黄土区坡地降雨入渗产流中的滞后机制及其模型研究

滞后作用的存在,不但影响降雨过程中的入渗特性,而且影响产流量。该文通过对入渗产流中的滞后机制分析,建立了考虑滞后作用的坡地降雨入渗产流模型。利用黄土高原沟壑区典型小流域坡地天然降雨入渗－产流的实测资料对模型进行了检验,结果表明：在降雨入渗－产流过程中,滞后作用加快入渗速率,减少径流量;滞后模型使土壤含水量、产流过程接近实测值。因此,在降雨入渗产流过程中考虑滞后作用的影响是必要的。     

花岗岩不同土地利用类型坡地产流和入渗特征

根据安溪官桥径流小区实测资料，确定了不同利用坡地临界产流降,专门化地果表明，植被较好的林果茶坡地很少有地表径流产业，以这类坡地为主的流域，坡地地表直接补给河流的比例很小，壤中流（表层流）和地下水流可能在造峰过程中起决定性作用，而在自然裸地，坡地地表直接补给洒流的径流比例可达７０％，地表快速汇流是造峰主导因素，坡地产流期内降雨损失率随产期内降雨平均强度的增大而增加，两者呈幂函数关系：f=ai^b,从Ｉ类→Ⅱ类→Ⅲ类→Ⅳ类坡地，a,b值减小，坡地土壤渗特征曲线呈f=ae^-bx关系。     

植被影响下的黄土坡地降雨漫流数学模型

利用径流实验小学观测资料分析了黄土坡地稀疏植被对降雨漫流中有效糙率的影响，提出了在数学模型中定量考虑植被作用的简化方法，并通过模拟计算进行了检验。坡地降雨浸流过程模拟精度的提高为进一步建立黄土坡地雨洪侵蚀过程数学模型打下了基础。     

模拟玉米茎秆流对土壤侵蚀的影响

玉米茎秆流是降雨过程中经玉米冠层截留后沿茎秆流向根部的水量,是种植坡地地表径流的重要组成部分,对植物根部的土壤侵蚀过程具有重要影响。采用人工模拟降雨方法,研究了成熟期玉米茎秆流对坡地土壤侵蚀的影响。试验土槽长为0.40 m、宽为0.23 m、深为0.14 m;采用直径为2 cm的PVC管模拟成熟期玉米茎秆,高度为1.2 m;模拟茎秆流量为5,10,15 g/s,用相同降雨条件下无茎秆流坡地作为对照措施;降雨强度为60,90,120 mm/h,降雨历时108 min,坡度为10°。结果表明:(1)与对照措施相比,茎秆流具有加快坡地地表产流的作用;(2)模拟茎秆流条件下地表产流量和产沙量均高于对照,相较无茎秆流坡地,3个降雨强度下各茎秆流量的产流贡献率为14.90%~43.10%,产沙贡献率为12.47%~26.75%;(3)茎秆流在茎秆周围地表形成细小股流,促使坡地土壤侵蚀过程由面蚀向细沟侵蚀转变,从而增加了坡地土壤侵蚀量。因此,在坡地水土流失计算与评价中应考虑茎秆流的土壤侵蚀作用。     

植被恢复演替初期对模拟降雨产流特征的影响

利用模拟降雨装置,研究了演替恢复初期不同植被覆盖以及不同处理下坡面降雨的产流过程和人渗率。实验研究结果表明,植被演替开始之初,由于地表土壤的土质比较疏松,土壤的人渗率比较大。随着植被演替的进行,土壤中有机质等物质的逐渐累积,土壤的理化性质发生了变化,土壤的人渗特征也随之降低。剪草降雨小区的实验研究结果说明,在降雨的初期,土壤的人渗性能相对较低,随着实验的进行,在雨滴的打击下,部分结皮被破坏,土壤的人渗率也随之增大。说明地表生物结皮的存在,降低了土壤的人渗性能。采取适当的措施破坏地表生物结皮,有利于提高土壤的人渗性能,增加干旱半干旱地区对降雨的利用程度。     

