نشریه علمی - پژوهشی مرتع و آبخیزداری

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استاد گروه مهندسی آبخیزداری، دانشکدۀ منابع طبیعی، دانشگاه تربیت مدرس، ایران.

2 دانشجوی دکتری علوم و مهندسی آبخیزداری، دانشکدۀ منابع طبیعی، دانشگاه تربیت مدرس، ایران.

3 دانشیار گروه مهندسی آبخیزداری، دانشکدۀ منابع طبیعی، دانشگاه تربیت مدرس، ایران.

چکیده

با توجه به نقش انکارناپذیر عامل فرسایندگی باران در شروع فرسایش آبی، مطالعه ویژگی‌های مختلف آن نقش مهمی در مدیریت بهینه منابع خاک و آب دارد. از طرفی عامل فرسایندگی باران در بسیاری از مدل‌های برآورد فرسایش و به‌منظور اهداف حفاظت خاک و آب استفاده می‌شود. حال آن‌که مطالعۀ کاملی در خصوص بررسی اثر طول و دورۀ آماری و هم‌چنین تعداد ایستگاه‌های مورد استفاده بر تغییرپذیری مقدار عامل فرسایندگی باران انجام نشده است. بنابراین پژوهش حاضر با هدف بررسی تغییرات زمانی عامل فرسایندگی باران در مقیاس‌های زمانی مختلف و نیز نقش طول، دورۀ آماری و تعداد ایستگاه‌ها بر مقدار عامل فرسایندگی  ویشمایر و اسمیت در هفتاد ایستگاه مطالعاتی با دورۀ مشترک آماری بیست سال در مقایسه با تحلیل‌های انجام شده در سطح کشور با هجده ایستگاه و دورۀ مشترک آماری بیست و سه سال و در دو دورۀ مطالعاتی متفاوت در ایران انجام شده است. بدین منظور مقدار عامل فرسایندگی بیش از دوازده هزار رگبار در پژوهش حاضر محاسبه و تغییرات زمانی آن در مقیاس‎های مختلف زمانی با استفاده از آزمون t مورد ارزیابی و تحلیل قرار گرفت. بر اساس نتایج به‌دست آمده، مقادیر حداکثر و حداقل فرسایندگی ماه‌ها و فصل‏ها در مطالعۀ حاضر و پیشین مشابهت نداشته است. هم‌چنین نتایج حاصل از آزمون t دلالت بر اختلاف معنی‌دار بین مقادیر عامل فرسایندگی باران در برخی ماه‌ها (05/0>p) و فصل‏ها (05/0>p) در پژوهش‌های مورد نظر داشته است. حال آن‌که اختلاف بین مقادیر فرسایندگی سالانه در پژوهش مورد نظر معنی‌دار (05/0<p) نبوده است.

کلیدواژه‌ها

عنوان مقاله [English]

Effect of Data Length, Study Span and Number of Stations on Amount of Rainfall Erosivity Factor Variability in Different Time Scales in Iran

نویسندگان [English]

  • Seyed Hamid Reza Sadeghi 1
  • Mohsen Zabihi 2
  • Mehdi Vafakh 3

2 Tarbiat Modares University

3 Tarbiat Modares University

چکیده [English]

Regarding the undeniable role of rainfall erositivity factor in initiating water erosion, studying its different aspects is important in optimal soil and water resources management. It is taken in to account in many soil erosion estimation models which are used for soil and water conservation. However, the impact of data length, study span, and the number of stations on variability of rainfall erosivity factor has been understudied. The present study therefore is an attempt to investigate the temporal variation of Wischmeier and Smith’s rainfall erosivity factor at different time scales and also the effect of data length, study span, and number of stations upon rainfall erosivity factor is scrutinized. Accordingly, the results of the present study with 70 stations, data span of 20 years and different study periods were compared with those obtained for another study with 18 stations and 23 years of data span. Rainfall erosivity factor of over 12,000 storm events was calculated in present study and mean values for different time scales were compared using t-Test. Results showed that the maximum and the minimum values of monthly rainfall erosivity factor in the country were different from each other. Besides, the results of t-Test showed significant difference between the calculated values of rainfall erosivity factor in some months (p<0.05) and seasons (p<0.05). Nonetheless, the difference between annual rainfall erosivity factor was not significant (p<0.05).

کلیدواژه‌ها [English]

  • EI30
  • R factor
  • Rain intensity
  • Rainfall kinetic energy
  • Temporal variation
  • Time scales
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