Abstract. The main objective of this study was to calibrate and validate the eco-hydrological model Soil and Water Assessment Tool (SWAT) with satellite-based actual evapotranspiration (AET) data from the Global Land Evaporation Amsterdam Model (GLEAM_v3.0a) and from the Moderate Resolution Imaging Spectroradiometer Global Evaporation (MOD16) for the Ogun River Basin (20 292 km2) located in southwestern Nigeria. Three potential evapotranspiration (PET) equations (Hargreaves, Priestley–Taylor and Penman–Monteith) were used for the SWAT simulation of AET. The reference simulations were the three AET variables simulated with SWAT before model calibration took place. The sequential uncertainty fitting technique (SUFI-2) was used for the SWAT model sensitivity analysis, calibration, validation and uncertainty analysis. The GLEAM_v3.0a and MOD16 products were subsequently used to calibrate the three SWAT-simulated AET variables, thereby obtaining six calibrations–validations at a monthly timescale. The model performance for the three SWAT model runs was evaluated for each of the 53 subbasins against the GLEAM_v3.0a and MOD16 products, which enabled the best model run with the highest-performing satellite-based AET product to be chosen. A verification of the simulated AET variable was carried out by (i) comparing the simulated AET of the calibrated model to GLEAM_v3.0b AET, which is a product that has different forcing data than the version of GLEAM used for the calibration, and (ii) assessing the long-term average annual and average monthly water balances at the outlet of the watershed. Overall, the SWAT model, composed of the Hargreaves PET equation and calibrated using the GLEAM_v3.0a data (GS1), performed well for the simulation of AET and provided a good level of confidence for using the SWAT model as a decision support tool. The 95 % uncertainty of the SWAT-simulated variable bracketed most of the satellite-based AET data in each subbasin. A validation of the simulated soil moisture dynamics for GS1 was carried out using satellite-retrieved soil moisture data, which revealed good agreement. The SWAT model (GS1) also captured the seasonal variability of the water balance components at the outlet of the watershed. This study demonstrated the potential to use remotely sensed evapotranspiration data for hydrological model calibration and validation in a sparsely gauged large river basin with reasonable accuracy. The novelty of the study is the use of these freely available satellite-derived AET datasets to effectively calibrate and validate an eco-hydrological model for a data-scarce catchment.
The present study assessed the water quality of Ogun river in southwestern Nigeria. Forty water samples were collected from twenty monitoring stations along Ogun River Basin between April 2013 and January 2014. Water samples were analyzed for important physical and chemical parameters such as temperature, pH, turbidity, total suspended solids (TSS), total dissolved solids (TDS), total solids (TS), electrical conductivity EC, dissolved --3-oxygen (DO), silica, anions (F , Cl , PO , NO ), hardness, alkalinity and metals (Fe, Pb, Cd, Na, K) using the 4 3 standard procedures. Data collected were subjected to simple descriptive (mean and standard deviation) and inferential statistics (Duncan Multiple Range Test, DMRT and Principal Component Analysis, PCA) using the Statistical Package for Social Sciences (SPSS, Windows' version 16.0). Results showed higher mean concentrations of turbidity (49.7±13.0 NTU) and total suspended solids (1205.2±4.7 mg/L) than the permissible limits of the World Health Organization (WHO) in drinking water. The values of phosphate (1.14±1.3 mg/L), Cd (0.02±0.01 mg/L) and Pb (0.33±0.05 mg/L) were also observed at higher concentrations than the permissible standards of the WHO. The sources of pollution to Ogun River Basin identified by varimax rotated PCA were industrial effluents, runoff, fertilizer and dissolved salts.ABSTRACT 375 https://dx.
This study was carried out to determine the potability of selected brands of bottled water in Abeokuta metropolis. Water quality parameters such as physical (Color, turbidity, total suspended solids (TSS), total dissolved solids (TDS), total solids (TS)), chemical (pH, total hardness, alkalinity, chloride (Cl-), free chlorine, sulphate (SO4 2-), nitrate (NO3-) and iron (Fe 2+)) and microbiological (total coliform) were determined using standard procedures. The results obtained were subjected to statistical analysis for analysis of variance using SPSS 15.0. Mean values of water quality parameters were compared to World Health Organization (WHO) standards in drinking water. Results showed that water parameters like colour (< 7.0 Pt. Co.), TDS (<150 mg L-1), free chlorine (<0.5 mg L-1), Cl-(<27 mg L-1), SO4 2-(15 mg L-1), NO3-(<2.0 mg L-1), Fe 2+ (<0.1 mg L-1) and total coliform (0.0 count mL-1) were within WHO standards for drinking water indicating the potability of the bottled waters and hence, could be consumed without any possible health problems. @ JASEM
comparing the simulated AET of the calibrated model to GLEAM_v3.0b AET, this is a product that has a different forcing 30 data to version of GLEAM used for the calibration, and (ii) assessing the long-term average annual and average monthly water balances at the outlet of the watershed. Overall, the SWAT model structure composed of Hargreaves PET equation and calibrated using the GLEAM_v3.0a data performed well for the simulation of AET and provided a good level of confidence for using the SWAT model as a decision support tool. The 95% uncertainty of the SWAT simulated variable bracketed most
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