降雨对施用两种尿素坡地氮素空间分布的影响

采用自动模拟降雨系统,设置恒定降雨强度,在室内对施用普通尿素和树脂包膜控释尿素的土槽进行模拟降雨试验。通过模拟降雨试验,比较研究了降雨对施用两种尿素的坡地氮素空间分布及氮素流失特征影响。研究结果表明:树脂包膜控释尿素在棕壤、褐土及红壤坡地上施用,均能显著减小降雨对坡地氮素空间分布的影响;与普通尿素相比,模拟降雨后,树脂包膜控释尿素处理的3种类型土壤坡地氮素残余量变异系数为普通尿素的14.08%~31.89%;且树脂包膜控释尿素显著缩小了降雨对3种类型土壤坡地表层与下层氮素空间分布影响间的差异;树脂包膜控释尿素在3种类型土壤坡地上施用均能减少降雨造成的氮素流失,与普通尿素施用相比,氮素流失分别减少了7.32%~17.35%(P0.05)、17.95%~24.24%(P0.05)、72.45%~78.84%(P0.01);同时,树脂包膜控释尿素还能减小降雨造成的坡地表层与下层氮素流失量间的差异,下层坡面氮素损失量仅比表层增加1.63%~5.02%。因此,降雨条件下,在坡地上施用树脂包膜尿素有利于控制氮素的分布失衡及流失。     

红壤丘陵区坡地降雨壤中流产流过程试验研究

在红壤丘陵区，对自然降雨条件下坡地（上层0～40cm，下层40～110cm）降雨壤中流产流过程进行了研究，结果表明：不同土地利用方式下，油茶林壤中流产流量大于同层恢复区；壤中流峰值流量恢复区大于同层油茶林；油茶林壤中流产流过程较恢复区开始早、结束晚。随着土层加深，滞后时间延长。同一土地利用方式下，产流量、峰值流量、滞后和拖尾均为上层小于下层。壤中流对降雨及地表径流的响应均为上层快于下层。不同的降雨类型，壤中流产流机理不同。峰值型降雨壤中流产流过程滞后时间较小，壤中流产流类型多为驱赶流。     

坡地雨水资源潜力分析及径流侵蚀的动态变化

通过人工模拟降雨,对宁南山区坡地改造后不同坡度的自然坡面进行试验研究。结果表明:相同降雨量下,降雨强度与土壤贮水量补充呈反比,入渗深度随坡度增大减小。比较人工降雨和双环法对稳渗速率的影响,人工降雨测定的土壤稳渗速率小于双环法测定的稳渗速率,双环法所测定的土壤稳渗速率与人工降雨法测定的土壤稳渗速率之间呈线性函数关系。对水平沟水分补充随坡度和雨强增大而增大,大雨对水平沟水分补充有重要意义。产沙动态分析,雨强较大时,随时间推移,单位体积泥沙含量递减,在较小雨强下,随时间推移,单位体积泥沙含量呈递增趋势。雨强和土壤侵蚀模数的关系符合幂函数方程:Q=0.017I2.5442     

基于滞后效应函数的土石坝渗流水位模型应用

根据长期观测资料用数理统计回归分析建立土石坝渗流效应量模型,是目前普遍采用的大坝安全监测资料分析方法。传统土石坝渗流效应量模型主要受库水位、降雨和时间3个因素直接影响,并考虑前期平均库水位和降雨的影响。然而采用前期平均法并不能真实有效的反映库水位和降雨对大坝渗流的滞后影响,近年来提出了考虑库水位、降雨动态效应权重的滞后效应函数法,可以更好的描述变化库水位及降雨作用下的大坝渗流场。以此为基础,建立较为合理的大坝渗流模型,对某水库的渗流水位进行了多元非线性回归分析,采用遗传算法及最小二乘原理优化求得滞后参数及各分量系数,并进一步分析了库水位滞后参数演变规律。基于滞后效应函数的渗流水位模型拟合效果好,很接近实际情况,有利于对大坝的运行工况做出准确、合理的判断。     

