شبیه‌سازی تصادفی زمین‌آماری هدایت هیدرولیکی اشباع خاک

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشیار گروه مهندسی آب دانشکدة آب و خاک دانشگاه زابل

چکیده

هدایت هیدرولیکی اشباع خاک یکی از پارامترهای اساسی در پروژه‏های زهکشی است. بنابراین، شناخت الگوی توزیع مکانی هدایت هیدرولیکی ضروری است. از طرفی، دست‌یافتن به چنین اطلاعاتی نیازمند اندازه‏گیری‏های متعدد هدایت هیدرولیکی و صرف وقت و هزینة بسیار است. انواع روش‏های کریجینگ می‏توانند برای برآورد و پهنه‏بندی هدایت هیدرولیکی خاک به ‏کار روند. با این ‏حال، مقادیر برآوردشده همواره با درصدی خطا همراه است. برخلاف کریجینگ، روش‏های شبیه‏سازی زمین‏آماری قادرند به موضوعات پیشرفتة دیگر، مانند ارزیابی عدم قطعیت تخمین و استفاده از آن در فرایندهای تصمیم‏گیری، بپردازند. در این تحقیق، روش شبیه‏سازی متوالی گوسی (SGS) و روش غیر پارامتری شبیه‏سازی متوالی شاخص (SIS) برای مدل‌کردن عدم قطعیت تخمین هدایت هیدرولیکی خاک، در منطقة خیرآباد استان خوزستان، به ‏کار رفت. 200 نقشة هدایت هیدرولیکی با احتمال وقوع یکسان به کمک روش‏های شبیه‏سازی تولید شد. نتایج نشان داد نقشه‏های شبیه‏سازی‌شده، برخلاف نقشة کریجینگ، می‌توانند هیستوگرام و نیم‏تغییرنمای داده‏های اولیه را به ‏طور رضایت‏بخش بازتولید کنند. در زمینة عدم قطعیت،‌ نتایج این تحقیق نشان داد واریانس کریجینگ مستقل از مقادیر داده‏هاست. بنابراین، محدودیت زیادی در استفاده از آن وجود دارد. نمودارهای صحت و نمودارهای عرض فاصلة احتمال نشان داد مدل عدم قطعیت به‏دست‌آمده با روش SGS دقیق‏تر از مدل به‏دست‌آمده با روشSIS  است؛ هرچند شاخص نکویی روش SGS (88/0) اندکی کمتر از روش SIS (94/0) به ‏دست آمد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Geostatistical Stochastic Simulation of Soil Saturated Hydraulic Conductivity

نویسندگان [English]

  • Masoomeh Delbari
  • Peyman Afrasiab
Associate professor, Department of water engineering, Faculty of water and soil, University of Zabol
چکیده [English]

Soil saturated hydraulic conductivity is a key parameter needed in many projects including drainage. So it necessitates knowing about the spatial distribution pattern of hydraulic conductivity. However, to obtain the knowledge, it is needed to have a lot of field measurements carried out which is time consuming, tedius, and costly. Different types of kriging can be used for estimating and mapping hydraulic conductivity over a study area. However, the estimated results contain some uncertainties. Unlike kriging, stochastic simulation can be used to model the estimation uncertainty and incorporate it into the decision-making processes. In this paper, Sequential Gaussian Simulation (SGS) and non-parametric Sequential Indicator Simulation (SIS) approaches were employed to model the uncertainty attached to the hydraulic conductivity estimates in KheirAbad plain in Khozestan. A number of 200 equally probable simulated maps of hydraulic conductivity were generated through either of the methods. The results revealed that unlike the kriged map, the simulated maps could reproduce the histogram and semivariogram of the raw data, reasonably well. Regarding local uncertainty, the results showed that the kriging variance does not depend on the actual data values and so there is a limitation in its use. The accuracy plot and width of probability interval plot indicated that the uncertainty model obtained through SGS is more accurate than that obtained through SIS; however the goodness coefficient was slightly smaller for SGS (0.88) than for SIS (0.94).

کلیدواژه‌ها [English]

  • Hydraulic conductivity
  • Uncertainty
  • geostatistical stochastic simulation
  • probability map
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