برآورد مولفه‌های فرسایش و رسوب با استفاده از مدل intero (مطالعه موردی: حوضه آبخیز کهورستان)

فرسایش خاک یکی از بزرگ‌ترین مشکلات محیط زیست جهان است و تهدیدی برای امنیت غذایی، محیط زیست، منابع طبیعی و مشکلات اقتصادی اجتماعی محسوب می‌شود. در این راستا، اهمیت برآورد مقدار فرسایش به منظور اتخاذ روش‌های مناسب مدیریتی در مناطق مختلف مشخص می‌شود؛ از این‌رو، مطالعه حاضر با هدف برآورد شدت فرسایش خاک و جریان خروجی در حوضه آبخیز کهورستان انجام و در آن از مدل جامع، سریع و موثر intero استفاده شد. پس از جمع‌آوری اطلاعات پایه، 26 متغیر ورودی با استفاده از نقشه‌های توپوگرافی، خاک‌شناسی، زمین‌شناسی، کاربری اراضی و داده‌های اقلیمی استخراج و محاسبه شد. نتایج نشان داد که ضریب فرسایش آبخیز کهورستان  0.918 و مقدار فرسایش خاک واقعی و فرسایش خاک واقعی ویژه در حوضه آبخیز مطالعاتی به‌ترتیب  631152.53 مترمکعب در سال و 150.14 مترمکعب بر کیلومترمربع در سال است. ضریب ته‌نشست مجدد رسوبات حاصل از فرسایش به مقدار 0.183 و مقدار رسوب تولیدی ناشی از فرسایش در سطح آبخیز مطالعاتی 345663.72 مترمکعب در سال محاسبه شد. نتایج به دست آمده بیانگر غالب بودن فرسایش شیاری در منطقه و انتقال رسوبات به خروجی حوضه است. با توجه به نتایج، این مدل در برآورد مقدار فرسایش در حوضه مطالعاتی دقت کافی نداشت، اما در برآورد مقدار حداکثر جریان خروجی از حوضه بر اساس آمار موجود نتایج خوبی داشت؛ به عبارتی، توصیه می شود از این مدل در برآورد مقدار جریان خروجی و سایر ویژگی‌ها استفاده شود، ولی برای برآورد مقدار فرسایش در مناطق با شرایط حوضه آبخیز کهورستان که در آن رگبارهایی با شدت زیاد و مدت کم وجود دارد پیشنهاد نمی شود؛ زیرا نمی تواند نتایج مناسبی را ارائه دهد.

estimation of erosion and sediment components using the intero model (case study: kahouristan watershed)

1- introductionsoil erosion is one of the most significant environmental problems in the world; it is a threat to food security, the environment, natural resources and causes socio-economic problems. in this regard, the importance of estimating the amount of erosion to adopt appropriate management methods in different areas has been established. among the existing models of soil erosion and sedimentation, models that can predict soil erosion and sediment performance can be useful and widely used. in this regard, the intero model, which is a graphical computer method based on the epm erosion potential method embedded in its algorithm, can be applied.2- methodologythis study aimed to estimate the severity of soil erosion and runoff using the comprehensive, rapid, and effective intero model in the kahouristan watershed. after collecting basic information, 26 input variables were extracted and calculated using topographic maps, geology, geology, land use, and climate data. in this regard, to estimate the inputs of the intero model, at first, the physiographic and topographic features of the kahouristan watershed were extracted using a 1: 25000 digital map and the boundary of the information range. also, the lowest and highest elevation points, the lowest value of the alignment line, and the equal distance between the alignment lines were determined. geological and land use characteristics of the region geological and land use maps were used. the maximum probable precipitation (pmp) method was used to achieve the height of torrential rainfall. finally, after preparing all the inputs of the intero model, the computational data for the kahouristan watershed were entered into the graphical environment of the software, and the components related to erosion and sediment as well as the maximum outflow from the kahouristan watershed were estimated using the model.3- results the results showed that the drainage density was 1.35 in the kahouristan watershed using the intero model, and the infiltration coefficient of the watershed and the vegetation cover coefficient were 0.67 and 0.84, respectively. also, the coefficient of water retention in the studied area was found to be 0.91 and the potential of water flow during flash floods was found to be 6597.04. on the other hand, the erosion energy coefficient in the study area was found to be 102.12 using the intro model, and the total erosion in the mentioned area was equal to 3456636.72, and the erosion coefficient of the kahouristan watershed was 0.918. the amount of real soil erosion and special real soil erosion in the studied watershed is 631152.53 m3/year and 150.14 m3/km2.year, respectively. the re-sedimentation coefficient of sediments due to erosion was 0.183.    4- discussion & conclusions the results of the current research showed that the permeability coefficient of the study watershed was 0.67, which according to the value of the vegetation coefficient which was 0.84, it can be said that the appropriate cover in the area has caused the permeability. however, the drainage density in the study area was 1.35, which indicates the resistance of the soil in the area against erosion.also, examining the results shows that the maximum output flow estimated by the mentioned model for the study watershed is about 1778 m3/s. examining the maximum outflow with the 21-year statistics of the kahouristan hydrometric station shows that the maximum outflow from the study watershed is about 1635 m3/s, which indicates the appropriate performance of the model in estimating the maximum outflow from the study watershed. based on this, it is recommended to use this model in estimating the output flow and other characteristics in the study watershed. another hand, the results showed the predominance of rill erosion in the area and the transfer of sediments to the outlet of the basin. according to the model results, estimating the amount of erosion in the study area was not accurate enough. however, estimating the maximum output current from the basin based on the available statistics indicated good results; in other words, the use of this model is recommended in estimating the output current and other characteristics, but in areas having similarities with kahouristan watershed conditions, heavy and short rainfalls for estimating the amount of erosion is not recommended due to its inability to provide appropriate results. finally, it is suggested that other models of erosion and sediment assessment for the kahouristan watershed and other watersheds with similar conditions in this respect be studied and compared with the intero model as well.