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1.
Understanding the variables regulating tile‐flow response to precipitation in the US Midwest is critical for water quality management. This study (1) investigates the relationship between precipitation characteristics, antecedent water table depth and tile‐flow response at a high temporal resolution during storms; and (2) determines the relative importance of macropore flow versus matrix flow in tile flow in a tile‐drained soya bean field in Indiana. In spring, although variations in antecedent water table depth imparted some variation in tile‐flow response to precipitation, bulk precipitation was the best predictor of mean tile flow, maximum tile flow, time to peak, and run‐off ratio. The contribution of macropore flow to total flow significantly increased with precipitation amount, and macropore flow represented between 11 and 50% of total drain flow, with peak contributions between 15 and 74% of flow. For large storms (>6 cm bulk precipitation), cations data indicated a dilution of groundwater with new water as discharge peaked. Although no clear dilution or concentration patterns for Mg2+ or K+ were observed for smaller tile flow generating events (<3 cm bulk precipitation), macropore flow still contributed between 11 and 17% of the total flow for these moderate size storms. Inter‐drain comparison stressed the need to use triplicate or duplicate tile drain experiments when investigating tile drainage impact on water and N losses at the plot scale. These results significantly increase our understanding of the hydrological functioning of tile‐drained fields in spring, when most N losses to streams occur in the US Midwest. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
2.
六盘山典型植被类型土壤中石砾对大孔隙形成的影响 总被引：4，自引：1，他引：4
六盘山山区土壤中存在大量的石砾,对土壤大孔隙的形成具有重要影响。为了深刻了解和评价土壤中石砾对大孔隙形成的可能作用,本研究分析了六盘山典型植被类型下土壤中的石砾体积含量、大孔隙度变异以及石砾体积含量对大孔隙度、大孔隙半径与密度的影响。结果表明,石砾含量增加导致土壤大孔隙的平均半径和体积增大,特别是导致半径大于1.4 mm的大孔隙密度的增大,但对较小半径的大孔隙密度影响不大;总体上,石砾对土壤大孔隙度的形成影响随土深的增加而越来越明显,说明六盘山地区土壤的大孔隙明显同时受到生物因素和石砾含量因素的影响。 相似文献
3.
土壤大孔隙流研究中分形几何的应用进展 总被引：7，自引：0，他引：7
土壤中普遍存在的大孔隙使水及溶质快速穿过土壤，污染地下水，确定土壤大孔隙流性质需要大量的野外和室内实验。本文在对分形几何概念进行简要阐述的基础上，介绍了分形几何在土壤大孔隙流研究中所取得的成果，结果表明应用分形几何确定土壤大孔隙流性质是一种省时、省力和具有广泛代表性的方法，最后对分形几何在土壤在大孔隙流研究中应用前景作了展望。 相似文献
4.
大孔隙流是土壤优先流的一种,在植被发育区土壤大孔隙比较常见,对径流形成过程产生重要的影响。介绍了大孔隙流的研究方法,系统总结了近50年植被发育区土壤大孔隙对降雨入渗过程及径流形成过程的影响:从水分入渗的角度,大孔隙可以加快降雨入渗过程;由土壤大孔隙流与山坡产流的关系,大孔隙促进了边坡雨水的运动进而引起了快速产流;世界范围内的研究都表明土壤管流或大孔隙流是径流组分重要贡献者。 相似文献
5.
This study was conducted to estimate macropore space, macropore flow and matrix flow in an experimental forest plot in the Ouachita Mountains of Arkansas. Lateral soil water fluxes and soil capillary potentials were observed in the isolated plot during applied rainfall experiments. Rainfalls were applied 17 times during the period 17 July to 10 October 1991. The subsurface hydrograph separation technique was used to estimate macropore space, macropore flux and matrix flux. The boundary between macropore and matrix flow was statistically determined by covariance analysis. The maximum estimated lateral macropore space was approximately 0.006 (cm3 cm?3). The maximum estimated lateral macropore and matrix flow were 0.042 and 0.00066 cm s?1, respectively. This report also emphasizes the need for further research on the hydrograph separation procedure for estimating macropores and macropore flow. 相似文献
6.
水及溶质在有大孔隙土壤中运移的研究（I）：田间实验 总被引：2，自引：1，他引：2
通过田间原状土和回填土渗透比较试验，揭示了大孔隙对水及溶质在土壤中运移的影响。通过回填土和原状土中含水率实验结果比较分析，指出回填土和原状土含水率的变化呈现不同分布特征。而对回填土和原状土中溶质浓度实验结果分析比较，发现回填土中水分运动和溶质运移的速度显著低于原状土，回填土和原状土都有位置深的检测点先于其上面的检测点出现溴离子的现象，回填土中硝酸根离子的浓度远低于其在原状土相应深度的浓度。 相似文献
7.
