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1.
水分胁迫条件下羊草群落生育期双作物系数计算方法的验证 总被引：1，自引：0，他引：1
基于浑善达克沙地2005-2006两个不同水文年对羊草、拂子茅、冰草构成的羊草群落生育期中气象因子及生理因子野外观测试验数据,用联合国粮农组织FAO-56分册中介绍的方法计算了羊草群落生育期基本作物系数和土壤蒸发系数,并对基本作物系数进行了地区气象因素和牧草单叶气孔阻力校正。用校正后的作物系数模拟计算的蒸腾、蒸发量与实际观测值间进行了拟合相关图、拟合优度参数法的有效性检验。结果表明:计算的蒸发、蒸腾量与实测结果基本接近。考虑水分胁迫时,有条件的地区应该对作物系数进行地区气象因素和单叶气孔阻力校正。 相似文献
2.
基于浑善达克沙地2005-2006两个不同水文年对羊草、拂子茅、冰草构成的羊草群落生育期生境中气象因子及生理因子野外观测试验数据,用联合国粮农组织FAO-56分册中介绍的方法计算了羊草群落生育期基本作物系数和土壤蒸发系数,并对基本作物系数进行了地区气象因素和牧草单叶气孔阻力校正。用校正后的作物系数模拟计算的蒸腾、蒸发量与实际观测值间进行了拟合相关图、拟合优度参数法的有效性检验。结果表明：计算的蒸发、蒸腾量与实测结果基本接近。考虑水分胁迫时,有条件的地区应该对作物系数进行地区气象因素和单叶气孔阻力校正。 相似文献
3.
Three different methods of measuring drainage were selected and applied to two irrigated citrus orchards for 3 years. The
methods were: (1) a simple soil water capacity model, (2) a chloride balance, and (3) the LEACHM model. In the first method,
the soil is assumed to have a given water holding capacity, plants cannot extract water from soil below a certain level, and
evapotranspiration varies with soil water content in a well-defined pattern. In the second method, drainage in a given period
of time is estimated from the chloride input to soil (mainly with the irrigation and rain water), the changes in soil chloride,
and the average chloride concentration of soil solution at the depth where drainage is estimated. In the LEACHM model, water
transport in soil is assumed to follow Richards equation, and evapotranspiration depends in soil water content, soil hydraulic
properties, the evaporative conditions of the air, and root properties and distribution. Two citrus orchards planted with
mature trees, under flood irrigation, were used for the comparison of methods. The three methods provided drainage estimates
that differed in most cases by less than 13%, although in some particular season and plot, a given method deviated from the
other two by up to 56%. The soil water capacity model is appealing because it only needs a few parameters for calibration,
and can be easily programmed in a spreadsheet. The main advantage of the chloride balance approach is that it requires neither
calibration nor an estimate of evapotranspiration; this latter fact converts the chloride balance into a good alternative
method of measuring evapotranspiration. The precision of the drainage estimates by chloride balance is mainly determined by
the spatial variability of soil chloride relative to the chloride input to the soil in the measurement period; in most cases,
to obtain a reasonable precision, this period should be longer than 1 or 2 months. The LEACHM model requires more data for
calibration, but it can provide additional information on water and solute distribution in the soil profile with time. 相似文献
4.
5.
Drainage is an intervention in the natural hydrology of the soil to alter the duration of adverse (waterlogged) soil conditions. The effects of drainage can be investigated by models that predict the position of the water table at a site in the presence of drainage. An inter-related series of models, which include the van Schilfgaarde non-steady state model, that have been used in the UK for the evaluation of drainage design options, are described. A simplified form of the van Schilfgaarde equation is presented, equivalent to a standard time series model, allowing both the efficient implementation of the model, and the inverse use of the model to derive performance parameters from observational data using statistical methods. A sensitivity analysis is used to investigate the relative importance of the two soil parameters, drainable porosity and soil hydraulic conductivity, on the performance of the model. This shows a far greater effect due to the variation of hydraulic conductivity.The use of a similar model to predict water tables in non-homogeneous soils has also been explored, including the investigation of a two-phase model to describe water movement in soils which are dominated by macropores. More useful, however, is the prediction of water table fluctuations in soils in which the soil hydraulic conductivity is a continuous function of soil depth, using the drainage theory of Youngs (1965). Solutions are presented for the logarithm of the hydraulic conductivity varying linearly with depth. The improvement in model performance is however gained at the expense of an additional parameter that describes the variation of hydraulic conductivity with depth. Some methods for deriving this parameter are discussed. Results from the use of this model are compared with those derived from the simple uniform conductivity model, showing superior performance.Lastly, the issue of soil lateral heterogeneity and the replicability of measurements is discussed. A detailed study of the variation of water table levels from a replicated drainage experiment indicates that in a practical situation very real limits exist on the accurate measurement of water tables, and that these present limits on our ability to verify models. 相似文献
6.
