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1.
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.  相似文献   

2.
The WaDI (water delivery for irrigation) model deals with the relations between the collective water supply and the demand within irrigated schemes. It is based on a separate modelling of the water supply and demand, including (i) a simplified representation of the hydraulic structure, characteristics and organizational parameters of the scheme, (ii) an assessment of the water demand of farms based on their total irrigated area, cropping pattern and irrigation practices, (iii) a farm typology, (iv) a confrontation between water demand and supply at each node of the scheme from pumping plants to tertiary canals, and (v) calculation of response factors between supply and demand during the peak demand period. “What-if” scenarios are simulated in order to enhance the stakeholders’ capacity to plan strategic decisions such as water delivery allocation rules or infrastructure investments. WaDI was implemented on two Brazilian schemes. It allowed broadening the stakeholders’ limited representation of collective water supply and demand into a more comprehensive understanding of these relations. The approach however showed some limits, along with the difficulty of assessing the real impact on the stakeholders’ capacity for strategic planning.  相似文献   

3.
During the last quarter of the 20th century, many irrigation schemes were constructed along the bank of the Senegal River in Mauritania. About 40,000 ha were developed but less than 23,000 ha remain irrigated today. A program for rehabilitation is now in place to counteract deterioration and abandonment of these schemes. This paper presents an evaluation of the rehabilitation of a small, representative irrigation scheme governed by a farmers’ cooperative in the village of Bélinabé. Before rehabilitation, the scheme covered 37.7 ha comprising 107 plots each of 0.33 ha, essentially all devoted to production of rice. Water for irrigation was pumped directly from the river into two head basins and distributed through open canals. After rehabilitation, the scheme was extended to 115 ha with new plots averaging 0.36 ha. Water is now supplied by a single cluster of pumps and conveyed through pipes and open canals. Evaluation of performance consisted in analysis of: capacity; distribution losses; flexibility, adequacy and reliability of the system; maintenance status; farmer's perception of system performance. Field data were collected during irrigation campaigns before rehabilitation in 2004 and during 2006 and 2007 afterwards. A model of network distribution and field water balance was developed to assist evaluation. It was established that before rehabilitation the scheme could operate satisfactorily if proper maintenance were practiced. After rehabilitation, more families have access to irrigation but reliability and flexibility of water distribution have been reduced. Furthermore, pumping capacity is now insufficient to cover crop water requirements. Recommendations are provided for future rehabilitation work and maintenance of schemes generally.  相似文献   

4.
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.  相似文献   

5.
The equitable distribution of canal water is imperative to ensure social justice as well as crop productivity. In north-west India and Pakistan, water from the tertiary canal (watercourse) is distributed to the farmers through a rotational system of irrigation. In this system the duration of supply to each farmer is in proportion to his holding in the outlet (watercourse) command, without considering the seepage loss. The rate of seepage loss increases with increase in length of watercourse from head to tail. Thus, the farmers in the lower reaches get much less water per unit area than the farmers in the upper reaches. The farmers must be compensated for the seepage loss. Therefore, a model was developed to ensure equitable distribution of water to the farmers located on a watercourse in proportion to their land holdings giving due compensation for the seepage loss. The model is based on the assumption that soil throughout the length of flow is homogeneous and loss through evaporation is negligible. The model developed ensures an equitable distribution of water to the farmers according to their land holdings. A comparison of existing and revised time allocation reveals that the farmers located in the upper reaches were getting more time (up to 12.2 min per unit area), while the farmers located in the lower reaches have been getting less time (up to 28.1 min per unit area). The existing allocation of time of 0.75 h per unit area to all the farmers according to the old rules was revised to 0.546–1.219 h per unit area from head to tail. The conclusions drawn suggest that the strategy developed here should be adopted elsewhere in the existing system of irrigation for equitable distribution of canal water. Received: 21 December 1999  相似文献   

