澜沧江漫湾电站拦沙能力评估

Assessment of sediment trapped by the Manwan Dam on Lancang River

澜沧江干流水文控制站旧州站和戛旧站分别是漫湾水库入库和出库水文站，在水库蓄水前已有28年（1965—1992）同步泥沙观测资料，并且两站年输沙序列具有很好的相关关系，建立此相关关系模型，根据水库蓄水后旧州站逐年输沙量，利用出、入库站在蓄水前建立的相关模型，推求出戛旧站1993—2003年假定未受水库蓄水影响的年输沙量，并与年实测输沙量相减，在不考虑其他环境因素影响情况下，其差值可视为漫湾库区的年淤积量；同时，利用戛旧水文站在漫湾电站建设前后的多年平均输沙量的差值，估算漫湾大坝的拦沙量。分析表明：漫湾大坝的年总拦沙量约为（26．9～28．5）×106t；运行11年共拦截泥沙（295．9～313．5）×10^6t，年拦沙造成的库容损失约为（20．7～21．9）×10^6m^3，至2003年，共损失库容约（227．6～241．2）×10^6m^3，占漫湾总库容的21．5％～22．8％。研究结果可为评估大坝的拦沙能力和环境变化对大坝的生态影响提供初步依据，对漫湾电站运行调度具有一定的参考价值。更可靠的结论，有待于对库区水下地形测量和对比变化分析。

Jiuzhou and Gajiu stations are the two hydrological stations for momitoring input and output sediment of the Manwan Reservoir on Lancang River. There existed 28-year measured sediment data at the stations, and their annual suspended sediment loads correlate well. This relationship was established through regression analysis. After the operation of the Manwan Dam in 1993, the relationship model was used to calculate the natural sediment loads in 1993- 2003 at Gajiu station based on the measured annual sediment load at Jiuzhou station. So the difference between the natural and measured sediment loads at Gajiu station is thought to be the reservoir sedimentation of the Manwan Dam. Calculation results show that annual sediment trapped by the Manwan Dam was about （2.69 - 2.85） × 10^7t, total sedimentation deposited in the reservoir was （29.59 - 31.35） × 10^7t in the period of ll-year operation, annual loss of reservoir capacity was （2.07 - 2.19） × 10^7m^3 , total loss of reservoir capacity was （2.276 -2.412） × 10^8m^3 till 2003, accounting for 21.5% -22.8% of the storage capacity of the Manwan Reservoir. This research could be a reference to assess the impact of hydropower station construction on the downstream sediment variation and the operation of the Manwan Dam in the future.