基于蒸渗仪测量的水文要素影响因素分析

降水入渗、地表径流、潜水蒸发等水文要素是研究流域水文及生态环境的重要因素。采用五道沟水文试验站蒸渗仪测量资料,统计分析前期土壤含水量、降水强度、地下水埋深及作物对降水入渗补给、地表径流及潜水蒸发的影响。结果表明:不考虑超渗产流,且在其它条件一致时,前期土壤含水量越大,降水强度越小,入渗补给和地表径流系数越大。无论地表有无作物覆盖,入渗补给、地表径流及潜水蒸发系数均随地下水埋深的增加而减少。降水量小于100mm时,无作物比有作物时的入渗补给系数大;降水量大于100mm时,无作物时的入渗补给系数较小。无作物比有作物时地表径流系数大、潜水蒸发系数小,而潜水蒸发系数的差异在作物生长旺季更为明显。研究成果对淮北地区水土流失治理和生态环境保护具有重要的理论和实际意义。     

Simulation of heat and moisture transfer through a surface residue—soil system

A simulation model suitable for describing the dynamic aspects of mass and energy transfer in a soil—residue—atmosphere system has been developed and used to determine soil heat and water budgets. The model has been programmed in BASIC and uses numerical methods suitable for microcomputer applications. It displays a fundamental coupling of the surface residue to the soil—atmosphere system, and uses network analysis to describe heat and moisture transfer. Short-wave and long-wave radiative transfer, changes in energy status, rainfall interception by the residue, infiltration, redistribution, evaporation, and drainage are all accounted for. Daily input requirements include global short-wave radiation, maximum and minimum air temperatures, average wind speed, precipitation, and temperature and water content deep within the soil. General site, residue, and soil characteristics are also needed.Surface residues are treated as a thin layer with uniform horizontal distribution and residue loading rate is 3000 kg ha⁻¹. Application of the model to energy and water budget studies using environmental data recorded at Pullman, WA during 1981/82 is discussed. Simulation results indicate that for the Pullman conditions surface residues decreased evaporation by roughly 36% when compared with simulations of bare soil evaporation. Monthly trends, however, indicate that the effectiveness of residues in conserving soil moisture decreases as the length of rain-free periods increases.     

Effects of tillage and traffic on crop production in dryland farming systems: II. Long-term simulation of crop production using the PERFECT model

Soil water conservation is critical to long-term crop production in dryland cropping areas in Northeast Australia. Many field studies have shown the benefits of controlled traffic and zero tillage in terms of runoff and soil erosion reduction, soil moisture retention and crop yield improvement. However, there is lack of understanding of the long-term effect of the combination of controlled traffic and zero tillage practices, as compared with other tillage and traffic management practices.In this study, a modeling approach was used to estimate the long-term effect of tillage, traffic, crop rotation and type, and soil management practices in a heavy clay soil. The PERFECT soil–crop simulation model was calibrated with data from a 5-year field experiment in Northeast Australia in terms of runoff, available soil water and crop yield; the procedure and outcomes of this calibration were given in a previous contribution. Three cropping systems with different tillage and traffic treatments were simulated with the model over a 44-year-period using archived weather data.Results showed higher runoff, and lower soil moisture and crop production with conventional tillage and accompanying field traffic than with controlled traffic and zero tillage. The effect of traffic is greater than the effect of tillage over the long-term. The best traffic, tillage and crop management system was controlled traffic zero tillage in a high crop intensity rotation, and the worst was conventional traffic and stubble mulch with continuous wheat. Increased water infiltration and reduced runoff under controlled traffic resulted in more available soil water and higher crop yield under opportunity cropping systems.     

不同覆膜开孔率下土壤水分和潜水蒸发的模拟研究

为研究蒸发阶段不同覆膜开孔条件下土壤水分运动,在室内进行蒸发模拟试验的基础上,采用HYDRUS-1D模型对不同覆膜开孔率和大气蒸发能力条件下土壤剖面含水率和潜水蒸发量动态变化进行了模拟,并与实测资料进行比较。结果表明:土壤剖面含水率同时受大气蒸发能力和覆膜开孔率的共同作用,随覆膜开孔率和大气蒸发能力的增加,土壤剖面含水率减小,且上层土壤含水率差异比下层土壤明显;覆膜开孔率和大气蒸发能力一定时,土壤剖面含水率在蒸发初期有所增加,蒸发后期基本保持稳定;覆膜对潜水蒸发的阻滞作用明显,但开孔率增加到一定数值时,表层盐分的影响大于覆膜的影响,使土壤含水率增大,累积蒸发量减小。经实测数据验证,模型精度较好,表明HYDRUS-1D模型用于不同覆膜开孔率下的土壤水分运动模拟是可行的。     

