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1.
《Agricultural Water Management》2001,48(2):103-116
In this paper, an economic optimisation model for hydrologic planning in deficit irrigation systems is proposed. Irrigation water allocation between agricultural demands is carried out following an economic efficiency criterion with the aim of maximising the overall economic benefits obtained, allocating available water to each user as a function of the water’s profit margin. Water resources constraints in the system are considered. Aggregated economic functions for each irrigation district are generated optimising the water used for the cropping pattern. Stochastic nature of water availability and irrigation requirements have been taken into account.Due to the complexity of the system, the problem has been broken down into three independent optimisation sub-problems that perform hierarchically. Each of these sub models takes into account a different resolution level of the system: crop, irrigation district and the whole basin.The proposed model has been used in a subsequent paper to optimise water allocation planning in a small basin in southern Spain; the Bembézar system. 相似文献
2.
《Agricultural Systems》1998,58(4):529-554
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. 相似文献
3.
《Agricultural Water Management》1998,37(2):163-182
The problem of planning intraseasonal irrigation requirements for the reservoir based projects with an extensive water distribution network is addressed. The network is hierarchical and consists of canals, distributaries or laterals and field turnouts or outlets. Irrigation requirements are estimated by considering the problem at two levels. At the first level, the intraseasonal weekly and biweekly irrigation requirements of crops at the field turnouts are estimated by a daily two layer soil water balance model. At the second level, the field level water requirements are transferred to the upstream nodes of the water distribution network after accounting for conveyance losses by a simple hydraulic model for flow in canals. The main questions examined are (i) whether there are significant year to year fluctuations in intraseasonal field level irrigation requirements of crops and (ii) whether a reliable sequence of target weekly/biweekly reservoir releases can be derived for irrigation planning at the project level. This is done in the context of a case study irrigation project in India. 相似文献
4.
《Agricultural Water Management》2005,73(3):193-221
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. 相似文献
5.
Optimization model of an irrigation reservoir for water allocation and crop planning under various weather conditions 总被引：1，自引：0，他引：1
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. 相似文献
6.
Deficit irrigation has been suggested as a way to increase system benefits, at the cost of individual benefits, by decreasing the crop water allocation and increasing the total irrigated land. Deterministic methods are common for determining optimal irrigation schedules with deficit irrigation because considering the inherent uncertainty in crop water demands while including the lower and upper bounds on soil moisture availability is a hard problem. To deal with this, a constraint state formulation for stochastic control of the weekly deficit irrigation strategy is proposed. This stochastic formulation is based on the first and second moment analysis of the stochastic soil moisture state variable, considering soil moisture as bounded between a maximum value and a minimum value. As a result, an optimal deficit irrigation scheduling is determined using this explicit stochastic model that does not require discretization of system variables. According to the results, if irrigation strategy is based on deterministic predictions, achievement of high, long-term expected relative net benefits by decreased crop water allocation and increased irrigated land may have a higher failure probability. 相似文献
7.
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. 相似文献
8.
The problem of real-time irrigation scheduling under limited water supply is considered. The goal is to develop an irrigation operation policy which maximizes crop yields and is responsive to current season changes in weather and other variables. Because irrigation decisions are sequential and dependent on crop and soil water status, and also because crop yields can only be known at the end of the season, the decisions are arrived at by a two-stage process. In the first or the design stage, irrigations are planned for the entire season at weekly intervals using historical data and an optimal irrigation scheduling model. In the second stage, the decisions for the subsequent weeks are revised each week after updating the status of the system with real time data up to that week and solving the irrigation optimization model once again for the new conditions. Thus, each week an irrigation decision is made, the entire planning horizon is kept in view. The procedure is illustrated by application to a case study. 相似文献
9.
《Agricultural Water Management》1988,15(2):165-175
The problem of scheduling irrigation at weekly intervals for a single crop when water supply is limited is considered. The mathematical formulation is based on a dated water-production function, weekly soil-water balance, and a heuristic assumption that water stress in the early weeks of a crop-growth stage leads to suboptimal yields. The allocation problem is solved at two levels, growth stages, and weeks. At the first level, the dated water-production function is maximized by dynamic programming to obtain optimal allocations for growth stages. At the second, the water allocated to each growth stage is re-allocated to satisfy weekly water deficits within the stage in a sequential order, beginning with the 1st week of the stage. Water delivery and soil-water storage constraints are included at both levels. The model is applied to a field problem to derive weekly irrigation programmes for cotton under various levels of seasonal water supply and initial soil moisture. 相似文献
10.
