تخمین هدایت هیدرولیکی اشباع و غیر‌اشباع زمین‌های شیبدار در حالت‌های ماندگار و غیر‌ماندگار

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشکده کشاورزی دانشگاه تبریز

2 دانشکده کشاورزی دانشگاه بوعلی سینا همدان

چکیده

یکی از روش­های ساده، دقیق و مناسب برای اندازه­گیری هدایت هیدرولیکی خاک در زمین­های شیبدار، استفاده از استوانه­های مضاعف و دستگاه نفوذسنج مکشی می­باشد. تحقیقات متعدد نشان می­دهد که شیب زمین روی خصوصیات هیدرولیکی از جمله هدایت هیدرولیکی اشباع و غیراشباع خاک تاثیر می­گذارد. هدف از این مطالعه تخمین و مقایسه مقادیر هدایت هیدرولیکی خاک با استفاده از داده­های نفوذ، در دو حالت ماندگار و غیر ماندگار در زمین­های با شیب مختلف می­باشد. آزمایش­های نفوذ با استفاده از دستگاه­های استوانه­های مضاعف و نفوذسنج مکشی در پنج شیب 0، 10، 20، 30 و 40 درجه و در چهار مکش صفر (با استفاده از استوانه­های مضاعف)، 6، 9 و 15 سانتیمتر (با استفاده از نفوذسنج مکشی) به انجام رسید. در حالت ماندگار، مقادیر هدایت هیدرولیکی اشباع با روش رینولدز و همکاران و هدایت هیدرولیکی غیر اشباع به روش آنکنی و همکاران محاسبه شد. در حالت غیر ماندگار، ابتدا پارامتر وابسته به هدایت هیدرولیکی معادله دو جزئی فیلیپ، از انطباق داده­ها با معادله استخراج گردید و سپس مقدار هدایت هیدرولیکی محاسبه شد. نتایج نشان داد در هر دو حالت ماندگار و غیر ماندگار با افزایش شیب زمین و مکش خاک هدایت هیدرولیکی کاهش می­یابد. در مکش­های کم میزان کاهش هدایت هیدرولیکی بیشتر است. در حالت ماندگار، با افزایش زاویه شیب از صفر به 40 درجه، کاهش هدایت هیدرولیکی در مکش صفر حدود 1/4 برابر کاهش آن در مکش 15 سانتیمتر بود. این مقدار در حالت غیر ماندگار 7/3 برابر بر آورد شد. مقادیر هدایت هیدرولیکی حاصل از معادله گاردنر تطابق بیشتری با حالت ماندگار جریان نسبت به حالت غیر ماندگار نشان داد. مقادیر اختلاف هدایت هیدرولیکی نسبی بین روش ماندگار و غیر ماندگار در تمام شیب­­ها و مکش­ها، کمتر از 7 درصد به دست آمد که بیانگر نزدیک بودن نتایج به دست آمده از دو روش مذکور می­باشد. 

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Estimating Saturated and Unsaturated Hydraulic Conductivities of Sloping Lands under Steady and Transient States

نویسندگان [English]

  • M Raoof 1
  • AH Nazemi 1
  • SAA Sadraddini 1
  • S Maroofi 2
چکیده [English]

Double ring and tension infiltrometer are simple, fast and suitable instruments for determining soil hydraulic conductivity. The effect of land slope on soil properties such as saturated and unsaturated hydraulic conductivities has been reported by various researchers. The aim of this study was to estimate and compare soil hydraulic conductivities at different slope gradients under steady state and transient flow regiones. Field experiments were conducted in a loamy soil with different slope gradients in Gonbad research station, Hamadan, Iran. Soil surface slope gradients, of 0 (level), 10, 20, 30 and 40 degree were selected in this station. For each slope gradient, water infiltration experiments were carried out using a double ring and a tension infiltrometer at tensions of 0, 6, 9 and 15 cm in three replications. Totally 60 infiltration experiments were carried out. In steady state, values of saturated and unsaturated hydraulic conductivities were estimated using Reynolds et al. and Ankeny et al. procedures, respectively. In transient statevalues of  the hydraulic conductivity, for different land slopes and water pressure heads, were calculated from the parameter of the second term of Philip’s two-term equation, Results indicated that the hydraulic conductivity values for both steady state and transient flow regines were decreased with increasing in tension and slope gradient values. The higher rate of hydraulic conductivity decreases was obtained for lower tensions. In steady and transient state, by increasing  in slope gradient from 0 to 40 degrees, decreasing of hydraulic conductivity in 0 tension was 4.1 and 3.7 times more than these in 15 cm tension, respectively. The fitness between the Gardner exponential model and steady state flow procedure was higher than that of transient flow procedure. In all experiments, values of relative difference of hydraulic conductivities were less than 7% that indicated good fitness between the steady state and transient flow procedures.
 

