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CHAPTER 6 WATER RESOURCES SYSTEM
Institute of Water Resources and Hydropower Research, Beijing 100044, China
The Chinese scholars in meteorology, environment and water resources etc. have been greatly involved in the research of the global-warming effect on water resources and the world-wide water shortage increasingly remarkable, especially during the recent decades, of which, both some highlights, including freshwater shortage, water pollution, continuous decline of groundwater level and the climate-warming effect on water resources etc., and the countermeasures of the protection and sustainable utilization of water resources are analyzed and studied (Zheng, 1999). Under the impetus of the focus-transfer in the study of water circulation from the static phenomenon of nature to the dynamic process between human and natural system, it is pointed out that transporting vapor from ocean to land is of the greatest importance in the relevant research of meteorology and hydrology, the interrelation of which has shown as Fig.1.
Fig.1．Water circulation between human and natural system.
In addition, the former focus on the average situation is inappropriate to the certain matter of fact that the water circulation is actually different from year to year and site to site, especially strengthened by greenhouse impact due to carbon dioxide discharge, which not only affects the water resources on land, but also leads to the off-balance between input and output of ocean water. The climate change caused by human activities is shown as Fig.2.
Fig.2. Effect on water circulation caused by climate change and by human activities.
It is certain that the sustainable development of human society on the basis of harmony between man and nature is of possibility, despite the current water shortage resulted from the conflict between human activity and the nature, since the earth is the planet with adequate water resources (Zhang, 1999). In the research of the phenomenon, process and effect on the change of world-wide water circulation and climate of the interaction between ocean and air at large scale, these issues including ENSO affair and the summer rainfall in China, the interaction between ocean and air in middle latitude, coupling model of ocean and air, the prediction of ENSO, and CO2 and ENSO etc. have been studied. The following research highlights mainly are: ① Recognizing the physical, chemical, biological and dynamic processes of water circulation and their interaction on greater depth; ② Reducing the climate model scale to increase distinguishability; ③ Strengthening the process on land to increase the forecasting accuracy; ④ Enhancing the cooperation and communication among hydrology, climatology and oceanography (Xing,1999).
The Chinese experts and scholars on meteorology, oceanography, hydrology and water resources take the effect of climate change on water resources into account by adopting the methods of various kinds. The scientific conference of 187th Fragrance Mountain in Beijing of China is held on July, 2002（Liu，Xia，2002），Theme is of“The global change and water cycle”. The key issues involve the global warming and hydrology cycle，interaction among atmosphere-land-ocean linked by water cycle, land water cycle and ecological system，adapting to the global changes into genially together with the water resources changing (Xia，1996，1999，2000)
In the research of the circulation and evolvement relation among atmospheric water, surface water and groundwater, both the “3-water” transform system and model structure with credible accuracy on water resources evaluation is achieved based on provincial units and taken precipitation as the input and water resources as output so as to give further analysis and research to water resources and its regeneration (Liu et al., 1999). It is pointed that: (1) The water regeneration consists of both in quality and in quantity; (2) The water regeneration ability consists of both in natural and in social——the former mainly refers to the replenishment in quantity and self-purification in quality through water resources recycle in the form of evaporation, precipitation and runoff caused by sun radiation and gravity and the latter to the regeneration both in quantity and in quality through the recycle in the form of water resources reutilization and polluted water disposal carried out by mankind. In addition, it is certain that the fact that the more excessive the exploitation and utilization of water resources than its regeneration possibility is, the longer the regeneration cycle becomes will hamper the sustainability of water resources (Zeng et al., 2001, Xia, 2000).
