Multi-dimensional analysis of soil moisture dynamics in trickle irrigated fields. I: Mathematical modelling

An approach is presented to model soil moisture dynamics in irrigated fields. A generalised conceptual model is proposed for moisture transfer in response to hydraulic and thermal gradients. A model to stimulate moisture extraction by roots is presented, based on a philosophy related to fundamental physical principles and recent experimental evidence. The combined models are interpreted numerically by the finite element method and a number of numerical techniques are developed to treat time-dependent, nonlinear and moving boundary conditions. The approach is sufficiently general and is independent of the method of water application being considered. Its benefits are particularly magnified in studies of localised irrigation, where complex soil-water distribution patterns evolve.     

室内滴灌施药条件下阿特拉津在土壤中运移规律的研究II.数值仿真

本文以实验室内所开展的滴灌施用除草剂——阿特拉津在土壤中运移的物理模拟实验为基础，运用所求得的供试土壤的水力学参数和溶质运移参数及阿特拉津在该土壤中的吸附特性参数和降解速率常数，应用数值模拟软件HYDRUS-2D，对物理模拟的实验结果进行了仿真，并就不同初始含水量、不同滴头流量对土壤水分和阿特拉津动态分布的影响进行了数值分析，结果表明：随着初始含水量的增加，土壤水分的湿润范围增大，而阿特拉津的分布范围基本不变；当滴灌施药历时相同、滴头流量不同时，随着滴头流量的增加，土壤水分和阿特拉津的运动范围均增大。     

地表点源滴灌土壤水分运动的动力学模型与数值模拟

本文提出了一种地表点源土壤水分入渗的数值模拟模型.采用ADI隐式差分格式将土壤水分入渗方程离散，用Gauess-Seidel迭代算法求解非线性差分方程.利用质量平衡原理对地表饱和区进行了动态处理.结果表明，数值计算结果较吻合于实测数据，所提出的数值模型既适用于均质土壤，也适用于成层土壤.     

地埋点源非饱和土壤水运动的数值模拟

根据非饱和土壤水运动理论，建立了地埋滴灌条件下土壤水分运动的数学模型，用有限差分法对模型求解，求解结果得到了田间试验的验证，应用所建立的模型初步分析了地埋滴灌土壤水分运动的基本规律。     

Development and testing of soil water regime simulation models

Four soil water balance simulation models corresponding to specific soil-crop relations were developed for application to irrigation planning and management. The forms of the models were inferred from 18 months of weekly and bi-weekly soil water data and daily meteorological data. Soil water change is computed by budgeting of the water inputs and outputs, namely precipitation, evapotranspiration, drainage, and runoff. Actual evapotranspiration was found to be dependent on both potential evapotranspiration and soil water content. Empirical drainage functions were developed, but semi-empirical ones inferred from theoretical knowledge of soil hydraulic properties performed at least as well. Runoff functions were required to explain only exceptional conditions of very heavy rainfall. A quantitative assessment of each model's prediction accuracy was performed. The uncertainty that can be expected for any predicted value with a cumulative probability of 0.95 is in all cases within an interval of 1% of the soil water content in average conditions.     

Comparison of soil moisture at different depths for drought monitoring based on improved soil moisture anomaly percentage index

To better understand the characteristics and mechanisms of droughts at different drought stages, this study selected the Xiangjiang River Basin in China as the study area, and evaluated soil moisture (SM) at different depths for drought monitoring, through SM data simulated with the variable infiltration capacity (VIC) model. To solve the problem of unreasonable drought/wetness classifications based on the soil moisture anomaly percentage index (SMAPI), an improved soil moisture anomaly percentage index (ISMAPI) was developed by introducing the Box–Cox transformation. The drought/wetness frequency generated by ISMAPI demonstrated preferable spatial comparability in comparison with those from SMAPI. The lag time of ISMAPI relative to the standardized precipitation evapotranspiration index was closely related to soil depth, and was characterized by a fast response in shallow soil layers and a relatively slow response in deep soil layers. SM in shallow soil layers provided a measure for monitoring short-term droughts, whereas SM in deep soil layers provided a better measure for long-term persistent drought events. Furthermore, the occurrence and mitigation time of drought events identified by SM in deep soil layers usually lagged behind that identified by SM in shallow soil layers. Compared with deep SM, SM in shallow soil layers responded faster to meteorological anomalies, thereby resulting in shorter periods of SM persistence in shallow soil layers than in deep soil layers. This can explain the differences of SM at different depths in drought monitoring.     

