نوع مقاله : پژوهشی
نویسندگان
1 استادیارگروه جغرافیای طبیعی، دانشگاه تهران، تهران، ایران
2 دانشجوی دکتری ژئومورفولوژی، دانشگاه تهران، ایران
چکیده
چکیده
دریاچهی ارومیه در شمال غرب ایران طی دهه های اخیر با یک خشکی تدریجی مواجه شده است. این مسئله باعث افزایش سطح زمین های شوره زار و به‌تبع آن مشکلات اجتماعی-محیط زیستی فراوانی شده است. پایش مناطق ساحلی و استخراج تغییرات این مناطق در فاصله های زمانی مختلف دارای اهمیت زیادی است؛ زیرا ماهیت خطوط ساحلی دینامیکی است و مدیریت چنین محیط های بوم شناختی حساسی، به کسب اطلاعات دقیق در فاصله های زمانی مختلف نیاز دارد. هدف از انجام این تحقیق، بررسی گسترش نمکزارهای شمال غربی دریاچه ی ارومیه با استفاده از داده های میدانی، تصاویر ماهوارهای لندست (MSS, TM, ETM+, OLI) و رخساره های ژئومورفیک منطقه است. برای انجام این تحقیق، نمونه هایی از رسوب دریاچه به صورت سطحی (عمق 0 تا 15 سانتی متر) در ترانسکت های مختلف از یک محدوده ی مشخص در شمال غربی دریاچه برداشت شد. در مرحله ی بعد با استفاده از تصاویر ماهوارهای و پیمایش میدانی، میزان شوری، گسترش نمکزارها و رخساره‌های ژئومورفیک استخراج گردید. در نهایت نتایج داده‌های میدانی و آزمایشگاهی، تصاویر ماهوارهای و همچنین رخساره های ژئومورفیک مقایسه و اعتبارسنجی شد. نتایج نشان داد مساحت سطح آب دریاچه بسیار کاهش یافته و در مقابل نمکزارها در سطح وسیعی گسترش یافـته اند و مناطقی که دارای تراکم نـمک بالاتری میباشند با خطوط نمکزار به دست آمده از تصاویر ماهوارهای و رخساره‌های ژئومورفیک مطابقت میکنند. بر اساس نقشه‌ی رخساره‌ها، محدوده‌ی مورد مطالعه دارای ۱۲ رخساره است که زمین‌های شوره‌زار با مساحت 1724 هکتار، از نظر وسعت در بین رخساره‌های محدوده، سومین رخساره میباشند؛ منطقه برداشت با مساحت 2641 هکتار و پهنه های ماسه‌ای به مساحت ۱۴ هکتار، به ترتیب دارای بیشترین و کمترین وسعت رخنمون رخساره در منطقه مورد بررسی میباشند.
تازه های تحقیق
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کلیدواژه‌ها
عنوان مقاله [English]
The Comparison and Analysis of the Expansion of Salt Lands of Lake Urmia Using the Field Data, Satellite Imagery and Geomorphic Faces of the Region
نویسندگان [English]
- Shirin Mohammad Khan 1
- Fatemeh Moradi Pour 2
- Anvar Moradi 2
1 Assistant Prof of Natural Geography, University of Tehran, Tehran, Iran, (Corresponding author), E-mail:mohamadkh@ut.ac.ir
2 Ph.D Candidate of Geomorphology, University of Tehran, Tehran, Iran
چکیده [English]
Introduction
Lake Urmia in the northwest of Iran has faced a steady decline over recent decades. This has led to an increase in the level of dry lands and, consequently, has caused many environmental and social problems.There are many ecological effects on the biodiversity and growth of Artemia, the Zooplankton, a native of Lake Urmia and major source of food for large birds. Consequently, the monitoring of coastal areas and the extract of changes in these areas in different time intervals have great importance because the nature of the coastline is dynamic. For this purpose, the remote sensing technology has a unique application in the acquisition of information about these phenomena because multi-spectral satellite images have advantages including their availability and digital interpretation.The purpose of this research was to investigate the development of the North West salt land in Lake Urmia using field data, satellite imagery, and geomorphic faces of the region.
Methodology
This research was an applied type and the data was collected through library, laboratory, and field studies. The statistical population was the water Retreat Zone of Lake Urmia Which suffered from wind erosion. This research was carried out using satellite imagery and multiple observations. Also, test sediments were obtained from this area using standard methods. Using remote sensing technology, when combined with land surveys and ground-based results, can provide better and more reliable results. For this purpose, in the present research, along with the use of remote sensing methods, field studies were also used. To carry out this research, samples of lake sediment were taken in different transects from a specific area in the northwest of the lake. The saturated extract of each sample was measured by EC meter. In the next step, using satellite imagery and field survey, the salinity, the expansion of salty and geomorphic faces were extracted. Finally, the results of the field and laboratory data, satellite imagery and geomorphic faces were compared and validated.
Results
The results showed that the surface area of the lake water was very low and spread to vast amounts of salt. Accordingly, the area of the salt land has significantly increased since 2000, especially over the past decade. According to the results of the field studies, areas with higher salt density matched the salt lines obtained from satellite imagery and geomorphic faces. The study area had 12 faces. The harvest area with a total area of 2,641 ha in the central part of the range and sandy areas with a total area of 14 ha in the northwestern part of the area had respectively the highest and lowest extent of outcrops in the studied area. Consequently, there was a close correlation between the field data and satellite imagery and salt land areas in satellite imagery and results of field studies. Due to the increase of the salinity levels in the area around the lake, local winds, and time lapse, the Agrarian lands of Azerbaijan general zone moved towards salinization and desertification. If this trend continues at the same speed, undoubtedly, in the long run, we have to wait for the enormous environmental crisis in the region.
Discussion and conclusion
The strongest indicator to extract the salt is the SI2 indicator with an accuracy of 97% and the weakest indicator is NDSI indicator with a precision of 52%. The EC value in 22 soil samples ranging from 0.9 to 78.37 indicates the high salinity variability in the region. There is the highest correlation with visible bands and infrared bands 1, 2, 3, and 4, which indicates that the saline soils in the visible and infrared areas have a higher reflection. Between 2006-2015, the range of salt land has been expanded. Altogether, with the decreasing trend of the size of Lake Urmia, in 1976 regular domain faces, in 1985 sediment removal, in 1990 harvested area, in 2000 wet area, harvested area, and salt deposits, in 2006 bar salt and salt zone, and between 2011 and 2015 salt zone were formed and expanded.
کلیدواژه‌ها [English]
- Keywords: Salinity of Soil
- Geomorphic faces
- Landsat satellite imagery
- Correlation
- Lake Urmia
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