1970—2015年秦岭北麓径流重建及变化

渭河流域能否高质量发展的一个关键就是水资源的问题,而秦岭北麓是渭河的重要产水区。为探究秦岭北麓近年水资源的变化特征,采用VIC(Variable Infiltration Capacity)模型,基于水文相似性原理,运用典型流域参证法,重建了1970—2015年秦岭北麓径流变化。结果表明:VIC模型在观测流域有着较高的适用性,在月径流模拟中,纳什系数(N_S)大于0.76,相关系数(R²)大于0.91,相对误差(RE)小于±15%; 通过水文参数移植法模型可以真实还原无观测流域径流变化,在验证期N_S,R²,RE分别为0.81,0.94,4.6。近46 a来北麓径流总量在(16.01～65.4)亿m³/a波动,1983年径流量最高达到65.4亿m³,而1977年最小值仅为16亿m³,丰水年份是枯水年份的4倍,径流年际变化明显,过去46 a秦岭北麓多年平均径流值为35.2亿m³/a。降水是径流变化的主导因素,并且也是水文模拟中最重要的影响要素。     

岔巴沟流域汛期径流模拟及地表产流特征分析

气候变化是影响流域水文循环过程的重要驱动因素,近年来,气候变化导致极端降雨—径流事件的频繁发生对人类社会经济发展构成了严重的威胁。因此,迫切需要开展流域水文模拟和产流特征分析。土壤和水评估工具(SWAT)是一种具有物理机制的分布式水文模型,已被广泛用于评价变化环境下的水文过程。以黄土高原岔巴沟流域为研究区,通过利用与黄土高原地区产流模式更为接近的Green-Ampt下渗法驱动SWAT模型模拟了岔巴沟流域日尺度的水文过程,并以水文响应单元为分析对象,结合4个降雨—径流事件的地表产流量和地表径流系数分析了降雨强度和前期土壤含水量对不同土地覆被产流特征的影响。结果表明：(1)基于Green-Ampt下渗法驱动的SWAT模型率定期和验证期E_NS为0.76,0.74,R²为0.78,0.75,模型能够较好地模拟日尺度流域水文过程;(2)流域不同土地覆被下地表径流系数随最大雨强的增加呈显著上升趋势,且最大降雨强度大于16 mm/h后地表径流系数显著增加,当土地覆被为耕地时降雨转化为地表径流的比例最大,其次为草地和林地;(3)前期土壤含水量的大小可以揭示大...     

Estimating evaporation: A comparison between Penman, Idso-Jackson, and zero-flux methods

A field evaporation—drainage study was conducted to compare three methods of predicting evaporative losses from a bare soil. Two of the methods (modified Penman combination and Idso—Jackson) are dependent only on measurements of atmospheric parameters whereas the third method (plane of zero flux) is dependent only on measurements of soil parameters.A Captina soil profile was wet up and allowed to dry by evaporation and drainage. For the initial two days after infiltration ceased all three methods predicted similar evaporative losses. Differences between the three methods occurred when the soil moisture content at the soil surface controlled the evaporation rates. Under the three drying conditions the three methods behaved somewhat differently in the prediction of the amounts of water evaporated from the soil surface. Lower losses by evaporation were predicted by the Idso—Jackson and zero-flux methods. In the case of the Idso—Jackson method this result was attributed to the influence of clouds on albedo, the impact of wind and the importance of albedo in the predictive equation. For the zero-flux method the decrease in evaporation was due to lower soil water contents and matrix potentials near the surface which resulted in lower transport rates of water to the surface.     

Carbon dioxide and energy flux partitioning between the understorey and the overstorey of a maritime pine forest during a year with reduced soil water availability

Carbon dioxide, water vapour and energy fluxes were measured above and within a maritime pine forest during an atypical year with long-lasting reduced soil water availability. Energy balance closure was adequately good at both levels. As compared with what is usually observed at this site the ecosystem dissipated less energy via latent heat flux and more via sensible heat flux. The understorey canopy was responsible for a variable, significant component of the whole canopy fluxes of water vapour and carbon dioxide. The annual contribution of the understorey was 38% (154 mm) of the overall evaporation (399 mm) and 32% (89 mm) of the overall sensible heat flux (274 mm). The participation of the understorey reached 45% of the overall evaporation and 30% of the daytime overall assimilation during significant soil water deficit periods in summertime. Even during winter, understorey photosynthesis was consistent as it compensated soil and understorey respiration. The ecosystem behaved as a sink of carbon, with a negative annual carbon budget (−57 g C m⁻²). However, due to high soil water deficit, the annual ecosystem GPP was 40% less than usually observed at this site. This budget resulted from a sink of −131 g C m⁻² for the overstorey and a source of +74 g C m⁻² for the understorey. Moreover, on an annual basis the overstorey layer contributed to almost two-thirds of the ecosystem respiration. Finally, the effect of long-lasting soil water deficit on the maritime pine forest was found more important than the effect of the heat wave and drought of summer 2003.     

