The Impact of Climate Change on Low Flows (Case Study: Sepid Dasht Sezar)

Low flow is one of the very effectual hydrologic parameters on the state of aquatic ecosystems as well as power production, reservoir management and industry. Therefore, it is necessary to investigate the changes in this parameter in the future periods under affecting factors such as climate change. In this regard, the impacts of climate change on low flows of Sepid dasht sezar catchment were evaluated, in this research. First, the ability of IHACRES rainfall-runoff model for simulation of low flows of this catchment was evaluated. After calibration and verification of model, in this study observed that the model has a good ability for simulating of mean daily flow (R2-log>0.7), also low flow (R2-inv>0.6). In addition, the ability of model to low flow indices (including Q95, AM7Q with different return period and QdefS)was evaluated. Then, The outputs of the temperature and precipitation of 10 general circulation models of the atmosphere under A2 emission scenario was used in order to assess the effects of climate change over the period 2015-2044. LARS-WG model was applied for downscaling of the output of these 10 models. Finally, downscaled values ​​of temperature and precipitation were introduced to the IHACRES rainfall - runoff model and the low flow in the future was assessed based on the low flow indices. Changes of two indices Q95 and AM7Q in the future period to the past, based on the median of 10 AOGCM model results is decreasing (-40% for Q95 and from -52% to -79% for AM7Q with different return period). Also, the QdefS index show the increasing change (30% based on the median of AOGCM model results). All three indices have confirmed each other's results and show that the expected climate change in the future, greatly affect the low flows.