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引用本文:周建军,杨倩,张曼.长江上游水库群的热环境效应与修复对策.湖泊科学,2019,31(1):1-17. DOI:10.18307/2019.0101
ZHOU Jianjun,YANG Qian,ZHANG Man.Thermal-effect of the upper Yangtze reservoirs and countermeasures. J. Lake Sci.2019,31(1):1-17. DOI:10.18307/2019.0101
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长江上游水库群的热环境效应与修复对策
周建军, 杨倩, 张曼
清华大学水利系, 北京 100084
摘要:
本文根据实测资料揭示三峡水库运行以来冬季下泄水温抬高5.32℃、夏初降低3.45℃、过程滞后30~43天,三峡水库冬季水温平均高于气温10℃,且随水库蓄水位和上游水库增加不断升高.长江是罕见的从高热河源流向低热潮湿地区的世界大河,干流三峡等大型水库流量大、库容大且基本没有温度分层,水库滞热、散热和下泄热量巨大,下游水温改变范围超过汉口.需要重视的两个宏观效应:一是超温大幅降低水库和下游水溶解氧(DO),影响程度已与长江平均化学需氧量(COD)等污染同数量级,加上加速COD等耗氧,水温升高的污染危害更大;二是水库冬季巨大散热,11-1月库区平均散热强度241 W/m2、总热功率2.43亿kW,下泄潜在热量3.16亿kW、超过天然1.73亿kW,水库散发和下泄热量相当于全国平均用电功率.2030年上游水电按规划全面建成后,冬季上游水库群还将附加吸热2亿kW(年热量2万亿kWh).DO是大坝对天然河流环境改变的重要方面,三峡支流库区现在连年水华、干流出现缺氧,水温升高进一步降低DO浓度和促进环境耗氧是当前库区和下游生态环境的主要问题之一.冬季干热河谷输出热水、2030年后更多梯级水库吸热并通过河流转移到三峡水库,巨大附加散热量对周边环境、水资源、土壤墒情和局部气候影响需要认真研究.建议在干热河谷梯级水库大规模布局水面光伏(PPV).一方面遮挡短波辐射抑制下游三峡入库水温进一步升高,另一方面利用梯级水电巨大储能、调节优势与光伏资源,互补互助、集约和大规模开发西南可再生能源与电力调节资源.本文研究显示PPV电量巨大和结构优势明显,是改善我国电力能源结构和提升水电的发展方向,还可带动更多绿色发展.
关键词:  水温  热效应  环境  修复  水面光伏  梯级水库  长江
DOI:10.18307/2019.0101
分类号:
基金项目:国家重点研发计划项目(2016YFE0133700)和国家自然科学基金项目(51509137)联合资助.
Thermal-effect of the upper Yangtze reservoirs and countermeasures
ZHOU Jianjun, YANG Qian, ZHANG Man
Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, P. R. China
Abstract:
In this paper, we use observational data to reveal that water temperature (T) discharging from the Three Gorges reservoir (TGR) downstream has been increased in excess of 5.3℃ in winters, and delayed by 30-43 days with the pool T exceeding the local air by 10℃ when comparing with the pre-impoundment situation. This fact is likely caused by the thermal effect of TGR and other reservoirs upstream, aggravation with the increasing impoundments upstream. Due to the enormous flow discharge, storage and well-mixed in the warmed pool, quantity of the modified heat is so huge that T change can extend over 690 km. Two effects should be listed as prior environmental issues currently:1) the effect on dissolved oxygen (DO) in the pool and downstream, which is probably lowered by a magnitude comparable to the level of the chemical oxygen demand of the Yangtze and 2) the effect of the additional heat released from the pool and discharged downstream of TGR in winter, which is estimated to be 243 GW (241 W/m2 in density) and 173 GW in average in Nov.-Jan. (2014-2016). In addition, another 200 GW heat is going to be trapped by pools that are planned to be impounded before 2030 upstream in the hot-valleys through water absorption of solar radiation, which will also a stressing forcing of warming for the TGR in the future. DO is known as a key eco-property for surface waters. At present, harmful algal blooms constantly occur in the tributary pools, and hypoxia has already been observed in 2014 in the main pool of the TGR. The declining environmental status warns us to take the increasing pool T and associated DO depression as prior issue in the Yangtze River environment protection. On the other hand, as the Yangtze is unique in world large rivers that originates from warmer and intensive solar radiation valleys to an artificial mainstream mega pool in dimming and humid basin with the storing and detention of huge heat induced from the upstream pools on water quality and local evapotranspiration, soil moisture and climate should thus deserve to be listed as key investigation. As a countermeasure, we suggest to restore the increasing thermal effect by installing pool photovoltaic power (PPV) in upstream hot-valleys. Except for inhibiting additional heat absorption, the PV in combination with the installing power and regulation advantages of the cascaded hydro power in southwest China can also produce significant renewable electricity and regulation facilities that are urgently desired by the coal dominant power system of China.
Key words:  Water temperature  thermal-effect  environment  restoration  pool photovoltaic power (PPV)  cascade reservoirs  Yangtze River
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