Simulation-Optimization Modeling of Conjunctive Use of Surface Water and Groundwater

Water resources management in semiarid regions with low precipitation and high potential of evapotranspiration is a great challenge for managers and decision makers. In those regions, both sources of water should be managed conjunctively so as to minimize shortages of water in dry seasons. In conjunctive use, the difficulty increases as one must represent the response of both systems interactions, and develop management strategies that simultaneously address surface water and aquifer regulation. This paper focuses on the simulation-optimization for conjunctive use of surface water and groundwater on a basin-wide scale, the Najafabad plain in west-central Iran. A trained artificial neural network model is developed as a simulator of surface water and groundwater interaction while a genetic algorithm is developed as the optimization model. The main goal of the simulation-optimization model is to minimize shortages in meeting irrigation demands for three irrigation systems subject to constraints on the control of cumulative drawdown of the underlying water table and maximum capacity of surface irrigation systems. To achieve the main goal, three scenarios are presented. Results of the proposed model demonstrate the importance of the conjunctive use approach for planning the management of water resources in semiarid regions.     

Conjunctive Use of Surface Water and Groundwater: Application of Support Vector Machines (SVMs) and Genetic Algorithms

Combined simulation-optimization models have been widely used to address the management of water resources issues. This paper presents a simulation-optimization model for conjunctive use of surface water and groundwater at a basin-wide scale, the Zayandehrood river basin in west central Iran. In the Zayandehrood basin, in the past 10 years, a historical low rainfall in the head of the basin, combined with growing demand for water, has triggered great changes in water management at basin and irrigation system level. The conjunctive use model that coupled numerical simulation with nonlinear optimization is used to minimize shortages of water in meeting irrigation demands for four irrigation systems. Constraints guarantee the maximum/minimum cumulative groundwater drawdown and maximum capacity of irrigation systems. A support vector machines (SVMs) model is developed as a simulator of surface water and groundwater interaction model while a genetic algorithm (GA) is used as the optimization model. Conjunctive use model runs for three scenarios. Results show that the accuracy of SVMs as a simulator for surface water and groundwater interaction model is good and that it is possible to decrease the water shortage for irrigation systems with application of proposed SVMs-GA model.     

Distributed Simulation‐optimization Model for Conjunctive Use of Groundwater and Surface Water Under Environmental and Sustainability Restrictions

Evolving optimal management strategies are essential for the sustainable development of water resources. A coupled simulation-optimization model that links the simulation and optimization models internally through a response matrix approach is developed for the conjunctive use of groundwater and surface water in meeting irrigation water demand and municipal water supply, while ensuring groundwater sustainability and maintaining environmental flow in river. It incorporates the stream-aquifer interactions, and the aquifer response matrix is generated from a numerical groundwater model. The optimization model is solved by using MATLAB. The developed model has been applied to the Hormat-Golina valley alluvial stream-aquifer system, Ethiopia, and the optimal pumping schedules were obtained for the existing 43 wells under two different scenarios representing with and without restrictions on stream flow depletion, and satisfying the physical, operational and managerial constraints arising due to hydrological configuration, sustainability and ecological services. The study reveals that the total annual optimal pumping is reduced by 19.75?% due to restrictions on stream flow depletion. It is observed that the groundwater pumping from the aquifer has a significant effect on the stream flow depletion and the optimal conjunctive water use plays a great role in preventing groundwater depletion caused by the extensive pumping for various purposes. The groundwater contribution in optimal conjunctive water use is very high having a value of 92?% because of limited capacity of canal. The findings would be useful to the planners and decision makers for ensuring long-term water sustainability.

