ABSTRACT
According to sustainable development theory, it constructed the multi-objective optimal model of water resources allocation based on coordinated development of economy, society and ecological environment which is solved by genetic algorithm of Matlab. Then takes water resources system of Xuzhou as research object, Pei Xian of Xuzhou is applied as a calculation analysis of samples which verifies feasibility and effectiveness of this method. This study can improve use efficiency of water resources, optimize comprehensive benefit of economy, society and ecological environment in Xuzhou. At the same time, this study can promote smooth implementation of South-to-North water transfer.
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DOI: 10.3923/jse.2015.785.796
URL: https://scialert.net/abstract/?doi=jse.2015.785.796
INTRODUCTION
During recent years, the shortage of resources, environmental degradation and the frequency of disasters has seriously hindered the development of our countrys economy. Especially the uneven distribution of water resources, more in the east and the south and uneven spatial and temporal distribution, causes a very low utilization of water resources (Xue et al., 2009). Therefore, how to allocate the limited water resources and improve the utilization rate of water has become an urgent problem to be solved. The regional water resources system is selected as the research object based on the sustainable development theories and technical, economic and management measures. And finally realize the coordinated development of society, economy and environment. This study selected Xuzhou as a case to show the allocation of water resources obviously and conveniently.
Xuzhou is located in the northwestern of Jiangsu province and at the junction of four provinces. It is a city of comprehensive transportation hub and the center of Huaihai Economic Region. In the early 1980s, Xuzhou has been listed as one of the 40 serious water shortage cities. Since the reform and opening, Xuzhou experienced rapid growth of population, economy and space. But at the same, it also suffered from the problems of shortage of resources and pollution of environment, especially the water resources and water environment. In recent years, the pollution-induced water shortage is becoming more and more serious and it has restricted the sustainable economic and social development of Xuzhou (Qian, 2009). So, how to allocate the limited water resources and improve the utilization rate of water has become an urgent problem to be solved in the economic and social development of Xuzhou. Optimal allocation of water resources is not only beneficial to the rational exploitation and effective utilization of water resources but also is very important to the smooth implementation of the South-to-North Water Transfer Project and improvement of the economy of the along region.
According to the above objectives, it built the multi-objective optimization model based on the harmonious development of economy, society and environment with the guiding ideology of the theory of sustainable development and it tried to get the solution which will bring the optimum multiple benefit of this region, by genetic algorithm in this search. At last, we chose Pei Country of Xuzhou as analysis of example to verify the feasibility and effectiveness of this algorithm.
MATERIALS AND METHODS
The connotation of optimal allocation of regional water resources is special. The optimization means mainly refer to the reasonable quality and quantity allocation of water and transformation among different applications of water. Allocation here means not only transformation of different uses of water resources in quality and quantity but also the allocation of water resources in the two-dimensional space of time and space. The optimal allocation of water resources should proceed from the situation of our country and water and according to the practical situation of the regional economy, society and environment and then find a suitable way in which it can be implemented the optimal development and utilization of water resources in stages (Matondo, 2002) and then get the optimum multiple benefit of the coordinated development of society, economy and environment.
Content of optimal allocation of water resources: The basic character of natural resources is quality, quantity, time and space. The contents of optimal allocation of water resources include these four basic configuration elements.
• | Element of water quantity: Quantity is the most basic of water resources elements. Different regions and departments have different water demands. So, it required the reasonable allocation of water resources among different regions and departments |
• | Element of water quality: Since each water-use department has different requirements of water quality, if the allocation of water to the water-use department does not meet the demand, then the function of water supply will reduce or even disappear. So, it should also consider the element of water quality and supply water according water quality and water quantity within the principle that high-quality water is used in important places and promotion of renovation of wastewater |
• | Element of the space: Water resources are very unevenly distributed in space because of its particularity and since the different development level of economy, society and environment among different regions, the demands of water are different. So the optimal allocation of water resources of Xuzhou must take consideration of the element of space differences |
• | Element of the time: Since water resources are affected by the natural rainfall which has great uncertainty and is different with the demand of water-use department. So it need to make that the time-allocation of water resources through engineering technical measures and scientific management methods to feed the time and quality requirement (Du, 2006) |
Attributes of optimal allocation of water resources: Water resources have natural attribute and social attribute at the same time. This means optimal allocation of water resources is a multi-objective (society, economy and environment), multi-water source (surface water, groundwater, south-to-north water and reclaimed water) and multi-agent (industry water, agriculture, domestic water and ecological water) complex decision system. In this study, the optimum comprehensive benefit is tried to get through allocation of water resources in each region and department with the help of system analysis and optimization technique.
