国际自然资源管理论文--国际水资源管理策略.pdf

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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 forpublication of original contributions and the exchange of knowledge and experience onthe management of water resources.In particular,the journal publishes contributions onwater resources assessment

2、,development,conservation and control,emphasizingpolicies and strategies.Contributions examine planning and design of water resourcesystems,and operation,maintenance and administration of water resource systems.Key words:water resource managment,issues,stratsgies.There is a water crisis today.But th

3、e crisis is not only about having little water to satisfy.Itis a crisis of managing water resources.Water resource managment issues and strategiesare what will be discussed in the following context.1.Water resources are becoming scarce1.1 Agricultural crisis1.1 Agricultural crisisAlthough food secur

4、ity has been significantly increased in the past thirty years,waterwithdrawals for irrigation represent 66%of the total withdrawals and up to 90%in aridregions,the other 34%being used by domestic households(10%),industry(20%),orevaporated from reservoirs(4%).(Source:Shiklomanov,1999)As the per capit

5、a use increases due to changes in lifestyle and as population increasesas well,the proportion of water for human use is increasing.This,coupled with spatial andtemporal variations in water availability,means that the water to produce food for humanconsumption,industrial processes and all the other u

6、ses is becoming scarce.1.21.2Environmental crisisEnvironmental crisisIt is all the more critical that increased water use by humans does not only reduce theamount of water available for industrial and agricultural development but has a profoundeffect on aquatic ecosystems and their dependent species

7、.Environmental balances aredisturbed and cannot play their regulating role anymore.Water stress results from animbalance between water use and water resources.Water stress causes deterioration offresh water resources in terms of quantity(aquifer over-exploitation,dry rivers,etc.)andquality(eutrophic

8、ation,organic matter pollution,saline intrusion,etc.)The value of thiscriticality ratio that indicates high water stress is based on expert judgment andexperience.It ranges between 20%for basins with highly variable runoff and 60%fortemperate zone basins.In this map,we take an overall value of 40%to

9、 indicate highwater stress.We see that the situation is heterogeneous over the world.1.31.3An increase in tensionsAn increase in tensionsAs the resource is becoming scarce,tensions among different users may intensify,both atthe national and international level.Over 260 river basins are shared by two

10、 or morecountries.In the absence of strong institutions and agreements,changes within a basincan lead to transboundary tensions.When major projects proceed without regionalcollaboration,they can become a point of conflicts,heightening regional instability.TheParana La Plata,the Aral Sea,the Jordan a

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

12、tainty is how climates will change and how they will be affected by mans activitieslike 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,andwhat changes will occur where.The main conclusion

13、 so far seems to be that climatechanges(natural and anthropogenic)are likely,that they are essentially unpredictable ona local scale,and that,therefore,water resources management should be flexible so as tobe able to cope with changes in availability and demands for water.This calls forintegrated wa

14、ter management where all pertinent factors are considered in the decisionmaking process.Such a holistic approach requires not only supply management,but alsodemand management(water conservation,transfer of water to uses with higher economicreturns,etc.),water quality management,recycling and reuse o

15、f water,economics,conflict resolution,public involvement,public health,environmental and ecologicalaspects,socio-cultural aspects,water storage(including long-term storage or waterbanking),conjunctive use of surface water and groundwater,water pollution control,flexibility,regional approaches,weathe

16、r modification,sustainability,etc.Agricultural watermanagement increasingly must be integrated with other water management andenvironmental objectives.The main issues discussed in this paper are global wateroutlook,underground storage of water through artificial recharge,water reuse,non-pointsource

17、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 crisisto be worsening.There is a increasing awareness that our freshwater resources arelimited and need to be protected both in terms o

18、f quantity and quality.This waterchallenge affects not only the water community,but also decision-makers and everyhuman being.Water is everybodys business was one the the key messages of the 2ndWorld Water Forum.3.13.1Saving water resourcesSaving water resourcesWhatever the use of freshwater(agricul

