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Results from a field experiment examining soil water fate within U.S. Golf Association (USGA) putting greens were used to examine the validity of a water flow simulation model. The experiment used six different sandy root zones each with depths of 300 mm overlying a 100 mm thick gravel layer. Data collected over two growing seasons consisted of measured rainfall, irrigation, drainage volume, and soil water contents; and calculated turfgrass evapotranspiration (ET). Turfgrass rooting was measured at the end of each growing season, and water retention curve and saturated hydraulic conductivity measurements were conducted at the end of the study. For each root zone treatment, HYDRUS-2D (H2D) was calibrated using a subset of the experimental data and then validated by comparing observed and predicted water contents at 76, 152 and 229 mm depth and over both growing seasons. Model efficiency (E) ranged from 0.33 to 0.78; Mean Absolute Error (MAE) ranged from 0.012 to 0.024 m3 m−3; and Root Mean Square Error (RMSE) ranged from 0.015 to 0.028 m3 m−3, for the six treatments and both years. Also, RMSE values were at best slightly larger than and at worst twice as large as the mean standard deviation values of replicate measurements. Thus, H2D simulation performed reasonably well in describing the water content results of the field study. The calibration results provide evidence of hysteresis in water retention where water retention properties from the field appear to follow the sorption or wetting curve as compared with the laboratory measurements following the desorption or drying curve. This suggests that standard laboratory measurements of water release would not precisely predict water retention behavior in the field and over estimate water storage of these capillary barrier soils. The validation results provide evidence for turfgrass use of perched water held within these profiles, even though turfgrass rooting is shallow and water storage principally occurs deep within the root zone. Thus, the perched water of USGA putting greens should serve reasonably well as a water reservoir for subsequent turfgrass use, allowing for water conserving irrigation practices that makes use of this stored water. 相似文献
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A linear programming (LP) based optimization model and a simulation model are developed and applied in a typical diversion type irrigation system for land and water allocation during the dry season. Optimum cropping patterns for different management strategies are obtained by the LP model for different irrigation efficiencies and water availability scenarios. The simulation model yields the risk-related irrigation system performance measures (i.e. reliability, resiliency and vulnerability) for the management policies defined by the optimization model. The alternative strategies are evaluated in terms of all performance criteria (i.e. net economic benefit, equity and reliability) simultaneously through a trade-off analysis using a multi-criteria decision making method (compromise programming). For the case study of the Kankai irrigation system in Nepal, with equal preference to the objectives, a management strategy with equal share of water among the project subareas appears to be the most satisfactory alternative under water shortage conditions. The existing water allocation policy is not economically efficient. Deficit irrigation in Early paddy appears attractive under favorable hydrologic scenario, particularly if accompanied by measures to improve existing irrigation system efficiency. 相似文献
4.
《Agricultural Water Management》2005,74(3):201-218
The water consumption, expressed as ‘actual evapotranspiration’ (ETa), plays an important role in understanding the soil–water–atmosphere–plant environment. This paper highlights two different methods to assess the water consumption of banana, a traditional and modelling approach, respectively.The first method to assess ETa was based on the water balance equation and thus included field measurements. The second method involved the simulation model soil water atmosphere plant (SWAP). The results showed that both methods led to comparative results.This study also aimed at evaluating the performance of the SWAP-model under very different circumstances as for which it has been used previously. The uncertainty about the parameters of the SWAP model remained rather high. The most important drawback of SWAP is the enormous amount of data that is required. Since these data were not always available, this resulted in a large amount of parameters to be estimated and involved in the sensitivity analyses and calibration process. The final simulation results showed several inconsistencies. It seemed that, for successful predictions, more data were needed to describe the bottom boundary condition (BBC) of the considered soil profile in greater detail, especially when there is influence of groundwater. This BBC has indeed a great impact on the simulation results. SWAP offers several ‘simplified’ approaches concerning the BBC in case no data are available. However, in all cases SWAP seemed to overestimate the moisture content. 相似文献
5.