The essence of optimal allocation of water resources is to realize the reasonable allocation of water resources in time, space and application. So this problem is a multi-level, multi-water source, multi-agent and multi-objective system (Chen, 2006) (Fig. 1).
Multi-water resources: Taking the water resources system of Xuzhou as example, the sources can be classified as surface water, groundwater, east line of south-to-north water and reclaimed water (sewage recycling). According to the water resources condition, economic level, engineering technology level and social customs of Xuzhou, surface water should be allocated at first and then groundwater, recycled water and the south-to-north water in turn.
Multivariate: Water resources are influenced by the factors such as: Quantity, quality, time and space, so the application of water in supplying water, generating electricity and shipping are decided by these factors. Water resources have two attributes of quality and quantity which depend on each other which mean that if the quality of water is not up to the standards, it will not realize some specific functionality, water quantity is too much of too less will also influence the effective use of water. The uneven distribution of water resources in space and time will also cause the waste of water (Li et al., 2007).
Multi-user: The essence of optimal allocation of water resources is to distributed the limited water resources to different uses through all kinds of measures. So it is important to master the information of different characteristics, demands and trends of the users to make the plan of water supply and scheme of water allocation. Water resource is divided into domestic water, agricultural water, industrial water and ecological water.
Fig. 1: | Attributed relationship graph of optimal allocation of water resources |
Within the demands of water laws and principles of fair and efficient, domestic water demands should be satisfied first and give overall consideration of agricultural, industrial, ecological and shipping water demands.
Multi-objective: The application of water resource is a multi-objective problem. Usually it was divided it into supply, generating electricity, shipping, aquaculture and ecological protection. In terms of benefit, it can also be divided it into financial objective, social objective and ecological objective. There are contradictions between different objectives and the contradictions are not commensurable. The traditional objective of water application is usually the blind pursuit of the maximum of the water quantity or the economic performance, while the optimal allocation of water resources in the frame of sustainable development is aimed at not only the economic performance but also the fair supply and the environmental integrity. This is a more complex multi-objective decision so it is better to solved this problem with the method combining qualitative analysis with quantitative analysis.
Model of optimal allocation of water resources the case of Xuzhou: Regional water resources include the local water and the foreign water. The local water can be divided into surface water, groundwater and reclaimed water and the foreign water resources mainly refer to the South-to-north water. Each resource of water has different characteristics and prices. So it is the optimal allocation and scheduling problem under the conditions of multi-resource, multi-objective and multi-user. An optimal allocation model of 4 water resources, 3 objectives and 4 users is builded in this study (Vairavamoorthy et al., 2008).
Region division and components of water resources and users
Region division: Xuzhou city has 5 scoping (Gulou district, Yunlong district, Tongshan district, Jiawang district and Quanshan district) and 5 counties (Feng County, Pei County, Suining County, Xinyi city and Pizhou city). According to the administrative division of Xuzhou, it can be divided Xuzhou into seven regions as Xuzhou urban district (include Gulou district, Yunlong district, Jiawang district and Quanshan district), Tongshan District, Feng County, Pei County, Suining County, Xinyi city and Pizhou city.
Level of users: There are many users in the water system and they may have different demands of water. So it is better to divide the users into different classifications according to the socioeconomic status of Xuzhou and the important degree of water resources to users: The first classification of users mainly refers to the domestic water and ecological water, because domestic water is more important to human beings than others, the second classification of users is industrial water, for industrial water can bring us more economic value, the third classification of users is agricultural water. The different levels of water users mean that it should give priority to the higher level of users when water is in short supply.
Level of water resources: The four kinds of water in the water system have different resources and different regulating ability. So it can be defined the water resources by the different characteristics and regulating ability. According to the reality of our countrys water resources, the sequence of water supply follows the order: Surface water, groundwater and reclaimed water. Because of the reality and its high cost, it usually give consideration of the South-to-north water at last. It should use water resources in the above sequence when supply water.
Objective functions: The goal of optimal allocation of water resources is to achieve the sustainable development of all regional resources, society, economy and environment. In general, the goal should cover three aspects: Economic objective, social objective and environmental objective. Since the incommensurable differences between these three goals, it chose to use the multi-objective optimization model to solve this problem and the objective functions are economic objective, social objective and ecological objective, respectively (Kondili and Kaldellis, 2006).
Economic objective: Maximize the net economic benefits after total cost generated by use of water:
(1) |
where, means water supply (m3) from water source i to user j in subinterval k, means benefit coefficient (yuan m¯3) from water source i to user j in subinterval k, means cost coefficient (yuan m¯3) from water source i to user j in subinterval k.