《Agricultural Water Management》2002,52(2):139-154
It is important to promote efficient use of water through better management of water resources, for social and economical sustainability in arid and semi-arid areas, under the conditions of severe water shortage. Based on the developments in deficit irrigation research, a recurrence control model for regional optimal allocation of irrigation water resources, aiming at overall maximum efficiency, is presented, with decomposition-harmonization principles of large systems. The model consists of three levels (layers). The first level involves dynamic programming (DP) for optimization of crop irrigation scheduling. The second level deals with optimal allocation of water resources among various crops. The last level concerns optimal allocation of water resources among different sub-regions. As a test, this model was applied to the combined optimal allocation of multiple water resources (surface, ground and in-take from the Weihe river) of Yangling, a semi-arid region on the Loess Plateau, China. Exemplary computation showed that not only are the results rational, but the method can also effectively overcome possible “dimensional obstacles” in dynamic programming of multiple dimensions. Furthermore, each sub-model is relatively independent by using various optimization methods. The model represents a new approach for improving irrigation efficiency, implementing water-saving irrigation, and solving the problem of water shortage in the region studied. The model can be extended in arid and semi-arid areas for better water management. 相似文献
11.
Regulated deficit irrigation during the kernel-filling period and optimal irrigation rates in almond
《Agricultural Water Management》2005,75(2):152-167
The use of Regulated deficit irrigation (RDI) in almond, applied during the kernel-filling phase, was evaluated over four consecutive years. To determine the reference optimal irrigation rate, three treatments were applied: T-100, which was irrigated by replacing crop evapotranspiration; T-130, which was irrigated by applying 30% more water than in T-100 and T-70, which received 30% less water than T-100. The RDI treatment received the same irrigation rate as T-100, but during the kernel-filling period irrigation was reduced to 20% of T-100. The optimum yield response was observed in treatment T-100, while T-130 trees never improved on T-100 kernel production over the 4 years of the study. During the first two experimental years, kernel dry matter accumulation did not decrease with drought in the RDI treatment. However, both cropping and kernel growth were reduced during the third and fourth years of the experiment. A possible explanation for this decrease could be found in a hypothetical depletion of the carbohydrate reservoir in RDI trees and also to the negative soil water balance that was evident in the T-70 and RDI treatments during winter and spring of the last 2 years. Although yield reductions for RDI trees were significant (20% with respect to T-100), the water savings obtained (about 60% of that applied with respect to T-100), may help to promote the adoption of RDI in areas, where water availability has been reduced. Bearing in mind the water conservation aspect in almond, RDI, as applied in this case, seemed more interesting than a seasonal sustained deficit irrigation strategy like T-70. 相似文献
12.
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
13.
A model for optimal allocation of water from a single-purpose reservoir to an irrigation project with pre-determined multiple cropping patterns was developed. The model consisted of two modules: (I) the intra-seasonal allocation model (non-linear programming) which is used for allocation of water among different crops for a definite combination of state variables (inflow class, rainfall class, reservoir storage classes at the beginning and at the end of the season) for the non-dormant season to maximize total farm income; and (II) the seasonal allocation model (stochastic-dynamic programming) which is used for the convergent operating policy over seasons for optimal expected farm income over a year. The model was applied to Ardak reservoir dam (I.R. Iran) in an arid region. Low river inflow in the dormant season at the study area could not admit the reservoir class changes for specific combinations of state variables, and therefore resulted in a non-usable result. Imposing a fictitious positive relative net benefit for all possible combinations of reservoir class changes eliminated this problem. It was also shown that rainfall did not play a marked role in the study area, which is an arid region, and its stochastic nature can be removed from the model. 相似文献
14.
