تأثیر اقدام‌های آبخیزداری بر خصوصیات جریان و مواد معلق در حوزه‌ی آبخیز فشند، هشتگرد

نوع مقاله : پژوهشی

نویسندگان

1 دانشجوی دکترای آبخیزداری، دانشکده منابع طبیعی، دانشگاه تهران

2 استاد دانشکده منابع طبیعی، دانشگاه تهران

3 کارشناس ارشد آبخیزداری، کارمند اداره منابع طبیعی شهرستان ساوجبلاغ

چکیده

اقدام­ های آبخیزداری شامل روش­هایی برای ایجاد، افزایش و حفظ پوشش گیاهی، برای کاهش روان‌آب، ‌مهارکردن سیل و کاهش فرسایش و غلظت رسوب در حوزه‌ی آبخیز است. عملیات اجرایی آبخیزداری در حوزه‌ی آبخیز فشند هشتگرد از 1375 تا 1377 با هدف تأخیر در بروز سیل انجام شده است که باعث افزایش زمان تمرکز، تخلیه‌ی تدریجی روان‌آب، تزریق و کاهش ‌زیان‌ها در زیر­حوزه­های تغذیه­کننده می‌شود. در این مطالعه، برای ارزیابی اثرهای اقدام‌های انجام‌شده در منطقه از تحلیل اثرهای کیفیت آب، منحنی جرم مضاعف و ‌مواد معلق استفاده شد. نتایج نشان­ دهنده تأثیر مثبت اقدام­های آبخیزداری است. به‌طوری که با انجام اقدام­های آبخیزداری نسبت کلسیم به منیزیم افزایش، و غلظت رسوب خروجی از حوزه آبخیز کاهش چشم‌گیری داشته است. شیب خط منحنی جرم مضاعف بارندگی-روان‌آب از0/3336  به 0/2033، و 60 % کاهش پیدا کرده، و میزان بار معلق از 1480 تن در سال به 317 تن در سال، و به میزان 4/66 برابر کاهش یافته است. پرشدن‌ سراب اکثر سازه‌های آبخیزداری سنگی­ملاتی، تورسنگ و سنگی نیز مؤید این مطلب است که سازه­های آبخیزداری، به­خصوص در دوره­ی اول بعد از اقدام‌های آبخیزداری، یعنی از سال تاسیس تا سال 1382 نقش خود را ‌به‌خوبی در منطقه ایفا نموده، و میزان روان‌آب و بار ‌معلق خروجی ‌را از حوزه‌ی آبخیز به میزان زیادی کاهش داده‌ا‌ند.

کلیدواژه‌ها


عنوان مقاله [English]

The Impact of Watershed Rehabilitation Measures on the Flow and Sediment Characteristics of the Fashand Catchment, Hashtgerd

نویسندگان [English]

  • Teimur Teimurian 1
  • Sadat Feiznia 2
  • Seyyed Davod Seyyedalikhani 3
1 Ph.D. student, Watershed Management, Faculty of Natural Resources, University of Tehran
2 Full Professor, Faculty of Natural Resources, University of Tehran
3 Master of Watershed Management, Department of Natural Resources, Savejbolag
چکیده [English]

Watershed management measures are ways and means to restore, enhance and maintain vegetative cover in order to reduce runoff, control flood and reduce erosion and sediment concentration in the watershed. Soil and water conservation structures (SWCS) were installed on the Fashand Catchment, Hashtgerd during the 1996–1998 period with the aim of delaying the onset of flooding, increasing the time of concentration, decreasing the runoff discharge, recharging groundwater and reducing damage on the sub-basins. The study was designed to evaluate the effects of those structures not only on the outflow of the basin, but also on the water quality. To this end the double mass analysis was performed. The results indicated the positive impact of the SWCS. The ratio of calcium to magnesium had increased, and the sediment concentration of the basin discharge had dramatically decreased. The slope of the double-mass curve of rainfall-runoff had decreased from 0.3336 to 0.2033, i.e. by 60 percent; the mean annual suspended load had decreased from 1480 tons to 317 tons, a 4.66 fold reduction. The SWCS had effectively trapped the bed and suspended loads up to 2003, when their upstream reservoirs were overflowed with sediment.

کلیدواژه‌ها [English]

  • double- mass curve
  • Fashand Catchment
  • suspended load
  • watershed measures
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