6.
SIMIS (the FAO Scheme Irrigation Management Information System) is a decision support system that integrates tools and performance indicators to facilitate the planning and management of irrigation schemes. The authors used SIMIS to compute performance indicators in an irrigation scheme in Southern Spain that were used to identify distribution system constraints affecting the flexibility of water deliveries and to identify scheme sectors where deliveries could not meet the predicted crop water demands. Applying SIMIS, the authors and the irrigation scheme manager evaluated measures to overcome the constraints for future irrigation campaigns, and to refine the water orders made every 2 weeks to the basin authority. On the other hand, SIMIS presented limitations to the evaluation of on-demand delivery schedules. To overcome these limitations, an external model, developed outside SIMIS, showed that the current distribution network of the scheme has the capacity to deliver water on-demand only if a slight water deficit is accepted during the peak demand period. The analysis showed that by relaxing the stringency of the quality of operation of on-demand systems, rotation systems may be transformed into on-demand systems without changing their structures. This analysis could also be done using Clément's hypothesis, but doing so resulted in overestimates of the quality of operation and of the relative irrigation supply.  相似文献   

7.
This paper describes a two-part methodology for managing the risk posed by water supply variability to irrigated agriculture. First, an econometric model is used to explain the variation in the production value of irrigated agriculture. The explanatory variables include an index of irrigation water availability (surface storage levels), a price index representative of the crops grown in each geographical unit, and a time variable. The model corrects for autocorrelation and it is applied to 16 representative Spanish provinces in terms of irrigated agriculture. In the second part, the fitted models are used for the economic evaluation of drought risk. Inflow variability in the hydrological system servicing each province is used to perform ex-ante evaluations of economic output for the upcoming irrigation season. The model's error and the probability distribution functions (PDFs) of the reservoirs’ storage variations are used to generate Monte Carlo (Latin Hypercube) simulations of agricultural output 7 and 3 months prior to the irrigation season. The results of these simulations illustrate the different risk profiles of each management unit, which depend on farm productivity and on the probability distribution function of water inflow to reservoirs. The potential for ex-ante drought impact assessments is demonstrated. By complementing hydrological models, this method can assist water managers and decision makers in managing reservoirs.  相似文献   

8.
针对龟石灌区农业用水效率低下、浪费严重等问题，提出了节水措施，分析了节水改造的潜力与效益。灌区水资源优化配置与合理利用，提高灌溉水利用率和水分生产率，富余水量用于城市供水及发电，提高单位水量的价值不仅是必要的，而且是灌区发展的必由之路。  相似文献   

9.
为缓解河西绿洲菘蓝种植水资源供需矛盾,解决灌溉过程中存在的灌溉决策粗放问题,提高灌溉水利用效率。本文通过参照Jensen模型、水量平衡方程等,根据河西绿洲干旱少雨的环境特征及菘蓝种植过程中各生育期耗水强度不同的生长规律,构建菘蓝灌溉决策模型并利用遗传算法对有限水资源在菘蓝灌溉中的合理分配进行求解。同时综合考虑各生育期灌溉水量约束条件、有效降水量、灌溉成本、产量等因素,在非充分灌溉理论指导下利用遗传算法结合现有菘蓝种植数据对灌溉决策进行优化,以达到节水、高效高产的目的,优化结果显示肉质根轻度水分亏缺可以显著提高灌溉水利用效率,同实际种植灌溉情况相符。  相似文献   

10.
In this work, remote sensing-based assessments of actual evapotranspiration using METRIC integrated with a water balance model provided accurate estimates of irrigation performance. This new methodology was applied and tested in the Genil–Cabra Irrigation Scheme located in southern Spain during the 2004–2005 irrigation season. The performance indicators used, the annual relative irrigation supply (ARIS) and the irrigation water productivity (IWP), required ET input data which were calculated using either METRIC or standard FAO methodology. The new procedure that used METRIC detected overirrigation (ARIS of 1.27) in situations where the ARIS calculated with the standard FAO methodology indicated near-optimal irrigation (ARIS of 0.98). Additionally, the proposed methodology allows the estimation of the volume of applied water at the field scale. Comparisons between the ARIS and IWP values obtained from actual applied water records against those calculated with the new methodology resulted in good agreement. It is concluded that the integration of the METRIC method to calculate actual ET with a water balance model allowed the determination of performance indicators in an irrigation scheme in a reliable and accurate fashion, requiring only very limited information at the field level.  相似文献   

