黄土区考虑滞后作用的坡地水量转化模型

建立了考虑滞后作用的坡地水量转化数学模型 ,并对模型不同情况下的定解条件进行了分析,利用陕西长武王以小流域坡地天然降雨－人渗－产流的实测资料的对模型进行了系统检验,结果表明该模型具有较高精度,考虑滞后作用时的模拟值更加接近实测值。在降雨入渗中,滞后作用对土壤含水率,人渗速率,径流过程,产流量都有相当大的影响。     

产流积水法测量降雨侵蚀影响下坡地土壤入渗性能

坡地土壤降雨入渗性能与下垫面对降雨的再分配过程密切相关。该文提出了测量坡地降雨条件下土壤入渗能力的产流积水法。由水量平衡原理,根据径流在坡面上推进的过程和积水情况下积水深度随时间变化的过程,推导得到了计算土壤入渗性能的数学模型。采用两种工况：1)雨强为60 mm/h、坡度5°、径流面与入渗面长度比为1∶2;2)雨强30 mm/h、坡度20°、径流面与入渗面长度比为1∶1。进行室内试验,计算得到了两种工况的入渗性能曲线。分析了这种新型测量方法和计算模型的合理性。将时段降雨量和累计入渗量进行对比,估计了两种工况的测量误差。该方法可以克服传统的降雨器和双环入渗仪方法的不足,用于测量坡地降雨、径流、土壤侵蚀等因素影响下的整个降雨入渗性能过程曲线。为相关研究提供有力的工具。     

产流积水法测量坡地降雨入渗动态过程及其精度估计

坡地土壤的降雨入渗性能对于水文过程、土壤侵蚀、水资源相关方面的研究和实践非常重要。产流积水法采用由实验得到的数据,分析了不同坡位土壤入渗率及累积入渗量随降雨时间的变化过程。结果表明不同坡位入渗过程曲线反映了坡面径流到达前后,实际入渗率从降雨强度控制阶段跃升到入渗性能控制阶段,并最终趋于稳定入渗率的全过程。入渗区不同坡位的累积入渗量从坡顶至坡底逐渐减少,而且径流在坡面上推进速度越快不同坡位上的累积入渗量差值越小。通过理论分析,确定了观测径流推进距离误差所引起的测量结果的误差。用水量平衡原理对产流积水法实验结果进行精度估计,并提出了由实测入渗率求入渗水量的解析方法,并将此与实际降雨量进行比较,间接地估计了测量结果的精度。结果表明,产流积水法测量坡地降雨/径流入渗性能具有很高的精度。     

黄土区不同下垫面农田降雨入渗及产流关系的数值模拟

在野外试验的基础上，建立了二维农田降雨入渗及产流关系的数学模型，并用中国科学院长武县王东沟农业生态站不同下垫面径流小区实测土壤含水率及产流资料对该模型进行验证。结果显示：该模型对降雨过程中土壤入渗、产流以及雨后蒸发条件下土壤水分的模拟都有很高的精度，可以用于黄土区降雨入渗及产流关系的模拟。     

模拟降雨条件下含砾石土壤的坡面产流和入渗特征

模拟降雨条件下研究了含砾石土壤的入渗过程,分析了砾石含量和坡度对土壤坡面产流时间和入渗的影响。研究结果表明:含砾石土壤的坡面产流时间与砾石含量和坡度密切相关,当坡度>5°时,产流时间与砾石含量呈线性负相关。当坡度<5°时,不同砾石含量的土壤入渗能力表现出明显差异;砾石含量为20%~30%时,土壤入渗相对增加;当坡度>10°时,砾石含量对入渗能力的影响不明显。利用Kostiakov入渗经验模型可以很好地模拟含砾石土壤的降雨入渗过程,模型中的经验系数K能够反映出降雨开始1 min内坡度和砾石含量对入渗的影响。     

坡地单元降雨产流分析及平均入渗速率计算

分析了坡地农田和草地生态单元降雨产流过程,提出了一种利用降雨产流资料计算坡地单元平均入渗速度的方法,此方法克服了双环法测定坡地土壤入渗速率的固有缺陷,为研究坡地水量转化提供了便利手段,计算结果表明,农田,草地生态单元土壤平均入渗速率随坡度的增加呈指曲线下降。     

