大通河流域水能水资源开发对河流水文过程和环境的影响

根据水文观测和引水与水电开发资料，分析了大通河流域水能水资源开发利用现状及其对河流水文过程与生态环境的影响.结果表明：由于区域用水和跨流域引水，使大通河中下游河道的水量减少，水环境容量减小，其中，青石嘴、天堂、连城(二)站3-11月平均流量分别减少0.6%~9.6%、0.5%~3.8%、1.7%~52.9%. 自1994年引大入秦工程建成跨流域引水后，连城(二)站年径流量开始减少，1994-2010年平均径流量比1977-1993年减少了5.7%；引大济湟工程建成通水后，加上引大入秦和引硫济金工程，引水总量将达到12.33×10⁸ m³，占大通河多年平均径流量28.16×10⁸ m³的43.8%，对河川径流的影响十分显著. 至2011年，大通河上已建成梯级电站34座，洪水期电站同时泄水会瞬间加大河道流量，枯水期蓄引水又使减水河段水量减少. 梯级水电站群无序蓄放水使洪水过程由天然的平稳状态转变为人工干预的剧烈变化状态，上下游洪峰不对应，对下游地区的防洪安全产生极大威胁. 过度的水能水资源开发，使大通河中下游部分自然河段出现淹没、断流，水生物和两岸的植物萎缩，水环境污染加重，对生态环境产生负面影响. 建议实行流域水资源统一管理，对梯级电站下泄水量统一调度，在减水河段预留必须的生态基流，确保河道内外生态用水；加强河道水位、流量、泥沙、水环境、水生物监测，为流域防汛、水资源管理、生态环境保护等提供决策依据.

Impact of Hydropower and Water Resources Development on Hydrological Processes and Ecology in the Datong River Basin

The Datong River basin is in the water resources forming region in the upper reaches of the Yellow River, where there are rich hydropower resources, good natural vegetation and biology, but the environment is very vulnerable owing to climate change and human activity. The hydropower and water resources development status of the basin is analyzed. It is believed that water quantity in the middle and lower reaches is decreasing caused by regional water use and inter-basin water diversion. Water environment capacity is reducing as well. Average discharge at Qingshizui, Tiantang, Liancheng (Ⅱ) hydrology stations decreases 0.6%-9.6%, 0.5%-3.8% and 1.7%-52.9% from March to November, respectively. Water use at the upper Tiantang station is less, but it becomes larger from Tiantang station to Liancheng station, with an average runoff flow reducing of 5.7% in 1994-2010 as compared with that in 1977-1993. To 2011, 34 cascade hydropower stations have been built, of which there are 30 of diversion type and 4 of gate dam type. With less capacity and no storage capacity, in flood period hydropower stations drain water at the same time, which will enlarge river discharge instantly; in low-water period, storage and diversion will reduce the discharge of water, greatly affecting river flow. For disordered storage and drainage of cascade hydropower stations, the flood process changes from natural steady status to artificial intervention status, and the flood peak in upper reaches and lower reaches is inconsistent, as a result, hydrological monitoring and flood forecasting are greatly troubled, which threaten flood control in downstream area. The submergence, discontinuous flow, shrinking of aquatic organisms and plants in both banks and heavier water environment pollution in the middle and lower reaches resulted from excessive hydropower and water resources development negatively impact environment. It is suggested to carry out integrated water resources management, unified control water discharge of cascade hydropower stations, reserve necessary ecological base flow, insure ecological water use, strengthen monitoring of river level, runoff, sediment, water environment and aquatic organisms, in order to provide policy decision basis for river basin flood control, water resources management and environment protection.