Assessing impacts of climate change on hydrological extremes of Rwizi catchment

Abstract

There is lack of understanding on the impact of climate change on hydrological extremes of Rwizi Catchment. This threatens the sustainability of water to support socio- economic activities in the Rwizi Catchment. The procedure for conducting the study was guided by three objectives. Firstly, Trend analysis showed that precipitation mainly increased whereas Potential Evapotranspiration (PET) exhibited a decrease. The trend in both precipitation and PET were mainly insignificant. The second objective focused on establishing the climate change signals on precipitation and PET based on Global Circulation Models (GCMs) from Coupled Model Inter-comparison Project phase 5 (CMIP5) outputs. This was done by considering the Representative Concentration Pathways 4.5Wm-2 (RCP4.5) and 8.5Wm-2 (RCP8.5) scenarios. The precipitation and temperature of the 2050s and 2080s were projected to increase as to compared to the control period (1956–2002). Two conceptual hydrological models were calibrated and used for the impact assessment. Their difference in simulating the flows under future climate scenarios were also investigated. For the Austrian Water Balance Model (AWBM), the assembled mean projections of the high flow of 10- year return period for the 2050s and 2080s were projected to decrease. Whereas, for the Hydrological Model focusing on Sub-flows’ Variation (HMSV), the assembled mean projections of high flows were projected to increase. The results for the low flows reveal decreasing low flow quantiles for AWBM for the 2050s and 2080s. However, for HMSV model, it showed increasing low flows quantiles. These impacts of climate change on the river flow show the need for a careful planning of relevant and appropriate adaption measures at a catchment scale. Keywords: Climate change, Climate models, Hydrological models, Rwizi Catchment.