在稻田淹水到排水干田的过程中,稻田的土壤水分由饱和态转为非饱和态,这一过程中稻田土壤水分运移规律的变化以及水量各平衡要素的转化对稻田水分管理以及减缓农业面源污染等方面具有实际意义.为探寻稻田不同阶段土壤水分状况下的差异性,基于重庆丘陵区紫色土常规轮作水稻土壤水分的连续监测数据,利用HYDRUS-1D模型对稻田淹水、排水落干和收获后3个不同干湿阶段(阶段Ⅰ,Ⅱ,Ⅲ)的土壤水力参数和土壤含水量开展验证模拟分析.研究表明:(1) 根据R2与RMSE的误差分析结果,HYDRUS可以实现对不同阶段稻田土壤水分变化的有效模拟.(2) 根据土壤水量平衡分析,阶段Ⅰ的稻田土壤水分以水分补充的形式为主;阶段Ⅱ和Ⅲ的土壤水分以水分损失为主,底层渗漏量分别占总水分损失量的52%和95%.(3)根据HYDRUS的模拟结果,降雨直接影响土壤上下边界流的变化;阶段Ⅱ的实际作物蒸腾量和实际地表蒸发量低于阶段Ⅰ的,阶段Ⅲ稻田土壤的地表实际蒸发量与日照时数的关系更密切. 相似文献
7.
Xihua Yang 《Agricultural Water Management》2008,95(4):439-446
DRAINMOD is a water management model developed to simulate the performance of drainage and water table control systems for shallow water table soils, and it has been widely used in the United States over the last 20 years. This model has been evaluated and applied for predicting water table fluctuations in a sugarcane field for acid drainage management in north-eastern New South Wales, Australia. The reliability of the model has been evaluated using 2-year experimental field data from water level recorders installed in a sugarcane field. Good agreement was found between the observed and simulated values with a standard error of about 0.07 m. However, the model is not readily applicable to daily water management in Australian soils since it requires extensive soil and climate data, which are normally not available for most Australian sugarcane areas. In this application, refinements have been attempted in evapotranspiration estimation and in soil input data preparation so that the model requires only easily obtainable input data but still retains acceptable accuracy. With these improvements, the model can be used as a practical tool for investigating drainage management options for different site conditions. This will assist decision-makers in providing appropriate subsurface drainage management policies, such as acid drainage management, in Australian estuarine sugarcane areas. 相似文献
8.
Numerical assessment of effective evapotranspiration from maize plots to estimate groundwater recharge in lowlands 总被引：1，自引：0，他引：1
To maximize the irrigation efficiency and to protect groundwater from agrochemical pollution, two variables must be known with good accuracy: effective evapotranspiration and infiltration, especially in lowland areas were the run-off is minimal. Three different experimental plots cultivated with maize were equipped with tensiometers and soil moisture probes to monitor every day the water movement in the unsaturated zone. Other relevant parameters of the various soil layers, as hydraulic conductivity and water retention curve, were obtained in laboratory experiments, while boundary conditions, as precipitations, temperature and root growth, were obtained on site. Inverse modeling was performed using HYDRUS-1D to assess the degree of uncertainty on model parameters. Results showed a good model fit of water content and head pressure at various depths, in each site, using Penman-Monteith formula for daily potential evapotranspiration calculation, but poor fit applying the Hargreves and Turk formulas. Best performance of model fit was observed for S-shaped equation employed to simulate the root water-uptake reduction with respect to Feddes equation. The soil parameters uncertainty was limited and remained within analytical errors, thus a robust estimation of cumulative infiltration and evapotranspiration has been derived. This study points out that evapotranspiration is the most important variable in defining groundwater recharge for maize crops in lowlands. 相似文献
9.
