University of Tehran Journal of Range and Watershed Managment 5044-2008 68 3 2015 09 23 Trend analysis of streamflow in Karkheh Rivers upstream: An evidence for climate change impacts on water resources systems Trend analysis of streamflow in Karkheh Rivers upstream: An evidence for climate change impacts on water resources systems 659 674 56344 10.22059/jrwm.2015.56344 FA Khaled Osati Assistant professor, University of Kurdistan Ali Salajegheh Professor, Faculty of Natural Resources, University of Teheran Mohammad Mahdavi Professor, Faculty of Natural Resources, University of Teheran Paul Koeniger Federal Institute for Geosciences and Natural Resources (BGR), Geozentrum Hannover, Germany. Kamran Chapi Assistant professor, University of Kurdistan 0000-0002-9466-665X Arash Malekian Associate professor, Faculty of Natural Resources, University of Teheran 0000-0001-8174-6784 Journal Article 2013 06 08 Within the climate change debate and its probable impacts on water resources systems, design and operation of management plans based on the assumption of stationary hydrology may cause serious challenge to accurately predict future supplies. Therefore this case study is trying to assess trend in hydroclimatic variables of Karkheh Rivers upstream by applying modified Mann-Kendall trend test on long term daily time series of temperature, precipitation and discharge. Temperature variables are mostly showing meaningful increasing trends but observed changes in assessed stations were not spatially uniform for precipitation. Streamflow variables depict a decreasing trend, though more noticeable in base flows. Decreasing trend is meaningful for annual discharge median in Holailan at 90% confidence level. Total yearly precipitation, number of precipitation days and number of days with precipitation equal to, or greater than, 10 mm/d show the most correlation with stream flow variables. Comparing monthly discharge with temperature and precipitation variables in the studied gages indicates a time-delay in system response to inputs. This may related to snowmelt contributions or contributions of water into streams after passing through different hydrological pathways such as groundwater. Some parts of streamflow changes, especially about base flows, is not completely verified by precipitation changes and can be attributed to changes in temperature or another factors such as groundwater overexploitation. <br />  <br /><strong> </strong> Within the climate change debate and its probable impacts on water resources systems, design and operation of management plans based on the assumption of stationary hydrology may cause serious challenge to accurately predict future supplies. Therefore this case study is trying to assess trend in hydroclimatic variables of Karkheh Rivers upstream by applying modified Mann-Kendall trend test on long term daily time series of temperature, precipitation and discharge. Temperature variables are mostly showing meaningful increasing trends but observed changes in assessed stations were not spatially uniform for precipitation. Streamflow variables depict a decreasing trend, though more noticeable in base flows. Decreasing trend is meaningful for annual discharge median in Holailan at 90% confidence level. Total yearly precipitation, number of precipitation days and number of days with precipitation equal to, or greater than, 10 mm/d show the most correlation with stream flow variables. Comparing monthly discharge with temperature and precipitation variables in the studied gages indicates a time-delay in system response to inputs. This may related to snowmelt contributions or contributions of water into streams after passing through different hydrological pathways such as groundwater. Some parts of streamflow changes, especially about base flows, is not completely verified by precipitation changes and can be attributed to changes in temperature or another factors such as groundwater overexploitation. <br />  <br /><strong> </strong> https://jrwm.ut.ac.ir/article_56344_4579897252fd6d1afe1ff6b4313db6ce.pdf