Iranian Jornal of Watershed Management Science&Engineering

fa تعیین روند خدمات نگهداشت رسوب با مدل InVEST و جبران خسارت اقتصادی ناشی از هدر رفت خاک با رویکرد هزینه-جایگزین در حوزه آبخیز افین خراسان جنوبی Determination of Sediment Retention Service Trends Using the InVEST Model and Compensation of Economic Losses Due to Soil Erosion with a Replacement Cost Approach in the Efin Watershed, South Khorasan تخصصي Special پژوهشي Research امروزه در بخش‌های مختلف کره زمین به خصوص مناطق خشک و نیمه خشک، متأثر از عوامل مختلف اقلیمی، انسانی و محیطی، تخریب سرزمین، فرسایش خاک و هدررفت عناصر غذایی ناشی از آن افزایش یافته است. این امر سبب شده تا در طول زمان، قدرت تکامل خاک و همچنین جوانه‌زنی، استقرار و رشد گیاهان در اراضی مرتعی و بهره‌وری گیاهان زراعی کاهش یابد. برای انجام پژوهش حاضر، در ابتدا داده‌های بارندگی روزانه هواشناسی سه ایستگاه افین، ذهان و مغیلان به ترتیب در خروجی، میانه و بالادست آبخیز و داده‌ها رسوب و دبی ثبت شده در ایستگاه افین در خروجی آبخیز برای دوره دوره 16 ساله از سال 1386 تا 1402 از سازمان هواشناسی و شرکت سهامی آب منطقه‌ای استان خراسان جنوبی اخذ شد. سپس ورودی‌های مدل InVEST شامل لایه‌های فرسایندگی باران، فرسایش‌پذیری خاک (R)، مدل رقومی ارتفاع (Dem)، شاخص نرمال شده تفاضل پوشش گیاهی (NDVI) و مدیریت زمین (P) برای دوره زمانی 1386 تا 1402 متناظر با داده‌های بارش و دبی، آماده و به سلول‌های 30 متری همسان‌سازی شد. نتایج پژوهش حاضر حاکی از آن است که مدل InVEST  با 58/0 و 30/13 درصد خطا در بازتولید رسوب مشاهده‌ای به ترتیب در دوره واسنجی و اعتبارسنجی، از کارایی مناسبی برخوردار بوده و قابلیت استفاده در این پژوهش را دارد. همچنین تحلیل بارندگی حاکی از کاهش بارش از ابتدا به انتهای دوره در ایستگاه‌های افین و مغیلان و افزایش در ایستگاه زهان است. بیشینه مقدار شاخص NDVI نیز در بیش‌تر سال&lrm;ها به دلیل وجود باغ‌های زرشک متکی به منابع آب زیرزمینی ثابت اما مقدار کمینه آن متفاوت تعیین شد. علاوه‌براین میزان رسوب خروجی در بازه مورد ارزیابی از 31910 تا 142310 تن در سال‌های مختلف متغیر است. در نهایت هزینه-جایگزین عناصر فسفر و پتاسیم به ترتیب 57/393 تا 17/1755 و 42/2890 تا 02/12887 میلیون ریال و هزینه کل از 00/3284 تا 19/14642 میلیون ریال در طول دوره آماری برآورد گردید. Introduction Today, in various parts of the world, especially in dry and semi-dry regions, land degradation, soil erosion, and loss of nutrients due to various climatic, human, and environmental factors have increased. This has led to a decline in the soil’s developmental capacity, as well as the germination, establishment, and growth of plants in pastures, reducing the productivity of agricultural plants. In other words, after every heavy rainfall and runoff, soil erosion occurs, which moves soil from the watershed area downstream, depleting soil nutrients and impoverishing the local soil. However, a lack of understanding of the amount of displaced nutrients and the costs associated with this issue has resulted in its minimal inclusion in the policies and planning of managers. Therefore, identifying and quantifying the extent of erosion and the lost nutrients due to it, as well as the replacement costs of these elements, can significantly aid in understanding the various dimensions of soil erosion. Accordingly, this study aims to determine the soil loss in the Efin watershed of South Khorasan and subsequently assess the costs of replacing the lost phosphorus and potassium elements to quantify the costs of compensating for soil erosion damages. Materials and Methods For this research, daily precipitation data from three meteorological stations (Efin, Zohan, and Moghilan), located at the outlet, mid, and upstream of the watershed, as well as sediment and flow data recorded at the Efin station at the outlet of the watershed, were collected for the available period (2007 to 2023) from the Meteorological Organization and the Regional Water Company of South Khorasan. Subsequently, the model inputs for InVEST, including Rainfall Erosion (R), Soil Erodibility (K), Digital Elevation Model (DEM), Normalized Difference Vegetation Index (NDVI), and Land Management (P) corresponding to the precipitation and flow data for the period of 2007 to 2023, were