Effect of Hydrologic Alteration on the Community Succession of Macrophytes at Xiangyang Site, Hanjiang River, China

With the intensification of human activities over the past three decades in China, adverse effects on river ecosystem become more serious especially in the Hanjiang River. Xiangyang site is an important spawn ground for four domestic fishes in the downstream region of Hanjiang River. Based on the field survey results of macrophytes during 1997–2000 and 2013-2014, community succession of aquatic macrophytes at Xiangyang site was evaluated and discussed. Two-key ecologic-related hydrologic characteristics, flow regime and water level, were identified as the main influence factors. The EFC (environmental flow components) parameters were adopted to evaluate the alteration of flow regimes at Xiangyang site during 1941–2013. Evaluation results demonstrate a highly altered flow process after being regulated by reservoir. The flow patterns tend to be an attenuation process with no large floods occurring but a higher monthly low flow. Furthermore, the water level decreased and fluctuation reduced after the dam was built, which caused the decrease of biomass but favored the submerged macrophytes during 1995–2009. However, with the water level increasing after 2010 and gently fluctuating, due to uplift by the hydraulic projects downstream as well as the flow attenuation, the dominant position of submerged macrophytes will be weakened.

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Effects of Water Level Fluctuations on the Growth Characteristics and Community Succession of Submerged Macrophytes: A Case Study of Yilong Lake, China

Water ◽

10.3390/w13202900 ◽

2021 ◽

Vol 13 (20) ◽

pp. 2900

Author(s):

Fengbin Zhao ◽

Xin Fang ◽

Zeyu Zhao ◽

Xiaoli Chai

Keyword(s):

Community Structure ◽

Water Level ◽

Water Depth ◽

Seed Bank ◽

Submerged Macrophytes ◽

Growth Characteristics ◽

Community Succession ◽

Submerged Plant ◽

Submerged Plants ◽

Emergent Plants

Water level fluctuation (WLF) has a significant effect on aquatic macrophytes, but few experimental studies have examined the effect of WLF on submerged community succession, especially from a large-scale perspective. In this study, field monitoring of WLF and submerged macrophytes was conducted in Yilong Lake (SE China) over two years, and the impacts of WLF on the growth characteristics and the community structure of submerged macrophytes were determined. The results show that the biomass of submerged macrophytes decreased significantly after the water level increased and submerged macrophytes could cope with the adverse environment by adjusting their growth posture, for example, increasing plant length and reducing branch number. However, different submerged plants have different regulatory abilities, which leads to a change in the community structure. Myriophyllum spicatum, Stuckenia pectinata, and Najas marina had better adaptation abilities to WLF than Najas minor and Utricularia vulgaris. Changes in water depth, dissolved oxygen, and transparency significantly contribute to the effect of WLF on submerged plant communities. Therefore, when determining the range of WLF, the above three critical factors and submerged plant species should be considered. WLF changed the spatial distribution of the aquatic plant community. When water levels rose, the density of the submerged macrophyte community in the original growth region reduced as the emergent plants migrated to shallower water, and the seed bank germination was aided by transparent water produced among emergent plants. This can be used as a pioneering measure to restore submerged plants in eutrophic lakes with low transparency. In addition, a suitable water depth created by WLF was conducive to activating the seed bank and improving the diversity of aquatic plants. Finally, a distribution map of aquatic plants in Yilong Lake is drawn.

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Effects of Water Depth on the Growth of the Submerged Macrophytes Vallisneria natans and Hydrilla verticillata: Implications for Water Level Management

Water ◽

10.3390/w13182590 ◽

2021 ◽

Vol 13 (18) ◽

pp. 2590

Author(s):

Qisheng Li ◽

Yanqing Han ◽

Kunquan Chen ◽

Xiaolong Huang ◽

Kuanyi Li ◽

...

