شبیه‌سازی تداخل آب شور و شیرین در ناحیۀ اشباع و غیر اشباع خاک با استفاده از مدل فیزیکی و عددی HYDRUS-2D

نوع مقاله : پژوهشی

نویسندگان

1 دانشجوی کارشناسی‏ ارشد آبیاری و زهکشی، گروه آبیاری و آبادانی پردیس کشاورزی و منابع طبیعی دانشگاه تهران

2 استاد گروه آبیاری و آبادانی، پردیس کشاورزی و منابع طبیعی دانشگاه تهران

3 استادیار گروه مهندسی آب، دانشگاه بین‌المللی امام خمینی‌(ره)، قزوین

چکیده

یکی از عوامل تهدیدکننده برای منابع آب شیرین، پیشروی آب شور و نفوذ آن به سفرۀ آب زیرزمینی است. این مسئله در مناطق ساحلی و حاشیۀ کویرها اتفاق می‏افتد و سبب کاهش کیفیت آب شیرین می‏شود. تبخیر از سطح خاک و عمق سطح ایستابی از عوامل تأثیرگذار بر پیشروی شوری و توزیع نمک در ناحیۀ اشباع و غیراشباع به حساب می‏آید. در پژوهش حاضر با ساخت مدل فیزیکی به ابعاد 1×1×4 متر شرایط قرارگیری آبخوان شور و شیرین در چهار گرادیان هیدرولیکی مختلف بررسی شد. هنگام انجام آزمایش از مدل فیزیکی، داده‏های رطوبت و شوری برداشت شد و سپس، توزیع شوری در مدل فیزیکی با استفاده از نرم‏افزار HYDRUS-2D به صورت عددی شبیه‏سازی شد. نتایج نشان داد مدل HYDRUS-2D به‌خوبی توزیع رطوبت و شوری را شبیه‏سازی می‏کند. بیشترین مقدار ریشۀ میانگین مربعات خطای نرمال‌شده (NRMSE) برای شبیه‏سازی رطوبت و شوری به‌ترتیب 28/9 و 69/21 درصد بود. نتایج نشان داد الگوی پیشروی و پسروی شوری متفاوت است. در شرایطی که سطح آب شیرین بالاتر است، در ناحیۀ اشباع مانع از پیشروی آب شور شده و در ناحیۀ غیر اشباع تأثیر زیادی بر کنترل شوری نداشته است که دلیل آن تبخیر از سطح خاک است. در ناحیۀ اشباع، در شرایطی که سطح آب شور و شیرین برابر بود، سه واحد افزایش شوری در ناحیۀ شور دیده شد و در شرایطی که سطح آب شور بالاتر بود، 5/6 واحد افزایش شوری در وسط دو مخزن آب شور و شیرین مشاهده شد.

کلیدواژه‌ها


عنوان مقاله [English]

Simulation of Saline and Fresh Water Interference in Saturated and Unsaturated Zones Using Physical and Hydrus-2D Model

نویسندگان [English]

  • Hossein Rabbaniha 1
  • Abdolmajid Liaghat 2
  • Masoud Soltani 3
1 MSc Student in Department of Irrigation & Reclamation Engineering, Campus of Agriculture and Natural Resources, University of Tehran
2 Professor in Department of Irrigation & Reclamation Engineering, Campus of Agriculture and Natural Resources, University of Tehran
3 Assistant Professor Water Sciences and Engineering Department Imam Khomeini International University, Qazvin, Iran
چکیده [English]

One of the threatening factors to fresh water resources is the advancement of saline water and intrusion into the groundwater aquifer. This problem occurs in coastal zones and desert margins which causes reduction in the quality of fresh water. Evaporation from the soil surface and the water table depth are factors affecting the salinity and salt distribution in the saturated and unsaturated zones. In this study, by constructing a physical model with dimensions of 4×1×1 m, the proposed situation of saline and fresh aquifer levels was studied in four different hydraulic gradients. During the experiment, moisture and salinity data were collected from the physical model and then the salinity distribution in the physical model was numerically simulated using Hydrus-2D software. The results showed that Hydrus-2D model simulates moisture and salinity distribution well. The Maximum Normalized Root Mean Square Error (NRMSE) for simulation of moisture and salinity were 9.28 and 21.69 percent. The results showed that the pattern of salinity progression and regression were different. In conditions where the fresh water level is higher, it prevents the advance of saline water in saturated zone, and in unsaturated zone it does not have a significant effect on controlling salinity due to evaporation from the soil surface. In the saturated zone, when the saline and fresh water levels were equal, three units’ salinity increase in saline zone and when the saline water level was higher, 6.5 units salinity increase was observed in the middle of the two saline and fresh water reservoirs.

کلیدواژه‌ها [English]

  • Groundwater
  • Salinity Front
  • Hydraulic gradient
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