《Agricultural Water Management》2004,64(2):123-142
Diagnosis of water management at the irrigation district level is required for the rational modernisation of the irrigation schemes and the subsequent increase in the efficiency of water allocation and application. Our objectives were to: (i) evaluate the global irrigation performance in the 5282 ha La Violada surface-irrigated district (Ebro River Basin, northeast Spain), and (ii) estimate the water that could potentially be conserved under two scenarios of modernisation and three increased irrigation efficiencies. The main district’s water inputs and outputs were measured (irrigation, precipitation, and outflow surface drainage) or estimated (canal releases, lateral surface runoff, municipal wastewaters, and actual evapotranspiration of crops) during the 1995–1998 hydrological years. The annual average water outputs were 23% higher than the corresponding water inputs, presumably due to canal seepage and lateral groundwater inflows from the 14 355 ha dry-land watershed. The district-level irrigation performance was poor (mean 1995–1998 seasonal irrigation consumptive use coefficient (ICUC)=48%), due to the low distribution (DE) and on-farm (ICUCf) efficiencies (i.e., mean estimates of 83% (DE) and 61% (ICUCf) for the 1995–1996 irrigation seasons). Thus, despite the high volume of applied irrigation water, the actual district ET was 16% lower than the maximum achievable ET, indicating that the water-stressed crops yielded below their maximums. Potential reductions in water allocation were estimated for three ICUC values (65, 75 and 85%) and two scenarios of modernisation (I and II). In scenario I, where the aim was to achieve maximum ET and crop yields, water allocation could be reduced from 8 to 30% of the current allocation. In scenario II, where the aim was to achieve the maximum conservation of water under the actual ET and crop yields, reductions in water allocation would be much higher (from 26 to 43% of current allocation). Thus, significant volumes of water could be conserved in the rehabilitation of this 50-year-old district by increasing the distribution efficiency and, in particular, the on-farm irrigation efficiency. 相似文献
15.
In this paper multi-objective differential evolution (MODE) approach is proposed for the simultaneous evolution of optimal
cropping pattern and operation policies for a multi-crop irrigation reservoir system. In general, farming community wants
to maximize total net benefits by irrigating high economic value crops over larger area, which may also include water-intensive
crops and longer duration crops. This poses a serious problem under water-scarce conditions and often results in crop failure.
Under varying hydrological conditions, the fixed cropping pattern with conventional operating rule curve policies may not
yield economically good results. To provide flexible policies, a nonlinear multi-objective optimization model is formulated.
To achieve robust performance by handling interdependent relationships among the decision variables of the model, the recent
MODE technique is adopted to solve the multi-objective problem. The developed model is applied for ten-daily reservoir operation
to a case study in India. The model results suggest that changes in the hydrologic conditions over a season have considerable
impact on the cropping pattern and net benefits from the irrigation system. Towards this purpose, the proposed MODE model
can be used to evolve different strategies for irrigation planning and reservoir operation policies, and to select the best
possible solution appropriate to the forecasted hydrologic condition. 相似文献
16.
《Agricultural Water Management》1996,31(3):237-251
Appropriate information is a pre-requisite for improving the management of irrigation systems. An effort was made to establish the information system required in management of an irrigation unit at the tertiary level (Ban-Rom Water Users' Association, Thailand). A computerized database was developed for use on a microcomputer using the combination of a commercial database management system and a linear programming optimizer. This information system was simple to operate through the use of menu-driven procedures.This database system can replace the previous manual system for data recording and retrieval of information related to the management of agricultural organizations and related irrigation aspects. The optimal solution for cropping pattern and water allocation obtained from the system can be used as a guideline in pre-season planning for irrigation delivery and crop selection. 相似文献
17.
《Agricultural Water Management》2004,68(2):117-133
Continuous cropping of winter wheat and summer maize is the main cropping pattern in North China Plain lying in a seasonal frost area. Irrigation scheduling of one crop will influence soil water regime and irrigation scheduling of the subsequent crop. Therefore, irrigation scheduling of winter wheat and maize should be studied as a whole. Considering the meteorological and crop characteristics of the area lying in a seasonal frost area, a cropping year is divided into crop growing period and frost period. Model of simultaneous moisture and heat transfer (SMHT) for the frost period and model of soil water transfer (SWT) for the crop growing period were developed, and used jointly for the simulation of soil water dynamics and irrigation scheduling for a whole cropping year. The model was calibrated and validated with field experiment of winter wheat and maize in Beijing, China. Then the model was applied to the simulation of water dynamics and irrigation scheduling with different precipitation and irrigation treatments. From the simulation results, precipitation can meet the crop water requirement of maize to a great extent, and irrigation at the seeding stage may be necessary. Precipitation and irrigation had no significant influence on evaporation and transpiration of maize. On the other hand, irrigation scheduling of winter wheat mainly depends on irrigation standard. Irrigation at the seeding stage and before soil freezing is usually necessary. For high irrigation standard, four times of irrigation are required after greening. While for medium irrigation, only once (rainy year) or twice (medium and dry years) of irrigation is required after greening. Transpiration of winter wheat is very close for high and medium irrigation, but it decreases significantly for low irrigation and will result in a reduction of crop yield. Irrigation with proper time and amount is necessary for winter wheat. Considering irrigation quota and crop transpiration comprehensively, medium irrigation is recommended for the irrigation of winter wheat in the studying area, which can reduce the irrigation quota of over 150 mm with little water stress for crop growth. 相似文献
18.
