Streamflow trends and climate linkages in the Zagros Mountains,Iran |
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| Authors: | I Masih S Uhlenbrook S Maskey V Smakhtin |
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| Institution: | 1.International Water Management Institute (IWMI),Colombo,Sri Lanka;2.UNESCO-IHE Institute for Water Education,Delft,The Netherlands;3.Department of Water Resources,Delft University of Technology,Delft,The Netherlands |
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| Abstract: | This paper examines trends in streamflow and their links with local climate in the Karkheh River and its major tributaries,
which originate from the Zagros Mountains, Iran. Streamflow records from five mainstream stations for the period 1961–2001
were used to examine trends in a number of streamflow variables. The studied variables were mean annual and monthly flows,
1 and 7 days maximum and minimum flows, timing of the 1-day maxima and minima, and the number and duration of high and low
flow pulses. Similarly, the precipitation and temperature data from seven climate stations for the period from 1950s to 2003
were used to examine trends in climatic variables and their correlation with the streamflow. The Spearman Rank test was used
for the detection of trends and the correlation analysis was based on the Pearson method. The results reveal a number of significant
trends in streamflow variables both increasing (e.g. December flows) and decreasing (e.g. May flows) for all stations. However,
some trends were not spatially uniform. For example, decline in low flow characteristics were more significant in the upper
parts of the basin, whereas increasing trends in floods and winter flows were noteworthy in the middle parts of the basin.
Most of these trends could be attributed to precipitation changes. The results show that the decline in April and May precipitation
causes the decline in the low flows while the increase in winter (particularly March) precipitation coupled with temperature
changes lead to increase in the flood regime. The observed trends at the Jelogir station on the Karkheh River reflect the
combined effect of the upstream catchments. The significant trends observed in a number of streamflow variables at Jelogir,
1-day maximum, December flow and low pulse count and duration, point to the changes in hydrological regime of the entire Karkheh
River system and are attributed to the changes in climatic variables. |
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