《Agricultural Water Management》1996,29(3):235-253
The performance of published pedotransfer functions was evaluated in terms of predicted soil water content, pressure heads, and drainage fluxes for a layered profile. The pedotransfer functions developed by Vereecken et al. (1989), Vereecken et al. (1990) were used to determine parameters of the soil hydraulic functions θ(h) and K(h) which were then used as input to SWATRER, a transient one-dimensional finite difference soil water model with root uptake capability. The SWATRER model was used to simulate the hydraulic response of a multi-layered soil profile under natural climatic boundary conditions for a period of one year. The simulations were repeated by replacing the indirectly estimated water retention characteristic by (1) local-scale, and (2) field-scale mean observed θ(h) relationships. Soil moisture contents and pressure heads simulated at different depths in the soil profile were compared to measured values using these three different sets of hydraulic functions. Drainage fluxes at one meter below ground surface have also been simulated using the same three sets of hydraulic functions. Results show that simulations based on indirectly estimated moisture retention characteristics (obtained from pedotransfer functions) overpredict the observed moisture contents throughout the whole soil profile, but predict the pressure heads at shallow depths reasonably good. The results also show that the predicted drainage fluxes based on estimated retention functions are about four times as high compared to the drainage fluxes simulated using measured retention curves. 相似文献
10.
华北冬小麦-夏玉米农田水分动态模拟研究 总被引：2，自引：1，他引：2
冬小麦-夏玉米连作是华北地区主要的粮食作物种植模式。根据华北季节性冻土区的特点,将全年划分为作物生长期与越冬期,分别建立了作物生长条件下农田水分运移模型、冻融条件下土壤水热运移模型。前一模型主要包括参照腾发量计算、腾发量分配、作物根系吸水、土壤表面蒸发、土壤水分特征参数和土壤水分运动等子模型;后一模型主要包括冻土水热耦舍迁移、地气水热交换等子模型。应用以上模型对冬小麦-夏玉米连作条件下的土壤水分过程进行模拟,根据北京永乐店试验资料对模型进行检验。模拟了不同降水水平年、不同灌溉处理下的农田灌溉制度及土壤水分过程,分析了降水、灌溉对农田蒸散、土壤水利用、深层渗漏等的影响。 相似文献
11.
L. L. Silva R. Ragab I. Duarte E. Lourenço N. Simões M. M. Chaves 《Irrigation Science》2013,31(4):651-659
The SALTMED model is one of the few available generic models that can be used to simulate crop growth with an integrated approach that accounts for water, crop, soil, and field management. It is a physically based model using the well-known water and solute transport, evapotranspiration, and water uptake equations. In this paper, the model simulated chickpea growth under different irrigation regimes and a Mediterranean climate. Five different chickpea varieties were studied under irrigation regimes ranging from rainfed to 100 % crop water requirements, in a dry and a wet year. The calibration of the model using one of the chickpea varieties was sufficient for simulating the other varieties, not requiring a specific calibration for each individual chickpea variety. The results of calibration and validation of the SALTMED model showed that the model can simulate very accurately soil moisture content, grain yield, and total dry biomass of different chickpea varieties, in both wet and dry years. This new version of the SALTMED model (v. 3.02.09) has more features and possibilities than the previous versions, providing academics and professionals with a very good tool to manage water, soil, and crops. 相似文献
12.
为研究关中冬小麦植株蒸腾和土壤蒸发规律,利用2 a冬小麦小区控水试验实测数据,率定和验证了双作物系数SIMDual_Kc模型在关中地区的适用性.用大型称重式蒸渗仪的实测蒸散量值(或水量平衡法计算值)与模型模拟值进行对比.结果表明:SIMDualKc模型可较准确地模拟关中不同水分条件下冬小麦蒸散量,且模拟精度较高.模型估算的平均绝对误差为0.643 3 mm/d.模型估算的冬小麦初期、中期和后期的基础作物系数分别为0.35,1.30,0.20.另外,模型还可以较准确地估算不同水分供应条件下的土壤水分胁迫系数、土壤蒸发量和植株蒸散量.冬小麦整个生育期,土壤蒸发主要发生在作物生育前期,中期较低,后期略微增大;植株蒸腾主要发生在作物快速生长期和生长中期,整个生育期中呈先增大后减小的趋势. 相似文献
13.
Performance of WATCOM (a numerical model) and CRPSM (a simple water balance model) were assessed in simulating root zone water
storage and water balance components under cowpea in Nigeria using a line source sprinkler system. Three sets of field data
were collected: the first was used for calibration and model parameters’ estimation and the other two for testing and comparisons.
The simulated soil water storage and crop evapotranspiration with WATCOM and CRPSM were in good agreement with field-measured
data though WATCOM performed significantly better (P < 0.05) under the stressed condition. The maximum average error between predicted and measured soil water storage was −0.95
and +1.47 mm for WATCOM and CRPSM, respectively, while that between measured and predicted actual crop evapotranspiration
was +2.7 and +11.38 mm, respectively, for the two models. WATCOM gave generally higher cumulative deep percolation and lower
evapotranspiration than that of CRPSM for all irrigation levels (P < 0.05), and values of deep percolation for WATCOM were in better agreement with field data than that of CRPSM. This suggests
that drainage below the field capacity needs to be included in CRPSM and that WATCOM will be a more useful management tool
when detailed soil parameter is required and under variable water regime. 相似文献
14.
