Beyond the farm-turn-out: on-farm development dynamics in the Kamphaengsaen irrigation project, Thailand

Many large-scale state-run irrigation projects in the world have been constructed with limited investment in on-farm infrastructure. In most cases, it was expected that local farmers would themselves make improvements on their farms. In general, insufficient attention is paid to water control which has a negative impact on productivity. Farmers' strategies to offset poor access to water are very varied and depend on site-specific factors such as topography, the existence of other potential water sources, market opportunities or capital availability. This article presents a case study in the Central Plain of Thailand and describes the patterns of land development which occurred since the construction of the Irrigation Project 25 years ago. It shows how land and water use evolved as both a mover and a response to on-farm development and who initiated new investments, such as ditch and tube-well digging, regulators in drains, which have allowed secondary water sources to be tapped, the development of conjunctive use, increased reliability in water supply and crop diversification. The importance of individual farm pumps is shown. Poor land levelling is conducive to high costs and reduced water use. Prospects for land consolidation are assessed.     

Automation of border irrigation in South-East Australia: an overview

There exists a growing interest in automating border irrigation after a large number of irrigated farms in South East Australia have upgraded their layout design. Several manufacturing companies are producing automated equipment which rely on controllers fitted with timers or field water sensors to monitor the advance of the water front down the border (bay). Labor saving together with potential for increase in pasture yield and additional flexibility to perform other farming tasks are the main benefits considered by farmers who decide to adopt automation. Environmental benefits can also be realized provided that the system is properly managed. Correct sensor placement and timer setting are critical factors to achieve high hydraulic performance as they can influence the application efficiency of a typical border irrigation event by as much as 40%. Further efforts will be required in future to incorporate feedback control, improve operational reliability and adapt existing systems or develop new ones to meet the requirements of new irrigation techniques such as surge flow.     

Estimation of a network irrigation efficiency to cope with reduced water supply

The overall irrigation efficiency, e_p, for the irrigationnetworks in the Thessaloniki plain, in Northern Greece, wasestimated from historical data, spanning eight years. Irrigationnetworks differ regarding the method of water delivery and themethod of field application. Overall irrigation efficiency is theparameter which helps to adjust water supply to meet the actualcrop water requirements. A method is introduced which calculatesnetworks e_p using spatially distributed data. Efficiencyvalues for all systems were calculated using the proposed method.Seasonally averaged e_p values for eight years for 32(surface and sprinkler) irrigation networks ranged from 0.38 to0.81. Analysis of the time series e_p values can identifyoperational factors that might affect network e_p. Sprinklerand surface network irrigation efficiencies did not show anysignificant difference.     

Optimization of design of on-farm channel network in an irrigation area

Lack of suitable technical criteria to find out the optimal design of on-farm channels leads to poor efficiencies of many irrigation schemes. It is desirable to design a channel network which is economical and the seepage loss is minimum. In this paper three network models viz. Minimal Spanning Tree, Shortest Path and out-of-kilter algorithms are used to find an optimal layout. In addition to the continuous supply, the results of the models are checked for their usefulness in a rotational irrigation system. All the three models were applied to three different areas of the Mae Klong Irrigation Project, in Thailand.     

Measuring conveyance efficiencies to improve irrigation water management

This paper presents a study of conveyance efficiencies of Canal de Salvaterra, in the Sorraia Irrigation Project, Portugal. The Canal and the Project are briefly described and the water measurement techniques and structures utilized are analysed. Results comprise the main aspects of the inflow-outflow balance with identification of water losses and conveyance efficiencies. Analysing the results showed that irrigation efficiencies are higher during work days and labour hours and lower during weekends and at night. This identified the need to improve operation and management of the irrigation system, adapting inflow to demand according travel time and response time of the conveyance (and distribution) system, of the different main sections of the system.     

