Optimisation model for water allocation in deficit irrigation systems: II. Application to the Bémbezar irrigation system

In this paper, the proposed optimisation model is applied to optimise water management in the Bembézar system, a small hydrological basin belonging to the Guadalquivir River basin in southern Spain that supplies water to the Bembézar River Irrigation District.In order to apply the model, the irrigation methods and performance in the irrigation district have been analysed through a set of field irrigation evaluations. Cropping patterns, crop productivity and other relevant agronomic and economic data have been collected.The influence of irrigation uniformity and the type of distribution of irrigation water on the crop yields, as well as the relationship between crop yields and irrigation scheduling have been analysed using the proposed model.A deterministic analysis has been carried out in the irrigation district in order to compare optimum water and cropping patterns management with actual ones.In order to account for the randomness of both climatic and water availability variables, a stochastic data generation has been carried out which considers the correlation between these hydrological series. The system is then analysed in a stochastic environment. Several simulations of the optimisation process have been carried out using generated data on climatic and water availability variables.The result of this analysis demonstrates that when only the satisfaction of the internal demands is considered, high quantities of water are allocated to the irrigation districts resulting in low economic benefits per unit of water used and lower irrigation efficiency. This situation has been compared with the solution provided by the hypothesis of a proposed water market in which it is possible to transfer part of the water of the system to other alternative uses at a fixed price. In this second hypothesis, water consumption in the irrigation districts was reduced.     

Optimal irrigation planning model for an existing storage based irrigation system in India

A weekly irrigation planning LP model is formulated for determining the optimal cropping pattern and reservoir water allocation for an existing storage based irrigation system in India. Objective of the model is maximization of net annual benefit from the project. In an irrigation planning of a storage based irrigation system, initial storage of the reservoir at the beginning of the reservoir operation, expected inflows into the reservoir during each intraseasonal period, capacity of channels, crop calendar and yield response to water deficit in each growth stage of crop play a vital role in deciding acreage and water allocation to each crop. The planning model takes into account yield response to water deficit in each intraseasonal period of the crop, expected weekly inflows entering into the reservoir, storage continuity of reservoir, land and water availability, equity of water allocation among sub areas and proportionate downstream river release. One year comprising of 52 weeks is considered as planning horizon. To account for uncertainty in water resources availability, the model is solved for four levels of reliability of weekly inflows entering into the reservoir (90%, 85%, 80% and 75%). Alternative optimal cropping patterns and weekly releases to crops grown in each sub area under each main canal are obtained for various states of initial storage at the beginning of reservoir operation and for various levels of weekly inflows into the reservoir. Results reveal the importance of initial state of reservoir storage for feasible solution and shows the impact on cropping pattern with the change in initial storage of reservoir for different levels of reliability of weekly inflows.     

An integrated water trading-allocation model, applied to a water market in Australia

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).     

灌溉渠系优化配水模型研究

灌溉渠系的优化配水问题可分为两类:一是以某种指标最优为目标的灌溉水量分配;二是以水量损失最小为目标的灌区各级渠道流量的优化调度。在非充分灌溉试验的基础上,做出了西北干旱灌区棉花膜下滴灌水分生产函数。根据作物水分生产函数,以农业效益和灌溉管理部门总体的经济效益最高为目标,建立了灌溉渠系优化配水模型。在提高灌区经济效益的同时,建立了配水渠道流量优化调度0-1线性整数规划模型,模型适用于支渠以下各级配水渠道在来水流量确定,分水渠道流量彼此相同且按"定流量,变历时"方式轮灌时的优化配水决策,通过实例对模型进行了求解。     

明确初始水权数量与质量的分配系

为解决水资源管理和水市场建设中涉及的水权问题，本文以内陆黑河干流为背景建立了干旱区水权分配系统。按照不同地区使用的水资源除了具有相对公平的数量，还应该具有相对公平的质量的原则，系统将以往模糊的流域水权界定对象清晰化，明确其为河流在某种社会经济条件下，为满足生态和水环境的要求，流域所能调配的水资源。为此，系统考虑与地区取水相关的经济和环境因素，运用基于水资源模型和区域水质模型的多目标规划方法计算流域各地区理论取水量，并将理论取水量结果用于改进目前的水权分配计算方法，不仅给出了流域各地区的水权分配比例，同时将各地区按水权分配到的水资源数量和质量也一并给出。实际应用证明了系统的有效性，给出的水权分配结果较以往类似成果加深了各地区对自身拥有的水资源状况、以及将面临的流域整体水资源形势的认识。     

熵权模糊物元模型在节水灌溉综合效益评价的应用

针对以往节水灌溉综合效益评价中多采用简单的多指标综合评价的不足,运用熵权法来确定评价指标的权重,建立基于熵权的物元可拓模型对灌区节水灌溉综合效益进行评价,分别从节水灌溉的社会效益、经济效益和生态效益3个方面入手,构建评价指标综合体系.并以吉安市的田南灌区、谷口灌区、银湾桥灌区和南车灌区共4个灌区为实例进行评价,结果显示:银湾桥灌区的节水灌溉综合效益级别为“一般”,田南灌区的节水灌溉综合效益级别向“一般”级别转化,谷口灌区的节水灌溉综合效益级别向“较好”级别转化,而南车灌区的节水灌溉综合效益级别向“好”级别转化,采用灵敏度分析方法进一步验证评价结果的稳定,所得评价结果科学可靠.说明熵权物元分析法在节水灌溉综合效益评价中具有一定的应用价值.     