Simulation of 1D surface and 2D subsurface water flow and nitrate transport in alternate and conventional furrow fertigation 总被引：3，自引：0，他引：3
Hamed Ebrahimian Abdolmajid Liaghat Masoud Parsinejad Enrique Playán Fariborz Abbasi Maryam Navabian 《Irrigation Science》2013,31(3):301-316
Increasing water and fertilizer productivity stands as a relevant challenge for sustainable agriculture. Alternate furrow irrigation and surface fertigation have long been identified as water and fertilizer conserving techniques in agricultural lands. The objective of this study was to simulate water flow and fertilizer transport in the soil surface and in the soil profile for variable and fixed alternate furrow fertigation and for conventional furrow fertigation. An experimental data set was used to calibrate and validate two simulation models: a 1D surface fertigation model and the 2D subsurface water and solute transfer model HYDRUS-2D. Both models were combined to simulate the fertigation process in furrow irrigation. The surface fertigation model could successfully simulate runoff discharge and nitrate concentration for all irrigation treatments. Six soil hydraulic and solute transport parameters were inversely estimated using the Levenberg–Marquardt optimization technique. The outcome of this process calibrated HYDRUS-2D to the observed field data. HYDRUS-2D was run in validation mode, simulating water content and nitrate concentration in the soil profiles of the wet furrows, ridges and dry furrows at the upstream, middle and downstream parts of the experimental field. This model produced adequate agreement between measured and predicted soil water content and nitrate concentration. The combined model stands as a valuable tool to better design and manage fertigation in alternate and conventional furrow irrigation. 相似文献
15.
P. Minderhoud 《Agricultural Water Management》1982,5(2):95-125
A model is presented that can be used to determine drainage measures and their costs. It has been elaborated for a wet tropical climate, for situations with open field drains, shallow groundwater table and a homogenous soil underlain by an impervious layer. The land is flat and the proposed agricultural use requires control of the groundwater table.A basic element of the model is a scheme to compute the water balance per day for a drainage parcel. Discharge, evapotranspiration, groundwater level and soil moisture storage are estimated as functions of rainfall, potential evapotranspiration, vegetation and soil characteristics and of an assumed drainage intensity. The water balance computation is performed for periods of 5–40 years of daily rainfall data, for a series of drainage intensities. The results can be subjected to a drainage criterion, from which a design drainage intensity and a corresponding drain spacing can be derived.Finally the layout of canals for a block of 4 × 1 km2 is determined and excavation and a series of canal characteristics are computed.A summary of some applications is included. 相似文献
16.
Asad Sarwar W.G.M. Bastiaanssen Th.M. Boers J.C. van Dam 《Irrigation and Drainage Systems》2000,14(4):257-280
A transient drainage simulation model,SWAP, was used to evaluate the performanceof drainage systems in (semi-) arid zones.Before application, the model wascalibrated by using 14-months datacollected from two sample fields of theFourth Drainage Project (FDP), Punjab,Pakistan. During the calibration process,emphasis was given to the accuratedetermination of soil hydraulic parameters,reference evapotranspiration, drainage fromsample fields and bottom boundarycondition. Laboratory determined soilhydraulic parameters were foundnon-representative of the field conditions.Difference between laboratory and fielddetermined soil water retention curves werefound significant. The pressure heads andsoil water contents measured in depthincrements of 15 cm were in good agreementwith the simulated values after applying afield measured retention curve. A closeproximity was also found between measuredand simulated average root zone salinity at0–1.0 m depth. The referenceevapotranspiration calculated by thePriestly-Taylor (PT-ET
o) methodwas found physically more realistic thanthe Penman-Monteith (PM-ET
o)method due to ignorance of the feed backmechanism of vapor pressure deficit onstomatal closure. The simulated cumulativedrainage from two sample fields wascomparable with the calculated values. Theanalysis of piezometer data shows thatthere is a negligible water exchangebetween the deep aquifer and theunsaturated zone. Therefore for scenarioanalysis, no flow conditions at the bottomof the soil profile can be applied as abottom boundary. 相似文献
17.