     

Development of Priority-Based Policies for Conjunctive Use of Surface and Groundwater

Abstract

A combined optimization-simulation approach was used to develop and evaluate the alternate priority-based policies for operation of surface and groundwater systems and is demonstrated with a case study. An optimization model was used to find optimal cropping pattern with and without the conjunctive use of surface and groundwater, as well as with and without socio-economic constraints. The optimization model, based on linear programming, maximizes the net benefit from irrigation activities subject to various physical, economical, and social constraints. A simulation model was used to evaluate the conjunctive operation of the system using the optimal cropping pattern derived from the optimization model. The developed policies have been verified with long-generated stream flow sequences. Three alternate priority-based policies differing in level of groundwater pumping and area of cultivation of rice crop have been evaluated: (1) irrigation with surface water only (Policy-1); (2) irrigation with conjunctive use of surface and groundwater, without socio-economic constraints (Policy-2); and (3) irrigation with conjunctive use operation and with socio-economic constraints (Policy-3). It was found that the use of available groundwater within three meters below ground level (Policy-2) to be optimal, and these results were used in simulation for further evaluation of policies. It was also found that the policy-3 of conjunctive use operation with a priority of 75 percent of maximum possible rice area (using groundwater available within four meters below ground level) resulted in a better scenario. Thus the conjunctive use Policy-2 and Policy-3 with 75 percent of maximum possible rice crop area can be used as better policies for the system studied.     

Application of Genetic Algorithms and Artificial Neural Networks in Conjunctive Use of Surface and Groundwater Resources

Abstract

In this paper, a methodology for conjunctive use of surface and groundwater resources is developed using the combination of the Genetic Algorithms (GAs) and the Artificial Neural Networks (ANN). Water supply to agricultural demands, reduction of pumping costs and control of groundwater table fluctuations are considered in the objective function of the model. In the proposed model, the results of MODFLOW groundwater simulation model are used to train an ANN. The ANN as groundwater response functions is then linked to the GA based optimization model to develop the monthly conjunctive use operating policies. The model is applied to the surface and groundwater allocation for irrigation purposes in the southern part of Tehran. A new ANN is also trained and checked for developing the real-time conjunctive use operating rules.

The results show the significance of an integrated approach to surface and groundwater allocation in the study area. A simulation of the optimal policies shows that the cumulative groundwater table variation can be reduced to less than 4 meters from the current devastating condition. The results also show that the proposed model can effectively reduce the run time of the conjunctive use models through the composition of a GA-based optimization and a ANN-based simulation model.     

Applying Genetic Algorithm and Neural Network to the Conjunctive Use of Surface and Subsurface Water

The conjunctive use of surface and subsurface water is one of the most effective ways to increase water supply reliability with minimal cost and environmental impact. This study presents a novel stepwise optimization model for optimizing the conjunctive use of surface and subsurface water resource management. At each time step, the proposed model decomposes the nonlinear conjunctive use problem into a linear surface water allocation sub-problem and a nonlinear groundwater simulation sub-problem. Instead of using a nonlinear algorithm to solve the entire problem, this decomposition approach integrates a linear algorithm with greater computational efficiency. Specifically, this study proposes a hybrid approach consisting of Genetic Algorithm (GA), Artificial Neural Network (ANN), and Linear Programming (LP) to solve the decomposed two-level problem. The top level uses GA to determine the optimal pumping rates and link the lower level sub-problem, while LP determines the optimal surface water allocation, and ANN performs the groundwater simulation. Because the optimization computation requires many groundwater simulations, the ANN instead of traditional numerical simulation greatly reduces the computational burden. The high computing performance of both LP and ANN significantly increase the computational efficiency of entire model. This study examines four case studies to determine the supply efficiencies under different operation models. Unlike the high interaction between climate conditions and surface water resource, groundwater resources are more stable than the surface water resources for water supply. First, results indicate that adding an groundwater system whose supply productivity is just 8.67 % of the entire water requirement with a surface water supply first (SWSF) policy can significantly decrease the shortage index (SI) from 2.93 to 1.54. Second, the proposed model provides a more efficient conjunctive use policy than the SWSF policy, achieving further decrease from 1.54 to 1.13 or 0.79, depending on the groundwater rule curves. Finally, because of the usage of the hybrid framework, GA, LP, and ANN, the computational efficiency of proposed model is higher than other models with a purebred architecture or traditional groundwater numerical simulations. Therefore, the proposed model can be used to solve complicated large field problems. The proposed model is a valuable tool for conjunctive use operation planning.     

