Hydrological Modeling of Tubo Watershed, Kaduna State using ArcSWAT Model

Abstract

Hydrological models have been used to model the processes of the watershed which could serve as a decision framework for harnessing alternative  water supply source. The simulation was carried out, for the most important hydrology parameters such as precipitation, evaporation, runoff, infiltration,  percolation and evapotranspiration respectively, using Soil and Water Assessment Tools (SWAT) model which is integrated with ArcGIS software. The  study location was Tubo Watershed along Tubo river, a sub-basin of Kaduna basin in Igabi local government area which is about 42km away from Kaduna  metropolis towards the northern part of Kaduna state, Nigeria. The model was run for the period from 1979 to 2014 with calibration using field measured  discharge data of watershed for four years (1983-1986) and validation performed for two years (1987-1988) respectively. Moreover, the  monthly simulated runoff of Tubo watershed for the calibration and validation periods were found to match with their measured discharge value of  coefficient of correlation (R²⁾ for both which are 0.80 and 0.73 respectively. Furthermore, the model simulated daily runoff is collaborated by reasonably  high Nash-Sutcliffe simulation coefficients (ENS) of 0.81 and 0.50. Based on the recommended statistical coefficients, the model evaluation indicated a  very good performance for both calibration and validation periods with (R²) and ENS to be 94% and 83% for calibration and 96% and 88% for validation  periods respectively. It can be concluded that there is good agreement between measured and simulated values of monthly scale discharge. The average  annual inflow volume at the watershed outlet was estimated and predicted to be 2.78575MCM in line with other predicted parameters during this study.  Also, the total water yield was estimated at 576.44 mm, Evapotranspiration (592mm), Potential evapotranspiration (2217.7mm), surface runoff  (311.70mm), Lateral flow (7.03mm), Groundwater flow (257.71mm) and Transmission loss (0.0mm) respectively.