11.
基于DP-PSO算法的灌区农业水资源优化配置   总被引：2，自引：0，他引：2  
针对引水灌区,考虑灌溉用水总量约束和时段可供水量约束,以单一作物非充分灌溉下灌溉制度优化为第一层,区域多种作物种植结构及水量分配为第二层,分别采用动态规划和粒子群算法求解,建立了基于DP-PSO算法的灌区农业水资源优化配置模型。针对多重约束问题,提出了一种初始化粒子群的方法,并通过粒子速度的动态变化来保证每代粒子都满足约束,提高了算法的收敛速度和收敛精度。以赣抚平原灌区为对象,考虑降雨和水源可供水量不同步的特点,计算了3种降雨频率、多年可供水条件下的农业水资源优化配置方案。结果表明,基于DPPSO算法的农业水资源优化配置模型合理可靠,为引水灌区农业水资源优化提供了一种新的方法。  相似文献   

12.
The primary objective of an irrigation organization is to provide efficient and effective management of water resources to achieve enhanced agricultural production. Performance assessment studies provide a tool to evaluate and promote this objective. The study examines the existing planning procedures and assesses irrigation performance of four Water User Associations (WUAs) located in Osh Province, Kyrgyzstan. Performance was evaluated using indicators of adequacy, efficiency, dependability and equity. Indicators were calculated for each irrigation season over the period 2003 to 2007. In general, all WUAs were found to be strong in terms of adequacy and efficiency standards. However, performance with respect to dependability and equity was poor. The results suggest that more effort is needed to improve temporal uniformity and equity in water distribution. In order to achieve this, estimations of irrigation requirements by WUA managers needs to be improved and mechanisms developed to request water in quantities, which are needed to maintain equity across the WUA outlets and among water users. The study concludes that the establishment of WUAs in Kyrgyzstan has helped to address the problem of water distribution and allocation among a large number of farmers. However, further training of farmers and managers is required to build their capacity to share water and ensure equity among users particularly during periods of less than optimal water supply. The findings of this research suggest that application of a pre-determined set of indicators can be a useful and cost effective tool to measure the performance of WUAs. This is particularly important for Central Asia where the performance of the recently established and state initiated WUAs to replace former collective farms is now a key element in future sustainable water management. The study identified uncertainties in the estimation of WUA water demands based on previous methods and suggests more attention and care required in calculating water requirements.  相似文献   

13.
基于多目标模糊规划的灌区多水源优化配置   总被引：2，自引：0，他引：2  
付强  肖圆圆  崔嵩  刘东  李天霄 《农业机械学报》2017,48(7):222-227，221
以黑龙江省和平灌区为例,构建基于多目标模糊规划的灌区多水源优化配置模型,该模型能够在提高农业灌溉用水净效益的同时有效减少农业灌溉水量,促进和平灌区多水源高效配置。采用具有非线性隶属度函数的模糊多目标规划求解模型,得到不同流量不同水源下的最优配水方案。结果表明:不同流量水平下水稻不同生育阶段均存在缺水现象,低流量下需从柳河水库引入外调水才能保证水稻的最小需水量。为保证灌区整体效益,按照引水工程、提水工程、井灌工程的先后顺序进行配水,并得到多目标配水模型在不同情景下的运行稳定情况。该模型可以高效地进行灌区多水源在作物各生育阶段的优化配置。  相似文献   