水蚀过程中裸露陡坡耕地土壤侵蚀特征

在坡耕地上,农业耕作措施改变了地表微地形,对坡地土壤侵蚀过程产生影响。深入了解耕作措施对坡地土壤侵蚀的影响,以便为开展陡坡耕地退耕还林(草)工程的水土保持效益评价提供科学依据。以30°陡坡耕地为研究对象,采用室内人工模拟降雨试验方法,对采用人工锄耕、人工掏挖和等高耕作的裸坡地土壤侵蚀特征进行研究。用相同坡度平整坡地作为对照措施。降雨强度为60,90,120mm/h,降雨历时80min。结果表明:(1)在陡坡耕地上,在雨强为60,90mm/h时,3种耕作措施都具有延缓坡地产流的作用,但在雨强为120mm/h时,人工锄耕和人工掏挖坡地产流开始时间与平整坡地无显著差异(P0.05);(2)对采用等高耕作的陡坡地,在3个降雨强度下,累计产流量均低于平整坡地,但采用人工锄耕和人工掏挖的陡坡地与平整坡地相比并无明显规律;(3)在降雨强度为120mm/h时,耕作陡坡地地表径流含沙量较高,土壤侵蚀量是平整坡地的2~5倍。因此,在裸露陡坡耕地上,当降雨强度偏大时,采用农业耕作措施不仅不能降低土壤侵蚀发生,反而会增加。     

模拟自然条件下黄土区坡地的大气、土表及土壤水交互作用的动力学模型及其应用

The mechanism of atmospheric,surface and soil water interactions( water transformation) in hillslope under natural conditions was analyzed,and a dynamic model was developed to simulate infiltration,overland flow and soil water movement during natural rainfall in hillslope,by bringing froward concepts such as rainfall intensity on slope and a correction coefficient of saturated soil water content for soil surface seal.Some factors,including slope angle,slope orientation and raindrop inclination,which affect the rainfall amount on slope, were taken into account while developing the dynamic model.The effect of surface seal on infiltration and water balance under a boundary condition of the second kind was aslo considered. Application of the model in a field experiment showed that the model simulated precisely the infiltration,overland flow and sol water monvement in hillsope under natural rainfall conditions.     

土壤初始含水率对坡面降雨入渗及土壤水分再分布的影响

在防止土壤侵蚀和雨后抑制蒸发的条件下，利用室内人工降雨试验，研究了土壤初始含水率对坡面降雨入渗、湿润锋运移及土壤水分再分布规律的影响。结果表明：初始含水率越高，产流越快，平均入渗率越小，达到稳定入渗率的时间也越短；当初始含水率均匀分布时，降雨入渗和再分布过程中湿润锋面平行坡面垂直向下整体运移，坡面降雨入渗过程可以简化为一维；当初始含水率非均匀分布时，初始含水率越高，再分布过程中湿润锋的运移速率越大，但在降雨入渗过程中，湿润锋的运移速率与土体的湿润程度和范围有一定的关系；坡面上方来水(径流)虽然对湿润锋运移速率影响不大，但对入渗有一定的促进作用；再分布过程中，土壤水分有沿坡向下运移的趋势。     

由降雨事件引起的坡面产流和土壤侵蚀的元胞自动机模拟

A novel quantitative cellular automata (CA) model that simulates and predicts hillslope runoff and soil erosion caused by rainfall events was developed by integrating the local interaction rules and the hillslope surface hydraulic processes. In this CA model, the hillslope surface was subdivided into a series of discrete spatial cells with the same geometric features. At each time step, water and sediment were transported between two adjacent spatial cells. The flow direction was determined by a combination of water surface slope and stochastic assignment. The amounts of interchanged water and sediment were computed using the Chezy-Manning formula and the empirical sediment transport equation. The water and sediment discharged from the open boundary cells were considered as the runoff and the sediment yields over the entire hillslope surface. Two hillslope soil erosion experiments under simulated rainfall events were carried out. Cumulative runoff and sediment yields were measured, respectively. Then, the CA model was applied to simulate the water and soil erosion for these two experiments. Analysis of simulation results indicated that the size of the spatial cell, hydraulic parameters, and the setting of time step and iteration times had a large impact on the model accuracy. The comparison of the simulated and measured data suggested that the CA model was an applicable alternate for simulating the hillslope water flow and soil erosion.     