基于前期雨量和降雨历时的SCS-CN模型改进

径流曲线法（Soil Conservation Service Curve Number,SCS-CN）对前期产流条件（Antecedent Moisture Condition,AMC）的概化,导致径流预测出现相应的突然跳跃,同时还忽略了降雨历时作为重要组成部分对地表径流的影响,影响了模型径流预测的精度。密云水库是北京市地表饮用水的重要来源,对其上游流域进行降雨径流预测有着重要的生态意义和经济意义。该研究将SCS-CN模型与前期雨量和降雨历时结合,采用API（Antecedent-Precipitation Index,前期降雨指数）模拟土壤前期水分条件,并且提出了一种考虑次降雨事件中土壤前期雨量和土壤入渗量的静态渗透方程,对SCS-CN模型进行了改进。其中,潜在最大蓄水等于前期土壤水分和土壤潜在蓄水量的和,最大静态渗透速度是流域土壤水分达到蓄满时的静态渗透速度,静态渗透系数是与土壤结构、土地利用等相关的无量纲。利用2006-2010年及2014-2020年石匣流域径流小区的200次降雨径流事件监测结果,对新改进的模型与原SCS-CN模型以及两种改进的SCS-CN模型进行了校准、验证和性能比较。结果表明,4种径流模型中,该研究改进的模型表现最好,纳什效率系数为0.77,决定系数为0.79,均方根误差为3.21 mm,相比于SCS-CN模型纳什效率系数、决定系数和均方根误差分别提高了319%、97.5%和107.5%。参数敏感性分析表明,潜在最大蓄水和静态渗透系数是最敏感的两个参数,最大静态渗透速度的参数敏感性一般,初损率的参数敏感性最差。该研究改进模型在密云水库上游潮白河流域降雨径流模拟中具有一定的适用性,可为其他地区产流计算提供参考依据。     

人工毛竹林生态水文过程对气候变化的响应

为揭示生态水文过程与气候变化的关系,以广西猫儿山典型流域人工毛竹林为研究对象,利用Hydrus-1D模型模拟了毛竹林土壤水分及其他水文要素,在此基础上,针对设定的不同气候变化情景,分析了人工毛竹林对气候变化的响应。结果表明:Hydrus-1D模型可满足人工毛竹林生态水文分析,人工毛竹林蒸散发量占总降水量的28.40%,径流以基流为主。在不同气候变化情景下,气温升幅控制蒸发和蒸腾的增幅,且冬季增幅大于夏季增幅。径流对降水变化更敏感,降水变化会更多地影响夏季径流,而气温则更易影响冬季径流。降水对夏季土壤储水量影响大于冬季,气温则更多地影响冬季土壤储水量。气温降水耦合情况下,土壤储水量对降水减少气温升高时敏感性最明显,总体表现为冬季土壤储水量更易受影响。研究结果可为区域生态规划、水资源开发利用等提供参考依据。     

表层有效土壤水分参数化及冠层下土面蒸发模拟

通过观测田间微气象数据、土壤表层水分变化状况及荞麦作物冠层下土面蒸发等资料,引进一个表面体积含水率的函数,构建了基于表层有效土壤水分的土壤蒸发模型。该模型包含了土面蒸发的2个过程:水蒸气从土壤孔隙中扩散到地表面及水蒸气由地表面传输到大气中。模型中表层有效土壤水分参数不仅取决于表层土壤含水状况,而且受风速影响。采用波文比能量平衡法及微型蒸发器观测荞麦地实际蒸腾蒸发量及冠层下土面蒸发的变化规律,并验证模型精度。结果表明,所构建模型可以成功预测冠层下土面蒸发,其平均相对误差为13.5%。该研究对于实现土壤蒸发及作物蒸腾的分离估算,减少无效水分消耗具有重要意义。     