14.
This paper evaluates the performance of the first drip irrigation scheme in commercial tea production in Tanzania with a view to making recommendations for improved management and providing data for investment decisions. Uniformity, efficiency and adequacy of irrigation were calculated and the scheduling of irrigation water was reviewed. Operators were interviewed to highlight the main benefits and problems of the system. Investment and recurrent costs of drip and overhead sprinkler systems were quantified and compared. Root development was assessed qualitatively using excavation pits. Irrigation uniformity DU and efficiency ranged between 88 and 95% in the 10 out of 14 irrigation blocks where endline pressures were at least 0.5 bars, and between 77 and 89% in the four blocks were endline pressure was less than 0.5 bars. Scheduling drip irrigation using tensiometers offered potential water savings of 26% in comparison to a water balance schedule, but these are not currently realised. Gross marginal income was very sensitive to tea price and yield. Economically optimal fertilizer rates vary in dependence of tea price and yield and appear to be lower than the current level of 300 kg N ha−1. The higher costs under drip, compared to overhead sprinklers, were mainly for purchase and installation and fertilizer. The costs of labour for applying water and fertilizer were reduced by nearly 50%. At average 2002 tea prices of 1.31 US$ kg−1, drip irrigation would improve the grower’s gross margin if an additional yield of at least 411 kg ha−1 was achieved. The main threats to drip system performance are discussed. Future research efforts should aim at establishing the yield response of tea to water and fertilizer under drip irrigation.  相似文献   

15.
针对西北干旱区灌区生态环境脆弱、水资源短缺、复杂不确定性等问题,以石羊河流域红崖山灌区为例,耦合2型模糊集、模糊可信度约束规划和多目标规划等理论方法,构建了基于2型模糊集的多目标农业-生态水土资源优化配置模型。模型以灌溉水损失最小、生态植被灌溉水满意度最大、生态植被灌溉水费用最小和主要粮食作物经济效益最大为目标,对红崖山灌区10个决策单元的地表水、地下水和粮食作物种植面积进行优化配置。求解模型得到不同可信度水平和不确定性程度下的水土资源优化配置方案。结果表明：耦合2型模糊集的模型能够提供丰富的配置方案,水量对可信度水平的敏感性高于不确定性程度,作物种植结构对可信度水平不敏感。以不确定性程度参数为0.5、可信度水平为0.7时为例,生态植被均通过地表水灌溉,作物通过地表水、地下水联合灌溉,玉米的产量和经济效益均大于小麦。相比前人研究,本研究考虑生态植被灌溉需求,优化结果更加真实合理。本研究可为决策者提供较为符合灌区实际的配置方案,为西北干旱区灌区现代化建设提供科学指导。  相似文献   

16.
Improvement of irrigation management in areas subjected to periods of water scarcity requires good knowledge of system performance over long time periods. We have conducted a study aimed at characterizing the behaviour of an irrigated area encompassing over 7000 ha in Southern Spain, since its inception in 1991. Detailed cropping pattern and plot water use records allowed the assessment of irrigation scheme performance using a simulation model that computed maximum irrigation requirements for every plot during the first 15 years of system operations. The ratio of irrigation water used to maximum irrigation requirements (Annual Relative Irrigation Supply, ARIS) was well below 1 and oscillated around 0.6 in the 12 years that there were no water supply restrictions in the district. The ARIS values varied among crops, however, from values between 0.2 and 0.3 for sunflower and wheat, to values approaching 1 for cotton and sugar beet. Farmer interviews revealed some of the causes for the low irrigation water usage which were mainly associated with the attempt to balance profitability and stability, and with the lack of incentives to achieve maximum yields in crops subsidized by the Common Agricultural Policy (CAP) of the European Union. The response to water scarcity was also documented through interviews and demonstrated that the change in crop choice is the primary reaction to an anticipated constraint in water supply. Water productivity (value of production divided by the volume of irrigation water delivered; WP) in the district was moderate and highly variable (around 2€ m−3) and did not increase with time. Irrigation water productivity (increase in production value due to irrigation divided by irrigation water delivered) was much lower (0.65€ m−3) and also, it did not increase with time. The lack of improvement in WP, the low irrigation water usage, and the changes in cropping patterns over the first 15 years of operation indicate that performance trends in irrigated agriculture are determined by a complex mix of technical, economic, and socio-cultural factors, as those that characterized the behaviour of the Genil-Cabra irrigation scheme.  相似文献   

