step toward ecosystem and water sustainability. Hence, this study examines geological formations and the quagmire of stream extinction in Southern Nigeria. Two different geological formations in Southern Nigeria were considered in this study which include the Coastal Plain Sands using Kwa Iboe River in Akwa Ibom State and Basement Complex in some parts of Cross River State. Six matured watersheds were purposively selected from each geological formation (six in Coastal Plain Sands and six in Basement Complex), making a total of twelve (12) watersheds. These cut across Idim Awankwo, Midim, Utu Abak, Anyang, Ibedu and Akpeti watersheds in the Coastal Plain Sands in the Kwa Iboe River and Iwuru, Uyanga, Abonabung, Akor Ako, Okpon and Inyang Iba watersheds in the Basement Complex in Cross River. The result of the summary of the morphometric characteristics shows lower bifurcation ratio in the CPS indicating watersheds in which the geologic structure does not exercise a dominant influence on the drainage pattern while the reverse is the case in BC. In area aspect, the result shows complicated values and high circularity ratio in BC due to the presence of a combination of lithological formations, leading to differential erosion and subsequently to watershed displacement. Statistical analysis using independent t-test analysis shows a p-value of 0.007 which is an indication that there is a significant difference in the morphological parameters of Basement Complex and Coastal Plain Sands as they relate to stream extinction. The summary of the study indicates that streams in the ancient basement complex rocks of Cross River State have restricted area, high values of basin relief and high bifurcation ratio due to inability of streams to erode easily, unlike the weak sedimentary rocks. More so, streams in the CPS recorded less influence from the geological structure of the basins, making the soil have loose particles and highly susceptible to infiltration and highest level of stream extinction. This supports the observable disparity on the basin resilience as one traverse along the river course. Hence, it was recommended that since the CPS is highly prone to stream extinction, desilting the stream channel should be given a priority by stakeholders.