黄土高原粗质地土壤剖面水分运动与浅层地下水补给可能性模拟

黄土高原水土流失严重,生态环境脆弱,水资源短缺,地下水对保障区域社会经济发展和维持生态系统平衡具有重要意义,而该区的地下水转化和补给机制尚不明确。为探究黄土高原水蚀风蚀交错区土壤剖面深层水分运动及降水对浅层地下水补给的可能性,利用六道沟小流域分布的粗质地风沙土样地2013—2016年土壤剖面0~600 cm含水量数据,运用HYDRUS-1D模型对各土层水力参数进行反演和验证,并用于模拟样地土壤深剖面0~1 500 cm水分运移过程。结果显示,在平水年2014年(439 mm)和干旱年2015年(371 mm),0~600 cm土壤含水量生长季末与生长季初持平或略有亏缺;降水充沛年2013年(669 mm)和2016年(704 mm)土壤含水量生长季末远高于生长季初,降水入渗深度超过观测深度(600 cm)。深剖面水分运动模拟显示,2014年和2015年剖面含水量变化不明显,水分向深层运移微弱缓慢;但是,2013年和2016年降水可分别入渗运移至1 100 cm和1 200 cm深度,远超过样地上生长的旱柳根系区域,可能补给浅层地下水。在4年模拟期间,平均土壤蒸发为14.87 cm·a-1,平均植物蒸腾为33.70 cm·a-1,土壤水分主要以植物蒸腾形式损耗。在2个丰水年,得益于较充足的降水和粗质地风沙土壤的高入渗率,降水大量转化为土壤水快速向下入渗运移,模拟显示当年生长季末降水最深运移至1 200 cm,至年末已超过模拟深度(1 500 cm),水分继续运移可能补给浅层地下水。相关研究结果为黄土高原水蚀风蚀交错区地下水来源和补给机制提供理论依据。     

The water balance of a sugar beet crop: A model and some experimental evidence

For a loes soil with sugar beets (Beta vulgaris L.) a model was developed with which the difficult-to-measure components of the water balance equation can be determined. Basic component of the model is the unsaturated soil moisture flow equation. This equation is solved numerically by a finite difference method. As boundary condition at the soil surface, expressions for the potential and the actual transpiration and for the potential and the actual evaporation are used. Besides the hydraulic functions of the soil, standard meteorological measurements, together with leaf area index and root distribution data of the crop, enter the model. For a period of 316 days, calculated and measured soil suction values in 10 different soil depths, are compared as well as transpiration and seepage vaules. The comparison shows that the model provides acceptable results. The model calculations indicate that of the 519 mm of precipitation received during the 316-day period, 503 mm were used for evapotranspiration and 119 mm left the soil profile as internal seepage.     

山西省孝义矿区不同植被恢复方式下土壤呼吸、温度和水分季节特征

对山西省孝义露天煤矿覆土,种植百脉根、苜蓿、柳树—圆柏混交林和油松林土壤的容重、pH值、有机碳、总氮以及土壤呼吸、温度、和水分的季节变化进行了测定,并对土壤呼吸与土壤温度、水分之间的关系进行了模拟分析。结果表明,不同的植被恢复方式对土壤容重、有机碳、碳氮比和土壤呼吸年均值影响较大,而对土壤pH值和总氮未产生显著影响。土壤温度季节变化曲线为单峰,高斯拟合结果为极显著水平相关;土壤水分随季节波动较大;土壤呼吸季节变化近似于单峰曲线,但高斯拟合的相关性并不显著。苜蓿地土壤呼吸与土壤温度单因子的高斯拟合,以及与土壤温度和水分的双因子拟合系数较高,而百脉根和油松林土壤呼吸与土壤水分相关性强。     

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。     

近地表土壤水分条件对坡面土壤侵蚀过程的影响

 采用人工模拟降雨实验,研究近地表土壤水分条件对安塞黄绵土和杨陵塿土土壤侵蚀过程的影响,尤其是土壤水分饱和条件下的土壤侵蚀过程。结果表明:土壤质地对入渗和径流过程有较大影响。对同一质地的供试土壤,随着前期近地表土壤含水量的增大,入渗量减少,而径流强度增大,坡面初始发生产流时间也越早。当前期近地表土壤含水量相近时,杨陵塿土的初始产流时间早于安塞黄绵土,坡面径流量和侵蚀产沙量也随前期近地表土壤水分含量的增加而增大。对于安塞黄绵土,当前期土壤含水量分别为饱和含水量的100%、75%和50%时,其径流量分别占饱和含水量的25%时的2.5、2.2和1.3倍,其侵蚀产沙量分别为50、25和1.3倍。而对于供试土壤为杨陵塿土,当前期土壤含水量分别为饱和土壤含水量的100%和50%时,其径流量分别是占饱和土壤含水量的25%时的1.1和1.0倍,其侵蚀产沙量分别为6.5和2.0倍。在降雨过程中,前期土壤含水量越大,片蚀发展为细沟侵蚀的时间越早,而且细沟侵蚀也越严重。     

