共查询到20条相似文献,搜索用时 62 毫秒
1.
2.
非充分灌溉条件下稻田优化灌溉制度的研究 总被引:13,自引:2,他引:11
在大量试验研究基础上,以水稻水分生产函数为依据,结合非充分灌溉条件下稻田水量平衡的特点,建立了非充分灌溉条件下稻田优化灌溉制度之动态规划模型,实例研究表明,模型是合理可行的。 相似文献
3.
基于作物水分生产函数下的限额灌溉制度优化研究 总被引:4,自引:0,他引:4
通过对小麦、玉米、棉花等主要农作物的分阶段受旱试验,获得了三年的限额灌溉试验观测数据;采用非充分灌溉条件下的土壤水分运动理论分析试验数据,建立了限额灌溉条件下的作物蒸发蒸腾模型。结合试验数据分析水分亏缺对作物产量的影响,采用多元回归分析法求解水分生产函数模型参数。采用动态规划法研究了水资源不足条件下的限额灌溉制度的多阶段优化法。研究成果表明,在产量能达到充分灌溉条件下产量的90%的情况下,可节约灌溉用水40%,能为水资源极其短缺地区的农业高效用水提供有力的技术支撑。 相似文献
4.
高产省水灌溉制度优化模型研究 总被引:13,自引:2,他引:11
本文针对我国干旱、半干旱地区农业水资源短缺的特点,提出了建立在非充分灌溉理论基础上的灌溉制度优化模型.该模型是一个两维状态及两维决策变量的多维动态规划模型,可利用动态规划逐次渐近法(DPSA)求解.以黑龙港地区为背景的实例研究结果说明了所建模型及求解方法的合理性和有效性,为节省缺水地区的农业水资源开辟了一条新的途径. 相似文献
5.
作物缺水条件下灌溉供水量最优分配 总被引:35,自引:1,他引:34
针对灌区水源短缺情况,建立了一种对有限水量在多种作物之间进行最优分配的两层分解协调模型:第一层为基于作物水分生产函数,求解单作物非充分灌溉条件下最优灌溉制度的动态规划模型;第二层为将有限水量在多种作物之间进行最优分配的动态规划模型实例计算表明,模型是合理可行的 相似文献
6.
研究非充分灌溉制度对南方灌区桃树生长的影响。结果表明,非充分灌溉抑制桃树营养生长,但提高了桃树叶片的叶绿素相对含量,表现出植物的耐旱机制和补偿效应。最优非充分灌溉处理的地径、冠幅和株高分别比CK(充分灌溉)降低6.6%、14.0%和17.3%,叶片SPAD值比CK高6.9%。采用层次分析法综合评价不同灌溉处理,获得最优灌溉制度为处理2(灌水定额减少12.5%的非充分灌溉),得分0.818分,可在不影响桃树生长的情况下,比常规滴灌又节水10%以上,非常适合水资源相对紧缺的丘陵缓坡地经济作物生产。 相似文献
7.
作物优化灌溉制度的研究 总被引:7,自引:0,他引:7
文中对非充分灌溉条件下作物优化灌溉制度如何制定进行了研究。其特点是将作物产量模型、耗水规律模型和土壤水分变化动态模型相结合,以产量最高为目标函数,建立了计算机优化决策系统。该研究成果可使有限的水量在作物生育期内发挥最大的效率,对优化配置水资源,实现农业高效用水具有重要作用。实例研究结果说明,所建模型及求解方法是合理与可行的。 相似文献
8.
根据山西临汾灌溉试验站2009年与2010年冬小麦试验资料,采用田间试验与理论分析相结合的研究方法,利用PS123作物生长模型,计算得出5种水文年型冬小麦潜在蒸发蒸腾量。以产量最大为目标,建立灌溉制度优化模型,确定5种水文年型优化灌溉制度。通过实际应用进行了检验,得出:冬小麦非充分供水条件下灌溉预报土壤水分下限值的理论计算方法,进一步完善了非充分灌溉预报理论,利于灌区动态计划用水与水资源优化配置,对于加强灌区用水管理、提高灌区用水效率具有重大的推动作用。 相似文献
9.