前期含水量对坡面降雨产流和土壤化学物质流失影响研究

在防止土壤侵蚀条件下,利用室内人工降雨实验,研究了土壤初始含水率对坡面降雨入渗、产流、溶质迁移规律的影响。结果表明:初始含水率越高,产流越快,达到稳定入渗率的时间也越短。在初始含水率不同时次降雨过程中养分的流失量与初始含水量具有较强的相关性。磷浓度的变化范围主要在5cm以内,随着含水量的增加有效磷向土壤中迁移的总量增加。随着含水量的增加土壤钾离子向土壤中迁移的总量减小。在相同条件下,EDI值大小顺序是:磷<钾<溴。     

水文条件对紫色土坡面土壤侵蚀及养分流失的影响

采用人工模拟降雨试验,研究水文条件对紫色土坡面土壤侵蚀及氮和磷养分流失的影响。试验处理包括2个施肥水平（低肥和高肥水平）,4个水文条件（自由下渗、土壤水分饱和、壤中流、壤中流＋降雨）和一个降雨强度（60 mm/h,历时60 min）。结果表明：壤中流＋降雨和土壤水分饱和条件下的土壤侵蚀量分别是自由下渗条件下的3.1和1.7倍,同自由下渗相比,壤中流、壤中流＋降雨和土壤水分饱和条件下,地表径流中NO3-N、HPO4-P的浓度和流失量有显著增加;低肥水平条件下,自由下渗、土壤水分饱和、壤中流和壤中流＋降雨地表径流中,NO3-N的浓度分别是0.88、58.90、698.41和87.80 mg/L,对应水文条件下地表径流中,HPO4-P的浓度分别是0.252、0.322、0.811和0.383 mg/L,高肥水平条件下,径流中的NO3-N和HPO4-P的浓度也有相同的趋势;土壤水分饱和条件下,地表径流中NO3-N和HPO4-P的流失量分别是自由下渗条件下的27～39和1.3倍,壤中流＋降雨条件下,地表径流中NO3-N和HPO4-P的流失量分别是自由下渗条件下的100～114和1.5～1.7倍,同时,壤中流＋降雨和土壤水分饱和条件下,泥沙中NO3-N和HPO4-P的流失量也比自由下渗条件下显著增加。     

Non-equilibrium water flow characterized by means of upward infiltration experiments

Upward infiltration experiments under tension were used to demonstrate the presence of non‐equilibrium flow in soils, the phenomenon that has important implications for the accelerated movement of fertilizers, pesticides, non‐aqueous liquids, and other pollutants. Data obtained from these experiments were analysed using the single‐porosity Richards equation, as well as a variably saturated, dual‐porosity model and a dual‐permeability model for characterizing non‐equilibrium water flow. The laboratory experiments were carried out on 0.10‐m‐long soil cores having an internal diameter of 0.10 m. Constant pressure heads of ?0.10 and ?0.01 m were used as the lower boundary condition. Each infiltration was followed by a single‐rate evaporation experiment to re‐establish initial conditions, and to obtain the drying soil hydraulic properties. Pressure heads inside the cores were measured using five tensiometers, while evaporative water loss from the top was determined by weighing the soil samples. The data were analysed to estimate parameters using a technique that combined a numerical solution of the governing flow equation (as implemented in a modified version of the Hydrus‐1D software) with a Marquardt–Levenberg optimization. The objective function for the parameter estimation was defined in terms of pressure head readings, the cumulative infiltration rate, and the final total water volume in the core during upward infiltration. The final total water volume was used, as well as the pressure head readings during the evaporation part. Analysis of flow responses obtained during the infiltration experiment demonstrated significant non‐equilibrium flow. This behaviour could be well characterized using a model of physical non‐equilibrium that divides the medium into inter‐ and intra‐aggregate pores with first‐order transfer of water between the two systems. The analysis also demonstrated the importance of hysteresis.     