19、ture,industry,domestic use),huge saving of waterand 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 anobvious and natural thing.With urbanization and changes in lifestyle,water consumption

20、is bound to increase.However,changes in food habits,for example,may reduce theproblem,knowing that growing 1kg of potatoes requires only 100 litres of water,whereas1 kg of beef requires 13 000 litres.There are several ways in the following.3.1.13.1.1Water storage via artificial recharge and water ba

21、nkingWater storage via artificial recharge and water bankingFuture climatic changes may also include more weather extremes,like more periods withexcessive rainfall and more periods with low rainfall that cause droughts.Also,in relativelydry climates,small changes in precipitation can cause significa

22、nt changes in naturalrecharge 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 buildwater reserves during times of water surplus for use in times of water shortage.Traditionally,such storage ha

23、s been achieved with dams and surface reservoirs.However,good dam sites are getting scarce and dams have a number of disadvantages likeinterfering with the stream ecology,adverse environmental effects,displacement ofpeople for new dams,loss of scenic aspects and recreational uses of the river,increa

24、sedwaterborne diseases and other public health problems,evaporation losses(especiallyundesirable for long-term storage),high costs,potential for structural problems and failure,and no sustainability since all dams eventually lose their capacity as they fill up withsediments(Pearce,1992 and Postel,19

25、99 and references therein).For these reasons,new dams are increasingly difficult to construct,except in some countries(mostly ThirdWorld)where the advantages of abundant and cheap hydro-electric power outweigh thedisadvantages of dams.In the US,several dams have already been breached and moreare sch

26、eduled for destruction,mostly for ecological and environmental reasons.If water cannot be stored above ground,it must be stored underground,via artificialrecharge of groundwater.Considering that more than 98%of th e worlds fresh liquid watersupplies already occurs underground,there is plenty of room

27、 for more.Artificial rechargeis achieved by putting water on the land surface where it infiltrates into the soil and movesdownward to underlying groundwater(Bouwer and Bouwer,1999).Such systems requirepermeable soils(sands and gravels are preferred)and unconfined aquifers with freelymoving groundwat

28、er tables.Infiltration rates typically range from 0.5 to 3 m per day duringflooding.With continued flooding,however,suspended particles in the water accumulateon the soil surface to form a clogging layer that reduces infiltration rates.Biological actionsfurther aggravate the clogging.Thus,infiltrati

29、on systems must be periodically dried toallow drying,cracking,and,if necessary,mechanical removal of the clogging layer.Taking drying periods into account,long-term infiltration rates for year round operation ofsurface recharge systems may be in the range 100400 m per year.Distinction is made betwee

30、n in-channel and off-channel infiltration systems.In-channelsystems consist of low dams across the stream bed or of T or L shaped levees in thestream bed to back up and spread the water so as to increase the wetted area and,hence,infiltration in the stream bed.Off-channel systems consist of speciall

31、y constructed shallowponds or basins that are flooded for infiltration and recharge.Where stream flows arehighly variable,upstream storage dams or deep basins may be necessary to captureshort-duration high-flow events for subsequent gradual release into recharge systems.Also,recharge systems can be

32、designed and managed to enhance environmentalbenefits(aquatic parks,trees and other vegetation,wildlife refuges,etc.).Since sand and gravel soils are not always available,less permeable soils like loamysands,sandy loams,and light loams are increasingly used for surface infiltration rechargesystems.S

33、uch systems may have infiltration rates of only 3060 m per year,for yearround operation.Thus,relative evaporation losses are higher and in warm,dry climatescould be about 36%of the water applied,as compared to about 1%for basins in morepermeable soils.Systems in finer textured soils also require mor

34、e land for infiltrationbasins.However,the larger land requirements enhance the opportunity for combining therecharge project with environmental and recreational amenities.Where sufficiently permeable soils are not available or surface soils are contaminated,artificial recharge also can be achieved v

