Future runoff assessment under climate change and land-cover alteration scenarios: a case study of the Zayandeh-Roud dam upstream watershed

In this study, hydrological responses to climate change and land-cover alteration on future runoff in the Zayandeh-Roud dam upstream watershed were assessed. In this regard, land-use maps in 1996, 2008, 2018, and 2033 were generated using Landsat time-series (TM and OLI), Support-Vector Machine (SVM), and the CA-Markov chain model, for analysing the effects of land-cover alteration on future runoff. Second, the Global Circulation Model (GCM) scenario time-series under RCP 2.6 and RCP 8.5 scenarios were downscaled to evaluate the impacts of climate change on future streamflow. Eventually, the HEC-HMS model was calibrated (1996–2018) for evaluating the impacts of climate and land-use map changes. Results showed that the percentage of the urban area and farmland in 2033 compared to 2018 were expected to grow by 0.1 and 2.39% upstream of the Eskandari station and 0.05 and 0.71% upstream of the Ghale-Shahrokh station, respectively, although the percentage of the barren area was expected to remain almost unchanged in both regions. The future stream flow of Eskandari and Ghale-Shahrokh stations in 2033 was expected to decrease by 57–63 MCM (for RCP 2.6 and RCP 8.5) and 295–403 MCM, respectively, where 68–72% and 79–86% were expected to decrease under climate change scenarios and remains are due to land-cover alteration.