国际自然资源管理论文--国际水资源管理策略

1、.国际自然资源管理论文-国际水资源管理策略Abstract :Water Resources Management is an international, multidisciplinary forum for publication of original contributions and the exchange of knowledge and experience on the management of water resources. In particular, the journal publishes contributions on water resources as

2、sessment, development, conservation and control, emphasizing policies and strategies. Contributions examine planning and design of water resource systems, and operation, maintenance and administration of water resource systems. Key words:water resource managment ,issues,stratsgies.There is a water c

3、risis today.But the crisis is not only about having little water to satisfy.It is a crisis of managing water resources.Water resource managment issues and strategies are what will be discussed in the following context.1. Water resources are becoming scarce1.1 Agricultural crisisAlthough food securit

4、y has been significantly increased in the past thirty years, water withdrawals for irrigation represent 66 % of the total withdrawals and up to 90 % in arid regions, the other 34 % being used by domestic households (10 %), industry (20 %), or evaporated from reservoirs (4 %). (Source: Shiklomanov, 1

5、999)As the per capita use increases due to changes in lifestyle and as population increases as well, the proportion of water for human use is increasing. This, coupled with spatial and temporal variations in water availability, means that the water to produce food for human consumption, industrial p

6、rocesses and all the other uses is becoming scarce.1.2 Environmental crisisIt is all the more critical that increased water use by humans does not only reduce the amount of water available for industrial and agricultural development but has a profound effect on aquatic ecosystems and their dependent

7、 species. Environmental balances are disturbed and cannot play their regulating role anymore. Water stress results from an imbalance between water use and water resources.Water stress causes deterioration of fresh water resources in terms of quantity (aquifer over-exploitation, dry rivers, etc.) and

8、 quality (eutrophication, organic matter pollution, saline intrusion, etc.) The value of this criticality ratio that indicates high water stress is based on expert judgment and experience . It ranges between 20 % for basins with highly variable runoff and 60 % for temperate zone basins. In this map,

9、 we take an overall value of 40 % to indicate high water stress. We see that the situation is heterogeneous over the world.1.3 An increase in tensionsAs the resource is becoming scarce, tensions among different users may intensify, both at the national and international level. Over 260 river basins

10、are shared by two or more countries. In the absence of strong institutions and agreements, changes within a basin can lead to transboundary tensions. When major projects proceed without regional collaboration, they can become a point of conflicts, heightening regional instability. The Parana La Plat

11、a, the Aral Sea, the Jordan and the Danube may serve as examples. Due to the pressure on the Aral Sea, half of its superficy has disappeared, representing 2/3 of its volume. 36 000 km2 of marin grounds are now recovered by salt.2. The main challengesWhile growing populations and increasing water req

12、uirements are a certainty, a big uncertainty is how climates will change and how they will be affected by mans activities like increasing emissions of CO2 and other greenhouse gases, particulate matter, etc. There still is no agreement among scientists how and when the climate will change, and what

13、changes will occur where. The main conclusion so far seems to be that climate changes (natural and anthropogenic) are likely, that they are essentially unpredictable on a local scale, and that, therefore, water resources management should be flexible so as to be able to cope with changes in availabi

14、lity and demands for water .This calls for integrated water management where all pertinent factors are considered in the decision making process. Such a holistic approach requires not only supply management, but also demand management (water conservation, transfer of water to uses with higher econom

15、ic returns, etc.), water quality management, recycling and reuse of water, economics, conflict resolution, public involvement, public health, environmental and ecological aspects, socio-cultural aspects, water storage (including long-term storage or water banking), conjunctive use of surface water a

16、nd groundwater, water pollution control, flexibility, regional approaches, weather modification, sustainability, etc. Agricultural water management increasingly must be integrated with other water management and environmental objectives. The main issues discussed in this paper are global water outlo

17、ok, underground storage of water through artificial recharge, water reuse, non-point source pollution of groundwater, and virtual water.3.Strategies to impove the situationWith the current state of affairs, correcting measures still can be taken to avoid the crisis to be worsening. There is a increa

18、sing awareness that our freshwater resources are limited and need to be protected both in terms of quantity and quality. This water challenge affects not only the water community, but also decision-makers and every human being. Water is everybodys business was one the the key messages of the 2nd Wor

19、ld Water Forum.3.1 Saving water resourcesWhatever the use of freshwater (agriculture, industry, domestic use), huge saving of water and improving of water management is possible. Almost everywhere, water is wasted, and as long as people are not facing water scarcity, they believe access to water is

20、an obvious and natural thing. With urbanization and changes in lifestyle, water consumption is bound to increase. However, changes in food habits, for example, may reduce the problem, knowing that growing 1kg of potatoes requires only 100 litres of water, whereas 1 kg of beef requires 13 000 litres.

