نوع مقاله : مقاله پژوهشی

نویسندگان

• حشمت اله آقارضی ¹
• علی اکبر داوودی راد ¹
• مهدی مردیان ²
• رضا بیات ³

¹ مرکز تحقیقات کشاورزی و منابع طبیعی استان مرکزی

² دانشجوی دکتری آبخیزداری دانشگاه علوم کشاورزی و منابع طبیعی ساری، ایران*

³ پژوهشکده حفاظت خاک و آبخیزداری

چکیده

چکیده
فرسایش خاک در حوزه­های آبخیز باعث تضعیف پوشش اراضی و کاهش کمیت و کیفیت منابع آبی می­شود. بنابراین ضرورت دارد که با شناسایی منابع تولید رسوب در مقیاس سطحی (دامنه) و خطی (آبراهه و رودخانه)، نوع و حجم عملیات آبخیزداری اصلاحی- تکمیلی به منظور کاهش فرسایش و رسوب­دهی در مکان­های بحران­زا مشخص شود. هدف از تحقیق حاضر نیز ارزیابی توزیع مکانی برنامه­های آبخیزداری اجرایی سال­های 74-1371 در حوزه آبخیز هفتان تفرش به منظور ارائه الگوی اصلاحی- تکمیلی این برنامه­ها است. بدین منظور امتیاز عامل­های مدل تجربی MPSIAC به کمک GIS برای شرایط قبل و بعد از عملیات آبخیزداری تعیین شد. سپس با مقایسه تغییر امتیاز عامل­ها، اثرگذارترین برنامه­های آبخیزداری مشخص گردید. همچنین با مقایسه تغییر مساحت کلاس­های درجه رسوب­دهی، ارزیابی از توزیع مکانی عملیات آبخیزداری انجام شد تا با تعیین نقاط ضعف پروژه، عملیات اصلاحی- تکمیلی پیشنهاد شود. نتایج تحقیق نشان داد امتیاز عامل فرسایش رودخانه­ای با 8/30 درصد، بیشترین تأثیر را در کاهش 1/4 درصدی رسوب­دهی داشته است. همچنین از مساحت کلاس درجه رسوب­دهی 75-50، مقدار 4/8 درصد کم شده است که عمدتاً این شدت رسوبدهی مربوط به اراضی بالادست حوضه است. با توجه به معنی­دار بودن تغییرات رسوب­دهی زیرحوضه­ها در سطح 05/0، نتایج حاکی از کارا بودن برنامه­های آبخیزداری در کاهش رسوب­دهی است. به منظور مدیریت منابع آب و خاک و اثرگذاری بیشتر برنامه های آبخیزداری در کاهش فرسایش و رسوب حوزه آبخیز هفتان، الگوی اصلاحی- تکمیلی برنامه­ها شامل بانکت توأم با بادامکاری در دامنه­های بحرانی، بذرپاشی و کپه کاری در    دامنه­های با شیب تند و عمق کم خاک، تقویت پوشش گیاهی دامنه­های مارنی و همچنین پایدارسازی کناره رودخانه­ پیشنهاد می­شود.
 

کلیدواژه‌ها

• واژه‌های کلیدی: برنامه­های حفاظت خاک
• ارزیابی توزیع مکانی
• کاهش رسوب­دهی
• MPSIAC
• حوزه آبخیز هفتان

عنوان مقاله [English]

Preparation a corrective- Supplementary Pattern of Watershed Management Programs to Sediment Rate reduce in the Haftan Watershed, Tafresh

نویسندگان [English]

• heshmatollah agharazai ¹
• ali akbar dadoodirad ¹
• mehdi mardian ²
• reza bayat ³

¹ Agricultural and Natural Resources Research Center of Markazi Province

² Ph.D. Watershed University of Agricultural Sciences and Natural Resources, Sari, Iran *

³ Soil Conservation and Watershed Management Institute

چکیده [English]

 
Extended Abstract
1-Introduction
Soil erosion is a major environmental problem that has devastating effects on natural and ecosystem. Although soil erosion has existed throughout history, but in recent years has intensified related to inappropriate land use. So, due to the damages caused by the increase of deposition in rivers, watershed management planning in area scale (slope) and linear (channel) to reduce the soil erosion are applicable. Also the project evaluation for before, during and after the implementation, according to the project objectives and environmental effects on watershed and its outside to verify the effectiveness of watershed management programs is essential.
The more researchers aim is the investigation of effects watershed management measures to reduce erosion and sedimentation and flooding potential in output of watersheds. However assessment of spatial distribution programs in most of these studies has been ignored. With attention to high cost in watershed management planning, these measured planning must be on based priority of critical areas of erosion rates. Identify and priority, while will provide a correction- supplementary pattern of watershed management programs, lead to cost management and also projects efficiency increasing in related to stakeholders welfare.
2- Methodology
In this study for a more investigation of spatial distribution the watershed programs, was selected the Haftan watershed, because the diversity of measures in slope and channels and also age 18 years of the project. Haftan watershed with 40.67 km² is located in the Markazi province, Tafresh city that has annual average precipitation equal to 304 mm and temperature with 10.6 C˚.
For the estimation erosion and sediment the before of watershed practices, was used MPSIAC model. In this research, nine factors the model was scored in ArcGIS 10 software. Then with overlay of nine layers, was prepared sediment rate map by calculating the sediment degree of each pixel. For after of watershed practices, with field survey, GPS and technical issues reports, the condition of vegetation and erosion were reviewed. Then factors of land use, land cover, runoff, and surface and channel erosion were updated. So erosion and sediment were estimated on based updated distribution maps after of watershed practices. In finally, with comparing the difference percent of sediment degree for before and after conditions using paired T-test in SPSS software was assessment the spatial distribution of watershed management measures.
3– Discussion
The results showed that land cover and land use have been the least variability with 1.1 and 1.8 percent, respectively. However the most variability is for channel erosion factor with 30.8 percent. These results are entirely consistent with the type and volume of practices in the Haftan watershed. So that biomechanical programs affecting on slope, has been implemented only in 101 hectares; but check dams are large numbers in the streams.
According to results, sediment rate degree is focused in classes of 25-50 and 50-75. After of watershed practices, the area class 50-75 is decreased equal to 8.4 percent. Also sediment variability in sub-watersheds is 0.7 to 8.7 percent that with attention to T-test statistical method, difference for before and after practices is significant. Although the results showed that watershed protection programs in slope scale of type almonds- contoured traces has high performance, but the volume it is low. So sediment decreasing is only 4.1 percent for whole the watershed.
4– Conclusion
Since biomechanical programs properly were implemented in slopes within sediment rate of class 50-75, but only 3.6 percent of area is covered. Therefore it is necessary that the cover protection program such as seeding and almost planting will become in the more area of class 50-75.
Because the most area of Haftan watershed is Eocene volcanic units with resistive category of medium, it is necessary to implement of biomechanical project that slopes with high potential of erosion and sediment. Therefore other slopes will be under biological practices that has lower cost.
With attention to high potential of erosion in marl unit, conservation practices in this zone must be on based management and biological practices. Due to the impact of 30.8 percent channel erosion factor, the protection and repair check dams is essential. Biological practices such as land use change and cultivation pattern in buffers can be effective for channel stability and diversity increasing in ecosystem. Since stakeholders have a key role in land management programs, it is suggested that will prepare further researches on based multiple objectives in a comprehensive and integrated watershed management.

کلیدواژه‌ها [English]

• Keyword: Soil conservation programs
• spatial distribution Assessment
• sediment rate decreasing
• MPSIAC
• Haftan atershed w