Integrated decision making for reservoir,irrigation, and crop management

An integrated approach to reservoir, irrigation, and cropping management which links four different models—a hydrologic model (PRMS), a crop growth simulation model (EPIC), an economic model based on linear programming, and a dynamic programming model—is developed and demonstrated. The demonstration is based on an irrigation district located in a subhumid climate with an irrigation reservoir large enough for over-year storage. The model is used to make repeated simulations for various planning horizons. Two different types of results are presented. The first provides the probability that each of the various farm plans (land/crop/water allocation) will be chosen as the optimum in the first year of the planning horizon. The second approach provides probability distributions of accumulated revenues over a chosen length of planning horizon. Each distribution is associated with an initial reservoir level and a particular farm plan in the first year of the planning horizon. The consequence of selecting certain farm plans at the beginning of a specified planning horizon is therefore quantified in a probabilistic way. Based on families of probability–revenue curves, an irrigation manager can simultaneously evaluate crop, irrigation, and reservoir management options.     

基于多目标模糊规划的灌区多水源优化配置

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。     

Model for performance based land area and water allocation within irrigation schemes

This paper focuses on irrigation schemes under rotational water supply in arid and semiarid regions. It presents a methodology for developing plans for optimum allocation of land area and water, considering performance measures such as productivity, equity and adequacy. These irrigation schemes are characterized by limited water supply and heterogeneity in soils, crops, climate and water distribution network, etc. The methodology proposed in this paper, therefore, uses a previously developed simulation–optimization model (Area and Water Allocation Model, AWAM) that considers the heterogeneity of the irrigation scheme in the allocation process, and modifies this to take account of equity and adequacy of supply to irrigated areas. The AWAM model has four phases to be executed separately for each set of irrigation interval over the irrigation season: 1. generation of irrigation strategies for each crop–soil–region combination (CSR unit), 2. preparation of irrigation programmes for each irrigation strategy, 3. selection of specified number of irrigation programmes for each CSR unit and 4. optimum allocation of land area and water to different parts of the irrigation scheme (allocation units) for maximizing productivity. In the modified AWAM model, the adequacy is included at Phase-2 (by including only the irrigation programmes for full irrigation of each CSR unit) and equity is included at Phase-4 (by including the constraints for equity). The paper briefly discusses the applicability of the modified AWAM model for a case study of Nazare medium irrigation scheme in Southern India. The results of the case study indicated that the performance measures of productivity, equity and adequacy conflict with each other.     

山东禹城引黄灌区非充分灌溉配水模型

为了制定有多种作物且灌溉水源为动态变化的灌区的配水计划，提出了由充分灌溉和非充分灌溉2级模型组成的配水模型。其中非充分灌溉配水模型包括优化模型和模拟模型2部分，优化模型的方案具有较好的经济效益，而模拟模型的方案便于实施。模型中联合运用引黄水和地下水，可减少因黄河缺水对农业造成的重大损失。在此基础上编制的山东禹城灌溉配水管理决策支持系统界面友好，实用性强，基本上可灌溉灌区的管理需要。     

西北现代生态灌区建设理论与技术保障体系构建

灌区是我国粮食安全和现代农业发展的基础保障,同时也是区域经济发展和生态环境保护的重要基石。然而西北地区独特的气候、地貌及社会经济状况导致了灌区生产能力和生态服务功能难以满足现代生态农业发展的需求。通过系统分析西北灌溉农业发展中面临的水资源过度开发、土壤盐碱化严重、生态环境功能低下等方面的问题,阐述了西北现代生态灌区的内涵与特征,并基于农业生产“功能水分”来源,将西北灌区划分成了灌溉依赖型灌区、灌溉主导型灌区、灌溉补充型灌区和灌溉提质型灌区4类。以灌区农业生产系统、物能输配系统、生态环境系统为建设对象,提出了灌区生态服务功能优化配置、灌区农田物能调控和灌区生态系统安全评估三大核心理论,构建了灌区系统控污与景观价值提升技术、灌排系统管控技术、作物生境要素综合调控技术三大关键技术,从而形成了西北现代生态灌区理论与技术保障体系,为我国西北灌溉农业高质量可持续发展提供理论与技术指导。     