Keyword(s):

Water Level ◽

Water Depth ◽

Deep Water ◽

Submerged Macrophytes ◽

Hydrilla Verticillata ◽

Water Level Fluctuations ◽

Total Biomass ◽

Intermediate Water ◽

Factors Affecting ◽

Vallisneria Natans

Water level is one of the most important factors affecting the growth of submerged macrophytes in aquatic ecosystems. The rosette plant Vallisneria natans and the erect plant Hydrilla verticillata are two common submerged macrophytes in lakes of the middle and lower reaches of the Yangtze River, China. How water level fluctuations affect their growth and competition is still unknown. In this study, three water depths (50 cm, 150 cm, and 250 cm) were established to explore the responses in growth and competitive patterns of the two plant species to water depth under mixed planting conditions. The results show that, compared with shallow water conditions (50 cm), the growth of both submerged macrophytes was severely suppressed in deep water depth (250 cm), while only V. natans was inhibited under intermediate water depth (150 cm). Moreover, the ratio of biomass of V. natans to H. verticillata gradually increased with increasing water depth, indicating that deep water enhanced the competitive advantage of V. natans over H.verticillata. Morphological adaptation of the two submerged macrophytes to water depth was different. With increasing water depth, H. verticillata increased its height, at the cost of reduced plant numbers to adapt to poor light conditions. A similar strategy was also observed in V. natans, when water depth increased from 50 cm to 150 cm. However, both the plant height and number were reduced at deep water depth (250 cm). Our study suggests that water level reduction in lake restoration efforts could increase the total biomass of submerged macrophytes, but the domination of key plants, such as V. natans, may decrease.

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What would have been the impacts of wetlands on low flow support and high flow attenuation under steady state land cover conditions?

Journal of Environmental Management ◽

10.1016/j.jenvman.2018.12.095 ◽

2019 ◽

Vol 234 ◽

pp. 448-457 ◽

Cited By ~ 5

Author(s):

Marianne Blanchette ◽

Alain N. Rousseau ◽

Étienne Foulon ◽

Stéphane Savary ◽

Monique Poulin

Keyword(s):

Steady State ◽

Land Cover ◽

High Flow ◽

Low Flow ◽

Flow Attenuation

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Species-Specific Responses of Submerged Macrophytes to Simulated Extreme Precipitation: A Mesocosm Study

Water ◽

10.3390/w11061160 ◽

2019 ◽

Vol 11 (6) ◽

pp. 1160 ◽

Cited By ~ 1

Author(s):

Yu Cao ◽

Yongwei Zhi ◽

Erik Jeppesen ◽

Wei Li

Keyword(s):

Water Level ◽

Extreme Precipitation ◽

Submerged Macrophytes ◽

Freshwater Ecosystems ◽

Maximum Height ◽

Sudden Increase ◽

Growth Forms ◽

High Coverage ◽

Macrophyte Community ◽

Species Specific

More frequent extreme climate events (e.g., extreme precipitation) are to be expected in the future, and such events may potentially have significant effects on freshwater ecosystems. In the present mesocosm study, the effects of simulated extreme precipitation on submerged macrophytes were evaluated for three different macrophyte community (MC) treatments (MC1, MC2 and MC3). MC1 consisted of only Vallisneria denseserrulata, while MC2 and MC3 included three and six species of various growth forms. Two treatments of extreme precipitation (EP) were simulated—an extreme treatment (E) simulating a sudden increase of water level from 75 cm to 150 cm within one day and a gradual treatment (G) simulating an increase to the same water level within 3 months, combined with two control treatments. Total macrophyte community biomass was resilient to the EP and MC treatments, while species-specific variations in responses, in terms of biomass, maximum height, and sexual reproduction, were found. For instance, E led to earlier flowering of Potamogeton lucens and production of more flowers, while it had adverse effects on the flowering of Ottelia alismoides. We conclude that freshwater ecosystems with high coverage of submerged macrophytes may be overall resilient to extreme precipitation under nutrient-limited conditions, especially communities with diverse growth forms.

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Long-Term (1986–2018) Evolution of Channel Bars in Response to Combined Effects of Cascade Reservoirs in the Middle Reaches of the Hanjiang River

Water ◽

10.3390/w12010136 ◽

2019 ◽

Vol 12 (1) ◽

pp. 136 ◽

Cited By ~ 1

Author(s):

Yingying Zhang ◽

Xiaobin Cai ◽

Chao Yang ◽

Enhua Li ◽

Xinxin Song ◽

...