Conserving One Water Source at the Expense of Another: The Role of Surface Water Price in Adoption of Wells in a Conjunctive Use System

One potential side-effect of irrigation water rate reform is groundwater substitution. As surface water prices rise, irrigators may find it cheaper to rely on on-farm wells than a regional irrigation district. The impact of surface water price on well adoption is examined in a conjunctive use system where both surface water and groundwater are used to meet irrigator demand. Results indicate that as the price of surface water approaches 62% of the marginal cost of pumping groundwater, irrigators are more likely to have on-farm pumping capabilities. This result suggests that proposed water rate reforms by the United States Bureau of Reclamation may result in irrigators substituting groundwater for surface water by adopting on-farm wells.     

Effect of Substitute Water Projects on Tempo-Spatial Distribution of Groundwater Withdrawals in Chikugo-Saga Plain,Japan

Due to large-scale agricultural irrigation and industrial production, groundwater had been excessively employed to benefit the economy development and life improvement in Chikugo-Saga plain since the middle of last century, which led to many environmental problems such as land subsidence, flooding inundation and water shortage. In order to mitigate the impact of environmental hazards, some water supply projects have been performed to substitute surface water for groundwater since 1970s. For the purpose of comprehending the influence of substitute water projects on groundwater withdrawals, a tempo-spatial groundwater withdrawals assessment model with the resolution of one month in time and one kilometer in space was initially established based on various data concerning meteorology, agriculture, land use, soils, surface water consumption and groundwater utilization by using GIS. According to the development of the substitute water projects, a 28-year study period 1979–2006 was then divided into four stages (i.e. 1979–1984, 1985–1995, 1996–2000 and 2001–2006) and the tempo-spatial distribution of groundwater withdrawals for each stage was represented by means of the proposed model. The tempo-spatial variation of groundwater withdrawals for various water use categories under the effect of substitute water projects was finally analyzed by comparing the distributions of groundwater withdrawals at different stages. The results show that with the advance of the substitute water projects studied, the groundwater pumpage for irrigation, industry or waterworks varies geographically and phasically in the plain. From the first stage to the last stage, there is a significant decrease by approximately 23 % in mean annual total groundwater withdrawals. During the study period, dramatic declines are found in agriculture-use groundwater pumpage in the downstream land of Chikugo river at the third stage, in industry-use pumpage in eastern Saga area at the second stage and found in waterworks-use pumpage in western Saga area at the last stage, while little change in agriculture-use pumpage in western Saga area and in industry-use pumpage in Chikugo area without the corresponding substitution projects. Moreover, it is indicated that the proposed assessment model of groundwater withdrawals is helpful to figure out the regional groundwater exploitation and its impact on the environment, particularly when there is the lack of groundwater pumpage data recorded. It is necessary to develop new substitute water supply plans to reduce the agriculture-use groundwater withdrawals in western Saga area and the industry-use withdrawals in Chikugo area, for more effective management of regional water resources in future.     

Appraisal and optimization of agricultural water use in large irrigation schemes: II. Applications

In this paper, the theoretical approach presented in Part I is demonstrated by means of case studies on the irrigation schemes of Rio Mendoza and Rio Tunuyán in the Province of Mendoza, Argentina. The object of the case studies was the determination of optimal allocation of surface water to reduce the use of groundwater. Current and optimal conjunctive allocation of ground and surface water is studied by means of the developed simulation and optimization models.The second case study was designed on the basis of the experience gathered during the first one: each step of the case studies is compared. The comparison between the two case studies illustrates how to apply the proposed approach when the amount and quality of available data are different. For the more detailed Rio Tunuyán study, we determined the following physical characteristics of all terminal nodes: on-farm rotational intervals, mean water application depth, actual soil water storage capacity, crop water requirements, depth of groundwater table, aquifer transmissivity, and efficiency of groundwater use.The performance of the entire system is sensitive to changes in the water application depth, as it was shown by a simulation study.The application of our optimization approach to the conjunctive use of ground- and surface water showed that the total water requirements over a year can be met by a reassignment of water that reduces the total costs of a great amount.     