黄土高原主要秋作物坡地降雨入渗特征参数研究

为揭示作物覆盖条件下坡耕地降雨入渗特征,以黄土高原3种典型秋作物(玉米、大豆和谷子)为对象,在3°~15°的坡地径流小区上,采用人工模拟降雨和水量平衡的方法,分析了作物全生育期降雨入渗过程中初始入渗率、稳定入渗率、平均入渗率和累积入渗量的数量特征及影响因素。结果表明:(1)作物坡地的降雨入渗过程随降雨历时的延长,入渗量呈由高到低的变化,波动性明显;(2)作物坡地的初始入渗率、平均入渗率和累积入渗量均高于裸坡地,而稳定入渗率除玉米坡地较大外,其余差异不大,4个参数值基本上与降雨强度和叶面积指数的增大成正比,与坡度成反比;(3)基于降雨强度、坡度及叶面积指数,通过多元回归分析建立了土壤初始入渗率、稳定入渗率、平均入渗率和累积入渗量多元回归模型,为入渗过程模拟提供了基础。     

黄土高原水土保持措施强化降雨入渗分析及灰色预测

黄土高原水土流失综合治理是以强化降雨入渗,减少地表径流,阻止土壤侵蚀为目的。因此,治理区降雨入渗量的大小是衡量水土流失治理效果的关键指标之一。目前入渗量的计算多利用年总降雨量,由于在黄土地区小雨量或小强度的降雨具有与水土流失治理的零相关性,因而会导致对水土流失综合治理强化入渗作用估计的较大误差。提出用1a中产生径流的次降雨总量(产流降雨总量)计算入渗量。以西川河流域为例,采用1997—2001年的降雨径流资料,分别用年降雨总量与产流降雨总量推求降雨入渗系数,对比分析了入渗量随流域水土流失治理度的变化,结果表明:利用产流降雨总量能比较清晰地反映流域治理程度对降雨入渗的影响。在此基础上,采用GM(1,1)灰色动态模型预测西川河流域降雨入渗量随水土流失治理度的变化趋势。结果表明,GM(1,1)灰色模型能够合理地预测黄土高原水土保持措施对自然流域入渗量影响的变化趋势。     

前期土壤含水量对坡面产流产沙特性影响的模拟试验

为了研究黄土区降雨前期土壤含水量对不同土壤坡面降雨入渗、产流和产沙特性的影响,采用室内降雨模拟试验方法,探讨了前期土壤含水量从风干土状态至近饱和条件下填土和砂黄土坡面降雨入渗、产流产沙的特征.研究结果表明:在雨强(80mm/h)和坡度(10°)较大情况下,前期土壤含水量对塿士坡面产流时刻、入渗和产流过程影响不明显;砂黄土坡面产流时刻受前期土壤含水量影响显著,随着前期土壤含水量的增大先延长后缩短,其极差值达到28.91min:前期土壤含水量在风干土～10%和15%～25%两段范围内,砂黄土坡面入渗产流规律差异十分显著.基于土壤水分累积入渗过程特征,填土前期含水量可分成"三区",砂黄土则可分成"两区";利用前期土壤含水量与坡面土壤流失量的二次多项式关系,分别确定出壤土和砂黄土坡面土壤流失量最少的前期含水量值为11.25%和12.74%,为黄土区坡地水土管理提供理论依据.     

前期土壤含水量对坡面产流产沙特性影响的模拟试验(简报)

为了研究黄土区降雨前期土壤含水量对不同土壤坡面降雨入渗、产流和产沙特性的影响,采用室内降雨模拟试验方法,探讨了前期土壤含水量从风干土状态至近饱和条件下塿土和砂黄土坡面降雨入渗、产流产沙的特征。研究结果表明：在雨强（80 mm/h）和坡度(10°)较大情况下,前期土壤含水量对塿土坡面产流时刻、入渗和产流过程影响不明显;砂黄土坡面产流时刻受前期土壤含水量影响显著,随着前期土壤含水量的增大先延长后缩短,其极差值达到28.91 min;前期土壤含水量在风干土～10%和15%～25%两段范围内,砂黄土坡面入渗产流规律差异十分显著。基于土壤水分累积入渗过程特征,塿土前期含水量可分成“三区”,砂黄土则可分成“两区”;利用前期土壤含水量与坡面土壤流失量的二次多项式关系,分别确定出塿土和砂黄土坡面土壤流失量最少的前期含水量值为11.25%和12.74%,为黄土区坡地水土管理提供理论依据。     

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。     

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。     

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.     