利用一维代数模型分析微咸水入渗特征

由于淡水资源短缺,微咸水的开发利用成为缓解农业水资源短缺的重要措施,为了研究微咸水条件下的土壤入渗过程,进行了室内微咸水垂直一维入渗试验,分析了不同矿化度的微咸水累积入渗水量随时间的变化过程,并利用一维代数入渗模型模拟计算了土壤含水率剖面。结果表明：含水率模拟计算结果与实测值相吻合。同时利用一维代数入渗模型和Green-Ampt模型对试验资料进行处理,结果表明两模型均可以比较精确地描述微咸水入渗过程,因此两模型可以互相计算参数,但长历时入渗用Green-Ampt模型计算更加精确。     

Interpreting soil and topographic properties to conceptualise hillslope hydrology

The sustainability of agricultural practices is enhanced when vegetation makes optimal use of natural hydrological processes. For example, planting tree belts where slope gradient sharply decreases can enable harvesting of run-on water. This can be beneficial for example in reducing water logging and enhancing tree production. There is a need for rapid and low cost identification of water flow paths and conceptualisation of hillslope hydrology so that local landuse planning can reflect such opportunities. The collection of detailed hillslope hydrological data is prohibitively expensive for such applications and so the use of soil morphology and visual observation of topography and surface condition is evaluated as an alternative.At a study site in south eastern Australia the soil physical profile was described down a hillslope with additional measurements of the hydraulic conductivity, bulk density, cation exchange capacity, electrical conductivity, and particle size distribution of the key horizons. This data was used to identify the perceived significant hydrological flow paths down the hillslope. Measurement of the surface runoff, subsurface lateral flow, and the distribution of saturation measured in piezometers were subsequently used to test the conceptual hydrological model.Soil morphology, particularly the soil colour and presence of redox concretions were useful in identifying the locations and depths where saturation and lateral flow occur. The morphology provides an integrated reflection of the dominant hydrological conditions, but care must be taken to ensure that the observations reflect the current hydrological environment and not relic conditions. Other collaborating information such as the history of geomorphological events at the site, a validation of plausible water sources for the potentially transmitting layers, surface soil condition and landholder observations give improved confidence. Combining soil morphological understanding with visual observations of other site characteristics enabled rapid conceptualisation of hillslope hydrological behaviour as needed for local landuse planning.     

坡面生物调控措施对土壤水分入渗的影响

为了研究不同生物调控措施的植被覆盖度、降雨强度和坡度以及各因素间交互作用对土壤水分入渗的影响,本文通过室外人工模拟降雨试验,对不同生物调控措施坡面的土壤水分入渗规律进行了探索。结果表明：1）有生物调控措施坡面的土壤稳定入渗率较裸坡偏大,且差异极显著,但生物调控措施坡面之间的差异并不明显。2）降雨强度、坡度与土壤稳定入渗率间不是线性单值函数,均存在使土壤稳定入渗率最大的临界雨强与临界坡度。稳定入渗率随植被覆盖度增加的速率是非恒定的,存在着增速变化的临界植被覆盖度。临界植被覆盖度前,稳定入渗率的增加速率很快,之后,迅速降低并趋于稳定。3）坡面径流调控度随雨强增大而减小;相同雨强下不同措施坡面径流调控度排序为：黑麦草＞春小麦＞苜蓿＞裸坡。4）采用SPSS软件通过逐步回归分析法提取了影响土壤稳定入渗率最显著的单因子交互作用项,建立了包含降雨强度、坡度和植被覆盖度在内的多因素非线性入渗模型,通过实测数据对其进行验证发现该模型精度较高。