21、There are several ways in the following .3.1.1 Water storage via artificial recharge and water bankingFuture climatic changes may also include more weather extremes, like more periods with excessive rainfall and more periods with low rainfall that cause droughts. Also, in relatively dry climates, sm

22、all changes in precipitation can cause significant changes in natural recharge of groundwater. To protect water supplies against these extremes and changes, more storage of water is needed, including long-term storage (years to decades) to build water reserves during times of water surplus for use i

23、n times of water shortage. Traditionally, such storage has been achieved with dams and surface reservoirs. However, good dam sites are getting scarce and dams have a number of disadvantages like interfering with the stream ecology, adverse environmental effects, displacement of people for new dams,

24、loss of scenic aspects and recreational uses of the river, increased waterborne diseases and other public health problems, evaporation losses (especially undesirable for long-term storage), high costs, potential for structural problems and failure, and no sustainability since all dams eventually los

25、e their capacity as they fill up with sediments (Pearce, 1992 and Postel, 1999 and references therein). For these reasons, new dams are increasingly difficult to construct, except in some countries (mostly Third World) where the advantages of abundant and cheap hydro-electric power outweigh the disa

26、dvantages of dams. In the US, several dams have already been breached and more are scheduled for destruction, mostly for ecological and environmental reasons.If water cannot be stored above ground, it must be stored underground, via artificial recharge of groundwater. Considering that more than 98%

27、of the worlds fresh liquid water supplies already occurs underground, there is plenty of room for more. Artificial recharge is achieved by putting water on the land surface where it infiltrates into the soil and moves downward to underlying groundwater (Bouwer and Bouwer, 1999). Such systems require

28、 permeable soils (sands and gravels are preferred) and unconfined aquifers with freely moving groundwater tables. Infiltration rates typically range from 0.5 to 3 m per day during flooding. With continued flooding, however, suspended particles in the water accumulate on the soil surface to form a cl

29、ogging layer that reduces infiltration rates. Biological actions further aggravate the clogging. Thus, infiltration systems must be periodically dried to allow drying, cracking, and, if necessary, mechanical removal of the clogging layer. Taking drying periods into account, long-term infiltration ra

30、tes for year round operation of surface recharge systems may be in the range 100400 m per year.Distinction is made between in-channel and off-channel infiltration systems. In-channel systems consist of low dams across the stream bed or of T or L shaped levees in the stream bed to back up and spread

31、the water so as to increase the wetted area and, hence, infiltration in the stream bed. Off-channel systems consist of specially constructed shallow ponds or basins that are flooded for infiltration and recharge. Where stream flows are highly variable, upstream storage dams or deep basins may be nec

32、essary to capture short-duration high-flow events for subsequent gradual release into recharge systems. Also, recharge systems can be designed and managed to enhance environmental benefits (aquatic parks, trees and other vegetation, wildlife refuges, etc.).Since sand and gravel soils are not always

33、available, less permeable soils like loamy sands, sandy loams, and light loams are increasingly used for surface infiltration recharge systems. Such systems may have infiltration rates of only 3060 m per year, for year round operation. Thus, relative evaporation losses are higher and in warm, dry cl

34、imates could be about 36% of the water applied, as compared to about 1% for basins in more permeable soils. Systems in finer textured soils also require more land for infiltration basins. However, the larger land requirements enhance the opportunity for combining the recharge project with environmen

35、tal and recreational amenities.Where sufficiently permeable soils are not available or surface soils are contaminated, artificial recharge also can be achieved via infiltration trenches or recharge pits or shafts (Bouwer and Bouwer, 1999). If the aquifers are confined, i.e. between layers of low per

36、meability, artificial recharge can be achieved only with recharge or injection wells drilled into the aquifer. The cost of such recharge often is much higher than the cost of infiltration with basins because wells can be expensive and the water must first be treated to essentially remove all suspend

37、ed solids, nutrients, and organic carbon to minimize clogging of the well-aquifer interface. Since such clogging is difficult to remove, prevention of clogging by adequate pretreatment of the water and frequent pumping of the well is better than well remediation. Increasingly, recharge wells are con

38、structed as dual purpose wells for both recharge and abstraction to allow recharge when water demands are low and surplus water is available (i.e. during the winter), and pumping when water demands are high like in the summer. Such storage and recovery (SAR) wells are used for municipal water suppli

39、es so that water treatment plants do not have to meet peak demands but can be designed and operated for a lower average demand, which is financially attractive ( Pyne, R.D.G., 1995. Groundwater Recharge and Wells: A Guide to Aquifer Storage and Recovery. Lewis Publishers, Boca Raton, FL.Pyne, 1995).

