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H. C. Van Ommen 《Agricultural Water Management》1985,10(4):293-304
Based on the mass balance equation, a pseudo-analytical solution for the chemical concentration in drainage water from a soil profile is given. The effects of linear adsorption, decomposition and plant water uptake as well as the water content and layer thickness may be specified separately for each layer. The phenomenon of bypass flow can also be taken into account. From the obtained relationship between the concentration of solute in the drainage water leaving the soil profile and the time, a coupling between the unsaturated and the saturated zone can be achieved as was described earlier. This leads to breakthrough curves of the solute leaving the combined system of unsaturated and saturated zones. Time-dependent input concentrations can easily be incorporated through the systems approach. The computer programs (written for an HP41CV pocket calculator), describing the quality of drainage water from non-homogeneous profiles and the breakthrough of a solute leaving the combined system, are given as an appendix. 相似文献
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小麦不同生育期微喷带水量分布均匀性 总被引：1，自引：0，他引：1
试验以常用的机械打孔的Ф32微喷带为研究对象,通过调节微喷带的工作压力,研究2种长度微喷带(20,40 m)下春小麦不同生育期水量分布均匀系数的变化规律,通过对不同高度春小麦遮挡下水量分布均匀系数的分析,探究大田试验中微喷带的水量分布均匀性.试验结果表明:作物遮挡会降低微喷带的水量分布均匀性,改变水量空间分布特征,不同作物高度截留的喷射水量不同,通过改变工作压力能改变喷射角度,进而减少作物遮挡对微喷带水量分布的影响,在文中的试验设置条件下,2种铺设长度下的最佳工作压力范围为40~45 kPa;为保证较好的灌溉均匀度,作用压力与微喷带极限铺设长度应合理设置. 相似文献
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灌排方案对避雨番茄需水特性与产量的影响 总被引：5，自引：0，他引：5
为了实现南方地区番茄节水、优质、高效生产,在避雨栽培条件下,研究了不同灌排方式对番茄需水特性与产量的影响.研究结果表明:各亏缺灌溉处理土壤含水率随时间总体呈下降趋势,暗管埋深08 m的处理较埋深06 m处理,土壤含水量下降更快但不明显.番茄不同生育阶段的蒸发蒸腾量差别较大,表现为始花坐果期>果实成熟与采收期>苗期.随着番茄的生长,其日蒸发蒸腾量大体呈逐渐上升的趋势.在不同灌排模式和避雨措施条件下,苗期的日蒸发蒸腾量变化范围为107～271 mm／d,始花坐果期日蒸发蒸腾量变化范围为160～309 mm／d,果实成熟与采收期日蒸发蒸腾量变化范围为178～335 mm／d.在相同的排水措施,不同灌溉条件下,番茄果实产量随着灌水量的减少而减少,水分利用率和灌溉水利用率却随着灌水量的减少而增大.研究可为南方避雨栽培下番茄灌排方式的选择及其节水、优质、高产提供参考. 相似文献
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为了节约农田灌溉用水,提高水资源利用效率,实现自动微灌控制,根据精细农业的实际需求,本文提出了基于CAN总线和Linux的微灌监控系统,该系统由数据信息采集模块、嵌入式中央处理模块、灌溉控制模块、CAN总线网络四部分组成,可按设定的时间间隔自动采集空气温湿度、光照辐射强度等信息,并结合作物生长信息,经理论计算,决策所需灌溉水量,利用电磁阀来自动调节控制水量补给,实现作物微灌的自动化,优化植物的生长环境,提高水利用率。系统运行稳定,效果良好,能够实现准确的信息采集和可靠的分布式控制。 相似文献
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乡镇发展要做好供水规划，包括全国规划、区域规划、工程规划三个层次；按国家确定的有关路线、方针、政策，提出乡镇供水必需遵循的原则；乡镇供水规划包括需水量预测、水源规划、发展规划、供水系统和工艺流程系统选择以及经济评价等内容。 相似文献
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Nigel W.T. Quinn 《Agricultural Water Management》2009,96(2):247-254
Seasonally managed wetlands in the Grasslands Basin on the west-side of California’s San Joaquin Valley provide food and shelter for migratory wildfowl during winter months and sport for waterfowl hunters during the annual duck season. Surface water supply to these wetlands contain salt which, when drained to the San Joaquin River (SJR) during the annual drawdown period, can negatively impact water quality and cause concern to downstream agricultural riparian water diverters. Recent environmental regulation, limiting discharges salinity to the SJR and primarily targeting agricultural non-point sources, now also targets return flows from seasonally managed wetlands. Real-time water quality management has been advocated as a means of continuously matching salt loads discharged from agricultural, wetland and municipal operations to the assimilative capacity of the SJR. Past attempts to build environmental monitoring and decision support systems (EDSS’s) to implement this concept have enjoyed limited success for reasons that are discussed in this paper. These reasons are discussed in the context of more general challenges facing the successful implementation of a comprehensive environmental monitoring, modelling and decision support system for the SJR Basin. 相似文献