Flood disaster is the one naturally caused by climate, precipitation and terrain etc. and artificially by human activity against water for land exploitation. In the 1990s, flood control in China enters its prime with largest construction scale and best effectiveness while suffering most from the serious flood disasters and losses. (1) Flood control situation: the extreme floods frequently taking place in those main rivers in the 1990s, typically including the major floods and extreme floods in 1991,1994,1995 and 1996, in middle and down streams of the Yangtze River and Taihu Lake and the 1998-extreme flood even covers the whole river basin; the extreme floods in 1994, 1995 and 1998 in the Pearl River; the major floods in 1992 and 1998, which are once a 50 to 100 years in the Min River; the extreme flood in 1991 in Huaihe River; the extreme floods in 1991 and 1998 in Nenjiang and the largest flood in the 20th century Liaohe River and Tarim He, are characterized as generally covering wide range, primarily influencing urban area and dramatically causing severe loss with annual direct economic loss amounting to 136.2 billion RMB and especially with above 200 billion RMB in 1998. (2) Flood control strategy: 1) keeping the way of thinking——“simultaneously adopting store and discharge, and giving priority to discharge” as guideline; 2) combining the engineering measures with the non-engineering, and combining adjusting nature and controlling flood with getting accustomed to nature and taking advantage of flood; 3) rationalizing further the flood control targets and standards to achieve best benefits in flood control and disaster reduction; 4) highlighting the flood control in urban area; 5) harmonizing the relationship between flood control and drainage; 6) emphasizing eco-environmental protection by forestation and mountain-soil reservation and recognizing dialectically its effects on flood control and disaster reduction (Xu Qianqing, 1999).
Evaluating flood control benefits, constituting flood control planning and making flood control and disaster reduction decisions——all these are on the dependence of scientific evaluation on the flood disaster loss. Consequently, it is certain that the two main evaluation methodologies adopted in China at present, namely the evaluation of direct economic loss and of the indirect, interfere with to some extent the accuracy of flood disaster loss evaluation and the improvement of the benefits made by flood control and disaster reduction since the two fail to show exactly the non-economic loss.
The integrated index system has been built up on the basis of analyzing the characteristics of flood disaster loss evaluation including man loss, economic and belongings loss, eco-environment loss and disaster rescue loss so as to provide a scientific, systematic method to the comprehensive, completed reflection of flood disaster situation (Fu et al., 2000).
Unquestionably, it is urgently necessary to adopt the theory of systemic science and modern scientific technologies, as computer remote sensing etc. and to adopt the integrated analytical methodology of simulating, predicting, evaluating and decision-making to meet the needs of effective flood control and flood regulation, since the traditional methodology incapable of making multifactor and multilevel integrated analysis is hardly adapted itself to the evaluation of flood disaster characterized as a complicated system affected by climate, land and atmosphere etc. From the systemic theory, the concept that flood disaster is a complicated, big system displaying the relationship between human and nature is put forward. On the basis of analyzing the two main conditions to bring about a flood disaster that (1) the disaster-causing factor and environment; (2) the disaster victims (allocation of person and property victimized by flood), the integrated qualitative and quantitative methodology and integrated analytical methodology are put forward by building up the physical model, mathematic model, graphics model and artificial intelligence model, and analyzing the flood disaster characteristics of process, action, system, index and model, to realize the integrated analytical system of flood disaster which provides the foundation to the establishment of flood disaster analysis and evaluation intelligence system so as to promote the research in this field more scientific systematic and quantitative (Wei et al., 1999).
In the researches of flood forecast, flood control calculation and flood regulation, many scholars adopt a variety of methods from different prospects and make certain progress.
In non-engineering measurement of flood control, hydrological forecasting plays a very important role. Owing to non-linearity and uncertainty of hydrological process, real-time forecasting has become an efficient approach. Xia (1997,2002) addressed the problems how to use observed information to update parameters of hydrologic models in real-time rainfall-runoff forecasting. A simple nonlinear model with a variable gain parameter that is called as the variable gain parameter model (VGPM) is developed. A separated calibration approach for updating parameters used in the runoff generation process and the response function in the flow routing is proposed. State space equations associated with the updating model parameters in real time scheme were developed. The VGPM approach is verified in terms of three kinds of representative catchments in the world. The performance of different updating schemes in rainfall-runoff modeling and real-time forecasting were tested. The results indicate that significant improvement on the efficiency of hydrological modeling can be obtained from the VGPM approach, relative to simple linear model (SLM). As far as the hydrologic real-time forecast is concerned, the efficiency improvement of such catchments whose variation of hydrological time process of both calibration period and verification period has consistent behavior is not notable at all. For the catchments with a rather time–variant characteristics, however, significant improvement of hydrologic forecast efficiency can be obtained by adaptive schemes. For the updating algorithm, the efficiency of real-time modeling by the self-adaptive Kalman Filtering algorithm is very close to that of the Recursive Lease-Square method.