40、The big advantage of underground storage is that there are no evaporation losses from the groundwater. Evaporation losses from the basins themselves in continuously operated systems may range from 0.5 m per year for temperate humid climates to 2.5 m per year for hot dry climates. Groundwater recharg

41、e systems are sustainable, economical, and do not have the eco-environmental problems that dams have. In addition, algae which can give water quality problems in water stored in open reservoirs do not grow in groundwater. Because the underground formations act like natural filters, recharge systems

42、also can be used to clean water of impaired quality. This principle is extensively used as an effective low-technology and inexpensive method to clean up effluent from sewage treatment plants to enable unrestricted and more aesthetically acceptable water reuse (see Section 4). The systems then are n

43、o longer called recharge systems but soil-aquifer treatment (SAT) or geopurification systems.3.1.2 Water reuseAll water is recycled through the global hydrologic cycle. However, planned local water reuse is becoming increasingly important for two reasons (Bouwer, 1993). One is that discharge of sewa

44、ge effluent into surface water is becoming increasingly difficult and expensive as treatment requirements become more and more stringent to protect the quality of the receiving water for aquatic life, recreation and downstream users. The cost of the stringent treatment may be so high that it becomes

45、 financially attractive for municipalities to treat their water for local reuse rather than for discharge. The second reason is that municipal wastewater often is a significant water resource that can be used for a number of purposes, especially in water short areas. The most logical reuse is for no

46、n-potable purposes like agricultural and urban irrigation, industrial uses (cooling, processing), environmental enhancement (wetlands, wildlife refuges, riparian habitats, urban lakes), fire fighting, dust control, toilet flushing, etc. This requires treatment of the effluent so that it meets the qu

47、ality requirements for the intended use. Adequate infrastructures like storage reservoirs, and canals, pipelines, and dual distribution systems are also necessary so that waters of different qualities can be transported to different destinations. Aesthetics and public acceptance are important aspect

48、s of water reuse, especially where the public is directly affected.The best treatment plant processes for unrestricted non-potable reuse are primary and secondary treatment followed by tertiary treatment consisting of flocculation, sand filtration and disinfection (ultraviolet irradiation or chlorin

49、ation) to make sure that the effluent is free from pathogens (viruses, bacteria, and parasites). Such tertiary effluent can then be used for agricultural irrigation of crops consumed raw by people or brought raw into the kitchen, urban irrigation of parks, playgrounds, sports fields, golf courses, r

50、oad plantings, etc., urban lakes, fire fighting, toilet flushing, industrial uses, and others. The tertiary treatment requirement was developed in California and is followed by most industrialized countries (Bouwer, 1993).The California tertiary treatment is relatively high technology and expensive

51、and is, therefore, often not doable in Third World countries. To avoid use of raw sewage for irrigation, and to still make such irrigation reasonably safe from a public health standpoint, the World Health Organization (1989) has developed guidelines that are based on epidemiological analyses of docu

52、mented disease outbreaks and that are achievable with low-technology treatment such as in-series lagooning with long detention times (about 1 month). While this treatment does not produce pathogen-free effluent, epidemiological studies have indicated that use of such effluent for irrigation of crops

53、 consumed raw greatly reduces health risks. As a precaution, however, the vegetables and fruit grown with such effluent should only be consumed raw by the local people that hopefully have developed some immunity to certain pathogens. Tourists and other visitors from the outside should not eat the lo

54、cal raw fruits and vegetables, and the produce should not be exported to other markets. Also, the lagooning treatment must be viewed as a temporary solution and full tertiary treatment plants should be built as soon as possible, especially when the lagoons become overloaded, detention times become t

55、oo short for adequate pathogen removal, and the lagoon system cannot be deepened or expanded.Additional treatment of secondary or tertiary effluent and lagoon effluent can also be obtained by using the effluent for artificial recharge of groundwater, using the underground formations as natural filte

56、rs (Bouwer; Bouwer and Bouwer, H., 1999. Artificial recharge of groundwater: systems, design, and management. In: Mays, L.W. (Ed.), Hydraulic Design Handbook. McGraw-Hill, New York, pp. 24.124.44 (Chapter 24).Bouwer, 1999). The resulting soil-aquifer treatment greatly enhances the aesthetics of wate

57、r reuse because the purified water comes from wells and not from sewage treatment plants and, hence, has lost its identity as treated sewage. Water after SAT also is clear and odorless. SAT is especially important in countries where there are social or religious taboos against direct use of unclean

58、water.Potable use of sewage effluent basically is a practice of last resort, although unplanned or incidental potable reuse occurs all over the world where sewage effluent is discharged into streams and lakes that are also used for public water supplies, and where cess pits, latrines, septic tanks,

59、and sewage irrigation systems leak effluent to underlying groundwater that is pumped up again for drinking. In-plant sewage treatment for direct potable reuse requires advanced processes that include nitrogen and phosphorous removal (nitrification/denitrification and lime precipitation), removal of organic carbon compounds (activated carbon adsorption), removal of dissolved organic and inorganic compounds and pathogens by membrane filtration (microfiltration and reverse osmosis), and disinfection. Even w