Hydro-period dynamics of some inland valley agroecosystems in southwest Nigeria

The potential use of inland valley ecosystems (a category of wetlands) for cropping has not been fully exploited due to their heterogeneity in hydrology, morphology, soil types and agro-economy. The study employed the hydro-period approach to investigate the dynamics of surface waters of six inland valley sites. Hydrographs and hydro-periods of the sites were determined using water-level fluctuation data collected using staff gages. Results show that water level rose gradually from the beginning of the rain season, peaked at the end of the season, and receded gradually until the hydrological peak of dry season in amphitheatre and valley-side valley types. In the low depression valleys, the plots indicate a more instantaneous response to rainfall events with little groundwater flow. The work concluded that amphitheatre and valley-side valleys types are perennial with high base flows and low flow variability, and hence should be suitable for year-round cropping with little or no application of irrigation. On the other hand, the stage-duration curves of the depression valleys are characteristics of seasonal streams occurring in low-sloped topography with largely rain-caused floods, low base flow, and high flow variability. Application of irrigation may be required for dry season cropping in these valleys.