The link between the main reservoir and its tributary bay is the hydrodynamic 539
condition, and it is mostly affected by water level fluctuations (Sha et al., 2015). Thus, 540
in previous chapters, we mainly discussed the effect of water level fluctuations in 541
detail. Air temperature and winds conditions were also important factors affecting the 542
results (Yu et al., 2013; Huang et al., 2016). Air temperature can affect the surface 543
water temperature by promoting the formation of thermal stratification (Jin et al., 544
2019). From July to August, air temperature was a dominant variable and the 545
stratification of water temperature was obvious. A comparison of the distributions of 546
the water temperature and water quality showed that air temperature had almost no 547
effect on the water quality distribution, while the water level fluctuation was a 548
Distance from the confluence (km)
M o n th 0 5 10 15 20 25 30 35 40 45 2 4 6 8 10 12 50 45 40 35 30 25 20 Eutrophic Mesotrophic Oligotrophic Oligotrophic
41
determining factor. The results were not sensitive to wind conditions because the wind 549
varied little throughout the year and the wind speed was small (1 - 1.8 m/s) in the 550
study area. 551
4 Conclusions and future work 552
In this paper, the effect of the backwater jacking and intrusions from the main 553
reservoir on the hydrodynamics and water environment of the Tangxi River, a 554
tributary bay of the TGR are studied. The following conclusions were reached as a 555
result of this research: 556
(1) The intrusion was weak when the water level of the main reservoir dropped, 557
and the tributary bay was mainly affected by the backwater jacking of the main 558
reservoir. The periods of intrusions in the tributary bay ranged from July to October. 559
Conversely, when the water level of the main reservoir rose, the tributary bay was 560
mainly affected by backwater intrusions from the main reservoir. 561
(2) The water from the tail flowed along the surface of the tributary bay or sank to 562
the bottom in each month. The backwater from the main reservoir entered the 563
confluence at different depths simultaneously, forming one or two circulations in the 564
tributary bay. The backwater had a greater impact on the tributary bay when the main 565
reservoir was at high water level and had a smaller impact when the main reservoir 566
was at a low water level. 567
(3) The water temperature of the tributary bay was not greatly affected by the 568
backwater from the main reservoir. The concentrations of COD and NH3-N in the
42
tributary bay were generally higher at the two ends of the bay and lower in the middle. 570
For TP and TN, there was an obvious quality concentration boundary in the tributary 571
bay, which was basically consistent with the regional boundary of the flow field. The 572
concentrations of TP and TN were higher at the side near the confluence. 573
(4) Nutrients in tributary bays were mainly from the main reservoir and the 574
nutrient levels were affected by the constantly changing hydrodynamic conditions and 575
environmental factors across seasons. The risk of eutrophication of the tributary bay 576
was high within 0.5 km of the confluence in May and June. 577
This paper only studied the influence of the main reservoir on the tributary bay in 578
terms of hydrodynamics and water environment. The operations of the main reservoir
579
may have common influences on the tributary bays, and tributary bays may also
580
influence the main reservoir. The influence of the tributary bay on the main reservoir 581
and the interaction between the main reservoir and the tributary bay are still unclear. 582
In the future, numerical simulation of the main reservoir’s hydrodynamics and water 583
environment based on the results of this paper should be carried out to explore the 584
interaction between the main reservoir and the tributary bay. 585
Future work should also explore control measures to improve the water 586
environment of the tributary bay based on its interaction with the main reservoir. At 587
present, some scholars have proposed that preventing and controlling eutrophication 588
in tributary bays can be achieved by the method of "double nutrient reduction", which 589
involves the simultaneous control of the nutrient inputs from the main stream and the 590
43
tributary (Liang et al., 2014). It is also possible to use ecological methods, such as 591
emergent plants, submerged plants, phytoplankton, benthic organisms and fish, to 592
improve water eutrophication (Srivastava et al., 2017; Li et al., 2013; Soares et al., 593
2011). In addition, the concept of improving the hydrodynamic conditions of the main 594
stream and controlling the eutrophication of the water body through manually 595
controlled operation has been widely accepted by many experts and scholars (Yao, 596
2011; Zheng et al., 2011; Naselli-Flores and Barone, 2005). It is believed that such
597
work mentioned above could help to propose better protection measures for the water
598
environment of tributary bays.Based on future research on the interaction between the
599
main reservoir and the tributary bay with the goal of ensuring the main function of the
600
main reservoir, water environment protection measures should be reasonably
601
proposed for tributary bays in the future.
