Assessment of regional precipitation trend in the Lake Urmia basin

Document Type : Full length article

Authors

1 Master Graduate, Faculty of Natural Resources, Urmia University, Urmia, Iran

2 Associate Professor, Faculty of Natural Resources, Urmia University, Urmia, Iran

3 Researcher at Hydraulics Division, Department of Civil Engineering, KU Leuven, Belgium

Abstract

Introduction
Recent global warming has led to a change in the global hydrological cycle and an increase in extreme events such as flood and drought at the global and continental scales. However, at the regional scale, the magnitude of warming and the resulting changes in water resources are different from one region to another. Unlike air temperature whose increase is evident throughout the world, there is no unique and defined pattern for global precipitation changes. In recent years, climatic changes and precipitation can decrease in water level of the Lake Urmia. Extension of salt flats near the lake has caused many adverse environmental and economic effects. This necessitates the analysis of precipitation changes as the main input of the lake and one of the possible reasons for the water level decrease. Most of the previous studies on precipitation trends have been performed using data from sparse synoptic stations. Therefore, this study analyzed precipitation time series from a dense rain gauge network in the Urmia Lake basin at the annual and seasonal scales.
 
Materials and Methods
The Mann-Kendall test is one of the most common non-parametric tests for trend analysis of hydrological and meteorological variables. The main advantage of this test is that it doesn’t need the data to be normally distributed. The Z statistic of the Mann-Kendall test for different series can be summed in the framework of a multivariate Mann-Kendall test. The multivariate Mann-Kendall test was used in this study for trend detection in the precipitation time series of the study area. The non-parametric Theil-Sen method was also applied for estimation of the trend magnitude. The existence of serial correlation in hydro-meteorological time series is one of the difficulties of performing a meaningful trend analysis. The effect of serial correlation in the precipitation time series on the trend results was limited in this study. After analyzing the trends using the aforementioned methods, the results were shown on interpolation maps prepared by the Inverse Distance Weighting (IDW) method in the ArcGIS environment.
 
Results and Discussion
The analysis of the annual precipitation time series using the multivariate Mann-Kendall test showed that most of the stations had an increasing trend. The Z statistic of the multivariate Mann-Kendall test revealed that all of the significant precipitation trends were found to be increasing. The precipitation decrease of 30% was observed in the central, eastern and southern parts of the basin, while in the western, northeastern, southwestern and most eastern parts an increase in precipitation was found. Most of the spring precipitation trends (about 60% of the stations) were found to be decreasing. Based on the results of the statistical tests, almost all of the decreasing trends in spring were statistically insignificant. The only significant (increasing) trend at the 95% confidence level was detected at Tamr station. For summer precipitation, the number of increasing trends was very larger than that of decreasing trends. Nevertheless, only nine stations showed a significant increasing trend in summer precipitation. According to the obtained results, there was a good agreement between the trend results of spring and autumn precipitation. The autumn precipitation time series revealed a decreasing trend at 33 out of the 37 study stations and an increasing trend for the remaining stations. The decreasing trends were found to be significant only at five stations, whereas the increasing trends were not statistically significant. For winter precipitation, an increasing (decreasing) trend was observed at 23 (14) stations. The statistical analysis confirmed the significance of only four increasing trends, while the decreasing trends were not significant.
 
Conclusion
In this research, the multivariate Mann-Kendall test and the Theil-Sen approach were used to detect spatial and temporal trends in precipitation at 37 stations in the Lake Urmia basin at the annual and seasonal scales. The results showed an increasing trend in annual precipitation at 54% of the stations. Seasonal and monthly trends provided a more detailed picture on temporal changes in precipitation time series at the basin. The majority of the trends in spring precipitation at the surveyed stations were found to be decreasing. The spring precipitation decrease in the southern part of the basin (between 20% and 30% or more) was more noticeable compared with the eastern part. As for the summer season, precipitation increased during the last 3 decades from 10% in the west to 20-30% in the east and south of the region. It is worthy to note that the obtained significant trends in summer precipitation series are not so reliable due to the existence of numerous zero values in these series in the study region. In the case of autumn precipitation, a decreasing trend was observed in the whole basin, ranging from 10% in the south to more than 30% in the eastern part of the lake. Winter precipitation had a moderate slope in most of the basin, with a slight decrease in the east and central parts.

