In terms of the current situation of China's water resources development and utilization, the water environment pollution, water resources waste and imperfect water resources management system is a more prominent problem. These aspects of the problem are closely related to the renewable capacity of water resources. Water pollution is becoming more and more serious, will make the cost of sewage treatment greatly increased, the sewage recycling rate is reduced, but also on the ecological environment to a certain degree of damage; serious waste of water resources makes the total amount of water resources can be renewed to reduce the renewable capacity of water resources is also weakened; efficient water resources management is to improve the water resources of the social renewable capacity of the key, the imperfect management system can not make the water resource cycle of each link is effectively guaranteed. The key to improving the renewability of water resources is efficient water management, and an imperfect management system will not guarantee the effectiveness of all aspects of the water cycle.
8.5.1 Establish a water-saving society and improve the utilization rate of water resources
The first step to greatly improve the efficiency of China's water use is to innovate the concept of water use, followed by the adoption of economic, technological, regulatory policies and public participation. As early as the end of the 20th century, the former Ministry of Water Resources, Director of Water Policy, Professor Ko Li Li in the "Groundwater" magazine published "set off a revolution to improve the efficiency of water use" of the article [14]. The article pointed out that: many countries, whether water-rich or water-poor countries, has gradually realized that strengthening water demand management
rather than constantly to meet the demand for water, the implementation of comprehensive water conservation, water-saving society, water-saving economic transformation, and constantly improve the efficiency of water use is the most economical and environmentally friendly measures to balance the contradiction between the supply and demand for water; at the same time, it can promote or avoid the construction of expensive water supply engineering design and sewage treatment costs, saving money, protecting the environment, and without affecting the economy and standard of living. However, this reform to improve the efficiency of water use is still mainly confined to the developed countries to carry out, in most developing countries have not yet generally attracted attention.
Research on water use efficiency and water conservation in the northern part of China (especially in the field of agriculture) is more frequent due to the relative lack of water resources in the northern part of the country. While the literature [15] starts from analyzing the relationship between agricultural water use and water tariff system in the southern region of China, and studies the utilization of water when water tariffs are levied according to the price of water per unit of cultivated area under the constraints of water right water quantity and water without water right water quantity, and the utilization of water when water selling is possible, and based on the principle of equilibrium of water use and the analysis of Lagrangian function of profit maximization, it is concluded that as long as the agricultural sector sells water to the outside (water right water quantity), both agricultural and non-agricultural sectors can increase the economic benefits of the conclusion. In recent years, China's water-saving irrigation has developed faster and made certain achievements. However, there is still a big gap compared with advanced countries, and there are still some problems in the following aspects [16]. First, water conservation policy research is not enough. The construction of policies, rules and regulations on water-saving irrigation is relatively lagging behind, and the agricultural irrigation water management system is not adapted to the requirements of the market mechanism. Second, the low level of water-saving irrigation technology. At present, China's water-saving irrigation area is less than half of the effective irrigation area, channel seepage control and pipeline irrigation and other methods still dominate, sprinkler irrigation and micro-irrigation and other water-saving irrigation methods accounted for only about 2.6% of the irrigated area, compared with developed countries there is still a big gap. Third, agricultural irrigation water prices are low. Low water prices are difficult to play the role of price leverage, is not conducive to the promotion of water-saving irrigation. Fourth, the capital investment is insufficient. Fifth, the awareness is not in place. The severity of China's water shortage, water shortage on the ecological environment, the national economy and social development caused by the impact is far from attracting enough attention. Some areas for the sake of immediate interests and short-term economic benefits, is still excessive water diversion or over-exploitation of groundwater, engaged in flood irrigation. Some basins have caused serious deterioration of the ecological environment downstream due to uncontrolled water use upstream.
On urban water use efficiency, the literature [17] made a comparative study on the level of water use, water supply loss and water use efficiency of cities at home and abroad. It is believed that when the national economic development to a certain extent, the family life of all kinds of water appliances have been equipped, the family life of water consumption will not continue to grow, will be stabilized at a corresponding level. China's current urban households, in addition to flush toilets, bathing facilities, washing machines, dishwashers and other water appliances and hot water systems are still in a stage of continuous improvement, per capita household water consumption will increase year by year. But in 2002, China's urban per capita household water use average indicator has reached 150.5L / d, has been close to the average value of 13 European countries, while some cities even more than 200L / d. This is from another side, China's residents should abandon some wasteful way of water use and habit of water saving household water has the potential to save. According to four different water supply leakage detection companies in 179 cities of China's 20731.6km water supply pipeline leakage results, the average unit length of water supply leakage rate of 1.55L/km-h. About three times the developed countries in Europe, than the average value of the countries is also 62% higher. And in the overall efficiency of water resources (unit of water resources used to produce GDP) data show that China's 2002 figures than the United States in 1998 figures more than 80 billion m3 or so, but GDP is only 1/64 of the United States, China's overall water efficiency, only 1/10 to 1/20 of the developed countries. Therefore, China's current formation of wasteful use of water and water use of the low efficiency mode Must be vigilant. China's water conservation potential is still very large.
