Estimating Rainfall Erosivity under Climate Change for Central Zone of Tigray Watersheds, Ethiopia

The rainfall erosivity factor (R factor) is one of the six erosion factors in the Universal Soil Loss Equation (USLE). Most research on rainfall erosivity deals with the assumption that climate stationarity over time. However, a warming climate might change the behavior of hyetograph rainfall data emphasizing the need for updating the assumption with climate change conditions. Thus, this study presents a generalized framework for estimating rainfall erosivity under climate changes scenarios for Central Zone of Tigray. Twenty- six years (1990 to 2015) rainfall data were collected and used for climate change prediction. Sixteen years of hyetograph rainfall data (2000-2015) were used for the estimation of erosion index and erosivity model development based on the method suggested by Wischmeier and Smith. Three climate change scenarios (RCP2.6, RCP4.5 and RCP8.5) were considered for future climate change prediction. The current time, maximum and minimum annual erosivity index were computed as 6991.9 and 68.58 MJ mm/ha.h.year respectively at Adwa weather station. The annual average erosivity has estimated to be 1707.21 MJ.mm/ha.hr.year for the current time. The erosivity models developed at Adwa weather station worked reasonably well and the coefficient of determination for the best selected model was 0.955. In addition, this study indicates that future rainfall erosivity under the emerging climate change scenarios at the study site would increase. The annual erosivity index increments ranges from the minimum value (38.09%) to maximum value (46.15%) at Adwa weather stations as compared to the current time. Therefore, more erosive rainfall events would be expected for the future timelines and will have major implications on watershed planning and management activities in the study area.