As for flood control calculation, a new calculation method with forecast period itself is developed, according to a kind of new array of difference, to attain a satisfying forecast value shown by many cases (Rui et al., 2000). These successful cases include the following——first of which, through 1951—1995 materials, the characteristics both of flood and drought in summer in the middle and down stream of the Yangtze River and of atmosphere circumfluence factors are analyzed and then some critical factors forecasting extreme flood and drought disasters are achieved (Li et al., 2000); second, taking the flood forecast system of the Tianshengqiao hydropower station ranked Class I in Nanpanjiang, Guangxi Province as another example, some technological problems about setting up a flood forecast system based on the water situation database, flood forecast model, database management system and model manager are discussed to experiment and improve real time flood forecast system (Zhang et al., 1999).
As for flood regulation, the follow-up objectives are proposed through concluding and analyzing the methodologies taken by the systematic, joint flood control regulation among reservoirs: (1) turning from regular methods to systematic, analytical methods; (2) combining the simulating method with optimizing method; (3) adopting network planning method gradually; (4) combining the multi-objective method with optimizing method; (5) combining the big-system analytical method with optimizing method; (6) studying indistinct optimizing and artificial nerve network method; (7) highlighting coupling method (Wang et al., 2001). In addition, the methodologies taken by rain-flood-forecast-based risk analysis for flood control decision-making are provided with relevant researches to clarify the types of flood control decision-making risks and to attain some concrete analytical or calculative methodologies and with case studies at Three Gorge-Luoshan reach that whether the various flood control programs including the detention area should be adopted or not to quantify decision-making risks (Huang et al., 2001).
Water resources sustainable development as a key point of sustainable development strategy focusing on harmonizing population, natural resources and environment with economic society receives great attention from the whole world with a variety of relevant academic achievements.
Not only a new strategy that the professionals from different subjects are to be organized together to develop the research of water conservancy construction but also a basic national policy that a new water-saving society is to be formed with the emphasis on water pollution control and flood control are undergoing through analyzing the new primary water resources problems, including the frequent flood disasters, industrial, agricultural and residential water shortage, serious water waste and heavy water pollution, faced by the 21st century China on the foundation of reviewing the great achievements in the water conservancy construction in New China (Zhang, 1999); There are four typical water resources problems in the 21st century China: (1) the remarkable contradiction in water supply and demand; (2) the more serious water crisis than water quantity crisis caused by water quality crisis; (3) the sharp conflict in water right caused by increasing agricultural-nonagricultural water transfer; (4) the severe eco-environmental problem. As soon as the four main problems are presented, the related researches and studies are carried out that first of all, the water resources security countermeasures of the 21st century China covering the aspects of improving water-utilizing efficiency, integrating water resources management, setting up efficient management system, emphasizing both strategic and technological water restoration, and developing proper market-facing resources trade are approved (Jiang, 2001); second, the definition, principle of water resources sustainable utilization (i.e. of integration, coordination, optimization, virtuous circulation) and the mathematics model including the model of static water resources exploitation and of dynamic water resources exploitation and of the equity between eras in water resources exploitation as well are discussed (Fu et al., 2000); third, from the systemic prospect, not only a sustainable development model and also a topological structure of qualitative and quantitative development based on analyzing the operation mechanism of river basin system are put forward to meet the needs of the river basin as an open, complicated and big system where water, of course, is the media to join human and nature together. Then the measuring index system of sustainable development in river basin is formed with a case study handled in the upstream of Minjiang, Sichuan Province whose findings got by the means of combination of gradation analysis and nerve network method and carried out from both static and dynamic aspects comply with the ones approved by related State's competent department and consultants (Wang et al.).