8.5.2 Greatly carry out the work of sewage resource utilization
Sewage is the water resource that is polluted and has little use value. Sewage resource utilization (also called sewage reuse) refers to the domestic sewage and industrial wastewater discharged in compliance with the standard after in-depth treatment, as a renewable resource back to the appropriate location, it is an important part of the sustainable development of water resources. Due to the expansion of population and the development of industry and agriculture, at present, China's resource water shortage and quality water shortage problems are very serious, people feel the unprecedented water crisis. The solution to the water crisis depends on the sustainable use of water resources, sewage resource utilization is to achieve sustainable use of water resources, to solve the contradiction between supply and demand of water resources effective measures. The city's sewage is a stable and reliable water resources, sewage resource utilization is necessary and feasible.
8.5.2.1 Utilization of sewage direction
In the face of such a serious water pollution status quo, to alleviate the shortage of water resources, improve the quality of the water environment, so that the depletion of water and the deterioration of water quality as soon as possible to be resolved has become imperative. After treatment of sewage, there are several directions of utilization as follows
Wang Jianxin: thinking about China's sewage resource utilization. See.
: ① to establish the status of sewage reuse in water resources. In the past, when people are looking for water, always give priority to groundwater, followed by surface water, near no surface water, long-distance water diversion. But generally do not put sewage reuse and these kinds of water resources equal treatment, in the planning of water resources, often do not see sewage as a resource, but as wastewater. The order of objective evaluation of water resources should be groundwater, surface water, urban reuse of sewage, and finally long-distance water diversion. Planning department in the future, while planning and evaluating the construction of the project, the water resources part should be added to the possibility of urban sewage reuse, otherwise it is not perfect. ② On the operating costs and charging policy of sewage reuse. The cost of secondary treatment of general municipal wastewater, according to the traditional activated sludge method, the cost of treatment is 0.33 yuan / m3 water (not counting depreciation). If as a source of industrial cooling water, there is still a need for additional treatment, in accordance with the general conventional treatment, coagulation and precipitation (lime method), filtration, disinfection, the treatment cost of 0.13 yuan / m3 of water (not counting depreciation). The total price of the last 1m3 of water reuse is 0.46 yuan, which is lower than the current tap water selling price of 1.5 yuan / m3 (residential water, industrial water prices are higher). But there is also a calculation method, the cost of secondary treatment 0.33 yuan / m3, not charged to the plant, only the cost of the latter part of the supplementary treatment, only 0.13 yuan / m3, which has a greater attraction to the plant, its price policy has played a role in encouraging the reuse of the role of this means that the implementation of the national financial support policy for the city's wastewater treatment. ③ Strengthen the scientific research and technical exchange of sewage treatment and reuse. Sewage reuse is a complex technical subject, including municipal wastewater treatment and a variety of industrial wastewater treatment involves technical problems are also very complex, such as equipment corrosion problems, microbial scaling problems ....... In order to reduce the occurrence of technical accidents and maintain the reputation of water reuse, it is necessary to carry out in-depth experimental research on the subject of water reuse technology, establish a national academic organization (Wastewater Reuse Association), under the leadership of the relevant professional committees of the Institute for academic exchanges, technical and economic policy analysis, participation in the water resources planning of major cities, coordination of scientific research and design tasks, and improve the exchange of domestic and international technical information for the leadership of the decision-making process. Provide reference.8.5.3 Make full use of rainwater resources
To achieve the sustainable use of water resources, in addition to the necessary water conservation measures, but also must actively explore the development of new water sources, such as the use of torrential rainfall floods - flood water resource utilization. Flood resourcing refers to the case of no disaster, try to use water conservation projects, reservoir barrage dams, natural depressions, artificial lakes, underground reservoirs and other water storage projects to intercept the flood, as well as to extend the retention time of the flood in the river, flood storage area, etc., to restore the water surface of the rivers and lakes, depressions, the water surface of the landscape, the human living environment, and to maximize the possibility of replenishment of groundwater [11]. Scientific and reasonable utilization of flood resources can obtain certain socio-economic benefits, such as replenishing surface water and groundwater resources, improving ecological environment, improving regional water resources carrying capacity, playing the role of multi-year regulation of reservoirs, carrying out aquaculture and irrigation, and tourism. Therefore, flood resource utilization and rainwater reuse can not only play a role in disaster mitigation, but also replenish water resources, so that water resources can be recycled to improve the regeneration capacity of water resources, and alleviate the contradiction between supply and demand of water.