A Numerical Simulation Model for Conjunctive Water Use in Basin Irrigated Canal Command Areas

Basin irrigation is a common practice for growing water intensive crops like paddy. Irrigation water, when supplied through a network of canal, is often found to be inadequate to meet the crop water requirement uniformly throughout the irrigated command area. The most deprived are the cultivators of the lower end of the command, who resort to supplementing the crop water requirement by extractions from the ground. This practice is noticeable in irrigation system without a proper canal water distribution schedule and often result in water logging in the upper command regions contrasted with excessively depleted groundwater table in the lower commands. The present contribution attempts to model the conjunctive water use of such a canal irrigated command using physically based numerical sub-models for simulating surface flow, groundwater flow and the interlinking process of moisture movement through the unsaturated zone for a given quantum of supplied water and crop water demand. Individual models are validated to demonstrate their applicability in an integrated framework. Various plausible conjunctive water use scenarios are tested on a hypothetical command area practising basin irrigation to identify the best possible water distribution strategy under given constraints.     

Estimating Land Use Impacts on Regional Scale Urban Water Balance and Groundwater Recharge

Anthropogenic activities have exerted increasingly large-scale influences on terrestrial ecological systems from the past century, primarily through agriculture; however, the impact of such changes on the hydrologic cycle is poorly understood. As one of the important land use (LU) in the coastal Dogo Plain of the Seto Inland Sea, Japan, paddy fields have been decreasing with the increase in urbanization in recent decades. As the main source of water in the Dogo Plain, groundwater plays an important role in providing people with fresh water and contributing to stream base flow. The purpose of this study is to analyze the water resource and evaluate the effect of LU change on groundwater table fluctuation in this coastal plain. Firstly, the observations of groundwater table and the investigation of water balance were carried out in this alluvial plain. Then, a distributed four-block three-layer water balance model was employed to analyze the groundwater table fluctuation with response to the change of paddy field area. Moreover, the role of paddy field in recharging groundwater in the basin has been clarified. Results show that groundwater table depends not only on rainfall and discharge from rivers, but also on irrigation water and topology of the study area. The net groundwater recharge was positive in irrigation periods whereas that in non-irrigation periods was nearly equal to zero or negative. The results of this study would be helpful to the urban development policy and land use planning decision.     

Conjunctive Water Use Planning in an Irrigation Command Area

In the present study, an integrated soil water balance algorithm was coupled to a non-linear optimization model in order to carry out water allocation planning in complex deficit agricultural water resources systems based on an economic efficiency criterion. The LINGO 10.0, optimization package has been used to evolve at optimal allocation plan of surface and ground water for irrigation of multiple crops. The proposed model was applied for Qazvin Irrigation Command Area, a semi-arid region in Iran. Various scenarios of conjunctive use of surface and ground water along-with current and proposed cropping pattern have been explored. Some deficit irrigation practices were also investigated. The results indicate that conjunctive use practices are feasible and can be easily implemented in the study area, which would enhance the overall benefits from cropping activities. The study provides various possible operational scenarios of the branch canals of the command area in the common and dry condition, which can help managers in decision making for the optimum allocation plans of water resources within the different irrigation districts. The findings demonstrate that for deficit irrigation options, the mining allowance of ground water value of the command area is greatly reduced and ground water withdrawal may be also restricted to the recharge to maintain the river–aquifer equilibrium.     

Multi-objective Planning for Conjunctive Use of Surface and Subsurface Water Using Genetic Algorithm and Dynamics Programming

The consideration of fixed cost and time-varying operating cost associated with the simultaneous conjunctive use of surface and subsurface water should be treated as a multi-objective problem due to the conflicting characteristics of these two objectives. In order to solve this multi-objective problem, a novel approach is developed herein by integrating the multi-objective genetic algorithm (MOGA), constrained differential dynamic programming (CDDP) and the groundwater simulation model ISOQUAD. A MOGA is used to generate the various fixed costs of reservoirs’ scale, generate a pattern of pumping/recharge, and estimate the non-inferior solutions set. A groundwater simulation model ISOQUAD is directly embedded to handle the complex dynamic relationship between the groundwater level and the generated pumping/recharge pattern. The CDDP optimization model is then adopted to distribute the optimal releases among reservoirs provided that reservoir capacities are known. Finally, the effectiveness of our proposed integrated model is verified by solving a water resources planning problem for the conjunctive use of surface and subsurface water in southern Taiwan.     

