三峡水库支流回水河段氮磷负荷与干流的逆向影响

 通过分析三峡库区大宁河回水河段氮磷的来源、数量及时空特征,研究三峡水库成库初期和稳定运行期,次级支流回水段受干流的逆向影响.结果表明,成库初期,支流回水段的氮磷分配特征初步呈现干流逆向影响效应,分别有19.05%TN、28.93%TP源于干流倒灌输入;由于干流顶托作用,氮磷呈现具峰值的空间分布特征.在稳定运行期,支流回水段的氮磷来源及数量将明显受干流逆向影响,在其中的藻类适宜生长期,大宁河回水段干流倒灌输入的TN、TP分别高出上游径流输入近3倍、10倍,明显高于成库初期.当运行水位从145m升至175m时,支流回水段纳受干流倒灌输入的TN、TP可分别达15484.99、1185.75t.研究表明,干流逆向影响可能加剧三峡水库水体的富营养化.

Nitrogen and phosphorus loadings in branch backwater reaches and the reverse effects in the main stream in Three Gorges Reservoir

Through analyzing the source, amount and time-space character of NP in the backwater reach of Daning river in Three Gorges Reservoir (TGR) area, the reverse effect of main stream on secondary branch backwater reach at the incipient and stable running periods of TGR formation was studied. At the incipitant period, the NP distribute character of branch backwater reach expressed initially the main stream reverse effect with respectively 19.05%, 28.93% of TN and TP from main stream reverse input. Due to the main stream top support action, N, P expressed possessing space distribution character of peak value. At the stable running period, the N, P source and amount of branch backwater reach should have obvious main stream reverse effect, in which adoptable to algae growth period. The TN, TP of Daning River backwater reach main stream reverse input were almost 3, 10 times higher than the upstream runoff input, higher obviously than incipient period of the reservoir formation. When the water level of TGR rose from 145m to 175m, the TN, TP from main stream reverse input could reach respectively 15484.99t, 1185.75t. The main stream reverse effect could aggravate the eutrophication of TGR water.