Hydraulic lift may buffer rhizosphere hyphae against the negative effects of severe soil drying in a California Oak savanna

Many studies have shown that the total abundance of hyphae in the soil covaries seasonally with soil moisture. We investigated the extent to which soil hyphal abundance varies as a function of depth and moisture availability within the soil profile during the dry season, and determined whether soil moisture compensation via hydraulic lift (HL) buffers rhizosphere fungi from the effects of severe soil drying. We measured soil water potential, isotopic composition of soil water and total hyphal length in a California coast live oak stand and adjacent grassland at the beginning and end of the 5-month summer drought period. Throughout the summer, oaks maintained predawn water potential values (−0.4±0.1 MPa) that were significantly above those recorded in the 0-200 cm soil depth interval, strongly suggesting root access to groundwater. Direct evaporation of soil water was much more intense and affected deeper layers of the profile in the grassland compared to the oak stand, as indicated by extremely negative water potential values and very enriched isotopic composition of soil water near the surface. Significantly higher soil water potential and less isotopically enriched soil water at 15-40 cm depth in the oak stand were consistent with oak root exudation of isotopically depleted groundwater or deep soil water not exposed to evaporation. Hyphal length in the soil profile declined markedly during the summer drought period in the grassland, particularly in upper layers (41-75% decrease at 0-40 cm depth), indicating rapid turnover of the arbuscular mycorrhizae (AMF) dominated hyphal carbon pool after grass senescence. By contrast, soil hyphal length in the ectomycorrhizal (EM)/AM oak stand remained remarkably constant throughout the summer drought period, with the only exception of the topsoil layer exposed to direct evaporation (49% decrease at 5 cm depth). The sustained exudation of water from roots to soil through HL may have buffered rhizosphere hyphae against the negative effects of extreme soil desiccation in the oak stand. These data suggest that HL by deep-rooted trees may influence the biogeochemical cycling of carbon and nutrients in seasonally dry ecosystems through effects on rhizosphere fungi.     

基于支持向量机的土壤湿度模拟及预测研究

基于中山大学珠海校区气象观测站日平均风速、日平均气温、日平均空气湿度、日平均水汽压、日平均总辐射量、日平均地表温度、日平均降雨量、日平均蒸发量以及日平均10 cm、20 cm、30 cm土层土壤的含水量,利用支持向量机方法建立气象因子与土壤湿度统计关系,并以此为基础建立土壤湿度模拟与预测模型.结果表明,土壤湿度对气象因子有一定滞后相关性,不同土层土壤湿度对气象因子的滞后相关性不同.研究发现考虑滞后相关性的预测模型在精度上要高于不考虑滞后相关性的预测模型.此外,利用气象因子对地下10 cm的土壤湿度模拟与预测精度较高,而对地下20 cm、30 cm的土壤湿度模拟精度较低.利用地下10 cm与20 cm、20 cm与30 cm的土壤湿度相关性大的特点,可以考虑利用支持向量机方法以10 cm土壤湿度模拟与预测20 cm的土壤湿度,以20 cm的土壤湿度模拟与预测30 cm的土壤湿度,分析结果表明模拟精度较高.     

重庆北碚区土壤水热耦合模型研究

以南方的土壤和气候条件为背景,在裸露土壤的非恒温模型一维非饱和水流运动方程后增加根系吸水函数项得到作物地的土壤一维非饱和水流运动方程,与土壤中非稳态热流方程构成作物地的土壤水热耦合运移模型,联合初始边界条件,采用隐式差分法进行数值求解.结果表明：该水热运移耦合模型模拟值与实测值基本吻合,其拟合精度随土层深度增加而提高.     

基于IPARM方法估算沟灌土壤入渗参数

为提高沟灌土壤入渗参数的估算精度,缩小沟灌模拟误差.该文以水量平衡方程为基础,采用IPARM方法建立了沟灌Kostiakov-Lewis入渗方程中参数的估算方法,并根据一组田间实测沟灌资料对入渗参数进行了估算,利用WinSRFR1.1软件对沟灌水流运动进行了模拟.结果表明:用水流推进和径流数据比只用水流推进数据计算的入渗参数的精确度高,可以提高累积入渗量模拟的准确性,并可以将模拟时间延长;在模拟径流量时预测值和实测值的吻合较好.预测精度较高.用IPARM方法估算土壤入渗参数在沟灌模拟和管理中具有较高的可靠性.