Reclamation of peat bogs for agriculture changes the physical and chemical characteristics of the peat matrix, for example, drainage and tillage accelerate decomposition, altering peat porosity, pore size distribution, and hydraulic properties. This study investigated changes in near-saturated hydraulic conductivity over time after drainage of peat soil for agricultural use by conducting tension infiltrometer measurements in a mire that has been gradually drained and reclaimed for agriculture during the past 80 years (with fields drained 2, 12, 40, and 80 years before the measurements). At pore water pressure closest to saturation (pressure head −1 cm), hydraulic conductivity in the newest field was approximately nine times larger than that in the oldest field, and a decreasing trend with field age was observed. A similar (but weaker) trend was observed with −3 cm pressure head (approximately four times larger in the newest field in comparison to the oldest), but at −6 cm head, there were no significant differences. These results indicate that peat degradation reduces the amount of millimetre-sized pores in particular. They also indicate that changes in peat macroporosity continue for several decades before a new steady state is reached. 相似文献
8.
A new method to characterize the spatial structure of soil macropore networks in effects of cultivation using computed tomography 
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下载免费PDF全文 Soil macropore networks are subsurface connected void spaces caused by processes such as fracture of soils, micro‐erosion and fauna burrows. Axial X‐ray computed tomography (CT) scanning provides a convenient means of recording the spatial structure of soil macropore networks. The objective of this study were to (1) based on CT technique and GIS digitized image method, construction a new technique for tracing, visualizing and measuring the soil macropore networks and (2) investigate the effects of farming activities on soil macropore networks characteristics. Our technique uses left‐turning and nine‐direction judgment methods, a combination of the layer‐by‐layer analysis method and the up‐down tracking algorithm. The characteristics for the overall structure patterns of macropores, the spatial distribution of the macropore networks and each single macropore network can be conveniently identified by our technique. Eight undisturbed soil columns from fields with two distinct land uses (under cultivation and not been cultivated) and four different depths (0–20, 20–40, 40–60 and 60–80 cm) were investigated. The soil columns were scanned using X‐ray CT at a voxel resolution of 0.075 × 0.075 × 3.000 mm. Results indicate that farming activities can destroy the initial structure of macropores, and those remaining are mainly small‐sized and medium‐sized networks with lower extension and hydraulic conductivity. The network properties show a significant difference between upper and lower layer. The results can provide beneficial reference to further research centered on non‐equilibrium flow prediction and chemical transport modeling in field soils. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
9.
Surface soil hydraulic properties are key factors controlling the partition of rainfall and snowmelt into runoff and soil water storage, and their knowledge is needed for sound land management. The objective of this study was to evaluate the effects of three land uses (native grass, brome grass and cultivated) on surface soil hydraulic properties under near‐saturated conditions at the St Denis National Wildlife Area, Saskatchewan, Canada. For each land use, water infiltration rates were measured using double‐ring and tension infiltrometers at ?0·3, ?0·7, ?1·5 and ?2·2 kPa pressure heads. Macroporosity and unsaturated hydraulic properties of the surface soil were estimated. Mean field‐saturated hydraulic conductivity (Kfs), unsaturated hydraulic conductivity at ?0·3 kPa pressure head, inverse capillary length scale (α) and water‐conducting macroporosity were compared for different land uses. These parameters of the native grass and brome grass sites were significantly (p < 0·1) higher than that of the cultivated sites. At the ?0·3 kPa pressure head, hydraulic conductivity of grasslands was two to three times greater than that of cultivated lands. Values of α were about two times and values of Kfs about four times greater in grasslands than in cultivated fields. Water‐conducting macroporosity of grasslands and cultivated fields were 0·04% and 0·01% of the total soil volume, respectively. Over 90% of the total water flux at ?0·06 kPa pressure head was transmitted through pores > 1·36 × 10?4 m in diameter in the three land uses. Land use modified near‐saturated hydraulic properties of surface soil and consequently may alter the water balance of the area by changing the amount of surface runoff and soil water storage. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
10.
Abstract The accuracy of six combined methods formed by three commonly-used soil hydraulic functions and two methods to determine soil hydraulic parameters based on a soil hydraulic parameter look-up table and soil pedotransfer functions was examined for simulating soil moisture. A novel data analysis and modelling approach was used that eliminated the effects of evapotranspiration so that specific sources of error among the six combined methods could be identified and quantified. By comparing simulated and observed soil moisture at six sites of the USDA Soil Climate Analysis Network, we identified the optimal soil hydraulic functions and parameters for predicting soil moisture. Through sensitivity tests, we also showed that adjusting only the soil saturated hydraulic conductivity, Ks , is insufficient for representing important effects of macropores on soil hydraulic conductivity. Our analysis illustrates that, in general, soil hydraulic conductivity is less sensitive to Ks than to the soil pore-size distribution parameter. Editor D. Koutsoyiannis; Associate editor D. Hughes Citation Pan, F., McKane, R.B. and Stieglitz, M., 2012. Identification of optimal soil hydraulic functions and parameters for predicting soil moisture. Hydrological Sciences Journal, 57 (4), 723–737. 相似文献