Social goal: Minimize the amount of water shortage:
(2) |
where, means water requirement of user j in subinterval k (m3).
Ecological goal: Maximize meet ecological water demand:
(3) |
where, means ecological water requirement of subinterval k (m3).
Constraint conditions: In addition to the above three goals, other constraint conditions must be taken into consideration in process of optimization calculation. One of the very important conditions is the water quantity restraint which includes constraint of water supply and water requirement. The constraint of water supply demands that the sum of water supply from one certain water source should not be more than its available water supply (Hsu et al., 2008). Based on the principle of conservation, constraint of water requirement demands that the sum of water supply for one certain user from different water sources should not be more than its requirement (Lansey and Mays, 1989):
• | Restraint of water quantity from water resources: Since different water sources have different characteristics, they also have different constraint conditions. Water sources can be classified as: Underground water, surface water, reclaimed water and the South-to-north water |
• | Constraint of surface water supply: Because the surface water supply depends on the scale of the regional water conservancy project and management style. Different regions have different surface water supply. In calculation interval, the sum of surface water diverted from one certain water source should not be more than the availability of this region. Manifested as: |
(4) |
where, means water supply (m3) from surface water resources to user j in subinterval k, means the total water supply (m3) for subinterval k from surface water resource l:
• | Constraint of the eastern water diversion: According to the water quantity from external source and water supply capacity, the total amount of use of diverted water should not be more than the availability of water supply from the main canal nozzle these time intervals: |
(5) |
where, means water supply from external water source to user j from subinterval k (m3), means total water supply quantity of external water in subinterval k (m3)
• | Constraint of groundwater and reclaimed water: Groundwater and reclaimed water have similar constraint conditions. With the groundwater as an example: The amount of water supply quantity of all users from all subintervals should not be more than available water supply in level year: |
(6) |
where, means water supply from shallow ground water to user j from subinterval k (m3), means total water supply quantity of shallow ground water in subinterval k (m3)
• | Constraint of water requirement: Constraint of water requirement means that the sum of water supply quantity of once certain user should not be more than the users requirement. Because of the difference of industrial, agricultural, life and environmental water demands, they also have different constraint of water requirements. Especially for life water demand which must be satisfied firstly since it is related to peoples basic living security |
Here, selected the industrial water demand constraints as an example to illustrate: The sum of water supply quantity from all water sources to one certain industrial water user should not be more than its requirement in level year:
(7) |
where, means water supply quantity of water source i in subinterval k (m3), means the total water demands of general industrial water in subinterval k (m3):
• | Constraint of reservoir storage: To ensure the reservoir storage capacity in the normal range, constraints of reservoir storage follows: |
(8) |
where, Vt means reservoir storage (104 m3), Vmin, Vmax mean the minimum and maximum of the reservoir storage (104 m3), the minimum is the dead storage capacity of reservoir, the maximum is the reservoir storage of flood control level in flood season: In non-flood season, the reservoir storage is normal
RESULTS
Results: It is quite difficult to solve the established multi-objective optimization model by some normal methods. So it gave more consideration to how to give continual improvement to the complex system optimization problems.
Genetic Algorithm is a highly parallel, random search and adaptive algorithm and it is developed from the natural selection and the evolution mechanism. Because the Genetic Algorithm has robustness, it is well suited for the complex and nonlinear problems that the normal methods cant solve. At the same time, MATLAB, matrix calculation software developed by Math Works, supplies the Genetic Algorithm and Direct Search Toolbox. With this software, users can adjust the Genetic Algorithm function by the toolbox and this gives great improvement of practicality and convenience. So, we try to solve this multi-objective problem through the Genetic Algorithm (Goldberg, 1989).
The toolbox of MATLAB 7.0 supply users a friendly interface. Users only need to input the necessary parameters to optimize the model by Genetic Algorithm (Chen et al., 2006). The calculation process is shown in Fig. 2.
Parameters determination:
Coefficient of benefit by unit water: According to the gross industrial output value (311.409 billion yuan), industrial demand of water (322086 thousand stere), gross agricultural output value (51.473 billion yuan) and agricultural demand of water (3428082 thousand stere) of Xuzhou city in 2010, it can be speculated the industrial benefit coefficient is 9668.505 yuan m-3 and the agricultural benefit coefficient is 137.954 yuan m-3. Since the benefit of domestic water and ecological water usually belongs to social benefit and its difficult to quantify.
