SEASONAL EFFECTS OF RUNOFF ON SURFACE WATER QUALITY FROM VARIOUS LAND USES IN ENUGU URBAN AREA, ENUGU STATE, SOUTH EASTERN NIGERIA.
Ph.D Thesis By Obuka, Esther Njideka – July 2019
The study combined experimental research design and Remote Sensing Satellite Imagery on six different rivers that make up the Nyaba basin. The aim of this research is to determine the seasonal effects of runoff on the surface water quality from various land uses (residential, commercial and agricultural) in Enugu urban area. The population of this study comprised of six rivers found in Nyaba basin. The water samples were collected within two seasons, rainy and dry season, a visit to each of these rivers for direct collection of the water samples was made. Two samples were collected from each river (upper and lower station) while three samples was from Ekulu river because it is the longest. A total of thirteen surface water samples were randomly collected from the existing rivers in Enugu urban area and eighteen parameters were tested. The methods of data analysis include laboratory test, statistical data and satellite imagery (Landsat8, 2017). Descriptive and inferential tools were used and include: Factor analysis, Independent Sample T- Test, One Sample T- Test and One way-Analysis of Variance (ANOVA).The result from hypothesis one revealed that there was identifiable source of variation in the hydrochemistry of surface water from runoff in Enugu Urban area. It shows how polluted the surface water is and the extent of variations of hydrochemistry (parameters) and is as a result of anthropogenic (46.9%), alkalinity (19.2%) and erosional (11.7%) factors and they are strong source of pollutants causing pollution in surface water quality. The result of the second hypothesis shows a significant difference in the surface water quality between the two seasons of the year in Enugu urban area (P < 0.05). The seasonal variation of parameters showed that temperature, pH, Ammonia values varied significantly (p < 0.001) in both seasons. Parameters like Total Suspended Solid, Total Solid, Turbidity, Nitrate, Dissolved Oxygen, Faecal and Total Coliform showed high mean values in rainy season relative to the dry season. Hypothesis three revealed that the urban runoff pollutant load present in the surface water significantly differ from the acceptable standard recommended by World Health Organization. Pollutant load was found to be significantly high in both seasons, the Turbidity, Dissolved Oxygen, Biochemical Oxygen Demand, Faecal Coliform, Ammonia and Total Coliform were significantly higher than WHO standard. Results of hypothesis four revealed that the nature of the surface water quality from runoff in various land uses in Enugu urban area differ significantly in the rainy season (F = 4.437, p = 0.042) and dry season (F = 10.288, p = 0.045).Total Solid was found to be significantly different between residential and commercial/agricultural land uses in the rainy season while turbidity was different between these land uses in dry season (P < 0.05). Result from Geostatistical Analysis (satellite Imagery) shows that large area of land use land cover were affected by TDS, pH and Total coliform especially residential, then commercial and agricultural land use .The results of this research suggest that land cover land use change is one of the key factors causing water quality changes in the study area. The study has added to the wealth of knowledge that runoff from different land uses do not have the same impact on the surface water body, runoff from residential areas pollute most, followed by commercial and then agricultural areas. This research is beneficial to Federal and State Ministry of water Resources, policy makers, environmental planners and managers in developing water management plans to protect and restore water quality conditions more effectively. There should be public enlightenment program which should educate the inhabitants on the dangers of drinking contaminated water.