非充分灌溉是利用作物自身生理节水与抗旱能力的一种节水技术,是灌溉农业的发展方向,引用试验和示范推广资料,简述非充分优化灌溉制度的形成和特点,论述了其节水增产效益,介绍应用方法和实例。 相似文献
10.
优化灌溉制度及经济灌溉制度的研究 总被引:2,自引:0,他引:2
在限额灌溉的条件下,灌溉水量在各个生育期的最优分配,可以在根据缺水灌溉试验得到的产量水分模型的基础上,以最大产量为目标,采用动态规划的方法求得。经济灌溉制度是在一定供水量的前提下,使灌溉净效益达到最高的灌溉制度。该文给出了数学模型,并依据民勤县的试验资料给出了结果。 相似文献
11.
The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L?1, the median total phosphorus was 0.29 mg L?1 and the median total nitrogen was 1.56 mg L?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd. 相似文献
12.
Carbon dioxide (CO2) and methane (CH4) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO2 and CH4 diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 106 t CO2eq km2 per year, or 24 × 106 t CO2eq per year. This corresponds to a plant emission factor of 3.18 kg CO2eq MWh?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO2eq per year, or 5.83 kg CO2eq MWh?1, which is in the lower range of the studied reservoirs. 相似文献
13.
River regulation in the headwaters and middle reaches of the Gunnison River, Colorado, significantly altered distributions and abundances of Trichoptera fauna. Twenty-five species were collected from mainstream samples, with the greatest species richness occurring at an unregulated, rhithron segment above the central reach dams. At sites immediately below the three hypolimnial-release dams and a reregulation dam, species richness was reduced 35–90 per cent and abundance > 95 per cent. Net-spinning caddisflies were the dominant trichopterans at unregulated sites; Arctopsyche grandis in the upper reaches (218 organisms, 586 mg dry mass m?2) and Hydropsyche cockerelli, H. occidentalis and Cheumatopsyche pettiti in the lower river (9041 total organisms, 6621 mg m?2), downstream from the last dam. The observed distributional pattern of low trichopteran densities in dam tailwaters and high hydropsychid densities at sites 60–80 km below the central reach dams is a classic expression of continuum resets and adjustments in response to stream regulation as predicted by the Serial Discontinuity Concept. 相似文献
14.
Peter M. Gibbs 《国际水》2013,38(4):547-557
Abstract A professional Land Surveyor (Geomatician) describes the Hydrogeologists' survey requirements of a major water resources assessment for the government of The Sultanate of Oman (1992 to 1996). The need for objective specifications is stated. Specialist terms like geoid, spheroid, Mean Sea Level are explained and how to relate spheroidal levels to the geoid. Methods like traditional survey, satellite survey, and photogrammetry are introduced. The paper encourages coordinated working for the benefit of water resource assessment and recommends employment of the professional land surveyor for major studies. 相似文献
15.
Suleyman A. Muyibi Abdul Raufu Ambali Garoot Suleiman Eissa 《Water Resources Management》2008,22(4):485-508
The paper examines the impact of development activities on water pollution in Malaysia. Hence, the main objective of this
paper is not just to examine the trends of development-induced water pollution around the region of the country but to know
where the problems are and the policy measures taken by the government. It evaluates the probable causative relationship between
problems introduced due to technology employed in water pollution control and governmental policy measures. It examines the
relationship between development indicators as sources of pollution and polluted rivers over a period of 12 years. The findings
of the paper have shown that despite the policy enforcement actions against the identified sources of water pollution, all
the three development indicators (chosen based on those identified sources) still accounted for high percentage of river pollution
in Malaysia. The findings of the paper were used to identify the central fact of the location of the problem. Some crucial
conclusions of where the problems likely to be, as reflected in the findings, are: (a) the issue of interactive-effects between
pollutants that many policy-makers are not aware of. This is when policy measures concentrate only on one source of water
pollution; (b) the enforcement strength and/or effectiveness of policy measures themselves; (c) financial constraints to invest
in appropriate technology especially sewerage systems for controlling human source of water pollution in the country; as well
as those confronting small polluting industries (d) finally, lack of cooperation between government and private business firms
to comply with regulatory policies for water pollution control. 相似文献
16.