Fig. 2: | Process of genetic algorithm |
To ensure that domestic water first, ecological water second and other kind of water demands next, it was endowed the domestic water benefit coefficient as 2000 yuan m-3 and the ecological water benefit coefficient as 15000 yuan m-3 (Gao, 2009).
Coefficient of cost of unit water supply: In this model, the coefficient can be expressed as the price of water supply from water resource i to user j. According to the statistical data of the price of water in Xuzhou, it can be found that:
• | Groundwater and surface water: Based on the statistics from the waterworks of Xuzhou, the price of comprehensive water supply is about 3.1 yuan, the price of industrial water is about 3.57 yuan m-3 and the price of domestic water is 2.72 yuan m-3. Because the surface drainage is the majority in Xuzhou, the price from the waterworks is assumed as the price of surface water and groundwater |
• | Reclaimed water: The cost of the reclaimed water from a new-water regeneration waterworks in a certain economic development zone is about 2.0-2.5 yuan m-3. Based on this fact, reclaimed water should be advocated no matter from economic angle or from saving angle |
• | South-to-north water: Based on the estimation of cost of water transfer project, it thought that the price of water in east line of the South-to-north water in Xuzhou is 3.8 yuan m-3 under the premise conditions that capital profit rate is about 8% (Zheng et al., 2011) |
Different water demands of each region: According to the twelfth Five-year Development Program of Xuzhou, The water demand of each region is forecasted as follows Table 1.
Different water supply quantities of each water resource in each region: According to the twelfth Five-year Development Program of Xuzhou, the water supply quantities of each water resources in each region are as follows Table 2.
Table 1: | Water demand of each region in Xuzhou (unit: 10000 m3) |
Table 2: | Summary statement of average water quantity of Xuzhou (unit: 10000 m3) |
Solving process (take Pei county as example): Because of the data missing and time limit during the process of research, here we took the Pei County as analysis of example of the optimal allocation by the method of Genetic Algorithm.
With the help of the Genetic Algorithm toolbox in MATLAB, the set of main parameters is as follows: Coding type is real coded, population size is 300, evolutional generation is 200. The running time of program is about 15 min in the computer with 2 GHz CPU Clock Speed and 2 GB memory (Gao et al., 2000). The system got 18 kinds of different configuration schemes and it chose 6 of them to conduct analysis (Table 3), the comparison of water quantity is as follows Table 4, the objective function values of each configuration scheme are as follows Table 5 and Fig. 3.
DISCUSSION
From Table 3 and 4 it can figure out that the optimized quantities of surface water, groundwater, reclaimed water and South-to-north water are all not exceed the available quantities of each water resources in six schemes. From Table 5 and Fig. 3, it can be found that the scheme 2 and 6 give more consideration to economic goals, scheme 4 is most efficient in economic benefit, scheme 4 gives the most consideration to social goals and then are scheme 1 and 3, scheme 2 has the worst effect in social goal, scheme 4 has the most remarkable effect in ecological goals and then are scheme 3 and 5, scheme 2 is the worst one in ecological goals. Combined Table 5 and Fig. 3, decision-makers can make their choices by their own needs.
According to sustainable development theory, we construct multi-objective optimal model of water resources allocation based on coordinated development of economy, society and ecological environment and calculate the Pareto Optimality by Genetic Algorithm of Matlab.
Fig. 3(a-c): | Comparison of allocation of water of Xuzhou in 2015, (a) Economic goal, (b) Social goal and (c) Ecological goal |
Table 3: | Results of optimal allocation of water resources in Pei County (unit: 1000 m3) |
Then we take Pei County of Xuzhou as example of analysis and calculate the optimized allocation of water resources for Pei County of Xuzhou in 2015. This will provide theoretical and practical basis for the high efficient utilization of water resources in Xuzhou and then bring the optimal comprehensive benefits of coordinated development of economy, society and ecological environment.
Table 4: | Comparison of optimized and original water quantities |
Table 5: | Function values of each configuration scheme |
Due to the constraint of time in data collection, this research is just a preliminary research. And for the further research, improvement should be given to the following several points:
• | Improve the objective functions and constraint conditions of optimized system and solve the problem of pollution-induced water shortage |
• | Expand the range of research and find the optimized allocation for whole Xuzhou (6 districts and 6 counties) |
• | Improve the solution method for uncertain multi-objective problems and try other methods (such as evolutionary algorithm and PSO particle algorithm) to find which is the best |
ACKNOWLEDGMENT
This study was supported by the MOE (Ministry of Education in China) Project of Humanities and Social Sciences (Project No. 11YJC630205).
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