Rainfall Intensity-Duration-Frequency Development for Soil and Water Conservation Interventions Under Changing Climate in Southern Tigray, Ethiopia

Abstract

Human beings, at a larger scale, are still in the hands of climatic influences, where extreme events of floods and droughts keep on claiming many lives all over the world . Rainfall Intensity Duration Frequency curves (IDF curves) are graphical representations of the amount of water that falls within a given period of time.  IDF relationship is an important hydrologic tool which will bridge the gap between the design need and the unavailability of design information especially in planning and design of water resources projects. Due to lack of these IDF relationships, the planning and design of Soil-erosion prevention practices, water resource development, irrigation and drainage schemes, soil conservation programs and other projects are based on some assumptions and empirical data from other countries. The methodology implemented to assess changes in rainfall magnitude resulting from climate change includes the following components: (1) development of climate change scenario of precipitation using SDSM model; (2) statistical analysis of rainfall of various durations, and development of IDF curves under changed climatic conditions; and (3) comparative analysis of IDF curves.  The climate scenario used in the analysis is climate change scenario that modifies the observed record according to GCM simulation outputs. Results of the study include tabular and graphical presentation of IDF curves  for return periods of 2, 5, 10, 25, 50 and 100 years for durations of 1, 2, 3, 5, 6, 12 and 24 hours. The simulation results indicate that rainfall magnitude will increase under climate change for all durations and return periods at the stations. the  comparison  of the IDF results between historic rainfall and climate change rainfall intensity data set, it is difficult to say whether it is decreasing or increasing  but the is a difference for the future time. Therefore, based on the results the IDF curves developed under climate change are believed to benefit the study areas in providing basic information’s on rainfall intensity, Duration and Frequency relationships to all intervention and to water professionals designers engaged in soil and water conservation and  in water resources under climate change .

keywords : Climate Change , General Circulation Models (GCMs), IDF Curve, Intensity, Duration , Frequency