بررسی روند تغییرات بارش و دبی در حوضه آبریز دریاچه اورمیه در طول چهار دهه اخیر

نوع مقاله: مقاله پژوهشی

چکیده

حوضه دریاچه اورمیه به دلیل اهمیت اقلیمی، اقتصادی، اکولوژیک و زیست محیطی یکی حوضه­های مهم در شمال­غرب ایران به­شمار می­رود. در این مطالعه به منظور بررسی علل افت سطح آب دریاچه، روند دو عامل دخیل در تغذیه آن، شامل بارش و دبی رودخانه­ها مورد مطالعه قرار گرفت. برای این منظور، داده­های مربوط به ایستگاه­های باران­سنجی و هیدرومتری در سرتاسر حوضه در مقیاس فصلی و سالانه جمع آوری گردید. سری زمانی طولانی مدت متغیرها تهیه شد و روند زمانی آنها با استفاده از آزمون من­کندال و کندال فصلی بررسی شد. نتایج نشان داد متغیر بارندگی سالانه در برخی نقاط روند افزایشی و در برخی روند کاهشی دارد اگرچه از نظر آماری روندهای مشاهده شده در اغلب ایستگاهها معنی­دار نیستند. علیرغم عدم وجود نشانه­هایی از روند کاهشی یکنواخت بارندگی سالانه، در بیشتر ایستگاه­های هیدرومتری متغیر دبی سالانه در سطح معنی­داری 5 درصد روند کاهشی دارد. بنابراین، به­طور آماری نمی­توان افت چشمگیر آبدهی رودخانه­های منتهی به دریاچه و در نتیجه افت سطح آب دریاچه را به کاهش مقدار بارندگی آن نسبت داد. در نتیجه عوامل دیگری از جمله افزایش روند تبخیر- تعرق ناشی از گرمایش اتمسفر، برداشت بی­رویه از آب­های زیرزمینی، تغییر کاربری اراضی و یا حتی ذخیره آب در مخازن سدها و کاهش جریان­های ورودی به مخزن دریاچه ممکن است باعث افت سطح آب دریاچه شده­اند که نیازمند تحقیقات بیشتر است

کلیدواژه‌ها


عنوان مقاله [English]

Study of Trends in Precipitation and Stream Flow of the Lake Urmia Basin During the Past Four Decades

چکیده [English]

The Lake Urmia basin in North West of Iran is one of the important basins of this country due to its climatological, economical, ecological and environmental condition. In this study in order to discover the likely causes of the lake shrinkage, trends of the two effective factors on its inflows (precipitation and rivers discharge), were investigated. For this purpose, rain gauges and hydrometric stations data at seasonal and annual scale across the basin were collected. Long time-series of variables were prepared and their trends were analyzed using the Mann-Kendall and seasonal Kendall test. According to the results although annual precipitation indicated decreasing or increasing trends at some stations, but most of them were not significant at 0.05 probability level. Despite lack of significant, decreasing trend for annual precipitation across the basin, the majority of hydrometric stations showed significant decreasing trend in the annual stream flow data at 0.05 probability level. Therefore, from statistical point of view, the significant decline at annual discharge of the streams draining into the lake and the shrinkage of the lake cannot be attributed to decline at annual precipitation. Therefore, some other causes such as increase in evapotranspiration due to atmospheric warm-up. Over-extraction of aquifers, extensive landuse changes, impoundment of water behind numerous dams and decline at the lake inflows might be effective on the Lake Urmia shrinkage.