基于改进多目标决策模型的大桥水库灌区渠系自适应规划方法

提出基于改进多目标决策模型的大桥水库灌区渠系自适应规划方法,合理规划大桥水库灌区渠系配水,提高水资源利用率,降低无效弃水以及对生态环境的影响。以配水结束后灌区各渠系缺水量、渠道输水损失量以及农作物生产带来的灰水足迹三者最小为大桥水库灌区渠系规划多目标决策函数,以渠道输水能力、水量和时间为约束条件,构建大桥水库灌区渠系规划的多目标决策模型;以栅格法构建路径规划的运行环境,通过移动几率优化、信息素挥发系数自适应调整两方面改进蚁群算法,通过改进蚁群算法寻优获取渠道缺水量、输水损失量、灰水足迹最小的水库灌区渠系规划结果。实验证明：该方法可以有效规划大桥水库灌区渠系的水资源,规划后的灌区渠系在缺水量、渠道输水损失量以及灰水足迹方面都有较好的表现,且效率高、应用性强。     

An integrated hydro-economic modelling framework to evaluate water allocation strategies I: Model development

In this paper an integrated modelling framework for water resources planning and management that can be used to carry out an analysis of alternative policy scenarios for water allocation and use is described. The modelling approach is based on integrating a network allocation model (REALM) and a social Cost Benefit economic model, to evaluate the physical and economic outcomes from alternative water allocation policies in a river basin or sub-basin. From a hydrological perspective, surface and groundwater models were first applied to assess surface and groundwater resource availability. Then an allocation model was applied to reconcile the calculated surface and groundwater resources. From an economic perspective initially the value of water allocated to different uses in each demand centre within the system was estimated. These values were then placed in a social Cost Benefit Analysis to assess the economic consequences of different allocation scenarios over time and space. This approach is useful as it allows policymakers to consider not only the physical dimensions of distributing water, but also the economic consequences associated with it. This model is considered superior to other models as water is increasingly being seen as an economic good that should be allocated according to its value. The framework outlined in this paper was applied to the Musi sub-basin located in the Krishna Basin, India. In applying this framework it was concluded that competition for Musi water is very high, the transfer of water from agriculture to urban users is likely to grow in future and the value of water used in different agricultural zones is very low.     

Optimization model of an irrigation reservoir for water allocation and crop planning under various weather conditions

This paper develops a non-linear programming optimization model with an integrated soil water balance, to determine the optimal reservoir release policies, the irrigation allocation to multiple crops and the optimal cropping pattern in irrigated agriculture. Decision variables are the cultivated area and the water allocated to each crop. The objective function of the model maximizes the total farm income, which is based on crop–water production functions, production cost and crop prices. The proposed model is solved using the simulated annealing (SA) global optimization stochastic search algorithm in combination with the stochastic gradient descent algorithm. The rainfall, evapotranspiration and inflow are considered to be stochastic and the model is run for expected values of the above parameters corresponding to different probability of exceedence. By combining various probability levels of rainfall, evapotranspiration and inflow, four weather conditions are distinguished. The model takes into account an irrigation time interval in each growth stage and gives the optimal distribution of area, the water to each crop and the total farm income. The outputs of this model were compared with the results obtained from the model in which the only decision variables are cultivated areas. The model was applied on data from a planned reservoir on the Havrias River in Northern Greece, is sufficiently general and has great potential to be applicable as a decision support tool for cropping patterns of an irrigated area and irrigation scheduling.     

金乡县田间节水技术的测试分析

针对当前大面积推广节水灌溉的急需和农村经济条件的现实，采用塑料软管输水到畦中间，将长畦分段灌水，作为实施短畦灌溉的手段，即把管道节水与畦灌节水融为一体，通过测试分析，提出了不同土质的合理畦长的塑料软管的经济直径。经应用证明，提高灌溉有效利用系数４４％。且费用低、效果好，易为农民接受。     

灌区灌溉用水时空优化配置方法

将传统的灌溉水量在作物间的优化分配模型和建立的渠系工作制度多目标优化模型与地理信息系统相集成,提出了基于空间决策支持系统的灌区灌溉用水优化配置的新方法.综合考虑了灌区内作物、土壤、气象站点、渠系布置的空间差异、年季间气象以及作物不同生育阶段对应参数的时间差异.与传统优化方法相比,该方法可根据管理者对优化精度的要求,灵活选择优化尺度,同时,简化了求解时空优化配水问题的繁琐程度,结果表现形式更加丰富.在此基础上建立的空间决策支持系统界面友好,运行效率高,可移植性和通用性强.经实例验证,优化后的配水方案与原配水方案相比较,灌溉总用水量减少296％,产量增加243％,水分生产率提高05 kg／m3,灌溉净效益增加168％.优化后配水方案具有将有限的水资源向经济价值较高作物转移的趋势.该方法为灌区灌溉用水优化配置提供了新思路.     