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چپی، ک.؛ غفاری، گ. و کریمی، م. (1390). بررسی اثرات تغییر اقلیم بر روند بارش‌های فصل بهار در استان کردستان، هفتمینهمایشملیعلومومهندسیآبخیزداری، دانشگاه صنعتی اصفهان.
حجام، س؛ خوشخو، ی. و شمس‌الدین وندی، ر. (1387). تحلیل روند تغییرات بارندگی‌های فصلی و سالانة چند ایستگاه منتخب در حوضة مرکزی ایران با استفاده از روش‌های ناپارامتری، پژوهشهایجغرافیایی، 168: 64 ـ 157.
حسین‌زاده طلایی، پ.؛ طبری، ح. و معروفی، ص. (1388). مقایسة روش‌های پارامتری و ناپارامتری در بررسی روند تغییرات ماهانه، فصلی، و سالانة دبی رودخانه و بارندگی در حوضة آبریز گاماسیاب، هشتمینسمیناربینالمللیمهندسیرودخانه، دانشگاه شهید چمران اهواز.
خلیلی، ع. و بذرفشان، ج. (1383). تحلیل روند تغییرات بارندگی‏های سالانه، فصلی، و ماهانة پنج ایستگاه قدیمی ایران در یکصدوشانزده سال گذشته، بیابان، 9(1): 25 ـ 33.
فرج‌زاده اصل، م. و فیضی، و. (1391). آشکارسازی تغییرهای زمانی- مکانی عناصر دما و بارش در ایران، برنامه‏ریزی و آمایش فضا، 16(4): 49 ـ 66.
Abghari, H.; Tabari, H. and Hosseinzadeh Talaee, P. (2013). River flow trends in the west of Iran during the past 40 years:Impact of precipitation variability, Global and Planetary Change, 101: 52-60. .doi.org/10.1016/j.gloplacha.2012.12.003.
Bouza-Deano, R.; Ternero-Rodrıguez, M. and Ferna´ndez-Espinosa, A.J. (2008). Trend study and assessment of surface water quality in the Ebro River (Spain), Journal of Hydrology, 361: 227-239.
Chapi, K.; Ghaffari, G and Karimi, M. (2011). Assement of the climate change effects on spring precipitation trend in kourdistan province, 7the National Conference on Science and Watershed Management Engineering, Isfahan University of Technology.
Deluis, M.; Raventos, J.; Gonzalez-hidalgo, J.C.; Sanchez, J.R. and Cortina, J. (2000). Spatial analysis of rainfall trends in the region of Valencia (East Spain), International Journal of Climatology, 20: 1451-1469.
Delju, A.H.; Ceylan, A.; Piguet, E. and Rebetez, M. (2013). Observed climate variability and change in Urmia Lake Basin, Iran, Theoretical and Applied Climatology January, 111(1-2): 285-296.
Farajzadeh Asl, M.; and Feizi, V. (2012). Detection of Spatio-temporal changes in temperature and precipitation elements in Iran. Spatial Planning, 16(4):49-66.
Fathian, F.; Morid, S. and Kahya, E. (2014). Identification of trends in hydrological and climatic variables in Urmia Lake basin, Iran, Theoretical and Applied Climatology, DOI 10.1007/s00704-014-1120-4.
Hansel, S.; Petzold, S. and Matschullat, J. (2007). Precipitation trend analysis for Central Eastern Germany, Bioclimatology and Natural Hazards' International Scientific Conference, Poľana nad Detvou, Slovakia, ISBN 978-80-228-17-60-8.
Hojam, S.; Khoshkhou, I. and Shamsaldin Wendy, R. (2008). Analysis of seasonal and annual precipitation trend changes in some of the selective station in centeral basin of Iran using nonparametric method, Geography Research quarterly, 64: 157- 168.
Hosseinzadeh Talaee, P.; Tabari, H and Maroufi, S. (2009). Comparsion of parametric and non parametric methods in the assement of monthly, seasonal and annual precipitation trend in Gamasiab basin. 8the International Seminar on River Engineering, Shahid Chamran University of Ahvaz.
IPCC (2013). Summary for Policymakers, Climate Change 2013: The Physical Science Basis, Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. In: Stocker, T.F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S.K., Boschung, J., Nauels, A., Xia, Y., Bex, V. and Midgley, P.M.e. (Eds.).