کلیدواژه‌ها [English]

  • saturated hydraulic conductivity
  • Unsaturated hydraulic conductivity
  • double ring and tension infiltrometer
  • steady and transient flow
Angulo-Jaramillo R, Vandervaere JP, Rolier S, Thony JL, Gaudet JP and Vauclin M, 2000. Field measurement of soil surface hydraulic properties by disc and ring infiltrometers: A review and recent developments. Soil Tillage Res 55: 1-29.
Ankeny M, Ahmed M, Kaspar T and Horton R, 1991. Simple field method for determining unsaturated hydraulic conductivity. Soil Sci Soc Am J 5: 467–470.
Bodhinayake WL, SiBC and Xiao C, 2004. New method for determining water-conducting macro- and mesoporosity from tension infiltrometer. Soil Sci Soc Am. J 68: 760–769.
Bower H, 1986. Intake rate. Cylinder infiltrometer. Pp. 825-843. In: A Klute (ed.) Methods of soil analysis. Psrt 1. Physical and mineralogical properties. 2nd ed. ASA, Madison, WI.
Cameira MR Fernando RM and Pereira LS, 2003. Soil macropore dynamics affected by tillage and irrigation for a silty loam and irrigation for a silty loam alluvial soil in southern Portugal. Soil Tillage Res 70: 131-140.
Casanova M, Messing I and Joel A, 2000. Influence of aspect and slope gradient on hydraulic conductivity measured by tension infiltrometer. Hydrol Processes 14: 155–164.
Dunn GH and Philip JR, 1991a. Macroporosity of a well-drained soil under no till and conventional tillage. Soil Sci Soc Am J 55: 817-823.
Dunne T and Black RD, 1970. An experimental investigation of runoff production in permeable soils, Water Resour Res 6: 478– 490.
Gardner WR, 1958. Some steady-state solutions of the unsaturated moisture flow equation with application to evaporation from water table. Soil Sci 85: 228-232.
Logsdon S and Jaynes D, 1993. Methodology for determining hydraulic conductivity with tension infiltrometers. Soil Sci Soc Am J 57: 1426–1431.
Marquardt DW, 1963. An algorithm for least squares estimation of nonlinear parameters. J SocInd Appl Math 11: 431-441.
Mendoza G and Steenhuis ST, 2002. Determination of hydraulic behavior of hillsides with a hill slope infiltrometer. Soil Sci Soc Am J 66: 1501–1504.
Mosley MP, 1982. Subsurface flow velocities through selected forest soils, South Island, New Zealand  J Hydrol (Amsterdam) 55: 65–92.
Perroux KM and White I, 1988. Design for disc permeameters. Soil Sci Soc Am J 52: 1205-1215.
Philip JR, 1957. The theory of infiltration  4. Sorptivity and algebraic infiltration equations. Soil Sci 84: 257-264.
Philip JR, 1991. Hill slope infiltration: Planar slopes. Water Resour Res 27: 109–117.
Reynolds WD, Elrick DE and Youngs EG, 2002. The soil solution phase. Single ring and double or concentric  ring infiltrometers. Pp. 821-826. In JH Jane and GC Topp(ed.) Methods of soil analysis: part 4. Physical methods, SSSA, Madison, WI.
Russo D, Bresler E, Shani U and Parker JC, 1991. Analysis of infiltration events in relation to determining soil hydraulic properties by inverse problem methodology. Water Resour Res
27: 1361-1373.
Sinai G, Zaslavsky D and Golany P, 1981. The effect of soil surface curvature on moisture and yield, Beer Sheba Observations. Soil Sci132: 367-375.
Smettem K and Clothier B, 1989. Measuring unsaturated sorptivity and hydraulic conductivity using multi-disc permeameters. J Soil Sci 40: 565–568.
Torres R, Dietrich WE, Montgomery DR, Anderson SP and Loague K, 1998. Unsaturated zone processes and the hydrologic response of a steep, unchanneled catchment. Water Resour Res
34: 1865–1879.
Van Genuchten MTh, 1980. A closed-form equation for predicting the hydraulic properties of unsaturated soils. Soil Sci Soc Am J 44: 892-898.
Walker C, Lin HS and Fritton DD, 2006. Is the tension beneath a tension infiltrometer what we think it is? Vadose Zone Journal 5: 860–866.
Watson K and Luxmoore R, 1986. Estimating macroporosity in a forest watershed by use of a tension infiltrometer. Soil Sci Soc Am J 50: 578–782.
White I and Sully MJ, 1987. Macroscopic and microscopic capillary length and time scales from field infiltration. Water Resour Res 23: 1514-1522.
Wooding R, 1968. Steady infiltration from a shallow circular pond. Water Resour Res 4: 1259–1273.
Zebarth BJ and de Jong E, 1989a. Water flow in a hummocky landscape in central Saskatchewan, Canada. I. Distribution of water and soils. J Hydrol 107: 309-327.
Zebarth BJ and de Jong E, 1989b. Water flow in a hummocky landscape in central Saskatchewan, Canada. III. Unsaturated flow in relation to topography and land use. J Hydrol 110: 199-218.
Zhang R, 1997. Determination of soil sorptivity and hydraulic conductivity from disk infiltrometer. Soil Sci Soc Am J 61: 1024-1030.