prepared and resampled to 30-meter cells. The period from 2007 to 2016 was considered for calibration, and from 2017 to 2023 for model validation. After calibrating and validating the InVEST model, the amount of sediment output from the watershed was estimated for each year. The levels of phosphorus and potassium in each kilogram of sediment were extracted from previous studies. Finally, based on the determined amounts of phosphorus and potassium in the eroded soil each year, as well as their market prices from agricultural jihad data, the replacement costs for these elements were calculated for each year. Results and Discussion The results of this study indicate that the InVEST model exhibited sufficient efficiency, with errors of 0.58% and 13.30% in reproducing observed sediment during the calibration and validation periods, respectively, and the model is applicable for this research. Additionally, rainfall analysis shows a decrease in precipitation from the beginning to the end of the period at the Efin and Moghilan stations, while an increase was noted at the Zohan station. The maximum NDVI index value remained relatively stable in most years due to the presence of jujube orchards relying on groundwater resources, though the minimum value varied. Moreover, the sediment output during the evaluation period ranged from 31,910 to 142,310 tons across different years. Ultimately, the replacement costs for phosphorus and potassium were estimated to be between 393.57 to 1,755.17 million rials and 2,890.42 to 12,887.02 million rials, respectively, with total costs ranging from 3,284.00 to 14,642.19 million rials over the statistical period. Given the approximate stability of land use throughout the statistical period, climate has a greater impact, with sediment increasing alongside precipitation. While the presence of jujube orchards, influenced by spring and qanat irrigation, shows a relatively stable NDVI maximum, degradation in pasture and barren land could exacerbate erosion due to its greater extent. Conclusion Soil erosion and the loss of nutrient resources in the long term have a significantly negative impact on the lives of local communities and soil-dependent organisms. In other words, the lack of nutrients not only reduces agricultural soil productivity but also leads to the destruction of biodiversity. Therefore, adequate attention to this issue can illuminate hidden aspects and provide a clear picture of the negative effects of erosion. As the study results indicate, erosion in the Efin watershed is influenced by rainfall, and sediment levels change with variations in rainfall shape and volume. In this context, the extensive and less-covered rangelands in the Efin watershed play a significant role in erosion and the increase of replacement costs. It is recommended that, considering the region’s dry and fragile climate, measures be taken to prevent surface soil degradation. Although rainfall is beyond human control and biological cover does not establish well due to the lack of precipitation, erosion can be prevented from intensifying and spreading by implementing biological-engineering projects and controlling the terrestrial factors affecting erosion.   اقتصاد خاک, بهره‌وری زراعی, عناصر غذایی, فرسایش, مدیریت خاک Agricultural Productivity, Erosion, Nutrient Elements, Soil Economics, Soil Management 0 0 http://jwmsei.ir/browse.php?a_code=A-10-787-4&slc_lang=fa&sid=1 Javad Chezgi جواد چزگی chezgi@birjand.ac.ir 100319475328460019190 100319475328460019190 Yes Birjand University دانشگاه بیرجند Reza Chamani رضا چمنی Reza.chamani@birjand.ac.ir 100319475328460019191 0009-0000-9913-8939 No Birjand University دانشگاه بیرجند Hadi Memaryan هادی معماریان h_memarian@birjand.ac.ir 100319475328460019192 100319475328460019192 No Birjand University دانشگاه بیرجند Halimeh Joloro حلیمه جلورو halime.joloro@modares.ac.ir 100319475328460019193 0009-0009-7141-9152 No UTM داتشگاه تربیت مدرس Negin Rashidi نگین رشیدی negin.rashidi@modares.ac.ir 100319475328460019194 0009-0001-9742-703x No UTM داتشگاه تربیت مدرس