受气候变化、梯级水库运行及支流入汇等多重因素影响,长江攀枝花—宜昌江段水温的时空分布发生了显著变化,其必将对河流生态系统产生深远影响。选择干支流控制性水文站1956—2016年近61 a水温资料,采用归因分析和多尺度对比分析,研究了该江段水温的时空变异特性及沿程分布。结果表明:攀枝花—宜昌江段干流升温趋势明显,而支流岷江受气温变冷带影响,1956—1990年间水温持续下降1 ℃,其后逐渐回暖;年内水温极差逐年减小,减小幅度为0.38~1.46 ℃/(10 a),水温年内过程趋于平坦;梯级水库建设使屏山站和宜昌站下游河道春、夏季水温降低而秋、冬季水温升高,其中4月份与12月份的变化幅度较大,这2个站点在4月份和12月份的水温分别较蓄水前改变-2.6 ℃和4 ℃左右;沿程水温格局总体稳定,即干流攀枝花—屏山江段持续升温超2 ℃;低温、量大(流量占比50%以上)的岷江水入汇,使屏山—朱沱江段水温下降0.6 ℃;嘉陵江高温水与乌江低温水由于流量占比不大,对朱沱—宜昌江段水温影响亦不大。研究成果可为上游梯级水库开展生态调度及建立生态补偿机制等提供科学依据。

Affected by multiple factors such as climate change, cascade reservoir operation, and tributary influx, the temporal and spatial distribution of water temperature in the segment of the Yangtze River from Panzhihua to Yichang has changed remarkably, which will surely have a profound impact on the river ecosystem. The water temperature data in nearly 60 years(1956-2016) of typical hydrological stations in mainstream and tributary were selected for analysis. The characteristics of spatial-temporal variation and distribution of water temperature along this segment were studied by using attribution analysis and multi-scale comparative analysis. Results revealed an apparent warming trend in the mainstream of Panzhihua-Yichang segment, while in the tributary Minjiang River, as affected by air temperature, the water temperature underwent a continuous drop by 1 ℃ between 1956 and 1990, and then gradually recovered. The range of the water temperature during a year decreased annually, with a declining range of 0.38-1.46 ℃ per decade, which means that the process of water temperature during a year tends to flatten. The construction of cascade reservoirs reduced the water temperature in the downstream rivers in spring and summer while increased in autumn and winter at Pingshan and Yichang stations. The changes in April and December after the impoundment were the largest, amounting to -2.6 ℃ and 4 ℃, respectively. The distribution pattern of water temperature along the stream was generally stable: the water temperature of the Panzhihua-Pingshan segment increased ceaselessly by 2 ℃; affected by large amount of low-temperature water (occupying over 50% of the discharge) from the Minjiang River, the water temperature of the Pingshan-Zhutuo segment dropped by 0.6 ℃; the high-temperature water in the Jialing River and the low-temperature water in the Wujiang River have little impact on the water temperature of the Zhutuo-Yichang segment due to small proportion of discharge.