کلیدواژه‌ها [English]

  • Discharge
  • Hydro climate
  • Mann Kendall
  • Non-Parametric
  • Urmia lake
anonymous, 2015. Annual Australian Climate Statement 2015. http://www.bom.gov.au/ announcements media-releases climate change.
CarbajalLR, Pellicciotti Fand Molnar P. 1993. Analysis of Hydro-climatic Trends in theAconcagua River Basin, central Chile. Institute of Environmental Engineering, Ethz Zurich, CH-8093, Switzerland.
Fathian F, Morid S and Kahya E, 2015. Identification of trend in hydrological and climatic variables in Urmia lake basin, Iran. Theoretical and Applied Climatology 119(3-4): 443-464.
Fujihara Y, Tanaka K, Watanabe T, Nagano T and Kojiri T 2008. Assessing the impacts of climate change on the water resources of the Seyhan River Basin in Turkey. Water Resources Management 21(3):533–556
Ghezel Seflo M, Dinpashoh Y, Ghorbani M and Fakheri Far A, 2011. Analysis of rivers flow time trend in East Azarbaijan province. Journal of Irrigation Science and Engineering 35(4):59-73. (In Persian)
Jones R, McMahon TA and Bowler JM, 2001. Modeling historical lakes levels and recent climate change at three lakes Western Victoria Australia. Journal of Hydrology 246: 159-180.
Kelt K and Sharabi M, 1986. Holocene sedimentology of hypersaline Lake Urmia northwestern Iran. Paleography Journal 54: 105-130.
Kendall MG, 1975. Rank Correlation Methods. Griffinco, London.
Lak R, Mohamadi A and Darvish Khatoni J, 2011. Cases of decreasing of the Urmia Lake level paleolymology studies.  Journal of Geotechnical Geology 4:243-258.
Mann HB, 1945. Nonparametric tests against trend. Econometrical 13: 245–259.
Mirabbasi Najafabadi R and Dinpashoh Y, 2010. Trend analysis of streamflow across the North West of Iran in recent three decades. Journal of Water and Soil 24(4): 758-768. (In Persian)
Mitchell JM, Dzerdzeevskii B, Flohn H, Hoftneyer WL, Lamb HH, Rao KN and Wallen CC, 1966. Climatic Change WMO Technical. World Meteorological Organization No. 79.
Neff BP and Nicholas JR, 2005. Uncertainty in the Great Lakes water balance. Scientific Investigation Report 2004-5100 US Geological Survey Lansing Ml No. 42.
Nik Ghojagh Y and Yarmohamadi M, 2008. Assessment climate change and survey its impacts on flow streams resources in Ziarat of Golestan Province. 3rd Iran Water Resources Management Conference Tabriz University. (In Persian)
Salehi Pour Milani A, Darvish Khatoni J and Mohamadi A, 2011. Survey of Fluctuations level of Urmia Lake from 1976 to 2011. Geological Organization. (In Persian)
Shahrokhvandy SM, Lashtivand M and khakpuor M, 2008. Hydrological drought investigation and its relationship with precipitation in Khoram Abad River Basin. Water and Soil Science – University of Tabriz 27(2): 1-15. (In Persian)
Sheikh V and bahrehmand A, 2009. Investigation of the hydrological processes in the Atrak Basin. Report of research project. Gorgan University of Agriculture & Natural Reassure Science.  (In Persian)
Sheikh V, Bahrehmand A, Moshakhian Y, 2011. Comparison of hydrological variable trend by non-parametric test in the Atrak Basin. Journal of Soil & Water Conservation. 18(2): 1-21. (In Persian)
Vincent-Serrano SM, and Lopez-Moreno JI, 2005. Hydrological response to different time scales of climatological drought: an evaluation of the Standardized Precipitation Index in a mountainous Mediterranean basin. Hydrology and Earth System Sciences 9: 523-533.
Werritty A, 2002. Living with uncertainty: Climate change river flows and water resource management in Scotland. The Science of the Total Environment 1-3:29-40.
Wu K and Johnston CA, 2007. Hydrological response to climatic variability in the Great Lakes watershed: a case study with the SWAT model. Journal of Hydrology 337: 187-199.
Xu CY, 2000. Modelling the effects of climate change on water resources in Central Sweden. Water Resources Management 14:177-189.
Yar ahmadi D, 2014.   Hydro climatology analysis of water level fluctuations in Urmia Lake. Physical Geography Research Quarterly 46(1): 13-25. (In Persian)