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.     

基于DP-PSO算法的灌区农业水资源优化配置

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。     

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.     

Analysis of deficit irrigation strategies for corn using crop growth simulation

Summary Corn yields for full irrigation and 4 different levels of deficit irrigation were simulated using a model developed by Stockle and Campbell (1985). Different irrigation levels were obtained by holding the application depth constant and allowing the irrigation interval to vary from 1 to 5 days. Silt loam and loamy sand soils, two root depths, two water contents at planting time, total pumping heads ranging from 0 to 800 m, four ratios of energy cost to commodity price and climatic data for the 1974 growing season at Davis, California were examined. The different variable combinations resulted in a wide range of crop water deficit and yield. Results indicated that, for given combinations, slight deficit (ratios of actual to potential transpiration larger than 0.89) provided higher net benefit than full irrigation. Larger deficits were never advantageous across the diverse range of conditions examined, indicating that potential benefits are associated with only a narrow range of irrigation deficits. This result illustrates the risk involved when deficit irrigation is practiced. Large soil water holding capacity, high soil water contents at planting and deep root exploration were found important for successful implementation of deficit irrigation. Total pumping head and the ratio of energy cost to commodity price were important factors in determining the feasibility of deficit irrigation for the conditions examined. It was also found that the level of irrigation which maximized net benefits tended to be lower for situations where the quantity of water available for irrigation was fixed and the amount of land which could be irrigated was unlimited than when there was sufficient water to fully irrigate the entire farm. Situations where deficit irrigation is a more effective way of reducing energy cost than reducing system operating pressure were ob served.Scientific Paper No. 7571 Project 0634, College of Agriculture and Home Economics, Washington State University, Pullman, WA 99164-6120, USA     

基于RS和GIS的灌区增产净效益最大配水模型

在有限供水条件下,为了使全灌区增产净效益达到最大。研究依据非充分灌溉中的调亏灌溉原理和作物的水分生产函数,推导出作物产量与土壤含水率之间的函数关系,并建立了全灌区某次供水增产净效益最大的优化配水模型。根据RS技术能够快速获取信息的特点,以陕西关中冯家山水库北干十一支灌区为例,用RS技术获取灌区土壤含水率情况,再用GIS计算出不同作物灌溉需水量数据,并根据来水量用Matlab计算软件对模型进行求解,可快速获得各斗渠优化配水量。模型在求解时不受灌区类型的限制,因此,模型具有较强的通用性、可操作性和推广性。     

Combining remote sensing-simulation modeling and genetic algorithm optimization to explore water management options in irrigated agriculture

We present an innovative approach to explore water management options in irrigated agriculture considering the constraints of water availability and the heterogeneity of irrigation system properties. The method is two-folds: (i) system characterization using a stochastic data assimilation procedure where the irrigation system properties and operational management practices are estimated using remote sensing (RS) data; and (ii) water management optimization where we explored water management options under various levels of water availability. We set up a soil–water–atmosphere–plant model (SWAP) in a deterministic–stochastic mode for regional modeling. The distributed data, e.g. sowing dates, irrigation practices, soil properties, depth to groundwater and water quality, required as inputs for the regional modeling were estimated by minimizing the residuals between the distributions of field-scale evapotranspiration (ET) simulated by the regional application of SWAP, and by surface energy balance algorithm for land (SEBAL) using two Landsat7 ETM+ images. The derived distributed data were used as inputs in exploring water management options. Genetic algorithm was used in data assimilation and water management optimizations. The case study was conducted in Bata minor (lateral canal), Kaithal, Haryana, India during 2000–2001 rabi (dry) season. Our results showed that under limited water condition, regional wheat yield could improve further if water and crop management practices are considered simultaneously and not independently. Adjusting sowing dates and their distribution in the irrigated area could improve the regional yield, which also complements the practice of deficit irrigation when water availability is largely a constraint. This result was also found in agreement with the scenario that water is non-limited with the exception that the farmers have more degrees of freedom in their agricultural activities. An improvement of the regional yield to 8.5% is expected under the current scenario.     