The important role which sustainable water utilization plays in China's development of western regions is such that the evaluation on the water resources sustainability there which is done from the two aspects——the influence of the water resources in western regions on the whole country and its current situation of exploitation is of special significance. It is pointed out that the water resources evaluation should be included within the evaluation against different environmental levels, and the sustainable management and relevant technological measures, such as establishing effective water resources evaluation structure, accounting the water resources value, controlling the total quantity of water utilization and compensating water resources etc. are made as well (Bao et al., 2001); Through analyzing the water resources quantity, available quantity and demanded water by human utilization, the water resources bearing capacity is evaluated drawn from the evaluation on the population bearing capacity in the northwestern part of China. The result shows that the Yellow River basin, Hexi area, Gansu Province and the eastern part of Xinjiang are to be overloaded with heavy population, namely population and economy development is to exceed the water resources bearing capacity (Wang et al., 2001).
In the research of water resources rational exploitation and optimized allocation, one of the important conditions for sustainable water utilization, and of important focuses in the field of water sciences nowadays, a series of comprehensive demonstrations either centering around the concepts of and relations among sustainable water resources utilization, rational water resources allocation and water resources bearing capacity or centering around the corresponding research contents and methodologies are fulfilled. The three concepts appeared from the end of 1980s to the beginning of 1990s which are increasingly accepted display the fact that the three cooperate all for the purpose of the harmonious development among population, resources, environment and social economy. The concept of sustainable development starting from the values of environmental resources primarily emphasizes the equality and sustainability of development; the concept of rational allocation mainly emphasizes the rational exploitation and effective utilization of resources and environment; and bearing capacity above all emphasizes the limit to development, namely the restriction on development mode, scale and speed made by resources and environment conditions (Li, Gan et al., 2000); As for the optimized allocation, a series of researches have been carrying out—— first of which, in the research of the theory and methodology of water resources optimized allocation, the integration of multi-platform software is handled to provide the users in the multi-platform integration with a communication method to send and receive data and controlling information and to be applied into the decision-making supporting system of water resources optimized allocation (Wang et al., 2001); second, in the case study covering six areas in the southern part of Hebei Province, water utilizing marginal benefit based allocation mode is shaped on the basis of the equilibrium model of marginal benefit of water resources allocation to enable the allocation and benefit of the transferred water at receivers' hands to realize optimization (Wang et al., 2001); third, based on the theory of multiphase and multi-object systemic indistinct optimized theory, multi-dimensioned indistinct optimized dynamic planning model extending one-dimension (a guest water) to multi-dimension (many a guest water) which has applied in Cangzhou, Hebei Province is accomplished (Cui et al., 2000); fourth, according to the decomposition and coordination principle, the method to optimize gradational model is got with the assistance of water resources optimized allocation model which has been adopted in the big irrigation area——Weigan River, Xinjiang to efficiently realize the water resources optimized allocation under the conditions of multi-water sources, multi-users and multi-security rates (Xiang et al., 1999).
In the research of water transfer across several basins, both the importance, necessity and relevant background knowledge of south-to-north water transfer, the most representative nationwide water transfer project and the burning issues like the world's water circle, water circulation, spatial and time water allocation, freshwater shortage, world-wide water crisis etc. are introduced and studied. Moreover, as for the south-to-north water transfer: above all, its overall arrangement, water transfer route, water transfer scale, project capacity, total investment, main engineering technological problem and its influence on the sustainable development of social economy and eco-environment——all these are delineated comprehensively and scientifically (Yan, Liu et al., 1999); second, the south-to-north water transfer project is characterized as: (1) a water resources allocation project owing to its relief on the water shortage in the northern part of China; (2) an eco-environmental project owing to its importance on the eco-environment improvement in the northwestern and northern parts of China; finally, not only the characteristics of water resources environment and social-economic development in transferring and transferred areas in the eastern, middle and western routes are analyzed. The process of decision-making and of project implementation is also discussed (Liu, 2000).