Simulating basin surface water flow with anisotropic roughness has practical significance. Based on the complete hydrodynamic model, a two-dimensional surface water flow model of basin irrigation with anisotropic roughness was developed in this study by constructing an anisotropic roughness model in the source terms of the governing equation. Then, the simulation performance of the proposed model was analyzed and compared based on typical experiments of basin irrigation. The results show that with basin surface anisotropic roughness, the proposed model can successfully simulate water flow in basin irrigation, and exhibits better simulation performance than the model with isotropic roughness. Three basin geometries and two kinds of inflow geometries were selected for the application of the proposed model. Applied results show that the anisotropic roughness can improve irrigation performance. When the basin width becomes narrow, the physical effect of the rotation angle in the anisotropic roughness model weakens, even becomes smooth. The two-dimensional surface water flow model of basin irrigation with anisotropic roughness provides a good numerical simulation tool for designing and evaluating the performance of basin irrigation system. 相似文献
6.
Temporary water trading is an established and growing phenomenon in the Australian irrigation sector. However, decision support and planning tools that incorporate economic and biophysical factors associated with temporary water trading are lacking. In this paper the integration of an economic trading model with a hydrologic water allocation model is discussed. The integrated model is used to estimate the impacts of temporary water trading and physical water transfers. The model can incorporate economic and biophysical drivers of water trading. The economic model incorporates the key trade drivers of commodity prices, seasonal water allocations and irrigation deliveries. The hydrologic model is based on the Resource Allocation Model (REALM) framework, which facilitates hydrologic network simulation modelling. It incorporates water delivery system properties and operating rules for the main irrigation and urban centres in a study area.The proposed integration method has been applied to a case study area in northern Victoria, Australia. Simulations were conducted for wet and dry spells, a range of commodity prices and different irrigation distribution system configurations. Some example analyses of scenarios incorporating water trading were undertaken. From these analyses potential bottlenecks to trade that constrain the economic benefits from temporary water trading were identified. Furthermore, it was found that in certain areas of the system, trading can make impacts of long drought spells worse for water users, e.g. irrigators. Thus, the integrated model can be used to quantify short-term and long-term third party impacts arising from temporary water trading. These findings also highlight the need to link “paper trades” (estimated by economic models) to physical water transfers (estimated by biophysical models). 相似文献
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In this study a simulation model for real-time irrigation scheduling of water deliveries at the tertiary and secondary canal levels of large irrigation systems has been developed. The model is responsive to current season changes in weather and other variables. The irrigation scheduling of the subsequent week is found out at the end of each week by updating the status of the system with real time data up to that week and then by solving the model for the new conditions. The model is based on water balance approach for lowland paddy and a soil moisture simulation approach for determining the irrigation requirements of upland crops. Expected rainfall at different probability levels during the irrigation season was used based on past rain fall data and Leaky law. The model was applied to an irrigation system in Thailand for determining the required irrigation deliveries. Result of the application indicate that the model can be used for determining water deliveries in a real-time basis. 相似文献
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《Agricultural Water Management》2002,57(2):111-126
