Hydrological Modeling and Climate Change Impacts on River Kuja Basin Using HEC-HMS and HEC-GeoHMS Models

Abstract

Climate change is real and the effects directly influence the general hydrology of a region. The assessment of these effects still remains an uncertainty owing to the fact that modeling of hydrological reactions is a factor of quality of the data and model limitations. This study sought to model the hydrology of River Kuja basin and the impacts of climate change on the river discharge. The research was carried out by determining the relationship between streamflow and rainfall variability using regression analysis. The HEC-GeoHMS and HEC-HMS models were used to model the impacts of climate change on the streamflow. Different streamflow scenarios were simulated and their effects and impacts on the downstream discharge assessed. The results of the study showed that there was a very significant decline in the streamflow in the drier months compared to the wetter months. Results from the regression analysis of streamflow against rainfall gave a coefficient of determination of 0.42 and correlation coefficient value of 0.65. This demonstrated a moderate but significant relationship between rainfall and streamflow. Both rainfall and streamflow trend analysis showed a decreasing trend for the period between 2000 to 2009. This analysis of the variability between streamflow and rainfall provided a moderately strong but significant relationship between the two variables. Results from the model calibration showed a satisfactory efficiency with an NSE value of 0.50. Simulations of three different future scenarios indicated that there would be a significant increase in the future streamflow as a result of increased rainfall during wet seasons due to climate change. The study therefore concluded that there will be high discharge in the future thus a risk in flash floods but consequently very low discharges during dry seasons. This study is useful to water professionals and managers in developing a robust integrated water and land management system. In addition, the findings from this study would inform policy makers to make informed decisions on river water resource management.