Innovations in irrigation management and development in Hunan province

Mass movement labor was an important contributor to irrigation system construction in China during the seventies, making up a third or more of system costs. Total per-ha system costs are roughly consistent with those in other Asian countries when contributed labor is valued at estimated farm wage rates, but less than average if zero labor opportunity cost is assumed.Innovative practices are being employed in managing and supporting irrigation system operations in Western Hunan Province. Many are ones which have been advocated repeatedly elsewhere but infrequently applied. These include the volumetric wholesaling of water to distribution organizations, farmer water charges with both fixed and volumetric components, financially autonomous irrigation management agencies, and delegation of water distribution and fee-collection responsibility to village-based organizations. Heavy emphasis currently rests on financial self-reliance of schemes as denoted by the slogan, let water support water. This has led to a proliferation of secondary income-generating enterprises associated with irrigation system management, as well as strenuous efforts to collect irrigation fees. Often the secondary enterprises generate a larger share of total income than does the irrigation service itself.Fee levels for rice generally fall into the $12 to $20 ha/yr range, intermediate to those prevailing in Pakistan at $8.50/ha for two crops of rice and the Philippines at $45/ha for double cropped rice. Collection of fees is typically handled by the village. Charges are usually levied on an area basis but one large system employed a more complicated system which had both fixed and variable components. Water allocation at lower system levels is also delegated to the village in many cases, with the state serving as a wholesale provider of water.Abbreviations and units ha-m hectare-meter - jin unit of weight equal to 0.5 kg - kw kilowatt - mu unit of land area equal to 1/15 ha - Rmb Renmimbi (Yuan) equal to US$ 0.27 officially in September 1988 and about half of that unofficially - RMD Reservoir Management Division - WCB Water Conservancy Bureau - WMD Water Management Department     

Comparative analysis of main on-farm irrigation systems in Portugal

Traditional irrigation systems still cover a large area of irrigated lands in Portugal. The needs for competitiveness leads to the gradual abandon of traditional systems, resulting in social and economic impacts. Pressurised on-farm irrigation systems provide labour savings but imply important investments. Surface irrigation does not require expensive equipment and is low energy and low labour consuming, if modern systems are implemented. Flexible-pipe, gated-pipe, surge-flow valve and cablegation are the main equipment issues available to Portuguese farmers for modern surface irrigation practice. Conditions for application of these systems have been studied relative to different soil and topographic conditions. Plane land, either horizontal or sloped and undulated fields can be irrigated by surface systems, if a convenient design is accomplished. The adequacy of the irrigation systems has been evaluated and a cost-benefit study was carried out. A case study of a situation with undulated land, representative of South Portugal, is presented in this paper, comparing surface irrigation issues and a sprinkler system. Conclusions show a particular economic interest on adopting surge-valve, gated-pipe and cablegation.     

From on-farm solid-set sprinkler irrigation design to collective irrigation network design in windy areas

In this paper, a contribution to the design of collective pressurised irrigation networks in solid-set sprinkler-irrigated windy areas is presented. The methodology is based on guaranteeing minimum on-farm performance, using a historical hourly wind speed database and a ballistic solid-set irrigation simulation model. The proposed method was applied to the Montesnegros Irrigation District (central Ebro basin, Spain). The district irrigates an area of 3493 ha using an on-demand schedule. The average wind speed in the area is 2.8 m s⁻¹. An analysis of district water records showed that farmers often reduce water demand when the wind speed is high, but their irrigation decision making is limited by the capacity of the irrigation network and by the unpredictable character of local winds. Simulations were performed for 11 irrigation seasons, 2 triangular sprinkler spacings (18 m × 18 m and 18 m × 15 m), and 2 sprinkler models. The percentage of monthly suitable time for irrigation was determined for four management strategies. The first one was based on a wind speed threshold (3 m s⁻¹), while the other three were based on three levels (standard, relaxed and restrictive) of two irrigation performance parameters: the Christiansen Uniformity Coefficient (CU) and the Wind Drift and Evaporation Losses (WDEL). The standard strategy classified the time as suitable for irrigation when CU ≥ 84% and WDEL ≤ 20%. The thresholds limits of the irrigation parameters for the relaxed strategy were CU ≥ 80% and WDEL ≤ 25%. Finally, the restrictive strategy used thresholds of CU ≥ 90% and WDEL ≤ 15%. The suitable time for the first strategy (56%) was always lower than for the standard and the relaxed strategies (with respective average values of 75 and 86%), and higher than for the restrictive strategy (30%). In order to design the collective network, the hydrant operating time was equalled to the suitable time for irrigation. The differences in the cost of the collective network plus the on-farm equipment were particularly relevant between the restrictive strategy and the other three. Differences in suitable operating time were clear between sprinkler spacings, and less evident between sprinkler models. The application of the proposed methodology may be limited by the availability of historical wind speed records and CU estimates for different combinations of sprinkler models, sprinkler spacings and wind speed.     