Recently, the research of the water demand management mode, integrating water resources integrated management with water demand management has been making dramatic progress at a high speed in China. Unquestionably, it is necessary to make adjustment from water supply management to demand management for the sake of the realization of sustainable water utilization under the pressures of heavy population, rapid economic development, sharp contradiction between water supply and demand, serious water pollution and low efficiency in water utilization etc. The development trend of water demand management on the dependence of analyzing its current situation and existing problems is molded that: (1) strengthening water resources legislation; (2) reinforcing water resources management system; (3) strengthening water saving; (4) reinforcing water resources protection; (5) taking the water resources appraisal of constructing project into effect; (6) rationalizing water pricing system from the marketing principle; and (7) studying the assets management on water resources (Huang et al., 2000).
The research of integrated water management (IWM), a worldwide popularized mode, regards IWM as the one based on the theory of complicated system, aware of the complex relations among different critical water resources elements and able to manage, control both the above-mentioned relations and the related stakeholders. IWM is a kind of management idea rather than a resources management system whose integrated contents cover not only the integration of inner elements of water resources and of functions and benefits among relevant departments but also the integration of stakeholders activities and of management methodologies of various kinds etc. Consequently, the major approaches to implement IWM mode are concluded as follows: (1) dealing with decision-making issues in water management from an integrated thought; (2) setting up IWM-mode management system; (3) conceiving of the systematic controlling countermeasures under IWM-mode (Zeng et al., 2001); at last, beginning with analyzing the current situation and existing problems of water resources management at home and abroad, regarding the practical problems in water resources management as cornerstone, and adopting the systematic analytical theory of the water resources in river basin and conflicting analytical theory, the integrated management mode, organization structure and technology route of water resources in river basin suitable for China's practical situation are put forward (Zeng et al., 2001).
The approaches that the water resources are classified with specific integrated allocation and management, according to different functions, into natural reserves area, hydropower development area, agricultural water-saving irrigation development area, water and soil conservation area, key flood control area provide the water resources in the Yellow River, the crucial highlight the China's development of western regions with strategic management (Lin et al, 2001).
Real time monitoring system of water resources, as a high-tech integration, consisting of the following portions——database, model base, information base, on-line data collecting subsystem, integrated information management subsystem, integrated analysis and decision-making supporting subsystem, real time management subsystem etc. is the major technological approach to meet the needs of rational water resources allocation and demand management. It is certain that the real time monitoring system of water resources is to be set up under the guidance of the process, “overall design→gradual implementation→pilot community experimentation→ nationwide diffuse” (Dong et al., 2000).
It is crucially necessary for the relief on water shortage and realization of sustainable water utilization to popularize the consciousness of water saving, improve water utilization efficiency and shape water-saving agriculture, industry and society. Therefore the water-saving and efficiency-improving researches cover a wide range as follows: first of which, from the prospect either of current situation of water utilization or of the sustainability of population, resources and environment, the significance of water-saving agriculture popularization is presented, the diffusion of water-saving irrigation and existing problems are reviewed and analyzed, and the guideline, object and highlight about the development of water-saving irrigation are accomplished too (Chen, 1999). What the solution of the contradiction between water supply and demand requires is nothing but the close cooperation among the three key factors (i.e. the water-saving policy, water-saving consciousness and water-saving technology) and the collaboration among the three aspects (i.e. the agricultural water-saving, industrial water-saving and urban water-saving) so as to mould a water-saving society gradually (Zhu, 1999); second, the research of farmland irrigation mode studies the major modes, such as channel irrigation, pipeline irrigation and sprinkle irrigation, worked within 3H-plain (Huang River-Huai River-Hai River), especially with a case study in Liaocheng, Shandong Province to give a set of comparative analyses to the real situations of the water demand, water consumption, energy consumption and land consumption under the different irrigation modes (Li et al., 1999); at last, centering around the prominent characteristics of agricultural irrigation and the severe situation of water shortage in the northern part of China, not only the innovative resource-typed and efficiency-typed concepts with the emphasis on the real water-saving volume but also a simplified calculation method are put forward, thus reflecting the contemporary new viewpoints, innovatory concepts and fresh ways of thinking in the world (Shen, Wang et al., 2000).
