با همکاری انجمن آبخیزداری ایران

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار پژوهشی بخش تحقیقات حفاظت خاک و آبخیزداری، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان فارس، سازمان تحقیقات، آموزش و ترویج کشاورزی، شیراز، ایران

2 دانشیار پژوهشکده حفاظت خاک و آبخیزداری، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران

چکیده

مسأله‌ فرسایش و رسوب حاصل از آن، از مهمترین مسائل آبخیزداری است. در این راستا، برآورد رسوب و اولویت‌بندی حوزه‌های آبخیز از لحاظ فرسایش آبی از اهداف مهم آبخیزداری است. یکی از راه‌های برآورد فرسایش خاک و تولید رسوب، استفاده از مدل­های تجربی است. هدف از اجرای این پژوهش، بررسی کارایی مدل EPM در استان فارس است. در این مدل، پارامترهایی مانند ضریب شدت فرسایش، فرسایش ویژه و میزان رسوب­دهی ویژه مورد بررسی قرار گرفتند. برای این کار، پنج حوزه‌ آبخیز کوچک در استان فارس انتخاب شدند. در خروجی این حوضه‌ها، بندهای خاکی و سنگی‌-ملاتی بنا شده که تا کنون سرریز نداشته و سن بیشتر آن‌ها نزدیک به 10 سال است. با استفاده از نقشه‌برداری دقیق، مقدار رسوبات ته‌نشین­شده در مخازن آن‌ها به­دست آمد. وزن مخصوص ظاهری رسوبات با عملیات صحرایی، تعیین و حجم رسوبات با در نظر گرفتن سال‌های رسوب‌گیری به وزن تبدیل شد. با استفاده از مدل EPM، مقدار حجم و وزن رسوب تولیدی حوضه‌ها تعیین شدند. کمینه و بیشینه‎ اندازه‌گیری رسوب ­بندها بین 0.89 تا 2.62 تن در هکتار در سال تغییر داشته، ولی میزان رسوب برآوردی مدل بین 3.3 تا شش تن در هکتار در سال متغیر بودهاست. نتایج درصد خطای نسبی برآوردهای مدل EPM نشان از بیش­برآوردی در تمام حوضه‌ها دارد (کمینه 5/121 و بیشینه 2/447 درصد). میانگین نسبی مربعات خطای مدل (RRMSE) برابر 2.39 محاسبه شد که نشان‌دهنده‎ خطای زیادی است. نتایج تحلیل آماری مقایسه‌ مقادیر رسوب­دهی واقعی حوزه­های آبخیز با مقادیر برآورد­شده به‌وسیله‌ مدل، با استفاده از روش آماری t زوجی، نشان می‌دهد که اختلاف معنی‌داری بین این مقادیر وجود دارد. بر اساس نتایج به­دست آمده از این پژوهش، مدل EPM برای مناطق مورد پژوهش پذیرفته‌شده نیست.

کلیدواژه‌ها

عنوان مقاله [English]

Technical Note: Evaluation of EPM empirical model using sediment survey of small reservoirs in Fars Province

نویسندگان [English]

  • Gholamreza Ghahari 1
  • Samad Shadfar 2
  • Hamid Hosseini Marandi 1

1 Assistant Professor, Soil Conservation and Watershed Management Research Department, Fars Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Shiraz, Iran

2 Associate Professor, Soil Conservation and Watershed Management Research Institute (SCWMRI), Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

چکیده [English]

Erosion and sediment resulting from it, is one of the most important factors in watershed management. The estimation of sediment yield and prioritization of watersheds in terms of water erosion is the main objectives of watershed management. One of the ways to estimate soil erosion and sediment yield is to use empirical models. The aim of this research is to evaluate the efficiency of the EPM Model in Fars Province. To examine this, five small watersheds were selected in Fars Province. Five basins in which the earth dams and check dams were built were selected. There is no overflow from these dams in rainfall events and the most of them was made near to 10 years. The amount of sediment deposited in upstream of the reservoirs was calculated by means of precision mapping. Deposit bulk density was determined in the field to convert the volume into the weight. In parallel, the sediment yield of the basins was determined by EPM Model. Results showed that the minimum and maximum sediment yield measurements varied from 0.89 to 2.62 tonh-1y-1, but the estimated sediment was between 3.3 to 6 tonh-1y-1. The results of the relative error of estimation of EPM Model in each of the studied basins showed an over estimation in all basins (minimum 121.5 and maximum 447.2 percent). The Relative Root Mean Square Error (RRMSE) of the model was calculated as 2.39, which indicates a too much error of the model. Statistical analysis results comparison of actual sediment yields of watersheds with estimated values by model, using paired t-test, shows that there is a significant difference between these values (t=8.728 and sig.=0.001). According to the presented findings, the results of this model estimation for the investigated areas are not accepted.

کلیدواژه‌ها [English]

  • Check dams
  • Empirical models
  • Fars Provinc
  • Sediment yield
  • Watershed
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