برآورد فرسایش خاک و نسبت تحویل رسوب با استفاده از مدل rusle در پایگاه تحقیقات حفاظت خاک سنگانه

فرسایش آبی در مقیاس جهانی به‌دلیل وسعت جغرافیایی و اثرات محیط زیستی آن از مهم‌ترین چالش‌های تخریب زمین است. در این راستا، تدوین روش‌ها و راهبردهای مدیریت حوضه‌ها و طراحی برنامه‌های حفاظت خاک مناسب از اهمیت بالایی برخوردار است. شناسایی مناطق اصلی تولید رسوب و هم‌چنین برآورد نسبت تحویل رسوب نقش به‌سزایی در تدوین این راهبردها دارد. هدف از تحقیق حاضر برآورد فرسایش خاک و نسبت تحویل رسوب با استفاده از اصلاح شده معادله جهانی فرسایش خاک (rusle) در پایگاه تحقیقات حفاظت خاک سنگانه است. برای این منظور سه حوضه کوچک به همراه کرت‌های فرسایشی موجود در آن‌ها انتخاب شد. سپس، 24 واقعه بارش مربوط به دو دوره 85-1388 و 96-1398 به همراه داده‌های متناظر رواناب و رسوب در حوضه‌ها و کرت‌ها ثبت شد. سپس با جمع‌آوری اطلاعات مورد نیاز، مدل rusle اجرا و با داده‌های مشاهداتی کرت‌ها مقایسه شد. در ادامه با اصلاح مدل rusle و داده‌های مشاهداتی رسوب‌دهی حوضه‌های مورد مطالعه، مقدار نسبت تحویل رسوب برآورد شد. یافته ها حاکی از آن است که برآورد های مدل rusle از وضعیت فرسایش و رسوب با نتایج داده‌های کرت های فرسایشی تطابق نداشت. اما پس از اعمال ضریب اصلاحی، این مدل توانست میزان متوسط فرسایش کل دوره را با خطای بین 2 الی 17 درصد برآورد نماید که در دامنه قابل قبول مدل­ سازی فرسایش خاک است. نسبت تحویل رسوب برای حوضه های e1، e4 و e6 به ­ترتیب 42/2، 41/5 و 39/7 درصد به دست آمد. در مجموع نتایج این تحقیق نشان داد که با استفاده از مدل اصلاح شده rusle امکان برآورد متوسط فرسایش خاک منطقه و هم‌چنین تخمین نسبت تحویل رسوب وجود دارد. بنابراین، می‌توان در برنامه‌های اجرایی در مناطق مشابه از این رویکرد استفاده نمود.

prediction of soil erosion and sediment delivery ratio using rusle at sanganeh soil conservation research station

introduction soil erosion by water is one of the most common environmental problems worldwide and is considered a serious risk for sustainability in developing countries. water erosion on a global scale is one of the most critical types of soil and environmental degradation due to its geographical extent and ecological effects. in this regard, effectively controlling sediment load is an important component in watershed management. in the formulation of a watershed management strategy, the estimation of sediment delivery ratio (sdr) plays a significant role. sdr is defined as the sediment yield from an area divided by the gross erosion of that same area. sdr is expressed as a percentage and represents the efficiency of the watershed in moving soil particles from areas of erosion to the point where sediment yield is measured. one of the problems in estimating the sdr in watersheds is the lack of proper information on the amount of soil erosion and sediment yield. in this context, the sanganeh soil conservation research station, having measured soil erosion and sediment yield of small watersheds, is a suitable place to evaluate the accuracy of the rusle model and estimate the ratio of sediment delivery on the scale of small watersheds. the current research aims to achieve two goals: a) determining the accuracy of the rusle model in estimating soil erosion based on the measurements in the erosion plots, and b) estimating the sdr using the estimated soil erosion values as well as the sediment yield measured at the outlet small watershed are planned. materials and methodsconsidering the importance of soil erosion and the study of sediment processes in semiarid rangeland ecosystems, the khorasan razavi agricultural and natural resources research center (kanrrc) assessed some microwatersheds for the collection of stormwise runoff and associated sediment. the sanganeh research microwatershed, located 100 km from mashhad city (northeast iran), is one of the watersheds selected for this study. the watershed area, the longest waterways, and the mean slope of the watershed are 1.2 ha, 145.0 m, and 31.2%, respectively. the study watershed consists of semiarid rangeland dominated by bromus tectorum and artemisia diffusa, with a coverage of 50%. the soil is entisol and aridosol, young, with a maximum depth of 30 cm. the mean electrical soil conductivity (ec), soil organic matter (om), clay, sand, silt, and surface rock fragments of soils are 1.81, 1.57, 10.6, 54.7, 34.7, and 5%, respectively. in this research, three experimental small watersheds with areas between 430012000 m2 were selected along with the erosion plots in them. then, 24 rainfall events related to two periods of 20062009 and 20162018 were recorded along with the corresponding data of runoff and sediment in watersheds and plots. in this study, water flow and sediment yield were monitored at the main outlet of the microwatersheds and plots. the runoff volume was calculated after each storm event by multiplying the depth of collected water, measured using an iron ruler at five points in the tank (corners and central), by the surface area of the collector. the collected runoff and sediment were then mixed thoroughly and one sample was taken to determine sediment concentration and sediment yield. then, by collecting the required information (includeing rainfall erosivity, topography, conservation practice, soil erodibility, and covercrop management factors), the rusle model was run and compared with the observation data of the plots. the stormwise soil erosion predictions were compared with observed data based on the criteria of the coefficient of determination (r2) and relative estimation error (re). in the following, by modifying the rusle model and observing the sedimentation data of the studied watersheds, the value of the sdr was estimated. results and discussionafter collecting the required information, the rusle model was implemented at the plot scale.