Hydrologic characteristics of a small tropical riverine wetland at Ulakwo, Imo State, Nigeria

The hydrologic and water-quality characteristics of a small tropical riverine wetland at Ulakwo, near Owerri, Imo State, Nigeria, were evaluated by analysis of stream hydrographs, the groundwater flow system, and geochemical analyses. This research is an initial step toward providing information needed to develop a programme of sustainable development of the ecosystem. The wetland is underlain by a layer of organic debris and hydromorphic soils, which in turn are underlain by an unconfined alluvial sand aquifer about 80 m thick. Horizontal and upward vertical hydraulic head gradients of about 0.002 and 0.001, respectively, and the results of a flow-net analysis suggest that considerable amounts of groundwater flow into the wetland.Low concentrations of Fe, NO₃, PO₄, and SO₄ in the wetland water column are probably due to short-term removal of these nutrients from the surface-water by adsorption on the surficial wetland organic matter and bottom sediments. The groundwater flow system is important in the maintenance of the wetland, which probably plays an important role in the flow stabilisation and improvement of the water quality of the river.