Water pollution and water eco-environmental deterioration, as one of the three major water problems in China, which has caused the loss no less than flood and drought disasters has aroused great attention from the State's competent departments, the experts and scholars of different fields and even from the whole society. The corresponding researches make spectacular progresses as follows: firstly, the target and methodology of water environment bearing capacity are identified in debt to the studies of the connotations and dialectical relation between water resources bearing capacity and water environment bearing capacity so as to further explore the reinforcement of integrated water resources management, water pollution control, and of the approach to improve water environment bearing capacity etc. (Wang, 2001); then, the environmental water conservancy mode, as a new subject combing water conservancy science with environment science, natural science with social science closely, which thermodynamically is a low entropy mode, and philosophically a “heaven-human unity” is put forward (Shen, 1999); third, a variety of countermeasures to attain water-saving irrigation, polluted water disposal and reutilization and water resources protection are provided specifically focusing on the deterioration of water resources and water environment due to water shortage, water waste and water pollution etc. appeared in farmland irrigation (Zhou et al., 2001); fourth, as for the technological aspect, not only the fast development of remote sensing technology in the recent decades and the critical approaches to adopt it in eco-environmental investigation and groundwater exploration at large scale are depicted. The technological methods and routes to adopt it to investigate eco-environment, to monitor and to explore water in the western part of China are also accomplished (Zhou, 2001). The adoption and latest research progress of GIS technology in water resources and water environment at home and abroad as well as the related technological issues are also concluded and studied (Peng et al., 2001).
Water resources, as the core of ecological system and eco-environment, play a spectacular part in eco-environmental protection. As for eco-environmental water demand, an important issue in water resources planning and water resources demand management, on the one hand, the concept of eco-environmental water demand, the relationship between eco-environmental quality and water resources and the type of eco-environmental water demand (i.e. water-soil conservation water demand, artificial eco-environmental water demand, natural eco-environmental water demand) are identified and analyzed; on the other hand, the calculative procedure and principle to quantify eco-environmental water demand is concluded (Cui et al., 2001); In addition, to quantify rationally the ecological water demand in the drought and half-drought northwestern part of China consists of the two primary topics——one is the spatial classification of eco-reserves through remote sensing and GIS, and the other is both the eco-protected object and eco-construction scale are clarified based on sustainable development strategy and the exploration and innovation on theoretical concept and calculative methodology, with the calculative result to quantify the eco-water demand in each eco-subordination in the northwestern part of China are made (Wang et al., 2002).
With the development of economy and urbanization, the emphasis on water resources protection and water pollution control is of more urgent importance in the face of increasingly severe water pollution mainly represented by more serious industrial and residential wastewater discharge and the surface source pollution. The related researches cover the following ranges: first of which, both the serious situation of non-point source pollution in China and management and existing problems to control non-point source pollution home and abroad are analyzed to put forward some specified countermeasures (He et al., 1999); second, since the water shortage in China is such that quite a lot waterworks have to use polluted water sources, the research of the current situation of water resources pollution and drinking water security are carried out to upgrade water cleaning techniques and ensure the drinking water security (Xiao et al., 2001); third, the significances, relevant technologies and prospects to make the polluted water disposed and utilizable are illustrated with a series of technological strategies and routes (Liu et al., 2001; Huo et al., 2000; Zhang et al., 1999); fourth, by optimizing the parameter in calculative formula with the adoption of genetic algorithm, an index formula suitable for varied water quality pollutants, to reflect the gradations of water quality pollution, which is noted for the explicit physical significance, simple calculative process, easy operational method and extraordinary universal and comparable feature is developed for the purpose of integrated water quality evaluation (Li et al., 2001).
