推荐回答(2个)
【利】
1、防洪
上游筑坝拦水可以调节水流量,降低洪水对中下游的影响,水利工程设施例如大堤还可以防止潮沙和河水对对岸的冲刷,保持水土,对低洼城市具有防洪作用,防止:洪水对农业的伤害。
2、用水
解决地方用水,合理分配水利资源。例如南水北调工程解决了北方缺水问题。也增加水资源承载能力,提高资源的配置效率。
3、航运
大坝蓄水后,使上游河道变宽变深,改善上游航运条件,减少了季节对航运的影响。
4、供电
水力发电是可持续发展的清吉能源,减少燃油,燃煤的使用对环境的污染,如三峡水电站有力的解决了中国南方的能源危机,带动经济的快速增长。
5、旅游
旅游增加周边地区的空(湿度,改善周围植被的生长,促进旅游业。
6、灌溉
如都江堰担负着四川盆地农田的灌溉、成都市企业和城市生活供水。以及防洪、发电、漂水、水产、养殖、林果、旅游、环保等多项目标综合服务,其灌区规模居全国之冠。
【弊】
1、对鱼类的影响
修库筑坝会改变流速、水温、水位等信息,必然会影响到鱼类的产卵和生长。其中一些大坝的建设更是切断了其洄游通道,使得一些鱼类无法产卵而数量明显下降,影响了种群繁殖。
2、泥沙问题
在河流上建坝,阻断了天然河道,导致河道的流态发生变化,进而引发整条河流上下游和河口的水文特征发生改变,这是建坝带来的最大生态问题,会导致了部分悬移质和推移质泥沙逐渐沉淀,造成水库淤积,对泄水建筑物腐蚀,进一步导致自然灾害频繁,土地盐碱化问题,上壤肥力下降,造成大面积土壤的久生盐碱化和沼泽化。
引发地质灾害,包括地震、滑坡、岩崩、泥石流等:多建在断裂带和地质灾变区上的水库,水体聚集,导致地壳结构变化,可能成为诱发地震的条件,如现在三峡工程的最大弊端,齐岳山东北断裂,并很可能引发地震。
利:1、提高了长江中下游的防洪能力,其效益巨大;2、输出强大清洁的水电能源,减少化石能源的消费,极大地减少了环境污染;3、将重庆以下的川江航道加深、加宽,极大地提高了航运能力(年运力已突破1亿吨),而水运是最经济的,因此也减少了环境污染;4、为南水北调中线二期工程提供加大供水的水源;5、提高了中下游枯水期的流量。
弊:1、相对而言的清水下泄会使中下游河床部分下切,造成局部的崩岸、取水高程降低(可采取局部的工程措施解决),河床下切后反过来对行洪是有利的;2、引起水库库区的地质问题,如滑坡(可加强监测或采取工程措施处理)。所谓的诱发汶川地震、改变了大气候,那是外行的无稽之谈。
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