Performance assessment of irrigation water management of heterogeneous irrigation schemes: 2. A case study

The non-uniformity of soils, weather, fields, cropping pattern and canal systems in most surface irrigation schemes makes irrigation water management complex, but optimum performance is important particularly in irrigation schemes with limited water supply. This paper focuses on the performance of irrigation water management during the area and water allocation with a case study of an irrigation scheme in the semi-arid region of India. Often the irrigation managers or authorities of these heterogeneous irrigation schemes also need to deal with different allocation rules. The allocation plans and the corresponding water delivery schedules during the allocation process were estimated with the help of a simulation–optimisation model for different allocation rules based on cropping distributions (free and fixed), water distributions (free and fixed-area proportionate), irrigation depth (full, fixed depth and variable depth irrigation) and irrigation interval (from 14 to 35 days). The performance measures of productivity (in terms of net benefits and area irrigated), equity (in water distribution), adequacy and excess were assessed for these different allocation plans and schedules. These were further compared with the performance measures of the existing rule (fixed depth irrigation at a fixed interval). The analysis revealed that these performance measures are in some cases complimentary and in other cases conflicting with each other. Therefore, it would be appropriate for the irrigation managers to understand fully the nature of the variation in performance measures for different allocation rules prior to deciding the allocation plans for the irrigation scheme.     

平移式喷灌机行走速度及喷灌均匀度试验研究

为研究低压喷灌下喷灌机行走速度合理取值以及喷灌均匀度对土壤含水率均匀度的影响,以自行研制的轻小型平移式喷灌机为研究对象,通过室内单喷头试验和田间喷灌试验,探究了特定灌水定额下喷灌机的工作压力与行走速度关系,并对其水量分布、喷灌均匀度以及土壤含水率均匀度随时间变化进行了分析.结果表明：通过确定灌水定额能够计算出平移式喷灌机的行走速度和工作压力：当灌水定额分别为10,15,20 mm时,40~120 kPa喷灌压力下喷灌机行走速度最小为17.27 m/h,最大为58.65 m/h;增大喷灌压力能小范围提高均匀度,40 kPa工作压力均匀度为0.696,60~120 kPa喷灌压力下均匀度变化范围为0.731~0.788,喷灌水在土壤中的二次分布均匀度明显高于地表喷灌均匀度,40 kPa喷灌压力下喷后6 h土壤含水率均匀度达到0.906,24 h后达到0.953,可相应降低喷灌均匀度设计值以降低运行成本,节约能耗.     

The use of measured water flows in furrow irrigation management — a case study in Swaziland

The use of measured water in controlling flows for the irrigation of sugarcane was found to be vital for the rehabilitation and management of surface irrigation on a 5000 ha sugarcane project. Methods of water delivery, measurement and control at Inyoni Yami Swaziland Irrigation Scheme (IYSIS) are described. Improvements to the irrigation, using existing methods of water measurement, were carried out over a period of four years. The lessons gained in this programme of improvements confirmed the benefits of using modulus gates which allow a constant, measured, discharge of water.     

灌水量对烤烟产量和水分利用效率的影响

灌水时期不当或灌水量过大会降低烟叶的产量,同时造成水分的浪费,探究烟草适宜的灌水量至关重要。在蒸渗仪中开展试验,研究了不同灌水量对土壤水分、烤烟的水分利用效率和产量的影响。结果表明：烤烟 K326各处理不同土层含水率变化规律比较一致,（0,10]cm 土层含水率受气温、日照等气候因素较大;（10,20]cm 土壤含水率变化较剧烈;（20,60]cm 土壤含水率在整个生育期变化比较平缓,尤其在成熟后期各处理均出现不同程度的回升趋势,结合烤烟成熟期生理活动减弱、需水量减少,说明成熟期采取较小的灌水量比较适宜。成熟期烤烟的干物质产量在一定范围内随灌水量的增大而增加,如果继续加大灌水量将出现“报酬递减”现象。结合烟叶产量、烟株长势、耗水量和水分利用效率的结果,表明2700～3000 m3／hm2可以作为烤烟K326适宜的灌水量。在烤烟生产中,应均衡协调产量、水分利用效率与耗水量之间的关系,在高产前提下,适当减少灌水量,可达到既高产又节水的协调统一。     