Intangible Flood Damage Quantification 总被引:3,自引:0,他引:3
Flooding is a natural disaster that may cause tremendous tangibleand intangible damage to the national economy. The tangible damage assessment, i.e. the monetary value of all direct and indirect physical damages, has already been studied, whileintangible damages have not yet been taken into account. Thisarticle, therefore, is the first systematic attempt to assess bothtangible and intangible damages. The new proposed Anxiety-Productivity and Income Interrelationgship Approach (API) has been developed to quantify the intangible damage in monetary terms. The Bangkok area has been selected as the research area because several severe flood events have occurredthere over the last two decades. The 1983 Bangkok flood caused 6600 million baht in damage, according to estimates by the National Statistical Office (NSO). This article examines the totalflood damage (including the intangible damage) at different flood magnitudes. Case studies with and without flood mitigation projects are studied and compared. Furthermore, thisarticle also discusses the improvements over the conventional approach offered by the new API methodology. 相似文献
17.
Floodplains are generally considered to be important locations for nutrient retention or inorganic‐to‐organic nutrient conversions in riverine ecosystems. However, little is known about nutrient processing in short‐hydroperiod floodplains or seasonal variation in floodplain nutrient retention. Therefore, we quantified the net uptake, release or transformation of nitrogen (N), phosphorus (P) and suspended sediment species during brief periods (1–2 days) of overbank flooding through a 250‐m floodplain flowpath on the fourth‐order Mattawoman Creek, Maryland U.S.A. Sampling occurred during a winter, two spring and a summer flood in this largely forested watershed with low nutrient and sediment loading. Concentrations of NO increased significantly in surface water flowing over the floodplain in three of the four floods, suggesting the floodplain was a source of NO. The upper portion of the floodplain flowpath consistently exported NH, most likely due to the hyporheic flushing of floodplain soil NH, which was then likely nitrified to NO in floodwaters. The floodplain was a sink for particulate organic P (POP) during two floods and particulate organic N and inorganic suspended sediment (ISS) during one flood. Large releases of all dissolved inorganic N and P species occurred following a snowmelt and subsequent cold winter flood. Although there was little consistency in most patterns of nutrient processing among the different floods, this floodplain, characterized by brief inundation, low residence time and low nutrient loading, behaved oppositely from the conceptual model for most floodplains in that it generally exported inorganic nutrients and imported organic nutrients. Published in 2007 by John Wiley & Sons, Ltd. 相似文献
18.
19.
N. N. Man'kina B. S. Fedoseev A. V. Kirilina Yu. A. Voropaev 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2004,38(2):95-98
Conditions of the process of steam-water-oxygen cleaning, passivation, and conservation (SWOC, P, and C) of internal heating surfaces of the boiler and the high-pressure feed heater (HPFH) piping over the steam side are presented. The process produces partial cleaning of the internal heating surfaces from scale and yields a corrosion-resistant protective film that hinders corrosion processes both in the operation of the boiler and in the idle period. 相似文献
20.
基于虚拟裂缝模型,针对钢筋混凝土试件在三点弯曲作用下开裂截面的受力特征,在合理假定的前提下,给出了一种计算钢筋混凝土三点弯曲梁的失稳断裂韧度的解析方法。然后,应用该方法计算了初始缝高比α0(初始裂缝长度与试件高度的比值)分别为0.2,0.3,0.4,0.5的三点弯曲试件的最大荷载和临界有效裂缝长度,进而求得了钢筋混凝土三点弯曲梁的失稳断裂韧度。通过对计算结果与试验数据的误差分析,发现失稳断裂韧度最大误差为4.915%,说明这种方法可以较为准确地预测三点弯曲梁的失稳断裂韧度。在此基础上研究了初始缝高比α0对失稳断裂韧度的影响,发现失稳断裂韧度基本上不随α0变化,失稳断裂韧度可以作为材料常数,应用于裂缝扩展状态的判断。 相似文献