مقایسه‌ای بین مدل‌های تجربی و فرکتالی در برازش به داده‌های اندازه‌گیری شده منحنی مشخصه رطوبتی خاک

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه کردستان، سنندج، ایران

چکیده

منحنی مشخصه رطوبتی خاک (SMCC) یکی از مهم‌ترین ویژگی­های هیدرولیکی خاک در مدل­سازی جریان آب و املاح در ناحیه غیر­اشباع بوده که اندازه­گیری مستقیم آن دشوار، زمان­بر و پرهزینه است. بنابراین هدف از این پژوهش، ارزیابی عملکرد برخی از مدل­های فرکتالی تخمین SMCC همچون Tyler and Wheatcraft (1990)، Rieu and Sposito (1991)، Perfect (1999) وBird et al. (2000) و مقایسه آن با برخی از مدل­های تجربی همچون Brooks and Corey (1964)، Campbell (1974) و van Genuchten (1980) می­باشد. بدین منظور، 54 نمونه خاک از اراضی زراعی واقع در دشت قروه-دهگلان به­صورت تصادفی جمع‌آوری ‌شده و برخی از ویژگی­های فیزیکی و شیمیایی آن­ها در آزمایشگاه تعیین گردید. سپس این مدل­های فرکتالی و تجربی تخمین SMCC، به روش حداقل مربعات خطا و با استفاده از جعبه ابزار Solver در نرم­افزار EXCEL، بر داده­های اندازه­گیری شده پتانسیل ماتریک و رطوبت حجمی برازش داده شدند. برای ارزیابی کارایی این مدل­ها از آماره­های ضریب تبیین (R2)، جذر میانگین مربعات خطا (RMSE) و معیار آکائیک (AIC) استفاده شد. نتایج نشان داد همه­ی مدل­های مورد مطالعه در تخمین SMCC دارای عملکردی مطلوب می­باشند (دارای R2­ی بین 75/0 تا 99/0). با توجه به مقادیر R2 بیشتر و RMSE و آماره AIC کمتر، به ترتیب مدل­های Bird et al. (2000) و
 van Genuchten (1980) به­عنوان مناسب­ترین مدل­ها در تخمین منحنی مشخصه رطوبتی خاک­های منطقه مورد­مطالعه پیشنهاد شدند. نتایج همچنین نشان داد مدل Rieu and Sposito (1991) در برآورد SMCC دارای ضعیف­ترین عملکرد می­باشد. هر چند باید در نظر داشت که میانگین R2 و RMSE آن نیز به ترتیب بیشتر از 75/0 و کمتر از cm3/cm3 071/0 است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

A Comparison Between Empirical and Fractal Models Fitted to the Measured Soil Moisture Characteristic Curve Data

نویسندگان [English]

  • Masoud Davari
  • Ziba Zalvaee
  • Mohammad Ali Mahmoodi
Department of Soil Sciences and Engineering, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran
چکیده [English]

Soil moisture characteristic curve (SMCC) is an important hydraulic properties in modelling of water movement and solute transport in unsaturated zone of soil, which its direct measurement in a laboratory is expensive, time-consuming and laborious. Therefore, the objective of this study was to compare the fitting capabilities of several SMCC fractal (Tyler and Weatcraft, 1990; Rieu and Sposito, 1991; Perfect, 1999 and Bird et al., 2000) and empirical models (Brooks and Corey, 1964; Campbell, 1974 and van Genuchten, 1980) to the observed data and to select the appropriate models. For this purpose, fifty-four soil samples were randomly collected from Ghorveh-Dehgolan plain and some important physical and chemical properties of soils were measured in the soil laboratory. The SMCC fractal and empirical models were fitted to the measured data based on the least esquare error approach using the solver toolbox of EXCEL software. In order to evaluate fitting quality of the proposed models, three statistical parameters including coefficient of determination (R2), root mean square error (RMSE) and Akaike information criterion (AIC) were used. The results indicated that all models did well with R2 ranging from 0.75 to 0.99. Bird et al., (2000) and van Genuchten (1980) models are selected as the best models, respectively, based on the highest R2 and the lowest RMSE and AIC. Rieu and Sposito (1991) model was the weakest, although the average R2 was greater than 0.75 and the average RMSE was smaller than 0.071 cm3/cm3.

کلیدواژه‌ها [English]

  • Fitting quality
  • fractal model
  • Ghorveh-Dehgolan plain
  • soil moisture characteristic curve
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