Forecasting the flooding in the site of the Zabol gas transmission line, in the Hamoun Wetland, using climate change and hydrological models

Hamoun wetland includes Hamoun Pozak, Saberi and Helmand as the largest freshwater lake in Iran and one of the most important wetlands of international importance. This wetland is located in the southeast of Iran in Sistan and Baluchestan province. Due to the increase in rainfall in Afghanistan and eastern Iran in 2018-2020, there is a possibility of flooding of the gas transmission pipeline from Dashtak Launcher Station to Zabol city in a part of Helmand wetland. Based on the Projection of the General Circulation models (GCMs), in the future there is a possibility of increasing temperature and decreasing rainfall in Sistan erea. Therefore, based on 5 models and two scenarios, RCP4.5 and RCP8.5, first the precipitation and temperature values in the period (2020-2040) were calculated and then the hydrological variables were predicted. In order to simulate water level changes in Hamoun Wetland, various scenario of the floods with different return periods in unstable flow mode was performed using HEC-RAS software and flood zoning was calculated as the maximum water depth at any point in Hamoun Wetland. Examination of rainfall and water discharge of Sistan and Helmand rivers showed that most river floods and flooding of wetlands occur annually in the period from February to May. The actual monthly hydrograph flood of the Helmand River (October 2002 to October 2012) showed that the peak of this flood has a return period of about 130 years. Simulation showed that the flooding of the gas pipeline will occur in places located at 20, 30, 68, 80 and 104 km of Dashtak crossroads and especially in the location of Shila waterway and the water depth varies between 1.5 to 5 meters. Therefore, in the above-mentioned places, the necessary measures should be taken to prevent the gas pipe from floating.