602
Declaration of Competing Interest. We declare that we have no known competing
603
financial interests or personal relationships that could have appeared to influence the 604
work reported in this paper. 605
Acknowledgements. This work was sponsored by the fund of Sichuan Province under
606
permission number 2018SZYZF0001. 607
Author contribution. All co-authors participated in the field collection, data analysis,
608
and/or writing of this manuscript. Ruifeng Liang was primarily responsible for 609
preparation and process of this manuscript. Xintong Li and Yuanming Wang 610
conceived of the study design and data analysis with input from all co-authors. 611
44
References 612
Bennett, M. G., Schofield, K. A., Lee, S. S. and Norton, S. B.: Response of 613
chlorophyll a to total nitrogen and total phosphorus concentrations in lotic 614
ecosystems: a systematic review protocol, Environmental Evidence, 6(1), 18, 615
https://doi.org/10.1186/s13750-017-0097-8, 2017. 616
Berger, C. J., and Wells, S. A.: Modeling the effects of macrophytes on 617
hydrodynamics. Journal of Environmental Engineering, 134(9), 778-788, 618
https://doi.org/10.1061/(ASCE)07339372(2008)134:9(778), 2008. 619
Bockelmann, B. N., Fenrich, E. K., Lin, B. and Falconer, R. A.: Development of an 620
ecohydraulics model for stream and river restoration, Ecological Engineering, 621
22(4-5), 227-235, https://doi.org/10.1016/j.ecoleng.2004.04.003, 2004. 622
Bowen, J. D., and Hieronymus, J. W.: A CE-QUAL-W2 model of Neuse Estuary for 623
total maximum daily load development, Journal of Water Resources Planning and 624
Management, 129(4), 283-294,
625
https://doi.org/10.1061/(ASCE)0733-9496(2003)129:4(283), 2003. 626
Cai, Q. and Hu, Z.: Studies on eutrophication problem and control strategy in the 627
Three Gorges Reservoir, Acta Hydrobiologica Sinica, 30(1), 7-11 (in Chinese), 628
https://doi.org/10.3321/j.issn:1000-3207.2006.01.002, 2006. 629
Carey, C. C., Ibelings, B. W., Hoffmann, E. P., Hamilton, D. P. and Brookes, J. D.: 630
Eco-physiological adaptations that favour freshwater cyanobacteria in a changing 631
climate, Water Research, 46(5), 1394-1407,
45
https://doi.org/10.1016/j.watres.2011.12.016, 2012. 633
Carlson, R. E.: A trophic state index for lakes. Limnology and Oceanography, 22(2), 634
361-369, https://doi.org/10.4319/lo.1977.22.2.0361, 1977. 635
Debele, B., Srinivasan, R. and Parlange, J. Y.: Coupling upland watershed and 636
downstream waterbody hydrodynamic and water quality models (SWAT and 637
CE-QUAL-W2) for better water resources management in complex river basins, 638
Environmental Modeling ＆ Assessment, 13(1), 135-153, 639
https://doi.org/10.1007/s10666-006-9075-1, 2008. 640
Deng, S. and Bai, Y.: Analysis on the role of environmental impact assessment in the 641
construction of water conservancy and hydropower projects, Environment and 642
Sustainable Development, 41(5), 101-102 (in Chinese), 643
https://doi.org/10.19758/j.cnki.issn1673-288x.2016.05.030, 2016. 644
Fang, J.: The Operating Simulation of Cascade Reservoirs and it’s Impacts on River 645
Eco-environment—A Case Study on Upper reaches of the Yangtze River. Ph.D, 646
Institute of Mountain Hazards and Environment Chinese Academy of Sciences, 647
2007. 648
Feng, J., Li, R., Liang, R. and Shen, X.: Eco-environmentally friendly operational 649
regulation: an effective strategy to diminish the TDG supersaturation of reservoirs, 650
Hydrology and Earth System Sciences, 18, 1213-1223, 651
https://doi.org/10.5194/hess-18-1213-2014, 2014. 652
Fu, B., Wu, B., Lu, Y., Xu, Z., Cao, J., Niu, D., Yang, G., and Zhou, Y.: Three gorges 653
46
project: efforts and challenges for the environment, Progress in Physical 654
Geography, 34(6), 741-754, https://doi.org/10.1177/0309133310370286, 2010. 655