Khalili, H. and Bazerfshan, J. (2004). Analysis of annual, seasonal and monthly rainfall trend of five old station of Iran in hundred and sixteen years ago, Desert, 9(1): 25-33.
Labat, D.; Godd_eris, Y.; Probst, JL. and Guyot, JL. (2004). Evidence for global runoff increase related to climate warming, Adv Water Resour, 27: 631-642.
Liu, B.; Xu, M.; Henderson, M. and Qi, Y. (2005). Observed trends of precipitation amount, frequency, and intensity in China, 1960-2000, Journal of Geophysical Research, 110: D08103. doi: 10.1029/ 2004JD004864.
Modarres, R. and Silva, V.P.R. (2007). Rainfall trends in arid and semi-arid regions of Iran, Journal of Arid Environments, 70: 344-355.
Onyutha, C.; Tabari, H.; Taye, M.T.; Nyandwaro, G.N. and Willems, P. (2015). Analyses of rainfall trends in the Nile River Basin, Journal of Hydro-environment Research, doi: 10.1016/j.jher.2015.09.002.
Partal, T. and Kahya, E. (2006). Trend analysis in Turkish precipitation data, Hydrological Processes, 20: 2011-2026.
Patra, J.P.; Mishra, A.; Singh, R. and Raghuwanshi, N.S. (2012). Detecting rainfall trends in twentieth century (1871-2006) over Orissa State, India, Climatic Change, 111(3): 801-817.
Raziei, T.; Daneshkar Arasteh, P. and Saghafian, B. (2005). Annual rainfall trend in arid and semi-arid region of Iran, In: ICID 21st European Regional Conference, 1-8.
Shifteh Some'e, B.; Ezani, A. and Tabari, H. (2012). Spatiotemporal trends and change point of precipitation in Iran, Atmospheric Research, 113: 1-12.
Tabari, H.; Shifteh Somee, B. and Rezaeian Zadeh, M. (2011). Testing for long-term trends in climatic variables in Iran, Atmospheric Research, 100: 132-140.
Tabari, H. and Hosseinzadeh Talaee, P. (2011). Temporal variability of precipitation over Iran: 1966–2005, Journal of Hydrology, 396: 313-320.
Tabari, H. and Aghajanloo, M-B. (2013). Temporal pattern of aridity index in Iran with considering precipitation and evapotranspiration trend, International Journal of Climatology, 33(2):396-409.
Tabari, H.; AghaKouchak, A. and Willems, P. (2014). A perturbation approach for assessing trends in precipitation extremes across Iran, Journal of Hydrology, 519: 1420-1427.
Tabari, H.; Taye, M.T. and Willems, P. (2015). Statistical assessment of precipitation trends in the upper Blue Nile River basin, Stochastic Environmental Research and Risk Assessment, 29(7):1751-1761.
Turkes, M. (1996). Spatial and temporal analysis of annual rainfall variations in Turkey, International Journal of Climatology, 16: 1057-1076.
Turkes, M. and Sumer, U.M. (2004). Spatial and temporal patterns of trends and variability in diurnal temperature ranges of Turkey, Theoretical and Applied Climatology, 77: 195-227
Yue, S. and Hashino, M. (2003). Long term trends of annual and monthly precipitation in Japan. Journal of American Water Resources Association, 39(3): 587-596.
Wahlin, K. and Grimvall, A. (2010). Roadmap for assessing regional trends in groundwater quality, Environmental Monitoring and Assessment, DOI 10.1007/s10661-009-0940-7.
Zhai, PM.; Zhang, XB.;Wan, H. and Pan, XH. (2005). Trends in total precipitation and frequency of daily precipitation extremes over China, Journal of Climate, 18: 1096-1108.
Zhang, Q.; Xu, C.Y.; Zhang, Z.; Chen, Y.D. and Liu, C.L. (2009). Spatial and temporal variability of precipitation over China, 1951–2005, Theoretical and Applied Climatology. Doi: 10.1007/s00704-007-0375-4.
Volume 48, Issue 4
January 2017
Pages 627-643
  • Receive Date: 14 April 2016
  • Revise Date: 17 July 2016
  • Accept Date: 11 August 2016
  • First Publish Date: 21 December 2016