According to the counter-boundary and counter-dynamic control theory, a precise calculative method of one-dimension convection diffusion equation is achieved specifically to identify the discharge density and total quantity of single or multi pollution sources. Compared with those best controlling methodologies at present, it is noticeable for its advantages to consider the diluted, mixed capacity along the river, and to follow the dynamic standard of water quality and change of social economy (Li, 1999).
6.4.3 Water-Soil Conservation
Water-soil conservation, as the core of water resources protection, eco-environmental construction and of water conservancy infrastructure construction, its corresponding research is handled in the following aspects: above all, both the water-soil erosion destruction and water-soil conservation value in eco-environment are received particular attention through analyzing both the current situation and characteristics of water resources home and abroad and the prominent water problems in the 21st century (He et al., 2001); second, water-soil conservation functions not only able to retain, absorb, scatter, filtrate and transform the runoff so as to accelerate virtuous circulation of water resources but also to utilize water efficiently are demonstrated (Chen et al., 1999); third, the utilization of the water resources in the Yellow River stresses the upper, middle and down stream cooperation, source-broaden and expenditure-reduced coherence, precipitation and river runoff co-exploitation, with a particular emphasis on water-soil conservation construction to exert its important influence (Liu, 1999); fourth, the findings of the research taking the Loess Plateau as an example to quantify the effect of water-soil conservation on reduction of water and sand show that on the one hand, generally speaking, the biological water-soil conservation can reduce water amounting to above 15%, and sand above 30%, of which the lands with forest or wood can decrease water amounting to above 80% and sand above 90%; cultivated water-soil conservation can reduce water amounting to above 35% and sand above 70%; engineering conservation can reduce water amounting to above 55% and sand above 85%; on the other hand, water-soil erosion mostly takes places in sloping farmlands, since crops exert the least effect on reduction of water and sand, that is, returning land for farming to forest and to grass is of tremendous necessity (Yuan et al., 2001).
6.5 OTHER ASPECTS
6.5.1 Soil Water Research
The research of soil water draws more and more attention from the whole society because soil water, as the crucial link between surface water and groundwater, the important part of water resources and the major factor in water circulation, plays a key role in the process of water resources formation, transformation and consumption. The research is currently characterized as follows: first of all, the multi-subjects amalgamation and cooperation, such as the coupling movement of water, heat and salt, water movement in frozen soil, water and heat movement in soil-plant-atmosphere continuum etc.; second, the improvement of the study in soil water movement mechanism at greater depth, such as the measure of priority flow and soil water parameter, spatial variability of soil water parameter etc.; third, the innovation on the numerical simulation methodology in the study of soil water, such as finite element analysis, characteristic finite element method, alternative direction finite element method etc.; at last, the expansion of the application of soil water research, such as water resources evaluation, relation between soil water and crop, water environment research etc. (Lei et al., 1999). The water exchange under the condition of irregular underlying surface and non-uniform medium lacks suitable consideration due to the preference on the exchange under the condition of regular underlying surface and uniform medium in the former research. Remote sensing method, numerical method and synthetic method among various methods deserve particular notice (Yang, 1999). The renewable and exploitable soil water resources and their effect on the relief of water resources shortage are particularly emphasized based on demonstrating soil water definition, analyzing soil water structure and depicting soil water evaluation method (Xia and Li, 2001); From the experiment carried out in Wangtong, Hebei Province, both the evaluation content and methodology of soil water resources are formed by means of regarding annual soil water replenishment and available soil water quantity in the growth duration as key evaluation indexes. In the pilot area, the evaluation result shows that the soil water utilization in the growth duration is: wheat 330-415 mm,corn 460-580 mm, cotton 630-680 mm (Jin et al., 1999).