Conjunctive water use for irrigation: Good theory,poor practice

There is growing interest in conjunctive water use in irrigation management. However, most systems are introducing ‘joint use’ of surface and groundwater to overcome problems of poor water delivery or quality, rather than systems which actually maximize water utility. This paper summarizes the findings of a literature review on conjunctive use research, including the variable objectives behind its promotion and the hydrological and agricultural planning models experimented with. Effective promotion and subsequent sound management of conjunctive use technologies in irrigation require interaction between a broad range of institutions, including rural development and agricultural support agencies as well as water management bodies.     

A water balance modelling approach to optimising the use of water resources in ephemeral sand rivers

Alluvial aquifers present a possibility for conjunctive use with surface reservoirs for the storage of water in ephemeral sand rivers such as the Mzingwane River in the Limpopo Basin, Zimbabwe. The Lower Mzingwane valley is a semi‐arid region with high water stress, where livelihoods have revolved around the large rivers for thousands of years. However, current water allocation favours the commercial user: of the 2600 ha irrigated in the 5960 km² (596 000 ha) region, only 410 ha are for smallholder farmers. A water balance approach was used to model the surface water resources and groundwater resources to determine the potential for expanding irrigation and to explore water allocation options. Using a combination of field and laboratory investigations, remote sensing and existing data, the Lower Mzingwane valley was modelled successfully using the spreadsheet‐based model WAFLEX, with a new module incorporated to compute the water balance of alluvial aquifer blocks. Results showed that the Lower Mzingwane alluvial aquifers can store 38 × 10⁶ m³ of water, most of that storage being beyond the reach of evaporation. Current water usage can be more than tripled: the catchment could supply water for currently‐planned irrigation schemes (an additional 1250 ha), and the further irrigation of two strips of land along each bank of the Mzingwane River (an extra 3630 ha)—without construction of any new reservoirs. The system of irrigating strips of land along each bank of the Mzingwane River would be decentralized, farmer or family owned and operated and the benefits would have the potential to reach a much larger proportion of the population than is currently served. However, there could be substantial downstream impact, with around nearly one‐third of inflows not being released to the Limpopo River. The approach developed in this paper can be applied to evaluate the potential of alluvial aquifers, which are widespread in many parts of semi‐arid Africa, for providing distributed access to shallow groundwater in an efficient way. This can enhance local livelihoods and regional food security. Copyright © 2010 John Wiley & Sons, Ltd.     

f-MOPSO: An alternative multi-objective PSO algorithm for conjunctive water use management

In recent years, evolutionary techniques have been widely used to search for the global optimum of combinatorial non-linear non-convex problems. In this paper, we present a new algorithm, named fuzzy Multi-Objective Particle Swarm Optimization (f-MOPSO) to improve conjunctive surface water and groundwater management. The f-MOPSO algorithm is simple in concept, easy to implement, and computationally efficient. It is based on the role of weighting method to define partial performance of each point (solution) in the objective space. The proposed algorithm employs a fuzzy inference system to consider all the partial performances for each point when optimizing the objective function values. The f-MOPSO algorithm was compared with two other well-known MOPSOs through a case study of conjunctive use of surface and groundwater in Najafabad Plain in Iran considering two management models, including a typical 12-month operation period and a 10-year planning horizon. Overall, the f-MOPSO outperformed the other MOPSO algorithms with reference to performance criteria and Pareto-front analysis while nearly fully satisfying water demands with least monthly and cumulative groundwater level (GWL) variation. The proposed algorithm is capable of finding the unique optimal solution on the Pareto-front to facilitate decisions to address large-scale optimization problems.     

Simulation supported scenario analysis for water resources planning: a case study in northern Italy.