Performance assessment of irrigation water management of heterogeneous irrigation schemes: 1. A framework for evaluation

Studies of the performance assessment of irrigation schemes have gained momentum since the late 1980s due to the common perspective that the resources (land and water) in irrigation schemes are not being managed appropriately. In this paper irrigation water management is considered as one of the activities of the irrigation scheme. Three phases of irrigation water management namely planning, operation and evaluation are identified. A framework for the performance assessment of irrigation water management in heterogeneous irrigation schemes is proposed in this paper, based on earlier studies made in this direction. The paper presents two types of allocative measures (productivity and equity) and five types of scheduling measures (adequacy, reliability, flexibility, sustainability and efficiency), together with the methodologies for estimating these for the scheme as a whole during different phases of irrigation water management.     

Social power,water control and irrigation systems

The principal finding of the study is that social power positions held by Egyptian farmers sharings a common watercourse do not have significant influence in the farmer's ability to control irrigation water distribution. Other variables used to describe irrigation management; location on the water course and farmers' use of more than one source of water to irrigate; also do not yield any explanations as to why particular farmers have more control over their irrigation than others. Farmers who have more control are less likely to be affected by other farmers' actions, physical problems on delivery canals, breakdown in pumps, and government officials actions. While differences in irrigation control among farmers exist, no single cause is identified. Two explanations for the findings are (1) water control is sufficient for a large percentage of Egyptian farmers, and (2) adequately explaining irrigation behavior cannot be done with separate variables.Deceased     

滚移式喷灌机压力对喷灌均匀性影响

为解决喷灌机械的喷灌均匀性差、移动不方便等问题,研制一种操控简单、适应性强的大型滚移式喷灌机,对其水量分布均匀系数和喷灌强度进行试验.试验采用单因素多重比较设计方法,选取距进水端距离分别为40,150,260 m处为测试处,喷灌压力分别为0.20,0.25,0.30,0.35,0.40 MPa,并运用Design-expert软件进行分析,研究各喷灌压力在各测试处对水量分布均匀系数和喷灌强度的影响.结果表明,各测试处的压力对水量分布均匀系数的影响均为显著性差异,且随喷灌压力上升,水量分布均匀系数升高.对喷灌强度的影响呈正相关性,但喷灌压力高于0.30 MPa时影响不显著.喷灌压力在0.40 MPa时,水量分布均匀系数平均可达88.75%,喷灌强度为12.3 mm/h,各处的水量分布均匀系数和喷灌强度能够保持均匀一致,并能够稳定作业,达到最优状态,完全满足大型滚移式喷灌机的性能要求.该项研究对于促进滚移式喷灌机推广和应用具有重要意义,为其深入研究提供了参考依据.     

基于水量平衡下的灌区用水计划编制方法综述

为了精准指导农田灌溉,合理优化渠系输配水,提高水资源的利用率、灌区的管理水平和总效益,对灌区用水计划的编制方法展开了理论研究.将用水计划的编制过程概括为实时灌溉预报和渠系配水两部分,分别进行归纳整理和分析.在对国内灌区用水计划的编制方式进行了解的基础上,着重介绍了利用土壤水分平衡方程进行实时灌溉预报的方法,总结各参数预测值和计算修正值的获取方法,分析对比各方法的适用范围,提炼普遍灌区实时灌溉预报中适用的方法.为了优化田间渠系配水次序和配水量,以保证作物得到及时有效灌溉,归纳总结了国内灌区常用的渠系配水模型,论述了常见的目标函数及相关约束的选取原则,并指出其局限性和可能的发展趋势.研究结果可为各灌区进行实时灌溉预报和建立优化配水模型提供借鉴与参考.     

灌水下限对甜瓜生长及水分利用效率的影响

为指导华北地区设施甜瓜节水高效生产,以日光温室甜瓜为试材,控制灌水下限分别为田间持水量的90%(T1),75%(T2)和60%(T3),研究了膜下滴灌条件下不同灌水下限对甜瓜生长指标、水分利用效率的影响.结果表明:相对较低的土壤含水量促进根系发育、分生,有利于甜瓜叶面积、茎粗的增加,但株高对灌水下限的响应不明显(P=0.1).75%田间持水量灌水下限有利于提高甜瓜产量和品质.甜瓜根系主要水平分布在以植株为中心20 cm的范围内,垂向主要分布于0~40 cm土层内.各处理的水分利用效率从大到小依次为T3,T1,T2.制订了甜瓜高效灌溉制度,各主要生育期作物系数分别为1.81,1.61,2.21,2.19.     