Controls of infiltration–runoff processes in Mediterranean karst rangelands in SE Spain

Semiarid karst landscapes represent an important ecosystem surrounding the Mediterranean Basin for which little is known on runoff generation. Knowledge of the sources and patterns of variation in infiltration–runoff processes and their controls is important for understanding and modelling the hydrological functions of such ecosystems. The objectives of this paper are to determine the infiltration rates and their controls in a representative mountain karst area (Sierra de Gádor, SE Spain) at micro-plots and to investigate the integrated response of rainfall on a typical hillslope. Rainfall simulations in micro-plots and natural rainfall-runoff monitoring on a hillslope were carried out complementarily. We investigated the role of soil surface components (vegetation, rock outcrop, fracture, and soil crust), topographic position, antecedent soil moisture, and rainfall characteristics in regulating infiltration–runoff processes. Results of rainfall simulation revealed the importance of vegetation cover and the presence of rock fractures in promoting the infiltration in the limestone karst landscape, while bare patches and rock outcrops acted as sources for runoff. All plots with > 50% vegetation cover had no runoff with up to 55 mm h^− 1 of simulated rain. In contrast, nearly all bare plots had runoff under the same simulated rain, with runoff coefficients ranging from 3.1 to 20.6% on dry soil surface conditions, and from 2.0 to 65.4% on wet soil surfaces. Runoff coefficients amounted to 59.0–79.5% for rock outcrops without cracks, but were drastically reduced by the presence of cracks. The surfaces with rock fragments resting on the soil (generally located in the middle of the slopes) prevented more effectively the runoff generation than those surfaces where rock fragments were embedded in the top soil. Antecedent soil moisture had significant impact on runoff generation, with wet soil having doubled runoff coefficient, shortened time to runoff, and increased runoff rate compared to the same but dry soil. Linear regressions indicated that the main controls for constant infiltration rate were the cover percentages of vegetation and litter, plus rainfall intensity; while the major controls for runoff coefficient were the bare soil and vegetation coverage, plus rainfall intensity. High infiltration rates measured at the micro-plots agreed with low intra-event runoff coefficients (mostly below 1%) observed under natural rainfalls at the hillslope. Runoff depth and coefficient at the hillslope was significantly correlated with rainfall depth, maximum hourly rainfall intensity and antecedent precipitation over 20 days (AP₂₀). During the 1.5-year monitoring period from Sep-2003 to Mar-2005, the overall infiltration was 41% of the total rainfall amount and the maximum infiltration rate was almost 94% of the largest single rainfall event. The results from this study contribute to improved understanding of the magnitude and controls of the surface runoff in semiarid karst mountain areas.     

Runoff generation in a degraded Andean ecosystem: Interaction of vegetation cover and land use

Tropical mountain regions are affected by rapid land use/-cover change, which may threaten their (eco-)hydrological functions. Although there is a growing interest in evaluating the effect of land use/-cover change on mountain hydrology, quantitative assessments of the impact of land use/-cover on hydrological processes are hampered by the lack of field measurements characterizing runoff generation processes. In this paper, we present results from field experiments of rainfall runoff mechanisms in the southern Ecuadorian Andes. A rainfall simulator was used to quantify the hydrological response of distinct land use/-cover types to intense rainfall (about 40 mm/h). The rainfall runoff experiments indicate that degraded and abandoned land generate surface runoff within a few minutes after the start of the rainfall event. These lands have a very rapid and sharp hillslope hydrological response, as Hortonian overland flow is the dominant runoff generation mechanism. In contrast, surface runoff on arable and rangelands is rare, as their soils are characterized by a high infiltration capacity (i.e. > 29 mm/h). Our experiments provide evidence that runoff generation in degraded Andean ecosystems is mainly controlled by the surface vegetation cover and land management. When reducing the surface vegetation cover, the soil is increasingly affected by rapid hillslope runoff as the presence of large amounts of smectites in the outcropping soft rocks makes the material very prone to sealing and crusting, thereby enhancing runoff generation.     