The macroscopic root water uptake approach was used in the numerical simulation model HYSWASOR to test four different pressure head-dependent reduction functions. The input parameter values were obtained from the literature and derived from extensive measurements under controlled conditions in the greenhouse. The simulation results indicated that the linear reduction function cannot fit the data satisfactorily. Most of the existing non-linear reduction functions can fit only half of the data range, while the best agreement is obtained with the non-linear two-threshold reduction function. The parameter values obtained by calibration differ only slightly from those of the experiments. Soil water pressure head heterogeneity over the root zone does not play an important role in water uptake. The roots appear to take up water from the relatively wetter parts of the root zone to compensate for the water deficit in the drier parts. While the simulated transpiration agrees closely with the experimental data, the main reason for the discrepancy between the simulated and actual water contents appears to be water uptake during the night. 相似文献
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针对农田分区灌溉需水量模拟过程中普遍存在的求解过程易陷入局部最小化、出现过度拟合,以及过度依赖历史用水数据,导致最终模拟结果存在显著误差的问题,研究基于贝叶斯神经网络的农田分区灌溉需水量模拟分析方法。以前一周需水量、年内月需水量占比、日内温度上限值及日降雨量为指标,通过聚类分析获取指标数据均值,对农田分区灌溉历史用水的样本数据进行聚类分析。构建贝叶斯神经网络模型,将指标数据均值输入模型,根据BP神经网络原理与贝叶斯规则训练指标数据,然后输出农田分区灌溉需水量模拟结果。试验结果显示数据聚类结果中数据间关联度高于95%,数据拟合效果较好,模拟需水量时具有更高的精度与稳定性。 相似文献
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In order to research the influence of liquid water content(LWC) on blade icing of wind turbine,a numerical simulation method for blade icing was established.The numerical simulation was based on low speed viscous N-S equation.The trajectory equation of water droplets was established by Lagrangian method.The mass and energy conservation equations of the water droplets impacting on the surface of the blade were solved based on control body theory.Three sections along blade span wise of a1.5 MW wind turbine were decided to simulate icing.Five kinds of LWC were selected for simulation including 0.2,0.4,0.6,0.8 and 1.0 g/m3 under two ambient temperatures of-10 ℃ and-20 ℃.The medium volume droplet diameter(MVD) was 30 "m.The simulations included icing shape on blade surface,dimensionless icing area and dimensionless maximum stagnation thickness.Furthermore,the flow fields around both the iced blade airfoil and the original one were simulated and analyzed.According to the results,the typical icing characteristics of icing shape,icing area and thickness were greatly affected by the difference of LWCs.This study can provide theoretical reference for the research on antiicing and deicing of wind turbine blade. 相似文献
11.
In Hawaii, pineapple is typically grown in raised beds covered with impervious plastic mulch. Field measurements of a commonly used herbicide (bromacil) mass beneath mulch-covered pineapple beds and inter-bed open areas revealed that open areas contained a mass of bromacil about 3.5 times greater than was originally applied, based on label instructions, to the entire field. The broadcast bromacil ended up in the inter-bed open areas through water runoff from the plastic mulch covering the pineapple beds. The objective of this study was to evaluate the impact of surficial management on water dynamics and bromacil concentration in the soil on a pineapple plantation using the one- (1D) and two-dimensional (2D) flow and transport models. Flow and transport processes were simulated in a 2D vertical cross-section perpendicular to the plant rows. The 1D simulation was limited to the open inter-bed areas. Several simulation scenarios were proposed to evaluate the effect of plastic mulch on bromacil transport in soil. In our simplified approach, the water and solute boundary fluxes for the non-covered areas were increased to simulate the water and solute contribution from the plastic mulch surface. The simulation results were compared with field observations of soil water potentials and resident bromacil concentration profiles. The field and laboratory-measured hydraulic and transport parameters were used for all simulation scenarios. Reasonably good agreement between the model-predicted and observed soil water potentials and bromacil concentration profiles was obtained. Biased 1D and 2D results were predicted when the water runoff from plastic mulch was neglected. The 1D approach to quantify bromacil transport beneath the inter-bed open areas seemed to be sufficient in case the water runoff from the mulch was taken into account. 相似文献
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Numerical models for the simulation of soil water processes can be used to evaluate the spatial and temporal variations of crop water requirements; this information can support the irrigation management in a rationale usage of water resources. This latter objective requires the knowledge of spatially distributed input parameters concerning vegetation status, soil hydraulic behaviour and groundwater interaction. This task can be achieved by a conjunctive use of remote sensing techniques, geographical information systems and hydrological simulation models. The present work focuses on the criteria applied for the implementation of a one-dimensional model for water flow in each parcel of an irrigation district in southern Italy having extension of 3000 ha. 相似文献