Gao, Q., He, G., Fang, H. and Huang, L.: Effects of vertical mixing on algal growth in 656
the tributary of Three Gorges Reservoir, Journal of Hydraulic Engineering 48(1), 657
96-103 (in Chinese), https://doi.org/10.13243/j.cnki.slxb.20160239, 2017. 658
Gao, X., Zeng, Y., Wang, J. and Liu, H.: Immediate impacts of the second 659
impoundment on fish communities in the Three Gorges Reservoir, Environmental 660
Biology of Fishes, 87, 163-173, https://doi.org/10.1007/s10641-009-9577-1, 2010. 661
Han, C., Qin, Y., Ma, Y., Zhao, Y., Liu, Z., Yang, C., and Zhang, L.: Cause of 662
Variation in Water Quality Distribution and Its Ecological Effects in the Daning 663
Bay of the Three Gorges Reservoir, Research of Environmental Sciences, 33(4), 664
893-900 (in Chinese), https://doi.org/10.13198/j.issn.1001-6929.2019.09.03, 2020. 665
Holbach, A., Bi, Y., Yuan, Y., Wang, L., Zheng, B. and Norra, S.: Environmental water 666
body characteristics in a major tributary backwater of the unique and strongly 667
seasonal Three Gorges Reservoir, China, Environmental Science Processes: 668
Processes ＆ Impacts, 17(9), 1641-1653, https://doi.org/10.1039/C5EM00201J, 669
2015. 670
Holbach, A., Norra, S., Wang, L. Yuan, Y., Wei, H. and Zheng, B.: Three Gorges 671
Reservoir: Density Pump Amplification of Pollutant Transport into Tributaries, 672
Environmental Science ＆ Technology, 48(14), 7798-7806, 673
https://doi.org/10.1021/es501132k, 2014. 674
47
Hu, B., Yang, Z., Wang, H., Sun, X., Bi, N. and Li, G.: Sedimentation in the Three 675
Gorges Dam and the future trend of Changjiang (Yangtze River) sediment flux to 676
the sea, Hydrology and Earth System Sciences, 13, 2253-2264, 677
https://doi.org/10.5194/hess-13-2253-2009, 2009. 678
Huisman, J., Pham Thi, N. N., Karl, D. M. and Sommeijer, B.: Reduced mixing 679
generates oscillations and chaos in the oceanic deep chlorophyll maximum, 680
Nature, 439(7074), 322-325, https://doi.org/10.1038/nature04245, 2006. 681
Hu, N., Ji, D., Liu, D., Huang, Y., Yin, W., Xiong, C., and Zhang, Y.: Field monitoring 682
and numerical simulating on three-dimensional thermal density currents in the 683
estuary of xiangxi river, Applied Mechanics & Materials, 295-298, 1029-1036, 684
https://doi.org/10.4028/www.scientific.net/AMM.295-298.1029, 2013. 685
Huang, L., Fang, H., He, G., Jiang, H. and Wang, C.: Effects of internal loading on 686
phosphorus distribution in the Taihu Lake driven by wind waves and lake currents, 687
Environmental Pollution, 219, 760-773,
688
https://doi.org/10.1016/j.envpol.2016.07.049, 2016. 689
Ji, D., Liu, D., Yang, Z. and Xiao, S.: Hydrodynamic characteristics of Xiangxi Bay in 690
Three Gorges Reservoir, Science China (Physics, Mechanics & Astronomy), 40(1), 691
101-112 (in Chinese), https://doi.org/CNKI:SUN:JGXK.0.2010-01-013, 2010. 692
Ji, D., Huang, Y., Liu, D., Yin, W., Yang, Z., Ma, J., and Xie, T.: Research progress on 693
the ocean estuary and its enlightenment to the study of the tributary in Three 694
Gorges Reservoir, Applied Mechanics and Materials, 295, 2215-2222, 695
48
https://doi.org/10.4028/www.scientific.net/AMM.295-298.2215, 2013. 696
Ji, D., Wells, S. A., Yang, Z., Liu, D., Huang, Y., Ma, J. and Chris, J. B.: Impacts of 697
water level rise on algal bloom prevention in the tributary of Three Gorges 698
Reservoir, China, Ecological Engineering, 98, 70-81, 699
https://doi.org/10.1016/j.ecoleng.2016.10.019, 2017. 700
Kasai, A., Kurikawa, Y., Ueno, M., Robert, D., and Yamashita, Y.: Salt-wedge 701
intrusion of seawater and its implication for phytoplankton dynamics in the Yura 702
Estuary, Japan, Estuarine, Coastal and Shelf Science, 86(3), 408-414, 703
https://doi.org/10.1016/j.ecss.2009.06.001, 2010. 704
Lewis, W. M., Wurtsbaugh, W. A. and Paerl, H. W.: Rationale for control of 705
anthropogenic nitrogen and phosphorus to reduce eutrophication of inland waters, 706