黑土区坡耕地横坡垄作措施防治土壤侵蚀的土槽试验

为了研究黑土区坡耕地横坡垄作防治坡面土壤侵蚀的效应,该文利用8 m×1.5 m的试验土槽,设计3个降雨强度(50、75和100 mm/h)、1个典型坡度(5°)以及横坡垄作和无垄作(平坡裸地对照试验)的试验处理进行模拟降雨试验,研究东北黑土区横坡垄作坡面在不同降雨强度下的防治坡面侵蚀效应。结果表明:横坡垄作在50 mm/h降雨强度下坡面基本不发生土壤侵蚀,但在75和100 mm/h降雨强度下会发生断垄,造成防蚀效应急剧降低。横坡垄作坡面的径流和侵蚀过程均明显存在以断垄时间为界的突变,在3个降雨强度下,横坡垄作断垄前可使坡面径流量和侵蚀量分别减少97.7%和99.1%以上,坡面蓄渗率达到97.2%以上;而断垄后坡面径流量和侵蚀量分别增加23.3~25.9倍和136.8~171.5倍,蓄渗率下降至50%以下。试验研究表明横坡垄作在≤50 mm/h的降雨强度下具有很好的坡面防治侵蚀效应,但当遇到强降雨时易发生断垄,防蚀效应急剧降低。     

不同植被格局对梁峁坡-沟坡的侵蚀动力作用机制

[目的]探究不同植被格局对梁峁坡—沟坡的侵蚀动力作用机制,为进一步揭示草地坡面侵蚀规律和植被减蚀效应研究提供科学依据。[方法]以梁峁坡—沟坡为研究对象,采用室内降雨模拟降雨和三维激光扫描技术,分析不同植被格局对梁峁坡—沟坡侵蚀动力作用机制。[结果]径流流速和含沙量共同影响着坡面侵蚀动力过程,径流流速是主要影响因素。坡面的侵蚀产沙来源主要位于沟坡内,不同植被格局下梁峁坡与沟坡产沙比例的不同,反映了植被调控侵蚀的范围和强度的不同。草带位于梁峁坡中下部时,不但能够有效降低梁峁坡的侵蚀程度,而且能够有效抑制和减缓沟坡内的径流流速,大幅度降低梁峁坡下部和沟坡内的侵蚀程度。[结论]不同植被格局可以通过影响径流流速和含沙量来调控梁峁坡—沟坡侵蚀动力。     

野外模拟降雨条件下坡面降雨入渗、产流试验研究

利用野外模拟降雨试验,研究了植被类型、降雨强度、地表结皮、覆盖杂草等对荒草地和裸地降雨入渗、产流的影响。结果表明:裸地因降雨易产生地表结皮,产流时间主要取决于降雨强度,两者的关系可用幂函数描述,达显著水平;荒草地由于植被覆盖度较高,产流时间主要取决于土壤初始含水量,两者的关系可用线性公式描述,达极显著水平;与裸地相比,荒草地能延缓产流,并有效拦蓄径流;裸地形成地表结皮后,产流提前,平均入渗率降低,但坡面覆盖杂草(尤其是坡中下部覆盖杂草)能有效拦蓄径流、延缓产流、增加入渗,并促进土壤水分向深层的运移,而雨后采用抑制蒸发的措施能起到类似的效果     

黄土区均匀坡面水文模型研究

应用Green—Ampt修正方程及运动波方程,构建了天然降雨条件下的黄土区均匀坡面水文预报模型,并利用野外天然降雨径流实测资料进行了验证。结果表明,总径流量预报相对误差在20%以下,预报径流过程与实测径流过程吻合很好,坡面水文模型可以较好地模拟黄土地区天然降雨条件下的均匀坡面水文过程。同时也指出,应深入研究复杂坡面上的水文预报模型,进一步完善黄土区坡面水文模型。