چکیده:
فرسایش و به تبع آن تولید رسوب باعث هدر رفت هر ساله هزاران تن از اراضی حاصلخیز کشور است. لذا لازم است که حوزه های تولید رسوب با شدت و میزان آن شناسایی شوند تا بتوان اقدام به طرح های آبخیزداری در این مناطق نمود. هدف از این تحقیق مقایسه دو مدل EPM و MPSIAC در برآورد فرسایش و رسوب حوزه آدینه مسجد از زیر حوزه های حوزه آبخیز کمال صالح واقع در جنوب غربی استان مرکزی با مساحت 15/11374 هکتار می باشد. بخشی از اطلاعات اولیه مورد نیاز مانند ویژگی های طبیعی و مورفولوژی حوزه از طریق مطالعات آبخیزداری و سایر اطلاعات از طریق پردازش تصاویر رقومی و مشاهدات و تهیه نقشه های مورد نیاز با استفاده از امکانات GIS برای تهیه فاکتورهای مورد نیاز مدل های EPM و MPSIAC به دست آمد. در مدل MPSIAC، میزان رسوب ویژه 713/112 (M3/Km2/year) و فرسایش ویژه 71/375 (M3/Km2/year) محاسبه شد، در مدل EPM میزان رسوب ویژه 95/213 (M3/Km2/year) و فرسایش ویژه 86/395 (M3/Km2/year) محاسبه شد. نتایج حاکی از این است که اگرچه دو مدل برای برآورد فرسایش و رسوب انطباق نسبی با هم دارند لکن نتایج حاصل از مدل MPSIAC با توجه به اینکه گستره ی بیشتری از عوامل دخیل را مورد ارزیابی قرار می دهد دارای کارایی بهتری نسبت به مدل EPM می باشد. بهرحال با توجه به فاصله نه چندان زیاد فرسایش برآوردی دو مدل، در صورتی که داده های مدل MPSIAC موجود نباشد، می توان از مدل EPM با داده های با سهولت دستیابی بیشتر استفاده کرد.
Introduction
Soil erosion is the process by which soil particles and components are separated from their main bed by an erosive agent and transported to another location. In the soil erosion process, there are three distinct phases: 1- separation of soil particles, 2- particle transfer and 3- sedimentation of transported materials. In water erosion, the erosive factors are rainfall and runoff. Erosion and the consequent reduction of soil fertility are among the issues that make it difficult to achieve sustainable agricultural development and environmental protection. It is important to study the quantity and quality of erosion in the country's watersheds and to prevent the loss of one of the richest and most valuable natural resources of the country, namely soil, and to fight against this process. (Tabatabai, 1392). Therefore, to calculate the rate of erosion and sediment production in most watersheds of the country that lack statistics or lack of statistics, the use of experimental models to estimate erosion and sediment is required. According to what has been said, the present study was conducted based on the following two main objectives 1- Estimation of erosion and sediment in Adineh Masjed watershed, which is one of the main sub-basins of Kamal Saleh Dam, using EPM and MPSIAC experimental models and 2- Investigation and comparing two models and choosing a better model for similar regions and climates.
Materials and methods
Adineh Masjid watershed is one of the sub-basins of Dez and the main sub-basin of Kamal Saleh dam. Temperature, isotherm, geology of the area, slope and available information were performed and finally, by interpreting the photos, types, land units, current land use were determined and updated with field control. For a more detailed study, first, according to the condition of the main waterway and changes in the appearance of the land and vegetation and new land material, the ridges separating the basin were divided into 15 sub-basins. In EPM model, four watershed erosion coefficient (Ψ), land use coefficient (Xa), rock and soil susceptibility coefficient to erosion (Y) and average basin slope (I) and in MPSIAC model, nine geological, soil, climate factor (Climate), runoff, slope, vegetation, land use, current erosion status and waterway erosion are examined. Each model was scored according to data analysis and digital images and then placed in the relevant formula. Finally, the amount of erosion and sediment in the basin was estimated and the sedimentation class of the area was determined.
Results
To determine the score of nine factors affecting soil erosion using MPSIAC method and the four factors of EPM model, each of the factors affecting erosion in units were analyzed. Finally, by weighting, the points of each factor in the models were calculated. The degree of R deposition from the sum of the nine factors of MPSIAC model and the degree of Z erosion was obtained by combining the four EPM factors. Then, the amount of sediment production and erosion in the field of relationships related to each model was calculated and compared and analyzed. In MPSIAC model, the amount of specific sediment (M3 / Km2 / year) was calculated as 112.713 and the specific erosion (M3 / Km2 / year) was calculated as 375.71. In the EPM model, the amount of specific sediment (M3 / Km2 / year) was calculated as 213.95 and Specific erosion (M3 / Km2 / year) was calculated to be 395.86.
Discussion and conclusion
The results of sediment and erosion estimation were estimated separately for each sub-area using two models and it was found that the two models are somewhat relatively compatible with each other. The results of MPSIAC model, have more accuracy and reliability, and therefore the results of the MPSIAC model can be used to estimate the amount of sediment entering the Kamal Saleh Dam. However, due to the small distance between the results of the two models, if we do not have access to MPSIAC model data in similar areas, the EPM model can be used with less data and more easily accessible. It was also observed that in the upper and entrance parts of the basin, where the slope is higher and the vegetation is less, the amount of sediment production and erosion is higher in these areas. So that the upper parts of the basin are in the medium erosion class and the rest of the basin is in the low erosion class.