Environmental Science & Technology, 45(24), 10300-10305, 707
https://doi.org/10.1021/es202401p, 2011. 708
Li, K., He, W., Hu, Q. and Gao, S.: Ecological restoration of reclaimed wastewater 709
lakes using submerged plants and zooplankton, Water and Environment Journal, 710
28(3), 323-328, https://doi.org/10.1111/wej.12038, 2013. 711
Li, Z. and Zhang, H.: Trophic State Index and its Correlation with Lake Parameters in 712
China, Acta Scientiae Circumstantiae, 13(4), 391-397 (in Chinese), 713
https://doi.org/10.13671/j.hjkxxb.1993.04.002, 1993. 714
Liang, L., Deng, Y., Zheng, M. and Wei, X.: Predicting of Eutrophication in the 715
Longchuan River Based on CE-QUAL-W2 Model, Resources and Environment in 716
49
the Yangtze Basin, 23(1), 103-111, https://doi.org/10.11870/cjlyzyyhj2014Z1015, 717
2014. 718
Lindim, C., Pinho, J. L. and Vieira, J. M. P.: Analysis of spatial and temporal patterns 719
in a large reservoir using water quality and hydrodynamic modeling, Ecological 720
Modelling, 222(14), 2485-2494, https://doi.org/10.1016/j.ecolmodel.2010.07.019, 721
2011. 722
Liu, D., Yang, Z., Ji, D., Ma, J. and Cui, Y.: A review on the mechanism and its 723
controlling methods of the algal blooms in the tributaries of Three Gorges 724
Reservoir, Journal of Hydraulic Engineering, 47(03), 443-454 (in Chinese), 725
https://doi.org/10.13243/j.cnki.slxb.20151304, 2016. 726
Liu, L.: Effects of vertical mixing on phytoplankton blooms in Xiangxi Bay of Three 727
Gorges Reservoir: Implications for management, Water Research, 46(07), 728
2121-2130, https://doi.org/10.1016/j.watres.2012.01.029, 2012. 729
Long, L., Ji, D., Yang, Z., Ma, J., Scott, A. W., Liu, D. and Andreas, L.: Density - 730
driven water circulation in a typical tributary of the Three Gorges Reservoir, 731
China, River Research and Application, 35(7), 1-11, 732
https://doi.org/10.1002/rra.3459, 2019. 733
Long, L., Xu H., Bao, Z., Ji, D. and Liu, D.: Temporal and spatial characteristics of 734
water temperature in Xiluodu Reservoir, Journal of Hydroelectric Engineering, 735
37(4), 79-89 (in Chinese), https://doi.org/10.11660/slfdxb.20180408, 2018. 736
Lu, Q., Li, R., Li, J., Li, K. and Wang, L.: Experimental study on total dissolved gas 737
50
supersaturation in water, Water Science and Engineering, 04(4), 396-404, 738
https://doi.org/10.3882/j.issn.1674-2370.2011.04.004, 2011. 739
Lung, W. S., and Nice, A. J.: Eutrophication model for the Patuxent estuary: Advances 740
in predictive capabilities, Journal of Environmental Engineering, 133(9), 917-930, 741
https://doi.org/10.1061/(ASCE)0733-9372(2007)133:9(917), 2007. 742
McGrath, K. E., Dawley, E. M. and Geist, D. R.: Total Dissolved Gas Effects on 743
Fishes of the Lower Columbia River, PNNL-15525, Pacific Northwest National 744
Laboratory, Richland, Washington, https://doi.org/10.2172/918864, 2006. 745
Mohseni, O. and Stefan, H. G.: Stream temperature/air temperature relationship: a 746
physical interpretation, Journal of Hydrology, 218(3), 128-141, 747
https://doi.org/10.1016/S0022-1694(99)00034-7, 1999. 748
Morgenstern, U., Daughney, C. J., Leonard, G., Gordon, D., Donath, F. M., and 749
Reeves, R.: Using groundwater age and hydrochemistry to understand sources and 750
dynamics of nutrient contamination through the catchment into Lake Rotorua, 751
New Zealand, Hydrology and Earth System Sciences, 19, 803-822, 752
https://doi.org/10.5194/hess-19-803-2015, 2015. 753
Naselli-Flores, L. and Barone, R.: Water-Level Fluctuations in Mediterranean 754
Reservoirs: Setting a Dewatering Threshold as a Management Tool to Improve 755
Water Quality, Hydrobiologia, 548, 85-99,
756
https://doi.org/10.1007/s10750-005-1149-6, 2005. 757
Noori, R., Yeh, H. D., Ashrafi, K., Rezazadeh, N., Bateni, S. M., Karbassi, A., 758
51
Kachoosangi, F. T. and Moazami, S.: A reduced-order based CE-QUAL-W2 759