Conjunctive use modeling for multicrop irrigation

A mathematical model is developed to arrive at an optimal conjunctive use policy for irrigation of multiple crops in a reservoir-canal–aquifer system. The integration of the reservoir operation for canal release, ground water pumping and crop water allocations during different periods of crop season (intraseasonal periods) is achieved through the objective of maximizing the sum of relative yields of crops over a year considering three sets of constraints: mass balance at the reservoir, soil moisture balance for individual crops, and governing equations for ground water flow. The conjunctive use model is formulated with these constraints linked together by appropriate additional constraints as a deterministic linear programming model. A two-dimensional isotropic, homogeneous unconfined aquifer is considered for modeling. The aquifer response is modeled through the use of a finite element ground water model. A conjunctive use policy is defined by specifying the ratio of the annual allocation of surface water to that of ground water pumping at the crop level for the entire irrigated area. A conjunctive use policy is termed stable when the policy results in a negligible change in the ground water storage over a normal year. The applicability of the model is demonstrated through a case study of an existing reservoir command area in Chitradurga district, Karnataka State, India.     

Evaluating strategies for improved water use in spring wheat with CERES

More efficient use of water in agricultural systems is widely needed. However, most irrigated systems are characterized by heterogeneous climate and soil conditions that interact strongly with irrigation management, making optimal irrigation decisions difficult to achieve. Here we investigated the impact of reduced irrigations on spring wheat yields in the Yaqui Valley of Mexico, a region experiencing increased water scarcity. Two years of field experiments containing three irrigation treatments each were used to evaluate the CERES-wheat crop model, with good agreement between observed and modeled yields. The model was then used in a sensitivity analysis whereby seven irrigation strategies were applied across a range of possible soil and climatic conditions. Results indicated that yield losses from reduced irrigations depend greatly on year, corresponding to large variations in rainfall between growing seasons. Estimates of the best timing strategy for a given number of irrigations were more robust with respect to climate variability. Soils also exhibited a strong interaction with irrigation, with the difference between initial soil moisture and wilting point deemed particularly important in this system. The optimal economic strategy was determined for each hypothetical soil based on the observed historical distribution of growing season climatic conditions. The results of this study demonstrate the need to consider soil and climate variability when interpreting experimental results, and the ability of the CERES model to serve this need by quantifying the relative importance of different heterogeneous factors.     

Crop production functions and the allocation and use of irrigation water

The economically optimal depth of irrigation water to apply depends on the relationship between crop yield and water use. Past research efforts to formulate and to explain the factors influencing irrigated crop production functions have therefore been briefly reviewed. Although it is not possible to obtain a unique relationship, by considering a possible range of functions, and by understanding the factors causing variations in the form of these functions, valuable conclusions can be drawn relating to the optimal depth of water application and the relative magnitude of benefits derived from efficient water management.     

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。     

Effects of deficit irrigation scheduling on yields and soil water balance of irrigated maize

This paper presents the findings of the effect of some selected deficit irrigation scheduling practices on irrigated maize crop in a sub-catchment in south western part of Tanzania. Field experiments, in which maize (TMV1-ST) variety was planted under total irrigation, were conducted during the dry seasons of 2004 and 2005. Surface irrigation method was used and the crop was planted in basins. The seasonal water applied ranged from 400 to 750 mm. Soil moisture content from both cropped and bare soils, leaf area index, dry matter, and grain yields were measured. The dry matter yield ranged between 6,966 and 12,672 kg/ha, and grain yields obtained were between 1,625 and 4,349 kg/ha. The results showed that deficit irrigation at any crop growth stage of the maize crop led to decrease in dry matter and grain yields, seasonal evapotranspiration and deep percolation. Deficit irrigation in any one growth stage of the maize crop only seems to affect grain production and no significant effect on biomass production, but deficit irrigation that spanned across two or more growth stages affect both biomass and grain production drastically. Crop water use efficiency (WUE) and Irrigation water use efficiency (IWUE) were strongly influenced by the number of growth stages in which deficit irrigations were applied and how critical the growth stages were to moisture stress rather than the amount of irrigation water applied. While maximum WUE was obtained under full irrigation, maximum IWUE was obtained in the deficit irrigation treatment at vegetative growth stage, which suggest that IWUE may be improved upon by practicing deficit irrigation at the vegetative growth stage of the maize crop.     