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。 相似文献
19.
《Agricultural Water Management》2006,85(3):314-322
Irrigation needs to be scheduled properly for winter wheat, the main food crop in North China where the water resources are limited. We optimized the irrigation timing of crops under limited water supply by integrating a soil water balance model, dated water production function with cumulative function of water sensitivity index, and a nonlinear search method. The optimization produced the optimal irrigation date series with the predetermined irrigation quota for each application, which aims to obtain higher crop yield with limited irrigation water and be convenient for irrigation management. This simulation–optimization model was used to investigate the irrigation scheduling of winter wheat in Xiaohe irrigation Area in North China. Results show that optimal irrigation date series, corresponding relative yield and relative evapotranspiration are all closely related to the irrigation quota and initial soil water conditions. For rich and medium initial soil water conditions in medium precipitation year, it takes four times of irrigation (60 mm each time) after greening in order to obtain higher crop yield. But it increases to five times for poor initial condition. With limited irrigation water, irrigation should generally be applied in the preferential sequence of early May or late April (in the jointing stage), then mid and late May (in the heading stage), and finally March (in the greening stage). Irrigation should be applied earlier with lower initial soil water storage. Higher irrigation quota increases the crop yield but tends to decrease the marginal value, especially when irrigation quota exceeds 180 mm. The study also indicates that the optimized relative yield is generally higher than that obtained in field experiment. Based on the optimization, we proposed to use the quadratic polynomial function to describe the frontier water production function, which shows the mathematical relationship between optimized relative yield and relative evapotranspiration. 相似文献
20.
Assessment of irrigation and environmental quality at the hydrological basin level: I. Irrigation quality 总被引：1，自引：0，他引：1
Irrigated agriculture notably increases crop productivity, but consumes high volumes of water and may induce off-site pollution of receiving water bodies. The objectives of this paper were to diagnose the quality of irrigation and to prescribe recommendations aimed at improving irrigation management and reducing the off-site pollution from a 15,500 ha irrigation district located in the Ebro River Basin (Spain). Three hydrological basins were selected within the district where the main inputs (irrigation, precipitation, and groundwater inflows) and outputs (actual crop's evapotranspiration, surface drainage outflows, and groundwater outflows) of water were measured or estimated during a hydrological year. The highest volume of water (I = 1400 mm/year) was applied in the basin with highly permeable, low water retention, flood irrigated soils where 81% of the total surface was planted with alfalfa and corn. This basin had the lowest consumptive water use efficiency (CWUE = 45%), the highest water deficit (WD = 5%) and the highest drainage fraction (DF = 57%). In contrast, the lowest I (950 mm/year), the highest CWUE (62%), and the lowest WD (2%) and DF (37%) were obtained in the basin with 60% of the surface covered with deep, high water retention, alluvial valley soils, where 39% of the cultivated surface is sprinkler irrigated and with only 48% of the surface planted with alfalfa and corn. We concluded that the three most important variables determining the quality of irrigation and the volume of irrigation return flows in the studied basins were (i) soil characteristics, (ii) irrigation management and irrigation system, and (iii) crop water requirements. Therefore, the critical recommendations for improving the quality of irrigation are to (i) increase the efficiency of flood-irrigation, (ii) change to pressurized systems in the shallow and highly permeable soils, and (iii) reuse of drainage water for irrigation within the district. These management strategies will conserve water of high quality in the main reservoir and will decrease the crop water deficits and the volume of irrigation return flows, therefore, minimizing the off-site pollution from this irrigation district. 相似文献