17.
The cost constructing for irrigation is often given in $/ha. In deciding whether a project is worth undertaking, it is important to weigh the anticipated benefits against the expected costs. In this study, unit area construction costs based on the way of project water supply (gravity, pump) and scheme type (classic canal, flume, pipe) were calculated for the 211 irrigation projects operated and constructed by DSI (State Hydraulic Works) in Turkey. In a case study of the 27 irrigation schemes constructed by DSI in the Büyük Menderes and West Mediterranean basins, construction costs per unit area, irrigation ratio, and amount of unproductive costs were determined. As a result, though the area of 76383 ha was constructed for irrigation schemes, this area wasn??t under irrigation services with several various reasons; therefore, 641 million $US according to water supply way, and 574 million $US to the scheme type were unproductive investment for irrigation projects researched in the basins.  相似文献   

18.
Irrigation is the dominant user of water worldwide, but provision of potable water and water for industry are higher priorities and give higher social and economic returns. Irrigation will continue to lose water to competing sectors and the productivity of irrigation systems (since food demand continues to grow) remains a central issue in water management. Performance assessment of irrigation has traditionally been difficult when based on field measurements of flows, deliveries and depths over large areas. Furthermore, performance measures have shifted from narrow engineering indicators to broader productivity issues of production achieved per unit of water consumed. Remote sensing, applied to the estimation of evapotranspiration (ET) over large areas, provides analysts of irrigation systems with extraordinary new tools for the objective assessment of consumption and production – constituting a quantum leap in the assessment of irrigation system performance. Awareness and utilisation of these tools is spreading, but important areas remain to be “converted” from traditional approaches that rely on an array of estimated parameters. The next challenge for remote sensing will be to map the frontier between the reliability of the irrigation service and the productivity achieved. Reliability provides the inducement for farmers to invest in higher productivity – to the benefit of themselves and society – and understanding better how the individual maximises profits within an uncertain irrigation environment can provide important guidance to managers and system designers.  相似文献   

19.
Irrigation policy makers and managers need information on the irrigation performance and productivity of water at various scales to devise appropriate water management strategies, in particular considering dwindling water availability, further threats from climate change, and continually rising population and food demand. In practice it is often difficult to access sufficient water supply and use data to determine crop water consumption and irrigation performance. Energy balance techniques using remote sensing data have been developed by various researchers over the last 20 years, and can be used as a tool to directly estimate actual evapotranspiration, i.e., water consumption. This study demonstrates how remote sensing-based estimates of water consumption and water stress combined with secondary agricultural production data can provide better estimates of irrigation performance, including water productivity, at a variety of scales than alternative options. A principle benefit of the described approach is that it allows identification of areas where agricultural performance is less than potential, thereby providing insights into where and how irrigation systems can be managed to improve overall performance and increase water productivity in a sustainable manner. To demonstrate the advantages, the approach was applied in Rechna Doab irrigation system of Pakistan’s Punjab Province. Remote sensing-based indicators reflecting equity, adequacy, reliability and water productivity were estimated. Inter- and intra-irrigation subdivision level variability in irrigation performance, associated factors and improvement possibilities are discussed.  相似文献   

20.
A multiobjective optimization model has been presented for allocating irrigation waters in a rice paddy area. Water-saving practices conducted on the field-plot basis are considered and expressed in the optimal water allocation problem in the regional scale. Irrigation water allocated to the blocks of paddy fields is divided into two components of a basic amount and a safety margin in order to mitigate the effect of hydrological and hydraulic uncertainties on the study area. Four competing management objectives with regard to total rice yield, total water-saving cost, equity of water allocation, and safety of water supply are defined in the linear programming formulation so that noninferior solutions can be procured which are informative and persuasive in decision-making. Applicability of the optimization model is examined using water allocation problems for a hypothetical irrigation system. It is demonstrated that the optimization model can provide satisficing solutions where the four objectives are harmonized under substantial variations of total water supply to the irrigation system.  相似文献   

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