Irrigation water management with water deficit index calculated based on oblique viewed surface temperature

In this study, the relationship between water deficit index (WDI) and a number of parameters related to soil water status, crop monitoring and yield were investigated with regard to drip irrigated dwarf green beans (Phaseolus vulgaris, humilis) in Ankara, Turkey during the 2004 and 2005 growing seasons. Three different WDIs were calculated based on three different spectral indexes and oblique viewed surface temperature. Soil water status was quantified by soil water content (SWC) and soil water deficit index (SWDI). Crop evapotranspiration (ET_c), leaf water potential (LWP), spectral indexes and crop water stress index (CWSI) were determined. Although the WDIs have statistically significant relationships with the parameters, it is hard to use WDIs based on oblique viewed surface temperature for irrigation scheduling purposes. However, total yield estimation and monitoring of seasonal crop water use status could be achieved through this kind of WDI.     

地面灌水技术优化组合节水高产机理研究

对不同地面灌水技术进行优化组合应用,根据全年作物连作的需水特点实施调亏灌溉使土壤水分消长过程在节水高产调控范围内,提高了水分效应,小麦和棉花水分生产效率达１．５３ｋｇ／ｍ３和０．４１ｋｇ／ｍ３的较高水平。同时还对其节水高产机理进行了探讨,为节水高产的地面灌水技术优化组合应用提供了科学依据。     

A partial root zone drying irrigation strategy for citrus—Effects on water use efficiency and fruit characteristics

In Australian irrigated citriculture, fruit yield and quality outcomes are not tightly related to levels of plant available water, which raises the possibility of using mild water stress applied to part of the root zone, i.e. partial root zone drying, to stimulate physiological mechanisms that reduce tree water use by changing the relationship between stomatal conductance and ambient evaporative conditions.The PRD technique alternates irrigation such that one side of the tree root zone is allowed to dry whilst the other side is irrigated. This significantly reduces the wetted soil volume at any point in time, whilst always maintaining a readily available water supply to part of the root zone. By adopting this irrigation strategy water use of mature Navel orange trees C. sinensis (L.) Osbeck was reduced and water use efficiency was increased. The technique did not induce excessive fruitlet drop and crop yield was unaffected. Both fruit size and juice percentage slightly decreased whereas total soluble solids percentage (TSS) and juice acid percentage increased. As water use was reduced and juice quality attributes were increased, this technique has obvious benefits for juice fruit production.PRD offers an advantage over conventional deficit irrigation strategies because it helps reduce water use by separating the biochemical signaling responses to water deficit in the dry part of the root zone from the physical effects of reduced stomatal conductance due to lower water availability, allowing developmental processes associated with plant growth to remain unperturbed. Irrigating a reduced root zone volume in this way reduces crop water requirement. However, it is also important to understand that this technique pushes the crop to its limits and should only be applied to well established healthy trees.When applying PRD irrigation, it is important that water is supplied with sufficient frequency and depth of wetting to meet the water needs of the whole plant.     

非充分灌溉研究现状及存在问题

介绍了非充分灌溉研究的理论基础，阐述了非充分灌溉研究中的作物-水模型及其敏感指标、土壤水分不足条件下作物蒸发蒸腾量的计算方法和有限水量在作物生育期内的最优分配问题，最后提出了对非充分灌溉问题的几点看法。     