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通过单喷头雨量分布室内试验,获取雨量分布信息及出水轨迹信息.利用三维建模、粒子系统等虚拟现实技术,结合实际的雨量分布数据及出水轨迹,模拟出喷头喷洒水雾的三维动态模型.研究喷灌机各跨同步行走时前进方向喷灌雨量分布均匀性,实现前进速度的最优化.分析喷头配置间距和喷头高度对横向灌溉均匀度的影响,优化平移式喷灌机喷头配置.在进行单喷头雨量分布室内试验的基础上,建立了雨量分布仿真模型.仿真结果和现场试验表明：改变驱动电机的频率可以实现纵向的变量灌溉,横向的灌溉均匀度取决于喷头的型号和压力,田间与仿真试验得到的水分分布数据最大相对误差为3.39%,证明仿真模型的可信度.为平移式喷灌机同步行走控制条件下变量控制对灌溉效果的影响和优化研究提供了手段. 相似文献
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《Agricultural Water Management》2006,81(3):282-294
Wetlands in arid and semi-arid regions often experience water shortage problems due to interrupted water supply. Rapid population growth and economic development have caused deterioration or total destruction of many wetlands in such regions. Protection or restoration of these wetlands require a good understanding of the relationship between water supply and the soil wetness. This paper presents a model simulation study of such a relationship based on weather and soil data from Xi’an, China. The study area has an average annual precipitation of 600 mm and evaporation of 1200 mm. The simulation results showed that, to produce a certain wet condition, the required amount of water supply varied with recharging time due to different evapotranspiration rates. To maintain a consecutive water table depth within 30 cm (1) for 5% of the growing season, water requirements varied from 7 cm to 16 cm for different recharging months; (2) for 12.5% of the growing season, water requirement varied from 9 cm to 20 cm; and (3) for 25% of the growing season, water requirements varied from 13 cm to 27 cm. The highest water requirement occurred in summer when the air temperature is the highest of the year. Simulation results also showed that the timing of recharge not only has an important effect on the threshold water requirement, but also on the overall soil wetness of a year. Recharging at earlier time of the growing season produced longer wet periods, but the overall water table remained low during the rest of the growing season. Later inflow only influenced the water table for a small portion of the growing season, but it maintained a generally high water table in winter months and the early part of the next growing season. 相似文献
15.
A simulation study on alternative water management strategies was carried out for Sirsa Irrigation Circle in Haryana, covering an area of about 4800 km2. Results showed that crop evapotranspiration and soil salinity development under reduction in canal water supply and increase in groundwater use, are largely influenced by the amount and distribution of rainfall. Reduction in canal water supply by 25% during the rainy season is unlikely to have any adverse effect on the salinity development in the study area. Reduction in crop evapotranspiration due to decreased canal water supply can partly be compensated by the increase in groundwater use. Leaching of salts due to monsoon rains in the study area shows that groundwater of even relatively poor quality can be used for irrigation without excessive long-term build up of soil salinity under deep groundwater depth conditions. However, increased groundwater extraction without associated actions will not be very effective to solve the problem of rising groundwater levels. 相似文献
16.
《Agricultural Water Management》2002,52(2):155-175
The Government of Egypt is currently implementing projects that expand irrigated area on the Sinai Peninsula and in the southern desert. Those projects will reduce the supply of Nile River water available to farmers in the Nile Delta, which is a heavily populated and highly productive agricultural region. The southern desert project will obtain water directly from Lake Nasser, while a mixture of Nile River water and drainage water will be delivered to the Sinai. The true costs of the projects include the opportunity costs of water and capital that could be used alternatively in the Nile Valley and Delta, or in other productive endeavors. Economic analysis generates optimizing criteria that describe the role of scarcity values (opportunity costs) in determining the allocation of Nile River water that will maximize net social benefits. Policy implications are derived by comparing those criteria with the criterion that farmers implement when maximizing profits from crop production. A small-scale simulation model demonstrates the potential impact of water allocation policies on regional net revenues. Results are discussed within the context of a broader view of national goals that include promoting economic growth, achieving food security, and enhancing the quality of life for Egyptians. 相似文献
17.
