Water Level and the Potentials for Wetland Formation and Sustainability in Lower Ogun River Floodplain, Nigeria

I.A Ogunyemi,O Oguntoke,C.O Adeofun

doi:10.4314/jasem.v24i6.15

Abstract

Identification, delineation and monitoring of wetlands which requires the understanding and application of their ecological characteristics are critical factors in wetland management and conservation. This study assessed the potentials of wetland formation and sustainability in the lower Ogun river basin by determining the levels of surface and ground water. The study area was divided into 1 km2 grids of 67 units using 0.052 % sampling intensity for the assessments in dry and wet seasons. Monthly water table levels were assessed in 50 cm soil pit while inundation levels were measured during the flooding event using staff gauge. Assessment was carried out for one year during which frequency and periodicity of water table and inundation events were recorded. Results revealed that low water table level ranged from 5 to 45cm of soil depth and occurred between August and September within 6 grids. Water table and surface water was recorded within a period of 2 – 10 weeks during the rainy season. The peak of water levels coincided with the peak of precipitation (> 200 mm) ranging from 30 to 280 cm between September and October while covering 28.75 km2. Conclusively, surface and groundwater levels were recorded during the rainy season having direct variation with the volume of precipitation for a duration that is long enough to support the formation of wetland hydrophytes and hydric soil. Keywords: Wetlands; Hydrology; Ground water; Surface water; Inundation; Precipitation

Highlights

Wetlands are transitional between terrestrial and aquatic systems where the water table is usually at or near the surface, or the land is periodically covered with shallow water, and which land in normal circumstances supports or would support vegetation typically adapted to life in saturated soil (Department for Water Affairs and Forestry, DWAF 2010)
Surface and groundwater levels were recorded during the rainy season having direct variation with the volume of precipitation for a duration that is long enough to support the formation of wetland hydrophytes and hydric soil
Studies involving the description of wetland hydrological system are important for conservation and easy detection of hydrological modifications which could help in restoration effort in the advent of reconstruction of degraded wetlands

Summary

Introduction

Wetlands are transitional between terrestrial and aquatic systems where the water table is usually at or near the surface, or the land is periodically covered with shallow water, and which land in normal circumstances supports or would support vegetation typically adapted to life in saturated soil (Department for Water Affairs and Forestry, DWAF 2010). Surface and groundwater levels were recorded during the rainy season having direct variation with the volume of precipitation for a duration that is long enough to support the formation of wetland hydrophytes and hydric soil. Like river basins that are presumed to have wetlands because of their proximity to water bodies could lose their wetland status due to hydrological modifications or change in precipitation patters.

Results

Conclusion