基于K-means聚类算法的草莓灌溉策略研究

为进一步提高日光温室封闭式栽培下草莓灌溉水肥利用率,研究了基质含水率和温度影响下的草莓灌溉策略优化方法。采用土壤水分传感器对草莓果期基质含水率进行实时监测,通过对基质含水率随时间变化的规律分析,并结合日平均温度进行K-means聚类分析,提出一种草莓优化灌溉策略。试验结果表明,灌溉第1阶段基质含水率快速上升,在灌溉结束时达到峰值,每次灌溉基质含水率平均提高21.5个百分点;第2阶段快速下降,在20 min内基质含水率平均下降3.5个百分点;第3阶段变化趋于平稳,在30 min内基质含水率平均下降1.2个百分点。在每个灌溉周期内,含水率呈线性下降趋势,在整个果期内,其斜率随日平均温度的升高逐渐增加,由0.0114增加至0.0365。研究结果表明,根据基质含水率变化和日平均温度区间进行定量灌溉,理论上果期每株草莓仅需要4.51 L水,可节水15.4%,该方法能有效提高水肥利用率,实现节水节肥。     

基于模糊决策理论的冬小麦精量灌

为了对作物进行适时适量的灌溉，节约大量的灌溉水资源，提高农作物的产量和品质，在考虑土壤-作物-大气连续体（SPAC）的基础上，在作物的不同生长阶段设定了不同的最佳土壤湿度；同时通过天气环境参数来预测作物的腾发量；最后根据土壤湿度、作物腾发量以及作物的生长阶段来模糊决策作物的灌水量。结果表明在考虑土壤、作物和大气的综合作用下，根据多因素对作物灌水量进行模糊智能决策，比根据单一参数预测作物的灌水量，预测结果更准确。     

Optimization of furrow irrigation system design parameters considering drainage and runoff water quality constraints

The design problem of furrow irrigation systems considering runoff and drainage water quality was formulated as an optimization problem, with maximization of net benefits as the objective. A power advance function with an empirically derived relationship between the furrow irrigation design variables and relative crop yield were used in the formulation. The generalized geometric programming technique was used to solve for the optimal values for the design variables that maximized the net benefits from a furrow irrigation system. The optimal efficiency for which the system must be designed under a given set of soil, crop, and economic conditions is not known in advance. In the design, the application efficiency was not specified a priori. It was an output from the optimal design. The analysis suggested that it might not be economical to design surface irrigation systems to achieve a high application efficiency that is specified a priori. In the absence of environmental degradation problems from irrigation, it may sometimes be profitable to design surface irrigation systems to operate at less than the standard application efficiency (55%–90%) that is routinely used in the design. Formulation of the design problem as an optimization problem would yield the optimal application efficiency that would maximize the net benefits to the farmer under any given set of conditions.     

夏玉米不同生育期亏缺-复水对蒸发蒸腾和产量的影响

[目的]探究不同时间尺度下夏玉米蒸发蒸腾量的变化规律.[方法]试验在夏玉米3个生育阶段(出苗—拔节期、拔节—抽雄期、抽雄—灌浆期)分别设置3个灌水水平(充分灌溉:100％ETa;中度水分亏缺:80％ETa;重度水分亏缺:60％ETa),其中ETa为蒸渗仪实测的充分灌溉条件下的蒸发蒸腾量,采用正交试验设计,共9个处理(C...     

Effect of irrigation uniformity on the profitability of crops

There are numerous models capable of simulating crop behavior under different water stress conditions. However, none of them takes into account the effect of irrigation water uniformity on yield. The model developed simulates the uniformity effect on yield and the repercussion on gross margin (GM). The application of the model to a maize crop in Albacete (Spain) indicates that for the same irrigation depth, an increase in uniformity of water in the soil (CU) corresponds to a 4% increase in yield for the common irrigation strategy in the area, and a 6.8% increase in yield for the optimal irrigation schedule established by the model. Values of percentage of adequately irrigated area (a) between 50 and 80% appear to be adequate for values of CU > 80%. This effect has special relevance on the GM mainly when designing the irrigation strategy of areas with limited water resources. This leads to improvement of CU from 75 to 95% for the common irrigation depth applied to maize and may increase GM up to 27%. For small irrigation depths, the effect of CU on GM is reduced. The maximum GM is reached at ET_a/ET_m < 1 and a <100%. The paper also describes a methodology for determining the most suitable irrigation schedule under regulated deficit irrigation conditions.