基于遥感和地面测量的多尺度土壤水分产品验证分析

遥感反演是大尺度土壤水分监测的有效手段,但地面验证一直是土壤水分遥感反演的瓶颈。针对地面土壤水分测量,频域反射仪(FDR)和宇宙射线中子法(CRS)在土壤水分测量中展现出较大的应用潜力。本研究选取不同像元尺度的土壤水分遥感反演结果,包括30 m分辨率Landsat土壤水分反演、1 km分辨率MODIS土壤水分反演和SMAP卫星3 km分辨率和9 km分辨率土壤水分反演产品,利用CRS和FDR土壤水分监测数据对不同像元尺度土壤水分结果进行精度验证分析。结果表明:CRS在30 m分辨率、1 km分辨率、3 km分辨率和9 km分辨率土壤水分反演结果中精度均较FDR方法高,其中1 km分辨率中CRS反演值的均方根误差小于3 km分辨率和9 km分辨率的误差。CRS测量方法对小降水事件较敏感,会带来一定误差。     

土壤水分上下限对北疆滴灌春玉米产量和品质的影响

为确定滴灌春玉米(Zea mays L.)各生育期适宜的土壤水分上、下限,从而为新疆玉米灌溉管理升级提供理论依据,以“太玉339”为试材,采用正交试验设计方法,在玉米拔节期、扬花-灌浆期、灌浆-完熟期分别设置3种水分上、下限(50%～80%FC、60%～90%FC、70%～100%FC,FC为田间持水量),共设9个处理(T₁～T₉),分析其对春玉米不同生育阶段的生长指标、产量、品质、水分利用效率(WUE)的影响。结果表明：当玉米各生育期土壤水分保持在50%～80%FC时,其株高、地上干物质量、叶面积指数(LAI)和产量均显著减小,但会提高水分利用效率(WUE)。总体而言,T₃处理的产量最高,为17 114.51 kg/hm²;T₄处理的WUE最高,为3.11 kg/m³;在灌浆-完熟期提高水分上、下限有利于增加玉米粗蛋白、粗脂肪及淀粉的含量,其中T₃处理该3个指标均为最高,分别为11.02、4.11、69.96 g/100g。以产量、...     

微集水种植技术对北方旱作农业区土壤水分影响

利用微集水种植技术,在我国北方旱作农业地区开展节水灌溉种植,研究不同微集水种植技术对该地区土壤水分的影响。研究结果表明：在不同降水年份,相对于传统种植模式,各微集水种植模式能够明显提高土壤蓄水保墒效果,在玉米生育期内,微集水处理在0-160cm土层的蓄水量要好于传统种植模式。     

土壤墒情自动化监控系统研究

土壤墒情自动化系统可为节水灌溉及排涝抗旱工作提供强有力的技术支持,将产生较大的社会与经济效益.对在作物生长过程中起关键作用的土壤湿度、降雨量、地下水水位等因子进行采集,并对作物的实时生长情况进行视频监控.在此基础上,通过构建计算机信息平台,对监测采集的数据进行存储计算.根据收集的土壤含水量数据信息,建立灌溉智能决策系统,通过开发基于B/S结构的系统网站访问模式,实现土壤墒情自动化监控.     

新安江模型在土壤墒情预报中的应用

近年来干旱已严重影响到自然生态环境的平衡及人类社会、经济的可待续发展。而墒情预报是干旱管理的一项基础工作。本文分析了国内外墒情预报的模型方法,将新安江模型移用于土壤墒情的预报研究中,建立了基于水量平衡的土壤墒情预报方案。从模型的预测结果可以看出,模拟预报结果和实测值基本一致,该方法精度是较高的。新安江模型预报土壤含水量的模型结构简单,涉及参数少且物理意义明确,易于调试优选,便于在实际工作中推广使用。     

新安江模型在土壤墒情预报中的应用

近年来干旱已严重影响到自然生态环境的平衡及人类社会、经济的可持续发展。而墒情预报是干旱管理的一项基础工作。本文分析了国内外墒情预报的模型方法,并将新安江模型移用于土壤墒情的预报研究中,建立了基于水量平衡的土壤墒情预报方案。从模型的预测结果可以看出,模拟预报结果和实测值基本一致,该方法精度是较高的。新安江模型预报土壤含水量的模型结构简单,涉及参数少且物理意义明确,易于调试优选,便于在实际工作中推广使用。     

砾石土质条件下葡萄滴灌生育期土壤含水率变化规律研究

为探究酿酒葡萄在砾石土质条件下的土壤含水率变化规律及合理灌溉制度,选取贺兰山东麓砾石土典型试验区,以五年生赤霞珠品种为研究对象,设计2 550、2 850、3 225、3 600 m3/hm24个不同定额的灌水处理,应用TDR土壤水分剖面仪和土壤水势仪,监测生育期滴灌前后不同土层含水率与水势变化,针对监测数据从灌水处理整体与单个生育期不同角度进行分析,研究酿酒葡萄在砾石土条件下不同滴灌定额土壤含水率变化规律,最终提出生育期适宜灌溉制度。研究结果表明:随着灌溉定额的增加,土壤含水率在0~40cm土层范围内变化较明显;不同深度土层土壤水势变化规律与灌溉定额的大小有关;1m深土壤水分蓄存比并不是随着灌水量的增加而增大,而是当灌水量达到某一定额时,随着灌水量的增加,土壤水分蓄存比减小,砾石土单次灌水量高于300 m3/hm2时,土壤水分蓄存比较低,易产生深层渗漏。     