Flooding is a precondition for the formation of floods, but floods are not disasters, it is the atmospheric precipitation in a short period of time into the trough and the formation of large runoff, its nature has the properties of freshwater resources. Floods as a resource, reasonable storage, utilization, not only can alleviate the serious shortage of freshwater in China, but also effectively play the role of "flood prevention and mitigation", to promote the elimination of harm, two birds with one stone. Li Changan et al [18] put forward four measures: ① strengthen the construction of reservoirs; ② return fields to the lake and fallow and wet; ③ artificial control of the lake; ④ full use of reservoirs, lakes and wetlands to store the flood water of the Yangtze River during the flood season for the northward transfer in the dry season. Due to China's special geographical location, precipitation inter-annual and intra-annual distribution is extremely uneven, often droughts and floods occur at the same time in different places and the same place continues to occur. Correctly handle the relationship between economic development and water, must be combined with flood control and drought, from the flood resource utilization. Literature [19] puts forward suggestions in three aspects: ① establish reservoirs and lakes risk scheduling mechanism; ② give full play to the role of river flood storage (Beijing and Jiaodong have successful examples); ③ establish basin or cross-basin flood utilization measures (river cascade and social security system for flood utilization, etc.). In mountainous areas, the development and utilization of rain and flood resources can be combined with soil and water conservation, such as the construction of slope water system projects (along the mountain drainage ditches, storage ponds, sand retention ponds, ponds and dams, etc.) and water cellar projects [20].
Rainwater reuse is also a new way of water resources development. It is characterized by light water quality pollution, low construction costs, and has a wide range of roles. Rainwater reuse can improve the natural water cycle, improve the urban ecological environment, slow down urban flooding, reduce the pressure of the construction and operation of urban drainage systems, and replenish groundwater resources. In short, rainwater reuse has a wide range of application prospects in urban industry, civil and other aspects [12].
References
[1] Zeng Weihua, Yang Zhifeng, Jiang Yong. Ruminations on the renewable capacity of water resources[J]. Advances in Water Science, 2001,12(2):276-279
[2]Li Chunhui, Yang Zhifeng. Social renewability of water resources and its basic theory[J]. China Population-Resources and Environment, 2004,14(6):54-55
[3]Yang ZF, Shen ZY, Xia XH et al. Basic theory of water resources renewability and its application in the Yellow River Basin[J]. China Basic Science-State Key Basic Research Program, 2002,5:5～6
[4]Feng Shangyou. Introduction to the Sustainable Utilization and Management of Water Resources [M]. Beijing: Science Press, 2000.7:3
[5]Guo Qishang, ed. Report on comprehensive planning of river basin (regional) in Meizhou City, Guangdong Province [R]. Meizhou City Water Resources Bureau, 2000.6:60-63,158
[6]Zhao XN, Wu PT, Wang WZ et al. Research on water demand of ecological environment[J]. Advances in Water Science, 2005,16(4):618
[7]Li Guanghe. Water Resources Utilization and Protection [M]. Beijing: China Construction Industry Press, 2002.6:13-14
[8]Shen Zhenyao, Yang Zhifeng, Liu Changming. Natural renewable capacity of water resources and its relationship with renewal rate[J]. Geoscience, 2002,22(2):162～165
[9]Ding Xiaowen, Shen Zhenyao, Yang Zhifeng. Evaluation of social renewability of water resources in typical cities in the Yellow River Basin[J]. Arid Zone Resources and Environment, 2005,19(1):72-73
[10]KONG Qingyu, BIAN Yijie. Research on sustainable development of water resources in Guangdong[J]. Guangdong Water Resources and Hydropower, 2000,12(6):33～36
[11]Guan Yanhai, Wei Zhanqi. Mitigation of regional water shortage and flood resourceization[J]. Jilin Water Resources, 2003,4:19-20
[12]Hou JT, Zhu DL. Rainwater reuse[J]. Science and Technology Garden, 2003,2:30～31
[13]Wang Zhonggen, Xia Jun, Liu Changming et al. Research on quantification method of water resource quantity renewability[J]. Resource Science, 2003,(7):31-36
[14]Ke Li-lian. Starting a revolution to improve water use efficiency--Talking about China's water resources strategic issues in the 21st century[J]. Groundwater, 1999,(12):141-145
[15]Chen Shaojin. Analysis of Agricultural Water Use Efficiency in Southern Region[J]. People's Yangtze River, 2004,(1):46～48
[16]Liu Gengxiao. Water-Water Resources-Water Saving in Agriculture[J]. China Engineering Science, 2000,(7):39～42
[17]Song Xu-Tong, Xu Jun-Yi. Analysis of urban water use development and water use efficiency in China[J]. Construction Science and Technology, 2004,(6):40~41
[18]Li Changan, Yin Hongfu. Fully recognizing and utilizing the freshwater resource attributes of floodwater--one of the ways to solve the shortage of freshwater resources in China[J]. Science and Technology Herald, 2001,(7):3-5
[19]Hu Wei. Making full use of flood resources and trying to solve the water shortage problem[J]. China Water Resources, 2001,(4):88
[20]Xu Xianghuai. Development and utilization of flood resources in mountainous areas[J]. Rule of Huaihuai, 2002(10)