State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China.
State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China; School of Civil Engineering, Sun Yat-sen University, China.
Sci Total Environ. 2021 Jun 1;771:144886. doi: 10.1016/j.scitotenv.2020.144886. Epub 2021 Jan 29.
As a key component of the global water cycle, river flow transports both freshwater and biotic/abiotic matters from land to sea, while in recent decades its rhythm has been strongly disturbed by human activities, especially damming. Yet little is known about the long-distance transport processes along the world's major fluvial systems and the impact of large dams on their timescales. Here, taking the Changjiang River (Yangtze River) as an example, we built a hydrodynamics-based model to investigate the water age and residence time in the mainstream from the upper reach ~700 km upstream of the Three Gorges Dam (TGD) to the estuary ~1900 km downstream of the TGD. We find that since the mainstream was dammed by the TGD, the water age increases significantly by approximately 2 to 5 times from the estuary to the dam. Downstream of the dam the longitudinal ageing rate of water becomes discordant in an annual cycle, and the replenished discharge in dry season accelerates the water transport. Due to the stationary assumption, the widely applied hydraulic residence time of water is substantially larger and smaller than the age-based dynamic residence time in the large reservoir during the impounding and releasing periods, respectively.
作为全球水循环的一个关键组成部分，河流将淡水和生物/非生物物质从陆地输送到海洋，而近几十年来，其节奏受到人类活动的强烈干扰，尤其是筑坝。然而，人们对世界主要河流系统的长途输送过程以及大型水坝对其时间尺度的影响知之甚少。在这里，我们以长江为例，建立了一个基于水动力的模型，以研究从三峡大坝上游约 700 公里的上游到下游约 1900 公里的河口的主流中的水龄和停留时间。我们发现，自从主流被三峡大坝阻挡以来，水龄从河口到大坝增加了大约 2 到 5 倍。大坝下游，水的纵向老化速度在年周期内变得不协调，枯水期的补给流量加速了水的输送。由于静止假设，广泛应用的水力停留时间的水明显大于和小于基于年龄的动态停留时间在大型水库在蓄水和放水期间，分别。
