利用青草沙上游取水口和下游排水口大量实测盐度资料, 统计分析了2010年冬季以来的10个咸潮年度中青草沙水域受到外海正面盐水入侵的特点. 分析结果表明, 近10年来青草沙水域外海正面盐水入侵与径流量、潮汐和风况等密切相关. 水库上游闸口共发生16次正面盐水入侵, 时间为9月到次年3月; 下游闸口共发生41次正面盐水入侵, 时间为9月到次年5月. 上游和下游闸口正面盐水入侵, 主要出现在每年的12月、1月和2月, 且一般容易发生在大通流量18 000 m³/s以下、持续偏北或西北风影响下的小潮或小潮后的中潮. 正面盐水入侵来临前几天, 偏北或西北风的强度和持续时间对正面盐水入侵起着重要的作用.

Qingcaosha Reservoir is the main water source for Shanghai, providing approximately 55% of its high-quality raw water needs, and effectively guarantees the safety of water supply for Shanghai. The waters near the Qingcaosha Reservoir experience saltwater spillover from the North Branch into the South Branch; the nearby waters, moreover, suffer from direct saltwater intrusion from the open sea. In this study, a large number of measured salinity data in the upstream and downstream sluice was used to statistically analyze the characteristics of direct saltwater intrusion near the Qingcaosha Reservoir waters in recent decades. The analysis results show that direct saltwater intrusion neat the Qingcaosha Reservoir waters in recent decades was closely related to the river discharge, tide, and wind. There were a total of 16 instances of direct saltwater intrusion at the upstream sluice that occurred from September to March of the following year; likewise, there were a total of 41 instances of direct saltwater intrusion at the downstream sluice that occurred from September to May of the following year. The direct saltwater intrusions at the upstream and downstream sluices appeared primarily in December, January, and February of each year. We found that saltwater intrusions occurred most commonly when the river discharge was less than 18 000 m³/s during neap tide and middle tide (after neap tide) accompanied by persistent northerly or northwesterly winds. We found that the strength and duration of the northerly or northwesterly winds in the days preceding saltwater intrusion had an important role on direct saltwater intrusion.