Rainfall Prediction and Runoff Modelling under Climate Change Scenarios for Tigris River from Mosul to Baghdad Cities

Abstract

The study aims to examine the impacts of future climate change on the rainfall quantiles for the main sites of the Tigris River basin, including Mosul, Tikrit, Sammara, and Baghdad. There are two approaches, first: the global climate models ( GCMs): (CMCC-CM2-SR5, CNRM/ESM2-1, EC-Earth3/Veg, MPI-ESM1/2-LR, MRI-ESM2/0, and NorESM2/MM) have been developed to show the future climate change depending on the precipitation data. They were designed along three periods, the reference period (1995-2015), the near-term (2020-2040), and the mid-term (2041-2060). Second, the prediction of the expected Rainfall-Depth (Q) for a return period (2-100 years) based on the rainfall data for 2000-2021 by applying the probability distribution function using the HEC-SSP software. Then, determined the expected Runoff-Depth depending on the results of the predicted probability of Rainfall-Depth for a specific return period and applied the Soil Conservation Service-Curve Number (SCS-CN) model to estimate the CN values of the catchment area from the soil classification according to maps of Land use/cover (LULC) and hydrologic soil grouping (HSGs) generated by the ArcGIS software from the FAO Soils Portal website using Harmonized World Soil Database (HWSD) and the HEC-HMS. The HEC-RAS program is used to create flood maps by simulating runoff depth for forecasting 100 years. The results of the (GCMs) models found the ensemble precipitation change tends to increase at Mosul and Tikrit sites, while Sammara and Baghdad sites noticed no significant changes for both the near and midterm. The flood map reveals that the expected runoff has covered the urban areas.