咸水灌溉对覆膜棉花生长与水分利用的影响

为了揭示棉花生长发育对咸水灌溉的响应特征,采用小区对比试验,研究了不同矿化度咸水灌溉对棉花出苗、株高、叶面积、果枝数、地上部干质量等形态指标以及产量构成、耗水量和水分利用率的影响.结果表明,棉花出苗率和成苗率随着灌溉水矿化度的增大而减小,但3 g/L灌水处理与对照间的差异不具有统计学意义,而5,7 g/L处理与对照间差异极具统计学意义.在移栽补全苗情况下,咸水灌溉对棉花形态生长指标产生了一定的抑制效应,灌溉水矿化度愈大,抑制作用愈大;对株高、叶面积和地上部干质量的影响在蕾期最明显,花铃期之后开始逐渐减弱;对果枝数和棉铃生长的影响程度随着棉花生育进程的推进而降低.处理间棉花的耗水量差异不具有统计学意义,籽棉产量和水分利用率的大小顺序,按灌水处理依次为3,1,5,7 g/L,其中7 g/L处理与对照间的差异具有统计学意义.与灌水前初始值相比,试验结束后1,3 g/L灌水处理的0~40 cm土层盐分未增加,5,7 g/L灌水处理则形成了积盐.研究结果可为咸水安全利用提供重要参考.     

Sensitivity analysis of optimal operation of irrigation supply systems with water quality considerations

A model for optimal operation of water supply/irrigation systems of various water quality sources, with treatment plants, multiple water quality conservative factors, and dilution junctions is presented. The objective function includes water cost at the sources, water conveyance costs which account for the hydraulics of the network indirectly, water treatment cost, and yield reduction costs of irrigated crops due to irrigation with poor quality water. The model can be used for systems with supply by canals as well as pipes, which serve both drinking water demands of urban/rural consumers and field irrigation requirements. The general nonlinear optimization problem has been simplified by decomposing it to a problem with linear constraints and nonlinear objective function. This problem is solved using the projected gradient method. The method is demonstrated for a regional water supply system in southern Israel that contains 39 pipes, 37 nodes, 11 sources, 10 agricultural consumers, and 4 domestic consumers. The optimal operation solution is described by discharge and salinity values for all pipes of the network. Sensitivity of the optimal solution to changes in the parameters is examined. The solution was found to be sensitive to the upper limit on drinking water quality, with total cost being reduced by 5% as the upper limit increases from 260 to 600 mg Cl l^–1. The effect of income from unit crop yield is more pronounced. An increase of income by a factor of 20 results in an increase of the total cost by a factor of 3, thus encouraging more use of fresh water as long as the marginal cost of water supply is smaller than the marginal decrease in yield loss. The effect of conveyance cost becomes more pronounced as its cost increases. An increase by a factor of 100 results in an increase of the total cost by about 14%. The network studied has a long pipe that connects two distinct parts of the network and permits the supply of fresh water from one part to the other. Increasing the maximum permitted discharge in this pipe from 0 to 200 m³ h^–1 reduces the total cost by 11%. Increasing the maximum discharge at one of the sources from 90 to 300 m³ h^–1 reduces the total cost by about 8%.     

Historical water storage for irrigation in the Fayum depression (Egypt)

Investigations into the much-discussed question of a historical manmade water storage lake within the Fayum depression were carried out in spring 1988. The results of the research into the dam between Itsa and Shidmuh indicate that there existed an artificial lake in the south-east of the Fayum as early as the 3rd Cent. B.C. The findings are in agreement with the reports of the classical writers. There is no reason not to identify this lake in the El-Mala'a basin with the lake the ancient (post-Ptolemaic) historians and geographers referred to as Lake Moeris. The question as to whether Herodotus in the 5th Cent. B.C. described the same lake or whether he saw the water level of the Birket el-Qarun at 19 to 21 m must, at present, remain unanswered.