滴灌系统运行方式和施肥频率对番茄根区土壤氮素动态的影响

在日光温室内开展田间试验，研究了滴灌施肥灌溉系统运行方式和施肥频率对番茄根区硝态氮在生育期内随时间的变化动态、空间分布特征以及氮肥利用效率和回收率的影响。系统运行方式包括不同灌水和施肥次序组成的3种方案。结果表明，在整个生育期内，在灌溉过程的前期施肥，硝态氮在各土层中的分配较为均匀；随着施肥次序向后推移，硝态氮在0～20cm土层的累积逐渐明显。随着施肥频率降低，硝态氮在生育期内随时间的变化逐渐加剧。在滴头的周围，硝态氮易随水流运动，并在湿润土体的横向边缘产生累积。随着施肥次序向前推移，硝态氮向湿润土体边缘运移的趋势愈加明显。剖面内的硝态氮总量随着施肥频率的降低而降低。随着施肥次序向后推移，氮回收率逐渐增大，氮肥利用效率逐渐减小。氮肥利用效率随施肥频率提高而增加。在滴灌施肥灌溉条件下，运行方式选用最初灌溉总时间的1／4时间灌水，再用1／2时间施肥，最后用1／4时间冲洗管道，施肥频率取每周一次较为适宜。     

喷灌均匀系数对土壤水分及冬小麦产量影响的试验研究

为了确定作物喷灌条件下灌水量和产量的空间结构及统计分布规律，定量评价喷灌均匀性对作物产量的影响，对冬小麦生育期内的冠层上、下喷灌水量、土壤水分、叶面积指数及产量的空间分布进行了监测。试验结果表明，在生育期内累计灌水量的相关距离约为5m，产量的相关距离为7--10m，但叶面积指数不存在空间结构。累计灌水量、叶面积指数和产量都可以用正态分布来表示。尽管在冬小麦灌溉季节内喷灌均匀系数变化于57%--89%，但土壤储水量均匀系数始终大于90%.喷灌均匀系数对作物产量的影响比预想的要小。     

太行山山地丘陵区雨季土壤水分动态规律研究——以崇陵流域为研究区

以河北易县崇陵丘陵山区为研究对象,在实验的基础上,针对主要土壤质地、坡度和植被,研究不同下垫面条件下土壤水分变化规律,得到典型土壤质地的物理参数,并对土壤水分的动态变化规律进行了研究。实验结果表明,土壤质地对土壤物理参数和土壤水分变化影响非常大,明显强于植被和坡度。土壤质地对表层和深层水分的变化影响很大,活跃层受质地影响相对较小。     

土层水量平衡模型在土壤墒情预报中的应用

针对宁夏项目区的实际状况,运用土层水量平衡模型来预报当地土壤墒情,发现该模型计算所得的土壤含水率与实测值比较符合,且应用时具有所需信息量少、实用性强和操作方便等特点。     

浅埋式滴灌土壤水分分布规律试验研究

以探寻合理的滴头埋深与流量为目的,开展浅埋式滴灌下土壤水分分布规律的试验研究。试验土箱净尺寸为30cm×30cm×60cm(长×宽×高),供试土壤取自新疆青河县阿苇灌区试验站。试验设置5、10、15 cm 3个滴头埋深,各埋深条件下设置不同流量的处理。结果表明:不同滴头埋深的情况下均存在土体破坏的临界流量,滴头埋深越大临界流量也越大,滴头埋深为5、10和15 cm对应的临界流量分别为1.0、1.7和2.5 L/h;随着流量的增大,滴头埋深过浅时,水量向湿润体上部聚集,当埋深超过一定深度时,水量向湿润体下部聚集;在临界流量情况下,湿润锋前60 min运移速率较快,随着滴头埋深的增大,灌水结束后湿润体的垂向湿润长度越长,土壤平均含水率值越小;滴头埋深为10 cm、流量1.7 L/h时,湿润体水分分布较为合理。     

辽河中下游土壤含水率的监测及分析

监测土壤含水率主要采用土壤水分传感器法和土壤烘干法,通过台安实验站的实验资料对上述两种监测方法进行对比分析,阐述其优缺点,分析各自出现的误差及误差产生的原因。为更好地监测土壤含水率提供了理论依据。     

Application of multi-criteria decision-making methods to identification of soil moisture monitoring sites in an urban catchment in South Australia

When choosing sites for monitoring of soil moisture for hydrological purposes, a suitable process that considers the factors influencing soil moisture level should be followed. In this study, two multi-criteria decision-making (MCDM) methods, the multi-influencing factor (MIF) method and the analytical hierarchy process (AHP) method, were used to identify the optimal soil moisture monitoring (SMM) sites in the Dry Creek Catchment in South Australia. The most representative areas for nine SMM sites were obtained using the MIF method, considering the factors of rainfall, soil type, land use, catchment slope, elevation, and upslope accumulated area (UAA). The AHP method was used to select the optimal sites using the site-specific criteria. 30.3% of the catchment area in the Australian Water Resources Assessment Landscape (AWRA-L) Grid_DC2 can be considered acceptable as representative area with the MIF method. Four potential sites were evaluated for each AWRA-L grid using the relative weights of the site-specific criteria with the AHP method. The Grid_DC2 required two sites that had the highest overall weight chosen with the AHP analysis. The procedure was repeated for the remaining four AWRA-L grids within the study area to select the required SMM sites.