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Criteria for the design of closed end irrigation borders are generally based on intake rate and irrigation advance for specified inflow and irrigation efficiency. Recession has seldom been included in the design. This study emphasizes inclusion of temporally varying intake rate, irrigation advance, vertical recession, horizontal recession and recession of impounded water. To determine the length of impounding, an iterative procedure is proposed correlating irrigation advance and recession with the depth of flow at the up-stream end. To evaluate the design, irrigation efficiencies are computed for specified conditions and are compared with those based on experimental data. 相似文献
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根据不同系列军用改装车辆的特殊要求,需要对方舱结构进行频繁改动。为避免CAD模型的重复建立,本文应用两类表达式实现了改装车辆的方舱结构快速设计。首先建立了原型方舱零件及其装配的参数化模型,然后定义了驱动参数及其所有零件的装配关系表达式。通过关系表达式的驱动实现了方舱结构的尺寸参数化;通过抑制表达式实现了方舱结构形式的特征参数化。讨论了参数化设计与建模的关系,提出了零件参数化的表达策略。 相似文献
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The People's Victory Irrigation System which diverts water from the Yellow River of China covers a total irrigable area of 59 000 ha. The system encountered some serious problems in the first decade of its operation — salinity and waterlogging of irrigated land, siltation of irrigation and drainage channels, as well as a low efficiency of water use. This paper describes a series of structural and functional measures which have been adopted in the past 24 years for the rehabilitation of the system, including: improvement of the existing drainage system and construction of new drainage system on agricultural land, conjunctive use of surface and groundwater supplies, a comprehensive programme to reduce the levels of siltation as well as the implementation of improved water management practices. A model for the optimal operation of the system by using system analysis theory as an aid in reducing the operation and maintenance (O & M) costs has been developed in recent years. The results are that the soil salinity has been controlled and the agricultural production has increased whilst the efficiency of water use has improved and the siltation levels reduced. Experience gained on this system has been successfully used in developing and managing other irrigation projects along the lower reaches of the Yellow River. The proposed procedure of solving the said optimal model has also embodied some benefits from reducing O & M costs in operation. 相似文献
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以受盐渍化威胁的干旱半干旱地区为研究对象,基于构建的农田排水再利用适宜性评价指标体系,采用模糊模式识别方法建立了农田排水再利用适宜性评价模型;综合分析相关文献和已有标准,制定出评价指标体系各项指标的分级标准值范围和标准值,采用层次分析法确定各评价指标的权重.以宁夏银北灌区5个典型排水再利用区域为例的评价结果表明,除前进农场外,其他区域评价等级均在2级“适宜”排水再利用范围内.其中灌溉中、后期利用排水灌溉的适宜性级别特征值低于前期,即排水再利用的适宜程度好于前期,该时期正是作物需水量较大和灌溉用水紧张期,处于作物盐分非敏感期,适宜地再利用一定量的农田排水是可行的. 相似文献
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在移动式防雨棚下,采用盆栽土培方法,以冬小麦（Triticum aestivum L.）为试验材料进行了调亏灌溉（regulated deficit irrigation,RDI）试验研究,目的在于了解RDI对冬小麦籽粒灌浆特性的影响,并对其进行模拟,为建立冬小麦RDI指标与模式提供理论依据与技术参数。试验采用二因素（水分调亏阶段和调节亏水度）随机区组设计。结果表明,RDI条件下冬小麦籽粒灌浆过程符合“缓-快-慢”的“S”型生长曲线,并可用Richards方程进行较好的模拟;不同水分调亏处理间最大灌浆速率及其出现时间、平均灌浆速率、灌浆持续期、活跃生长期和3个灌浆阶段灌浆持续期,以及最终千粒质量等特征参数差异达显著水平;其中,越冬期轻度调亏具有最高的平均灌浆速率（每百粒0.234 g/d）、最大灌浆速率（每百粒0.369 g/d）、最高的第3阶段灌浆速率（每百粒0.099 g/d）和最高的千粒质量（58.46 g）。经相关和逐步回归分析灌浆参数与千粒质量的关系,结果表明,多数参数间存在着显著或极显著的相关性,其中,与千粒质量有显著或极显著相关关系的参数有最大灌浆速率、平均灌浆速率、活跃生长期和第3阶段灌浆速率等。 相似文献
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Johannes Hendrikus Barnard Leon Daniel van Rensburg Alan Thomas Peter Bennie 《Irrigation Science》2010,28(2):191-201
With the optimization of irrigation, more salts accumulate in the root zone of soils, due to less over-irrigation. On-farm
irrigation management requires a certain amount of leaching to ensure sustainability. The objective is to quantify the pore
volume of water required to efficiently leach excess salts from two saline soils, widely irrigated in central South Africa.
