تدقیق برآورد فرسایش آبی در ایران

نوع مقاله : پژوهشی

نویسندگان

1 عضو هیأت‌علمی پژوهشکده‌ی حفاظت خاک و آبخیزداری، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران

2 عضو هیأت‌علمی پژوهشکده‌ی حفاظت خاک و آبخیزداری، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران

3 باشگاه پژوهشگران جوان و نخبگان، واحد علوم و تحقیقات، دانشگاه آزاد اسلامی، تهران، ایران

چکیده

مقدار فرسایش آبی خاک کشور، براساس نقشه‌ی شدت فرسایش تهیه‌شده در پژوهشکده‌ی حفاظت خاک و آبخیزداری با کاربرد روش توان فرسایش ‌(EPM)، 976 میلیون تن در سال برآورد شده است. این نقشه از نظر شناسایی مناطق حساس‌‌‌تر به فرسایش در هر منطقه، مناسب است، ولی مقادیر برآوردی مدل، نیاز به واسنجی با مقادیر مشاهده‌‌‌ای را دارد که براساس آمار رسوب 276 آبخیز کشور انجام شده است. کمینه و بیشینه‌ی ‌رسوب‌دهی سالانه‌ی مشاهده‌‌‌ای، به‌ترتیب 4 و 5591، و رسوب‌دهی سالانه‌ی برآوردی با مدل، به‌ترتیب 31 و 2946 تن در کیلومترمربع ‌به‌دست آمد. نسبت اصلاحی در هشت منطقه‌ی همگن، با تقسیم میانه‌ی مقادیر متناظر رسوب مشاهده‌‌‌ای به برآوردی، از 57/0 تا 43/1 محاسبه شد. با اعمال ضریب اصلاحی، مقادیر فرسایش سالانه به تفکیک مناطق همگن محاسبه شد که بیشترین و کمترین میانه به ترتیب با 1063 و 130 تن در کیلومترمربع، به آبخیزهای دریای عمان (منطقه‌ی 8) و کویرها (منطقه‌ی 6) تعلق دارد. مقدار فرسایش سالانه‌ی کشور، 895 میلیون تن (معادل 5/5 تن در هکتار در سال) برآورد شد که بیشترین و کمترین سهم به‌ترتیب به منطقه‌ی 8 (33%) و منطقه‌ی 1 یا ساحلی خزر (5/2%) مربوط است؛ همچنین، ملاحظه شد که ‌برخلاف انتظار، رسوب‌دهی ویژه‌ی مشاهده‌‌‌ای با افزایش مساحت، اضافه می‌‌‌شود که دلایل احتمالی آن در متن ارائه شده است.

کلیدواژه‌ها

عنوان مقاله [English]

Improving Water Erosion Estimates for Iran

نویسندگان [English]

  • Mahmood Arabkhedri 1
  • Samad Shadfar 1
  • Ali Jafari-Ardakani 1
  • Reza Bayat 2
  • Elias Khajavi 3
  • Mohammad Hossein Mahdian 1
1 Soil Conservation and Watershed Management Research Institute, Agriculture Research, Education and Extension Organization, Tehran, Iran
2 Soil Conservation and Watershed Management Research Institute, Agriculture Research, Education and Extension Organization, Tehran, Iran
3 Young Researchers and Elites Club, Science and Research Branch, Islamic Azad University, Tehran, Iran
چکیده [English]

The amount of country's water erosion is estimated at a rate of 976 million t.yr-1 by Erosion Potential Method (EPM) based on the national erosion map prepared at the Soil Conservation and Watershed Management Research Institute. This map is suitable for identifying the most sensitive areas to erosion in each region, but the estimated values ​​of the model need calibration, which was estimated ​​based onthe observed sediment yield data of 276 watersheds. The minimum and maximum annual observed sediment yields were 4 and 5591t.km-2, and estimated by the model was 31 and 2946 t.km-2, respectively. Correction ratio in the eight homogeneous regions was between 0.57 to 1.43 by dividing the median of the observed sediment yields to the corresponding ​​estimates in the studied watersheds. These ratios then were used to improve the erosion values ​​for homogeneous regions between 1063 and 130 t.km-2.yr-1, belonging to the Oman Sea (Region 8) and the internal desert (Region 6) basins, respectively. The annual erosion of the country was estimated to be million 895 t.yr-1. The(5.5 t.ha-1.yr-1), with the highest and lowest contribution, respectively to the Region 8 (33%) and the Region 1 or Caspian Sea coastal basins (2.5%). It was also found that the observed specific sediment yield had a positive correlation  with an increasing area unlike the expectation, with its probable reasons have been explained in the paper.

کلیدواژه‌ها [English]

  • erosion
  • EPM
  • homogeneous regions
  • sediment yield

مراجع

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سابقه مقاله

  • تاریخ دریافت: 27 فروردین 1397
  • تاریخ بازنگری: 14 خرداد 1397
  • تاریخ پذیرش: 27 مرداد 1397

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