model for simulation of nitrate concentration in dam reservoirs, Journal of 760
Hydrology, 530, 645-656, https://doi.org/10.1016/j.jhydrol.2015.10.022, 2015. 761
Oldani, N. O. and Claudio R. M. Baigún: Performance of a fishway system in a major 762
South American dam on the Parana River (Argentina–Paraguay), River Research 763
and Application, 18(2), 171-183, https://doi.org/10.1002/rra.640, 2002. 764
Paerl, H. W., Hall, N. S. and Calandrino, E. S.: Controlling harmful cyanobacterial 765
blooms in a world experiencing anthropogenic and climatic-induced change, 766
Science of the Total Environment, 409(10), 1739-1745, 767
https://doi.org/10.1016/j.scitotenv.2011.02.001, 2011. 768
Pan, X., Tang, L., Feng, J., Liang, R., Pu, X., Li, R., and Li, K.: Experimental 769
Research on the Degradation Coefficient of Ammonia Nitrogen Under Different 770
Hydrodynamic Conditions, Bulletin of Environmental Contamination and 771
Toxicology, 104, 288, https://doi.org/10.1007/s00128-019-02781-0, 2020. 772
Peng, C., Chen, L., Bi, Y., Xia, C., Lei, Y., Yang, Y., Jian, T. and Hu, Z.: Effects of 773
flood regulation on phytoplankton community structure in the Xiangxi River, a 774
tributary of the Three Gorges Reservoir, China Environmental Science, 34, 775
1863-1871, https://doi.org/10.1097/NEN.0000000000000183, 2014. 776
Ran, X., Alexander, F. B., Yu, Z. and Liu, J.: Implications of eutrophication for 777
biogeochemical processes in the Three Gorges Reservoir, China, Regional 778
Environmental Change, 19(1), 55-63, https://doi.org/10.1007/s10113-018-1382-y, 779
52
2019. 780
Reynolds, C. S.: The ecology of phytoplankton, Cambridge University Press, London, 781
2006. 782
Romarheim, A. T., Tominaga, K., Riise, G., and Andersen, T.: The importance of 783
year-to-year variation in meteorological and runoff forcing for water quality of a 784
temperate, dimictic lake, Hydrology and Earth System Sciences, 19, 2649-2662, 785
https://doi.org/10.5194/hess-19-2649-2015, 2015. 786
Sha, Y., Wei, Y., Li, W., Fan, J. and Cheng, C.: Artificial tide generation and its effects 787
on the water environment in the backwater of Three Gorges Reservoir, Journal of 788
Hydrology, 528, 230-237, https://doi.org/10.1016/j.jhydrol.2015.06.020, 2015. 789
Singh, S. P. and Singh, P.: Effect of temperature and light on the growth of algae 790
species: A review, Renewable and Sustainable Energy Reviews, 50, 431-444, 791
https://doi.org/10.1016/j.rser.2015.05.024, 2015. 792
Soares, M., Vale, M. and Vasconcelos, V.: Effects of nitrate reduction on the 793
eutrophication of an urban man-made lake (Palácio de Cristal, Porto, Portugal), 794
Environmental Technology, 32(9), 1009-1015,
795
https://doi.org/10.1080/09593330.2010.523437, 2011. 796
Srivastava, A., Chun, S. J., Ko, S. R., Kim, J., Ahn, C. Y. and Oh, H-M.: Floating 797
rice-culture system for nutrient remediation and feed production in a eutrophic 798
lake, Journal of Environmental Management, 203, 342-348, 799
https://doi.org/10.1016/j.jenvman.2017.08.006, 2017. 800
53
Tang, Q., Bao, Y., He, X., Fu, B., Adrian, L. C. and Zhang, X.: Flow regulation 801
manipulates contemporary seasonal sedimentary dynamics in the reservoir 802
fluctuation zone of the Three Gorges Reservoir, China, Science of the Total 803
Environment, 548-549: 410-420, https://doi.org/10.1016/j.jenvman.2017.08.006, 804
2016. 805
Thomas, M. C. and Scott A. W.: CE-QUAL-W2: A two-dimensional laterally 806
averaged hydrodynamic and water quality model, Version 3.6, Department of 807
Civil and Environmental Engineering, Portland State University, Portland, 2008. 808
Wang, Q.: Influence on fishes of dissolved gas supersaturation caused by high-dam 809
discharging and its countermeasures, Proceedings of 2011 International 810
Symposium on Water Resource and Environmental Protection, Xi’an,