A total of 30 lysimeters, 15 per soil type arranged in two parallel rows under a moveable rain shelter, were used. Five different
salinity profiles per soil type, replicated three times, were leached using irrigation water with a 75 mS m−1 electrical conductivity. During irrigation the residual more saline pore water was displaced from the top downward through
the root zone. The mean salinity of the soil profiles approached an equilibrium concentration equal to that of the irrigation
water after 0.9 pore volume of soil was displaced by drainage water. For the sandy soil 0.2 and for the sandy loam soil 0.3
pore volumes were required to efficiently remove 70% of the excess salts. The remainder of the water was needed to leach the
remaining 20% of the excess salts. This, however, was not efficient in terms of the amount of water required. 相似文献
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Hans Charles Komakech Marloes L. MulPieter van der Zaag Filbert B.R. Rwehumbiza 《Agricultural Water Management》2011,98(11):1719-1726
Although spate irrigation systems are risk-prone, they can be an important component for livelihood security in semi-arid areas. Spate uses water (flood water), which upstream users often do not require, as rainfall during these periods is more than sufficient. The use of this flood water for spate irrigation is therefore a good opportunity to convert water with a low opportunity cost to high value water. As more rivers are closing, due to socio-economic and climate changes, spate irrigation may become increasingly relevant in semi-arid areas. Spate irrigation systems pose institutional and technical challenges: collective action is challenged by complex upstream-downstream interactions between users within the system, and the high labour demands for regular reconstruction of temporary diversion weirs and intake structures. This paper describes a spate irrigation system in Makanya village, Tanzania that emerged in response to increased upstream water use. We use three of the four dimensions (hydrological, hydraulic and sociological) of spate irrigation proposed by Van Steenbergen (1997) to assess the Makanya spate irrigation system. The Makanya spate irrigation system has an organisational structure that is similar to the canal irrigation (furrow) committees located upstream, and effectively deals with the institutional demands of managing water in spate irrigation systems. Water allocation is reminiscent to the water sharing arrangements existing in the full irrigation system, which previously was in place at the site and in the high- and midlands of the Makanya catchment and therefore set this system apart from the traditional spate irrigation practice elsewhere. Technically, a major challenge is the reconstruction of the head works after each flood. Another aspect is the changes in the river bed. Flash floods carry sediments that deposit on the fields, raising the elevation of the irrigated land every year and making it increasingly difficult for the river water to enter the plots. Improving system efficiency through modernisation of the diversion and distribution structures in this case is not feasible due to the huge amounts of sediments delivered to the system each year. Instead investments in conjunctive use of groundwater could be the solution because it involves a relatively small intervention, minimises the physical disturbance of the system, and therefore is likely to respect the existing locally developed water management arrangements. 相似文献
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调亏灌溉对冬小麦根冠生长影响的试验研究 总被引：3，自引：1，他引：2
以冬小麦为试验材料,采用防雨棚下桶栽土培方法,就调亏灌溉(RDI)对作物根、冠生长的影响进行了试验研究。试验采用二因素随机区组设计,冬小麦设置5个水分调亏阶段,每个调亏阶段设置3个水分调亏程度,另设全生育期充分供水处理为对照(CK)。分别在水分调亏期间和复水后测定各处理根系参数和地上干物质质量。结果表明,RDI对植株根冠生长发育的影响因不同水分调亏阶段和不同水分调亏度而有所不同。在水分调亏期间冬小麦根系生长受到强烈抑制,但复水后根系具有"补偿生长效应"或"超补偿生长效应"。冬前适度水分调亏(调亏度55%FC～65%FC)对根系生长具有正效应;返青—拔节阶段不同程度水分调亏复水后均有"补偿生长效应"或"超补偿生长效应",而且这种"补偿生长效应"随水分调亏度加重呈增强趋势。冬小麦水分调亏均增大根冠比(R/S),且随水分调亏度加重,R/S明显增大。因此,RDI可以作为冬小麦根冠生长调控的有效方法。 相似文献
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Optimal Allocation of Short-Term Irrigation Supply 总被引：2，自引：0，他引：2
An optimization model has been developed toaid decision making in real time fordeficit irrigation when conflict betweenwater supply and demand arises in amultiple crop irrigation scheme. The resultis the optimal allocation of short-termsupply of irrigation water. Theoptimization model is based on DynamicProgramming. In the optimization model, theshort-term supply is optimized in functionof a specified strategy determined by theuser. The strategies that the user canselect from are: maximum benefit, equitablebenefit, equitable yield and maintainingequity in the system. The potential of themodel has been assessed through applicationof the model to Perkerra irrigation schemein Kenya. In the 680 ha scheme, maize,onion and chili are cultivated in theirrigation season. Analysis of the resultsfor the 1999/2000 season, where the watersupply was 35 percent smaller than thedemand, indicates that improvements in cropproduction can be achieved throughapplication of the optimization model.Sensitivity of production system to variouslevels of water restriction is demonstratedby sensitivity analysis. 相似文献