金沙江下游流域水沙格局变化研究

金沙江下游水沙变化对梯级水库淤积进程和优化调度有重要的影响，随着大型梯级水库的建设运用，金沙江下游水沙格局发生了显著的变化。本文基于金沙江下游干支流历年实测水沙资料，分析了流域水沙变化过程，提出了不同时段流域水沙格局。从时间上看，金沙江下游干支流径流量年际变化均不大，干流输沙量显著减少；支流雅砻江、龙川江、牛栏江输沙量明显减少，其它支流输沙量没有明显变化趋势。从水沙来源分布上看，不同时期，金沙江干流径流量和流域支流径流量的占比变化不大，金沙江干流、雅砻江和其他支流占比分别为46%、45%和9%左右。而输沙量占比变化显著：1999年以前金沙江、雅砻江和其它主要支流占比分别为40%、36%、24%；在二滩水库蓄水拦沙后的1999—2010年三者的占比分别为61%、13%、26%；金沙江中游梯级水库蓄水拦沙的2013—2020年三者的占比分别为16%、31%、53%。进一步考虑未控区的影响，金沙江干支流水库运行后，来水格局仍未发生明显变化，干流、雅砻江、其他支流和未控区间径流量占比分别为40%、40%、9%和11%。但来沙格局变化显著，水库运行前干流输沙量占比为21%，雅砻江为19%，其他支流为12%，未控区间为48%，水库运行后区间来沙占比明显增大，达到了97%，其中未控区间占比为82%，区间支流占比为15%，未控区间来沙是金沙江下游流域泥沙的主要来源。

Study on the spatial-temporal variations of runoff and sediment in the lower reach of Jinsha River

The variations of the runoff and sediment have a great impact on deposition process and the optimal operation of the large cascade reservoirs in the lower reach of the Jinsha River(LJR).Along with the construction of the large cascade reservoirs, the patterns(space-time) of runoff and sediment have changed significantly in the LJR.Based on the observed hydrological data of main stream and tributaries in the LJR over the years, the variation process of the runoff and sediment were analyzed and the patterns of the runoff and sediment in different periods were proposed.In terms of time line, the annual variations of the runoff coming from the Jinsha River stem, the main tributaries of Yalong River, Longchuan River and Niulan River, as well as the other small tributaries were not remarkable;while the sediment load variation trends of the above-mentioned three source parts were declined significantly, obviously and not so obviously, respectively.In terms of distribution, the proportions of the runoff in the Jinsha River stem, the largest tributaries Yalong River and other tributaries changed little in different periods around 46%, 45% and 9%;while the proportions of the sediment load in these regions changed significantly in different periods.Before 1999, the proportion of the sediment load in the Jinsha River, the Yalong River and other small tributaries were 40%, 36% and 24%;after Ertan Reservoir constructed, which located in Yalong River, from 1999 to 2010, the proportions changed to 61%, 13% and 26%, respectively;while, after the cascade reservoirs in the middle reaches of the Jinsha River constructed from 2013-2020, the proportions were 16%, 31% and 53%, respectively.Furthermore, separating the unobserved area as independent region as concerning, there were no significant changes for the incoming runoff of the LJR neither in different periods of the large reservoirs constructed in the main stream and its tributaries, nor in the distributions of Jinsha River, Yalong River, other tributaries and unobserved area, the proportions of which were around 40%, 40%, 9% and 11%, respectively.On the contrary, the incoming sediment load distribution changes remarkably in different period.Before the reservoirs constructed in 2013, the proportions of the sediment load in the Jinsha River, the Yalong River, other tributaries and the unobserved areas were around 21%, 19%, 12% and 48%.While owing to the reservoir sediment retention of middle Jinsha River, 97% of the sediment load comes from the both sides of the LJR catchment, including 82% from unobserved areas and 15% from the main tributaries.It should be draw the conclusion that, currently, the sediment from the unobserved areas is the main source of sediment at present in the lower reach of Jinsha River.