《Agricultural Water Management》2006,84(3):240-248
Relative performance of artificial neural networks (ANNs) and the conceptual model SALTMOD was studied in simulating subsurface drainage effluent and root zone soil salinity in the coastal rice fields of Andhra Pradesh, India. Three ANN models viz. Back Propagation Neural Network (BPNN), General Regression Neural Network (GRNN) and Radial Basis Function Neural Network (RBFNN) were developed for this purpose. Both the ANNs and the SALTMOD were calibrated and validated using the field data of 1998–2001 for 35 and 55 m drain spacing areas. Data on irrigation depth, evapotranspiration, drain discharges, water table depths, mean monthly rainfall and temperature and drainage effluent salinity were used for ANN model training, testing and validation. It was observed that the BPNN model with feed forward learning rule with 6 processing elements in input layer and 1 hidden layer with 12 processing elements performed better than the other ANN models in predicting the root zone soil salinity and drainage effluent salinity. Considering coefficient of determination, model efficiency and variation between the observed and predicted salinity values as the evaluation parameters, the SALTMOD performed better in predicting root zone soil salinity and the BPNN performed better in predicting the drainage effluent salinity. Therefore, it was concluded that the BPNN with feed forward learning algorithm was a better model than SALTMOD in predicting salinity of drainage effluent from salt affected subsurface drained rice fields. 相似文献
18.
《Agricultural Water Management》1988,15(1):19-36
A stochastic lower-boundary condition for an unsaturated water-flow domain is presented, which can be used in the numerical solution of the unsaturated water-flow equation for soils with a shallow groundwater-table. The resulting stochastic model can be useful in studying the influence of spatially variable soil hydraulic properties and groundwater levels on soil water regime and plant transpiration. The lower-boundary condition employed assumes an exponential relation between the discharge of a watershed and the groundwater level at a specific location. Since it was found that groundwater levels were influenced by the presence of low-conductive clay in the soil profile, tubes from which groundwater levels were measured are divided into two classes. These classes were based on the presence of clay within the first 1.2 m of the soil profile. Scaling was then used to obtain a reference discharge-groundwater-level relationship for each class and for two years. This relationship in combination with its frequency distribution of the set of scale-factor values for each class and year can be used as the stochastic lower-boundary condition for an unsaturated water-flow model to simulate water transport in a soil with a shallow groundwater-table. An application of such a variable lower-boundary condition is given in two simulation examples. 相似文献
19.
《Agricultural Water Management》2002,54(3):173-188
Two tillage and two water table control treatments under continuous maize cropping were evaluated over a 3-year period (1992–1994) for their effects on evapotranspiration, surface runoff (SR), tile drainage (TD) and soil water content in the root-zone on a clay loam soil in southern Ontario. The tillage treatments included soil saver (SS, reduced tillage) and moldboard plow (MP, conventional tillage). The water table control treatments included controlled drainage-subirrigation (CDS) and regular tile drainage (DR). There was no significant difference (P<0.05) in evapotranspiration estimates between the SS and MP tillage treatments. The SS tillage increased SR compared with MP tillage during the non-cropping periods in 1993 and 1994, but not in 1992. Relative to MP, the SS tillage increased soil profile water content during the cropping period but decreased soil profile water content during the non-cropping period in 1992. The CDS treatment produced significantly higher (P<0.05) evapotranspiration and soil water content than the drainage treatment during the dry 1993 and 1994 years, but not during the wet 1992 year. The CDS treatment also had significantly lower (P<0.05) TD and higher SR than the drainage treatment. For all the treatments, over 65% of SR and TD occurred in the 5 month non-cropping period from November to March. Of the total annual water input (precipitation and/or subirrigation) to the field site, 8% was partitioned to SR, 30% was partitioned to TD, 55% was removed by crop and soil evapotranspiration and 7% was accounted for by changes in soil profile water content. 相似文献
20.
基于遥感的农业用水效率评价方法研究进展 总被引：3，自引：0，他引：3
遥感技术的发展为区域尺度蒸散发计算、作物分布识别及估产提供了一条有效途径,为基于遥感信息的灌区灌溉水利用效率及作物水分利用效率定量评价奠定了基础。回顾总结了遥感蒸散发模型、瞬时蒸散发升尺度方法、日蒸散发插值方法、作物分布识别方法及作物估产模型的研究进展,评述了遥感蒸散发及作物估产结果在灌区灌溉水利用效率及作物水分利用效率评价中的应用情况。提出了相关领域需要进一步研究的问题,包括适合非均匀下垫面特点且具有较强物理基础的灌区遥感蒸散发模型、日蒸散发插值中灌溉或降雨引起土壤含水量突变情况的处理、农田蒸散发中灌溉水有效消耗量的准确估算、能适应复杂种植结构并且适用于多年的作物分布遥感识别模型以及精度较高且可操作性强的遥感估产模型等。 相似文献