• 关键词：三峡水库  香溪河  神农溪  水质指数(WQI)  水质评估  水体倒灌

• 基金项目：国家重点研发计划（No.2017YFC0404702）；国家自然科学基金（No.51909135，51779128）

• 田盼
• 1. 三峡大学水利与环境学院, 宜昌 443002;2. 中国环境科学研究院国家长江生态环境保护修复联合研究中心, 北京 100012

• 王丽婧
• 中国环境科学研究院国家长江生态环境保护修复联合研究中心, 北京 100012

• 宋林旭
• 三峡大学水利与环境学院, 宜昌 443002

• 纪道斌
• 三峡大学水利与环境学院, 宜昌 443002

• 李亚莉
• 三峡大学水利与环境学院, 宜昌 443002

• 李虹
• 中国环境科学研究院国家长江生态环境保护修复联合研究中心, 北京 100012

• 李莹杰
• 中国环境科学研究院国家长江生态环境保护修复联合研究中心, 北京 100012

• 赵星星
• 三峡大学水利与环境学院, 宜昌 443002

• 成再强
• 三峡大学水利与环境学院, 宜昌 443002

• 杨凡
• 1. 三峡大学水利与环境学院, 宜昌 443002;2. 中国环境科学研究院国家长江生态环境保护修复联合研究中心, 北京 100012

• 摘要：为探究三峡水库特殊调度运行模式下支流水质分布特征及其主要影响因素，以库区一级支流香溪河和神农溪为例，于2018年7月（汛期）和10月（蓄水期）现场采样分析，利用水质指数（WQI）法进行水质评估和水质特征分析，并综合三维水动力观测资料、干支流水量交换分析识别水质变化的驱动因素.结果表明：①影响香溪河和神农溪WQI的主要参数为TN、NH₄⁺-N，且两支流WQI在7月为63~69，水质一般；10月为74~82，水质良好.水质在10月显著好于7月（p<0.01），两支流间的WQI无显著差异（p>0.05）；另外，WQI在中间段要大于近河口和近上游段.②长江干流倒灌水体对支流水质的好坏起主导作用.汛期倒灌强度小但倒灌水体营养盐浓度较大，会增加支流营养盐浓度；蓄水期倒灌强度大但倒灌水体营养盐浓度较小，会稀释支流营养盐浓度.③支流流域面源污染协同加剧支流水质污染.汛期降雨驱动了面源污染的增加，在多因素共同作用下支流库湾TN、NH₄⁺-N在7月的累积量高于10月.研究结果可为当地水环境管理和治理提供方向，丰富大型河道型水库水环境演变相关科学认识.

• Abstract：To explore the water quality distribution characteristics and main influencing factors of tributaries under the special operation mode of the Three Gorges reservoir, this study took Xiangxi River and Shennong River, the primary tributaries of the Three Gorges Reservoir area, as an example to conduct on-site sampling and analysis in July (flood season) and October (impoundment period) of 2018. The WQI (water quality index) method was used for water quality assessment and water quality characteristics analysis. Then, the driving factors of water quality change were identified by combining the three-dimensional hydrodynamic observation data and flow exchange analysis of main and branch. The results indicated that:①The main indexes affecting the WQI of Xiangxi River and Shennong River were TN and NH₄-N, respectively. The WQI of the two tributaries was in the range of 63~69 in July and in the range of 74~82 in October, and the water quality was general and good in the above two months, respectively. The water quality in October was significantly better than that in July (p<0.01), and there was no significant difference in WQI between the two tributaries (p>0.05), and the WQI of middle section was larger than that near the estuary and upstream.②The backflow of the main stream of the Yangtze River played a leading role in the water quality variation of the tributaries. In flood season, the backflow intensity was low and the nutrient concentration of the backflow water was high, the backflow of water increased the nutrient concentration of tributaries.In impoundment period, the backflow intensity was high and the nutrient concentration of the backflow water was low, a amount of backflow water diluted the nutrient concentration of tributaries. ③The non-point source pollution in tributary watershed synergistically aggravated the water quality pollution in tributaries, which was increased by rainfall driving during the flood season.Resulting from combined effect of several factors, the accumulation of TN and NH₄-N in July was higher than that in October in tributary bays. The research results can provide direction for local water environment management and governance, and enrich the scientific understanding of water environment evolution of large river reservoirs.

• Key words：Three Gorges Reservoir  Xiangxi River  Shennong River  water quality index(WQI)  water quality assessment  water body backflow

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