The work presents the results of a comprehensive modelling study of surface and groundwater resources in the Muzza-Bassa Lodigiana irrigation district, in Northern Italy. It assesses the impact of changes in land use and irrigation water availability on the distribution of crop water consumption in space and time, as well as on the groundwater resources. A distributed, integrated surface water-groundwater simulation system was implemented and applied to the study area. The system is based on the coupling of a conceptual vadose zone model with the groundwater model MODFLOW. To assess the impact of land use and irrigation water availability on water deficit for crops as well as on groundwater system in the area, a number of management scenarios were identified and compared with a base scenario, reflecting the present conditions. Changes in land use may alter significantly both total crop water requirement and aquifer recharge. Water supply is sufficient to meet demand under present conditions and, from the crop water use viewpoint, a reduction of water availability has a positive effect on the overall irrigation system efficiency; however, evapotranspiration deficit increases, concentrated in July and August, when it may be critical for maize crops.     

南水北调中线工程与天津地面沉降防治关系研究

天津市资源性缺水,多年持续地下水超采导致严重的地面沉降。截至2009年,天津市地面沉降覆盖区域约8 900km2,全市最大累积沉降量超过3m。南水北调中线工程初定于2014年实现通水,天津引水段工程设计方案中的供水、调蓄和输水工程均位于天津地面沉降区范围内。一方面,地面沉降导致引水工程中的重要调蓄水库设计高程和库容丢失,供水管线不均匀累积沉降对工程的运行具有一定影响。另一方面,南水北调中线工程可每年供给天津地区10.2亿m3水量,有效利用水量达8.16亿m3,这部分水量除保证重点地区用水需求外,可用来实施大规模的地下水水源转换工程。天津控制地面沉降历史经验和数值模拟结果表明,南水北调中线天津引水工程通水及大规模水源转换能有效防治地面沉降。     

Basement Groundwater as a Complementary Resource for Overexploited Stream-Connected Alluvial Aquifers

The use of groundwater from alluvial aquifers largely affects stream discharge by capturing the stream resources. This affects hydrological processes and riparian biodiversity. In this study, complementary water resources are investigated in an effort to ease human pressure on alluvial systems and, eventually, on stream-aquifer relationships. Discharge and hydrochemical data along a 5 km reach of the Tordera River (NE Spain) provide evidence that groundwater fluxes, associated with a regional hydrogeological system related to the basement fracture network, contribute to alluvial recharge and to stream flow. End-member mixing analysis considering upstream discharge, groundwater flows, and human inputs to the stream as major flow sources shows that regional basement groundwater fluxes are responsible for as much as 20 % of the total discharge, which also explains unexpected rises in stream flow. This suggests a possible new approach to local water resources planning, indicating that conjunctive use might actually be feasible.     

Irrigation development and environmental degradation in developing countries — a dynamic model of investment decisions and policy options

In the wake of increased environmental and sustainability concerns associated with agricultural development, developing countries are faced with the dilemma of choice between the short-run technological gains and the long-run environmental conservation. A dynamic investment decision model is developed to optimize the use of scarce public investment funds in the magagement of irrigation water supply, depth to water table and soil salinity. Four major classes of investments with different impacts on the hydrological balance within the Indus basin are considered: (a) expansion of the surface irrigation network, (b) public drainage projects, (c) tax and subsidy policies designed to influence the rate of private groundwater exploitation and (d) investment in improving the efficiency of the existing canal system by reducing conveyance losses. The crop area lost due to water logging and salt accumulation is treated as a damage cost of increasing the application of surface irrigation water. The resulting optimality conditions from the model are used to assess the development and operation of public drainage projects. The model results are compared for areas underlain by fresh and saline groundwater. The model is also used to analyze recent policy debate which has focused on the use of incentives such as subsidized credit, energy subsidies, and electrical grid expansion to accomplish the transfer of tubewell operation from the public to the private sector. Optimal switching conditions for such transfers are derived. The results show that a private farmer's optimal decision will diverge more from the societal optimal decision as more externalities from surface irrigation are accounted for.