35、ia infiltration trenches or recharge pits or shafts(Bouwer and Bouwer,1999).If the aquifers are confined,i.e.between layers of lowpermeability,artificial recharge can be achieved only with recharge or injection wellsdrilled into the aquifer.The cost of such recharge often is much higher than the cos

36、t ofinfiltration with basins because wells can be expensive and the water must first be treatedto essentially remove all suspended solids,nutrients,and organic carbon to minimizeclogging of the well-aquifer interface.Since such clogging is difficult to remove,preventionof clogging by adequate pretre

37、atment of the water and frequent pumping of the well isbetter than well remediation.Increasingly,recharge wells are constructed as dual purposewells for both recharge and abstraction to allow recharge when water demands are lowand surplus water is available(i.e.during the winter),and pumping when wa

38、ter demandsare high like in the summer.Such storage and recovery(SAR)wells are used formunicipal water supplies so that water treatment plants do not have to meet peakdemands but can be designed and operated for a lower average demand,which isfinancially attractive(Pyne,R.D.G.,1995.Groundwater Recha

39、rge and Wells:A Guide toAquifer Storage and Recovery.Lewis Publishers,Boca Raton,FL.Pyne,1995).The big advantage of underground storage is that there are no evaporation losses fromthe groundwater.Evaporation losses from the basins themselves in continuously operatedsystems may range from 0.5 m per y

40、ear for temperate humid climates to 2.5 m per yearfor hot dry climates.Groundwater recharge systems are sustainable,economical,and donot have the eco-environmental problems that dams have.In addition,algae which cangive water quality problems in water stored in open reservoirs do not grow in groundw

41、ater.Because the underground formations act like natural filters,recharge systems also can beused to clean water of impaired quality.This principle is extensively used as an effectivelow-technology and inexpensive method to clean up effluent from sewage treatmentplants to enable unrestricted and mor

42、e aesthetically acceptable water reuse(see Section4).The systems then are no longer called recharge systems but soil-aquifer treatment(SAT)or geopurification systems.3.1.23.1.2Water reuseWater reuseAll water is recycled through the global hydrologic cycle.However,planned local waterreuse is becoming

43、 increasingly important for two reasons(Bouwer,1993).One is thatdischarge of sewage effluent into surface water is becoming increasingly difficult andexpensive as treatment requirements become more and more stringent to protect thequality of the receiving water for aquatic life,recreation and downst

44、ream users.The costof the stringent treatment may be so high that it becomes financially attractive formunicipalities to treat their water for local reuse rather than for discharge.The secondreason is that municipal wastewater often is a significant water resource that can be usedfor a number of pur

45、poses,especially in water short areas.The most logical reuse is fornon-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 re

46、quires treatment of theeffluent so that it meets the quality requirements for the intended use.Adequateinfrastructures like storage reservoirs,and canals,pipelines,and dual distribution systemsare also necessary so that waters of different qualities can be transported to differentdestinations.Aesthe

47、tics and public acceptance are important aspects of water reuse,especially where the public is directly affected.The best treatment plant processes for unrestricted non-potable reuse are primary andsecondary treatment followed by tertiary treatment consisting of flocculation,sandfiltration and disin

48、fection(ultraviolet irradiation or chlorination)to make sure that theeffluent is free from pathogens(viruses,bacteria,and parasites).Such tertiary effluentcan then be used for agricultural irrigation of crops consumed raw by people or broughtraw into the kitchen,urban irrigation of parks,playgrounds

49、,sports fields,golf courses,road plantings,etc.,urban lakes,fire fighting,toilet flushing,industrial uses,and others.The tertiary treatment requirement was developed in California and is followed by mostindustrialized countries(Bouwer,1993).The California tertiary treatment is relatively high techno

50、logy and expensive and is,therefore,often not doable in Third World countries.To avoid use of raw sewage forirrigation,and to still make such irrigation reasonably safe from a public health standpoint,the World Health Organization(1989)has developed guidelines that are based onepidemiological analys