Effects of cascade reservoirs in the Yangtze River Basin on estuarine saltwater intrusion and freshwater resources during late summer and early autumn

doi:10.3969/j.issn.1000-5641.2014.01.010

Abstract

Abstract:

Large cascade reservoirs in basins impound water in late summer and early autumn and release water in the dry season of the following year. These activities affect seasonal river discharge into the sea which, in turn, affects saltwater intrusion in estuaries and the utilization of freshwater resources. This study evaluated the effective storage capacity of large cascade reservoirs and the value of cross-basin water transfers by the South-to-North Water Transfer Project in the Yangtze River Basin. The estuarine and coastal three-dimensional numerical model ECOM-si was used to simulate and analyze the impact of major projects on estuarine saltwater intrusion and freshwater resources. In 2020, the effective storage capacity of large reservoirs built in the middle and upper reaches of the Yangtze River Basin was 70.611 billion cubic meters with a mean reduction in monthly river discharge of 13,398 m³/s during the storage period of September to October. By 2035, the completion of additional reservoirs in the basin will raise the total effective storage capacity of these reservoirs to 94.388 billion cubic meters and reduce the average monthly runoff by 17909 m³/s during the storage period. Using data on average monthly river discharge measured at the Datong Hydrological Station from 1950 to 2020, and by taking into account variations in river discharge by major projects in the basin, the average monthly river discharge from August to October from 2020 to 2035 in regular- and extra dry hydrological years was calculated. Numerical simulation results show that saltwater intrusion from September to October will increase due to impoundment in cascade reservoirs and decreased river discharge. During regular hydrological years, freshwater can be obtained from the four water reservoirs in the South Branch of the Yangtze River Estuary from September to October. However, water from the Dongfengxisha, Taicang, Chenhang, and Qingcaosha reservoirs is unsuitable for water intake during these months, particularly in extremely dry years. In 2020, the total number of consecutive days with unsuitable water intake from the four reservoirs was 28.75, 24.99, 29.63, and 37.47 days, respectively, and is predicted to rise to 46.53, 44.18, 47.56, and 50.75 days, respectively, in 2035. The impoundment of basin reservoirs in late summer and early autumn during average- and extremely dry hydrological years exposes them to strong northerly winds which can significantly decrease water intake. Basin reservoirs should reduce storage capacity and release water during extremely dry years to ensure the safety of freshwater resources in the Yangtze River Estuary.

Key words: basin reservoirs, river discharge, the Yangtze River Estuary, saltwater intrusion, numerical simulation

CLC Number:

P731.2

Zhi JIN, Jianrong ZHU, Wei QIU. Effects of cascade reservoirs in the Yangtze River Basin on estuarine saltwater intrusion and freshwater resources during late summer and early autumn[J]. Journal of East China Normal University(Natural Science), 2024, 2024(1): 90-103.

Figures/Tables 16

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水电站	河流	建成时间	有效库容/亿m³
乌江渡	乌江	1983年	13.50
宝珠寺	白龙江	1998年	13.40
二滩	雅砻江	2000年底	33.70
三峡	长江西陵峡	2003年	221.50
洪家渡	乌江	2004年7月	33.61
紫坪铺	岷江	2006年5月	7.74
彭水	乌江	2008年	5.18
构皮滩	乌江	2009年7月	31.54
瀑布沟	岷江	2010年12月	38.94
亭子口	嘉陵江	2014年5月	17.50
溪洛渡	金沙江下游	2014年6月	64.60
向家坝	金沙江下游	2014年7月	9.03
锦屏一级	雅砻江	2014年11月	49.10
观音岩	金沙江中游	2016年5月	5.55
乌东德	金沙江下游	2020年6月	30.00
岗托	金沙江上游	2020年7月	5.35
白鹤滩	金沙江下游	2022年	104.00
两河口	雅砻江	2023年	65.64
拉哇	金沙江上游	2024年2月	8.24
双江口	大渡河	2024年	19.17
叶巴滩	金沙江上游	2024年	5.37

参数	站位	CC	RMSE	SS
水位	堡镇水文站	0.96	0.26 m	0.98
	崇西水文站	0.96	0.26 m	0.98
	南门水文站	0.97	0.27 m	0.98
流速	1#浮标站	0.74/0.73/0.69	0.29/0.25/0.22 m/s	0.83/0.83/0.81
	2#浮标站	—	—	—
	3#浮标站	0.69/0.75/0.64	0.38/0.32/0.30 m/s	0.82/0.84/0.78
	4#浮标站	0.77/0.85/0.89	0.31/.018/0.09 m/s	0.81/0.88/0.94
	5#浮标站	0.91/0.89/0.77	0.28/0.29/0.27 m/s	0.93/0.92/0.88
	6#浮标站	0.87/0.87/0.86	0.30/0.26/0.21 m/s	0.92/0.93/0.92
盐度	1#浮标站	0.81	3.33	0.90
	2#浮标站	0.94	1.93	0.96
	3#浮标站	0.88	0.83	0.93
	4#浮标站	—	—	—
	5#浮标站	0.84	0.51	0.90
	6#浮标站	0.89	0.07	0.91

试验	8—10月各月径流量/(m³·s^–1)	风场	说明
Exp0	44392、43271、36332	多年10日平均	本底试验, 平均径流量, 不考虑流域工程对径流量调节
Exp1	43392、28873、21934	多年10日平均	基于Exp0, 考虑至2020年已建水库和南水北调工程
Exp2	42792、23762、16823	多年10日平均	基于Exp1, 考虑至2035年已建水库和南水北调工程
Exp3	42792、23762、16823	除了强风时段, 其余时间多年10日平均	基于Exp2, 考虑 9 月中下旬小潮期间3 d强北风, 风速12 m/s
Exp4	42792、23762、16823	除了强风时段, 其余时间多年10日平均	基于Exp2, 考虑 9 月中下旬小潮期间8 d强北风, 风速20 m/s
Exp5	42792、23762、16823	除了强风时段, 其余时间多年10日平均	基于Exp2, 考虑10月中下旬小潮期间3 d强北风, 风速12 m/s
Exp6	42792、23762、16823	除了强风时段, 其余时间多年10日平均	基于Exp2, 考虑10月中下旬小潮期间8 d强北风, 风速20 m/s
Exp7	27272、24967、20876	多年10日平均	本底试验, 特枯水文年, 不考虑流域工程对径流量调节
Exp8	26272、10569、6478	多年10日平均	基于Exp7, 考虑至2020年已建水库和南水北调工程
Exp9	25672、5458、1367	多年10日平均	基于Exp7, 考虑至2035年已建水库和南水北调工程

水库站点	不同数值试验下连续不可取水天数/d
水库站点	Exp0	Exp1	Exp2	Exp3	Exp4	Exp5	Exp6	Exp7	Exp8	Exp9
东风西沙	0	0	0	0	2.22	0	6.58	0	28.75	46.35
太仓	0	0	0	0	5.37	2.31	8.01	0	24.99	44.18
陈行	0	0	0	0	6.05	2.75	8.65	0	29.63	47.56
青草沙	0	0	0	5.48	11.64	7.28	11.4	0	37.47	50.75

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