纵向岭谷区农业水管理调控措施

为实现纵向岭谷区农业水管理调控,宏观上以流域水资源综合规划为基础,从需求入手,采取强化节水措施,提高水的利用效率,抑制需水的不合理增长,到2030年农田有效灌溉程度达到32%,灌溉水利用系数提高到0.581,农业灌溉需水总量控制在89.8亿m3,需水年均增长率仅0.52%,以MKIE BASIN模型的配置结果显示,各规划水平年能达到水资源供需平衡;微观上应建立数字流域工程,提高对流域雨水工情的实时监测.推行农业高效节水灌溉制度,建立和完善包括实时灌溉预报、渠系动态配水、实时信息采集和预报修正、灌区空间信息管理等内容的流域单元农业灌溉用水及水资源的实时调度系统,利用水资源配置成果与短期实时调度相结合,实现流域单元的农业高效用水调控.     

北京市再生水灌区规划研究

以北京市大兴区和通州区境内的再生水灌区为研究对象,在分析灌区水文、气象、水资源开发利用与水量平衡状况、水利工程现状以及作物需水、灌溉水源等资料的基础上,采用系统工程的方法,通过构建多水源联合调度模型,统筹调度再生水、地表水、地下水等灌区内可利用水资源,使再生水灌区供水保证率得到显著提高,基本实现了地下水的采补平衡。提出了再生水灌区规划重点应围绕地表调蓄工程、田间配套工程、水网扩建工程以及灌区水资源管理信息化工程等4项内容。研究成果提升了再生水灌区规划的科学化水平,促进再生水资源高效合理利用。     

Stochastic efficiency analysis of deficit irrigation with standard risk aversion

The main objective of this research was to develop an expected utility optimisation model to economically evaluate deficit irrigation within a multi-crop setting while taking into account the increasing production risk of deficit irrigation. The dynamic problem of optimising water use between multiple crops within a whole-farm setting when intraseasonal water supply may be limited was approximated by the inclusion of multiple irrigation schedules into the optimisation model. The SAPWAT model (South African Plant WATer) was further developed to quantify crop yield variability of deficit irrigation while taking the non-uniformity of irrigation applications into account. Stochastic budgeting procedures were used to generate appropriately correlated matrixes of gross margins necessary to incorporate risk into the water use optimisation model. Special care was taken to represent risk aversion consistently between the alternatives through the use of a new procedure to standardise values of absolute risk aversion. The model was applied to study the impact of increasing levels of risk aversion on the profitability of deficit irrigation under limited water supply conditions. The main conclusion from the analyses was that although deficit irrigation was stochastically more efficient than full irrigation under limited water supply conditions, irrigation farmers would not willingly choose to conserve water through deficit irrigation and would be expected to be compensated to do so. Deficit irrigation would not save water if the water that was saved through deficit irrigation were used to plant larger areas to increase the overall profitability of the strategy. Standard risk aversion was used to explain the simultaneous increasing and decreasing relationship between the utility weighted premiums and increasing levels of absolute risk aversion and was shown to be more consistent than when constant absolute risk aversion was assumed.     

Integrated hydrologic-economic modelling for analyzing water acquisition strategies in the Murray River Basin

We describe a coupled hydrologic-economic spreadsheet model for the Murray-Darling Basin that allows analyses of water allocation and use by different sectors including agriculture and environment under alternative policy scenarios. The model is a simple, lumped optimisation model which includes partitioning of rainfall into runoff and evapotranspiration, a reach by reach water balance of the river system, irrigation demand and revenue generation. Groundwater is not considered because groundwater use is a small part of the overall water use. The model is used to optimize profit, diversions and flows subject to hydrological and economic constraints determined by the policy scenario.We use the model to examine approaches of acquiring water for reallocation to the environment, and their impacts on irrigation water use and regional income from agriculture. We show that the optimal approach for acquisition depends on: economic factors, including the cost of water and the profits generated by its use; institutional factors, such as restrictions to trade between regions; and, hydrological factors, particularly the connectivity of and losses within the river network.The volume of water to be acquired does not, in general, equal the volume to be allocated. For a downstream site, water must be acquired from upstream, and more water must be acquired than is to be allocated: the volume acquired is that to be allocated plus transmission losses between the locations of acquisition and allocation. For upstream sites, it is optimal to acquire some water from downstream, and less water must be acquired than is to be allocated: the volume acquired is that to be allocated, less the transmission losses no longer incurred between the locations of acquisition and allocation.The volumes of water that must be acquired to satisfy an allocation target and maintain flows in the river system are affected by restrictions on trade between sub-catchments.