برآورد و مقایسه تغییرات فرسایش خاک ناشی از اتلاف پوشش گیاهی در زیر حوضه‌های شرقی آبخیز دریاچه ارومیه

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشیار، گروه پژوهشی ارزیابی و مخاطرات محیط زیستی، پژوهشکده محیطزیست و توسعه پایدار، سازمان حفاظت محیطزیست، تهران، ایران

2 استادیار، گروه پژوهشی اقتصاد محیطزیست، پژوهشکده محیطزیست و توسعه پایدار، سازمان حفاظت محیطزیست، تهران، ایران

3 استادیار، گروه مطالعات محیطی ، پژوهشکده تحقیق و توسعه علوم انسانی (سمت) ، تهران ، ایران

4 استادیار، گروه پژوهشی تنوع زیستی و ایمنی زیستی، پژوهشکده محیطزیست و توسعه پایدار، سازمان حفاظت محیطزیست، تهران، ایران

چکیده

فرسایش خاک و رسوب‌گذاری در آبخیز در صورت تشدید می‌توانند پیامدهای محیط زیستی سنگینی به همراه داشته باشند. هدف این تحقیق معرفی یک روش مدل‌سازی با کاربرد در برآورد میزان تغییرات در فرسایش خاک در طول زمان و ارزیابی اثر پوشش گیاهی بر فرسایش در محدوده‌های بحرانی است. در این تحقیق برای مدل‌سازی هم‌زمان تغییرات پوشش گیاهی و فرسایش خاک از مدل سامانه پشتیبان سیاست‌گذاری جهانی آب (WWPSS)، استفاده شد. برای ارزیابی تغییرات پوشش گیاهی در بازه زمانی 2020-2000 از داده‌های پایگاه داده‌های مدل که از تصاویر ماهواره‌ای MODIS VCF اخذ می‌گردد، استفاده شد. همچنین برای سنجش مقدار و تغییرات در فرسایش خالص خاک (فرسایش منهای رسوبگذاری در همان محل) در دو وضعیت پایه و جاری (قبل و بعد از کاهش پوشش گیاهی)، از نقشه‌ها و محاسبات حاصل از اجرای مدل بهره گرفته شد.

بر اساس یافته‌های این تحقیق، میانگین درصد پوشش علفی- مرتعی حوضه مورد مطالعه در بازه زمانی مورد نظر، از 36/78% در شرایط پایه (سال 2000) به حدود 47% در شرایط موجود کاهش یافته است. مقدار میانگین فرسایش خالص خاک در دو زیر حوضه آجی چای و مردوق چای به ترتیب بیش از 277% و 33% افزایش یافته است که این دو زیرحوضه را در میان چهار زیرحوضه مورد مطالعه به‌عنوان محدوده‌های بحرانی فرسایش خاک تعیین می‌نماید. درمجموع همان‌گونه که انتظار می‌رفت، اتلاف 40 درصدی پوشش گیاهی در محدوده مورد مطالعه، پیامدهای مخاطره‌آمیزی را طی دوره زمانی موردبررسی بجای گذاشته است و به‌صورت تجمعی منجر به تخریب بیش از 8 میلیون تن خاک طی 15 سال شده است. روش به کار گرفته شده در این تحقیق می تواند با کاربرد در ارزیابی های کمّی و سریع محیط زیستی که نیازمند تعیین کمیت های دقیق تری از پیامد های محیط زیستی مانند فرسایش خاک هستند، مفید واقع گردد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Estimating and Comparing Changes in Soil Erosion due to Vegetation Loss in the Eastern Sub-watersheds of the Lake of Urmia

نویسندگان [English]

  • Ardavan Zarandian 1
  • Roya Mousazadeh 2
  • Majid Ramezani Mehrian 3
  • Seyed Ghasem Ghorbanzadeh Zaferani 4
1 Associate Professor, Research Group of Environmental Assessment and Risk, Research Center for Environment and Sustainable Development (RCESD), Department of Environment, Tehran, I.R. Iran.
2 Assistant Professor, Research Group of Environmental Economics, Research Center for Environment and Sustainable Development (RCESD) , Department of Environment, Tehran, I.R. Iran
3 Assistant Professor, Department of Environmental Studies, The Institute for Research and Development in the Humanities (SAMT), Tehran, I.R. Iran.
4 Assistant Professor, Research Group of Biodiversity & Biosafety, Research Center for Environment and Sustainable Development (RCESD), Department of Environment, Tehran, I.R. Iran.
چکیده [English]

 
Heavy soil erosion and sedimentation at the watershed level can trigger intense environmental consequences. This research proposes a modeling technique to estimate changes in incremental soil erosion over time and evaluate the effect of vegetation cover on soil erosion in critical areas. For this, the study employed the Water World Policy Support System (WWPSS) for simultaneous modeling of changes in vegetation cover and soil erosion. Changes in vegetation cover from 2000 to 2020 were studied by extracting data from the model databases received from MODIS VCF satellite images. The study further used maps and calculations of the run model to measure the amount of net soil erosion (erosion minus sedimentation in the same place) and subsequent change in its level under two baseline (before loss of vegetation cover) and current (post-vegetation loss) situations. It was found that the average percentage of grass-pasture cover in the studied watershed has declined from 78.36% (under the baseline situation in 2000) to about 47% (under the current situation). The average amount of net soil erosion in the two sub-watersheds of Aji Chai and Marduq Chai has increased by more than 277% and 33%, respectively, signifying them to be the most vulnerable sub-watersheds (among all the four studied sub-watersheds) to soil erosion at critical areas. Overall as expected, a 40% loss of vegetation in the studied watershed has provoked adversely hazardous consequences during the studied period while cumulatively leading to over 8 million tons of soil deterioration in 15 years. The proposed method is assumed to be advantageous by providing quantitative and rapid environmental assessments that entail precise quantification of environmental consequences like soil erosion.

کلیدواژه‌ها [English]

  • Vegetation
  • Soil Erosion
  • Modeling
  • WWPSS Model
  • East Lake Urmia Watershed
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