As for water rights, water price and water market, the theoretical research and the function of water market exerting in rational water resources allocation become the highlights in the current water resources field. The researches involving in water resources ownership, usufruct and water market at greater depth point out explicitly: first, clarification of property rights and water rights is the premise of water resources optimized allocation; second, the concept of onerous water rights is the theoretical foundation to establish water market; third, among the variety of water prices, resource-type water price is the most important, and simultaneously the adjustment of water prices and the establishment of water market are two important ways to optimize water resources allocation; finally, the efficient combination of governmental macro control, democratic negotiation and water market regulation is the institutional guarantee to realize optimized water resources allocation (Wang, 2001).
As for water resources value, the connotation of water resources that theoretically, it is a kind of natural resources formed by precipitation and able to be used by man and practically, is all the water able to be used by man including the exploited engineering water, disposed return water and usable seawater etc. is characterized by the maintenance of water resources sustainability, that is, it is impossible for any water body or water volume used by man irreversibly destroying eco-environment, such as the waste and polluted water for irrigation, overdraft groundwater and drinking water below sanitation standards to be included within water resources. According to the definition, generally, water resources can be divided into three categories as the resource-type, engineering-type and regeneration-type, while the engineering economy regards the last two as one and therefore the resource-type is valued by ownership and scarcity of water resources and the sustainable engineering-type is valued by the theory of labor values, land rent and margin. The realization of resources value lies in the rational water resources utilization, and is calculated basically according to water resources shadow price (Wang et al., 1999). Moreover, combining with the characteristics of water resources, the approaches to study water resources value, especially the economic value, both the calculative model to price water resources and follow-up research direction in this aspect are designed and shaped (Xie et al., 1999) with a case study in the north of China that rising the current seriously low water price to the one covering cost or making meager profit will dramatically restrain water resources demand and thus is full of water saving potentials, for example, if the agricultural water price there is raised from 0.03 yuan/m3 to 0.2-0.3 yuan/m3, and industrial water price raised from 0.5-1.5 yuan/m3 to 3.0-4.0 yuan/m3, and residential water price from 0.3-1.0 yuan/m3 to 1.30-2.50 yuan/m3, the water demand decreases by 25%-50%, amounting to 13 billion m3-25 billion m3 (Jia and Kang, 2000).
Sustainable water resources utilization, as the key point of the sustainable development of economy, society and eco-environment in drought and semi-drought areas, makes the limitation of usable water resources recognized and the effect of water resources utilization on eco-environment noticed. Consequently, standpoint of water resources evaluation is to turn from the evaluation on economic benefit to the evaluation on integrated benefit with a wide range of economy, society, resources and environment (Pan et al., 1999). Inland drought areas primarily characterized by oasis economy and irrigated agriculture have been suffer from the irrational utilization of water and soil resources leading to desert and natural vegetation regression because of the close relation between oasis ecology and agricultural development. The influence of the change of groundwater level on the ecological barrier on the edge of oasis is such that the maintenance of a certain artificial ecology plays an important part in social-economic development owning to the interaction between artificial ecology and natural ecology (Liu et al., 2001). In China's development of western regions, the development of big agriculture is of special importance. In the western part of China, dry farming agriculture occupying 68.9% of the total farmland, with great potential, its strategic status should be tremendously strengthened. (Wang et al., 2001).
Water resources forecast and prediction in the dry season, as a crucial point of drought crisis management have drawn a lot of relevant research achievements not only in the aspect of water resources real-time forecast and prediction in the dry season covering wide range from forecasts and predictions on the river runoff, groundwater level and exploitable volume in the dry season to the prediction theory and methodology of water demand etc. but also in the comprehensive research of the mechanism of conflux formation and the relationship between groundwater replenish runoff and discharge in semi-arid and sub-humid area under the deep immerged condition with a case study in Baoding, Hebei Province (Xie et al., 2000).
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