为了改善时段划分对作物水模型模拟精度的影响，依据山西水利职业技术学院试验基地2006和2008年棉花田间试验资料，将棉花全生育期等间隔地划分为不同时段，用非线性优化方法求得了不同时段数条件下的作物水模型参数，分析研究了模型参数与时段数的关系，据此在作物水模型的水分敏感指数累积函数中引入了时段数，并与现有的作物水模型进行了比较。结果表明，引入时段数的作物水模型模拟产量的相对误差随时段数的增加而减小，当时段数大于11时，相对误差平均值和最大值分别减小到7%和15%以下，与现有的作物水模型比较，模拟精度有所提高，但参数个数未增加。该模型更多地反映了水分胁迫时间对作物产量影响的信息。 相似文献
18.
《Agricultural Systems》2001,69(3):165-182
Using daily water balance simulation in rainfed ricelands, the study estimates the probable supplemental irrigation (SI) requirement to meet the water deficits during the reproductive stage of rice and surface runoff (SR) generated that can be harvested in OFR for meeting the aforesaid SI. Value of SI of rice during reproductive stage at 25% probability of exceedence (PE) was found to be 144 mm, neglecting distribution and application losses. Water harvesting potential of the study area indicates that at 50% PE, 85% of SI of rice can be met from the SR generated from the ricelands and stored in OFR. Rest amount of SI can be met from the direct conservation of rainfall in a lined OFR of 2 m depth with 1:1 side slope occupying 9% ricelands. Economic analysis of OFR irrigation system reveals that OFR of 9% ricelands gives net profit (NP) of Indian Rupees (Rs.) 13445 (US $295.49) for 1 ha sown with dry seeded rainfed upland rice with benefit–cost ratio (BCR) of 1.25. Values of NP and BCR indicate that investment in OFR irrigation system is profitable in the study region. 相似文献
19.
PID控制的泵供水系统仿真试验 总被引：1，自引：0，他引：1
为了进行泵供水系统试验,通过建立泵供水系统基本结构和各环节的传递函数,组成系统动态结构图,在MATLAB Simulink下进行仿真试验以观察系统输出响应.使用稳定边界法、根轨迹超前校正法和直接设置比例-积分-微分（PID）参数3种方法进行控制器设计.通过仿真观察泵供水系统的输出特性,比较并找出合适的控制器设计方法.通过仿真观察输出响应得到稳定边界法和根轨迹超前校正法不适合调节泵供水系统.而采用直接设置PID参数的方法,利用MATLAB的仿真集成环境Simulink设置修改PID参数,选择其中一组较好的PID参数,使泵供水系统得到了满意的输出响应.仿真结果为搭建试验平台提供了理论基础依据. 相似文献
20.
Effects of the micro-scale advection on the soil water movement in micro-irrigated fields 总被引：1，自引：0，他引：1
The objective of this study was to explore the soil water dynamics under micro-advective conditions. A numerical model was introduced to estimate the airflow turbulence generated by the crop canopy. The vapor pressure and air temperature in the vicinity of the soil surface were estimated from the wind velocity predicted by this model. The energy budget on the soil surface was estimated using wind velocity, vapor pressure, and air temperature simulated by numerical models. The soil water content and temperature were predicted using the simulation model describing the water and heat transfer in soil. Using the energy budget, the accuracy of this model was experimentally verified using a wind tunnel. Spatial changes of the soil water content simulated by this model were reproduced by the experiment. This indicated that the numerical model for estimating the soil water movement under micro-scale advection considering the crop body was satisfactory. 相似文献