Keyword(s):

Water Level ◽

Water Conservation ◽

Hydrological Regime ◽

High Water ◽

Combined Effects ◽

Strong Negative Correlation ◽

Cascade Reservoirs ◽

Hanjiang River ◽

Over Exploitation ◽

Channel Bar

Channel bars are essential landforms and their evolution is crucial to aquatic and riparian biodiversity, river’s water-sediment process, and economic development. With the development of water conservation facilities and hydropower projects, numerous changes have been taken place in hydrological regimes and morphology. There have been many changes on channel bars in the middle reaches of Hanjiang River due to the combined effects of cascade reservoirs. However, little was known about such dynamics and their linkages to cascade dams across the entire downstream area. Using Landsat remote sensing images from 1986–2018 and the threshold binary Otsu extraction method, this study completed comprehensive monitoring of nine mid-channel bars (DX1–DX7, XZ1, and XZ2), and three shoal group (XZ3–XZ5) dynamics. Results showed that the mid-channel bars’ area in the reach from Danjiangkou to Xiangyang (DX) decreased over the past 33 years, with the exception of DX4, while the total area decreased by 23.19%, this channel bars’ area change was mainly influenced by backwater from the Cuijiaying Reservoir with high water level after 2010 (r = −0.93, p < 0.01). The total channel bar area from Xiangyang to Huangzhuang (XZ) decreased by 16.63% from 1986 to 2018. The total channel bar area in XZ had a strong negative correlation with runoff at Huangzhuang hydrologic station (r = −0.79, p < 0.05), which was partly attributed to upstream precipitation according to the high correlation between runoff and precipitation (R2 = 0.65). In general, the DX section was under equilibrium between scouring and deposition compared to downstream Xiangyang, the bars in DX section were mainly affected by water level, and bars in XZ section during 1986–2018 were complicated because it was upstream eroded and downstream deposited. In addition, vegetation cover, revetments, flood events, sand mining, land use, and over-exploitation may cause channel bar area dynamics. Hence, more continuous investigations are suggested to focus on effects of cascade reservoir operation on hydrological regime, as well as the changing morphology of channel bars in the middle reaches of the Hanjiang River.

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How water level management affects cladoceran assemblages in lakes lateral to a reservoir

Marine and Freshwater Research ◽

10.1071/mf14281 ◽

2016 ◽

Vol 67 (12) ◽

pp. 1853 ◽

Cited By ~ 3

Author(s):

José Roberto Debastiani-Júnior ◽

Marcos Gomes Nogueira

Keyword(s):

Steady State ◽

Water Level ◽

Submerged Macrophytes ◽

Tropical Reservoir ◽

Main River ◽

River Reservoir ◽

Continuous Application ◽

Water Level Management ◽

Loss Of Diversity ◽

The Right

This study analysed the effects of induced water level depletion for macrophyte control in a tropical reservoir on the cladoceran fauna of two differentially connected lateral lakes. One lake, Pedra Branca, is located in the right margin and has a narrow connection to the main river–reservoir channel as well as a higher proportion of submerged macrophytes. On the opposite margin is Lake Guaritá, which is shallower and has a wider connection. Samples were collected over 16 consecutive months, including periods before, during and after depletion. Both lakes showed closely related trends in depth, pH, DO, conductivity, chlorophyll, temperature, suspended matter, phosphorus, nitrogen, silicate and ammonium variation, although a wider amplitude in variation was observed in Pedra Branca. This lake also had higher cladoceran diversity and a predominance of Chydoridae, whereas Bosminidae prevailed in Guaritá. Depletion caused a reduction in richness and an increase of Bosminidae in both lakes, although this was more pronounced in Pedra Branca. The management moderately affected both lakes but continuous application of this procedure may lead to a shift in the system steady-state and a loss of diversity that could be difficult to reverse.

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Viscid-Inviscid Interaction of Incompressible Separated Flows

Journal of Applied Mechanics ◽

10.1115/1.3423877 ◽

1976 ◽

Vol 43 (3) ◽

pp. 387-395 ◽

Cited By ~ 5

Author(s):

W. L. Chow ◽

D. J. Spring

Keyword(s):

Viscous Flow ◽

Pressure Coefficient ◽

Separated Flow ◽

Inviscid Flow ◽

Turbulent Jet ◽

Tunnel Wall ◽

Flow Process ◽

Jet Mixing ◽

Flow Problems ◽

Flow Components

A flow model has been devised to deal with the viscid-inviscid interaction of a class of two-dimensional incompressible separated flow problems. It is suggested that the corresponding inviscid flow of these problems is described by the free streamline theory with few unspecified parameters and their values are, in turn, determined by the viscous flow considerations. The problem of a flow past a backward facing step is selected for study in detail. The viscous flow components of turbulent jet mixing, recompression, and reattachment are delineated and studied individually. When they are later combined, it is found that the point of reattachment behaves as a saddle-point-type singularity in the system of differential equations describing the viscous flow process. This feature is employed to the determination of the aforementioned free parameters and thus the establishment of the overall corresponding inviscid flow field. The resulting base pressure coefficient for the specific case agrees reasonably well with the available experimental data. Additional calculations are performed to demonstrate the influence of higher Reynolds numbers and the values of the similarity (or spread rate) parameter σ of the “constant pressure” turbulent jet mixing process. Further studies of redevelopment of the viscous flow after reattachment, the turbulent exchange within the recompression and redevelopment regions, and the effect of wind tunnel-wall interference on the overall flow patterns have been suggested and discussed.

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High-Resolution Flow-Simulation in Typhoon 21, 2018: Massive Loss of Submerged Macrophytes in Lake Biwa

10.21203/rs.3.rs-134971/v1 ◽

2020 ◽

Author(s):

Satoshi Nakada ◽

Hiroki Haga ◽

Maho Iwaki ◽

Keisuke Hatano ◽

Kohji Mabuchi ◽

...

Keyword(s):

High Resolution ◽

Water Level ◽

Lake Biwa ◽

Submerged Macrophytes ◽

Circulation Model ◽

Climate Change Scenarios ◽

The South ◽

Fluid Force ◽

South Basin ◽

Massive Outflow

Abstract Global activities of typhoons and hurricanes are gradually changing, and these storms can drastically affect lake ecosystems through the recession of submerged macrophytes that regulate the water quality in lakes. Using an echosounder, we captured the short-term, massive loss of submerged macrophytes attributed to the abnormal fluctuation of the water level induced by the approach of a catastrophic super typhoon in the south basin of Lake Biwa, Japan. This paper investigates the physical processes responsible for the loss of vegetation using a high-resolution circulation model in Lake Biwa as a pilot study area. The circulation model was coupled with dynamical models of the fluid force and erosion acting on the vegetation. Our simulation successfully reproduced the water level fluctuation and high-speed current (torrent) generated by the typhoon gale. The simulated results demonstrate that the fluid force driven by the gale-induced torrent uprooted submerged macrophytes during the typhoon approach and that this fluid force (rather than erosion) caused the outflow of vegetation. As a result, this uprooting attributed to the fluid force induced the massive loss of submerged macrophytes in a large area of the south basin, which might have increased primary production and reduced the stock of fish such as bluegill in the lake. Our approach is practical for evaluating changes in lake environments attributed to the massive outflow of submerged macrophytes under various climate change scenarios. (227 words)

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A Physical Model Study of the North Shore Wastewater Treatment Plant Pump Station

10.32920/16850224.v1 ◽

2021 ◽

Author(s):

Maryam Shahab

Keyword(s):

Wastewater Treatment ◽

Water Level ◽

Physical Model ◽

Flow Condition ◽

Numerical Models ◽

Vortex Formation ◽

Low Flow ◽

Bell Mouth ◽

Pump Station ◽

Potential Vortex

<div>Large scale water pumps with bell mouth intakes have been broadly used by municipal wastewater services to move sewage to wastewater treatment plants. Swirling of the flow when entering the suction bell of the pump intake can cause free-surface and/or sub-surface vortices, resulting in poor pump operation. In order to properly design, the wet well of sewage pump station both physical and numerical models are used to analyze the flow condition entering the pump intake and the associated flow pattern and potential vortex formation. In cooperation with WSP Canada Ltd., a physical modelling study of the First Narrows Sewage Pumping Station was conducted by the Ryerson research team at Ryerson University’s Centre of Urban Innovation Laboratory. During the physical model testing, uneven flow distributions including vortices were observed at the intake chamber under three pump-working conditions. To achieve an even flow distribution with minimal vortices, alternative slot designs at the entrance of the chamber were analyzed.</div><div>Additionally, a tapered design of the suction bell intake was tested for potential vortex formation. The results showed that a reduced area of the entrance slot could distribute the inflow evenly in the chamber. Moreover, no vortex formation around the tapered suction bell was found under (a) a low flow condition of 10 l/s at a water level -5.10 m below datum and (b) a cleaning cycle scenario of 16 l/s at a water level -4.9 m below the datum. However, there was observed water rotations at the backwall side. For tight and intense water rotations, it might cause vortex formation. This study has provided design changes that can smooth the flow and reduce vortices at the bell mouth intakes of the pump intake chamber.</div>

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Influence of Longitudinal Fluctuation in Long Corridor Surge Tank on Hydraulic Transients

Volume 1: Symposia, Parts A, B and C ◽

10.1115/fedsm2009-78547 ◽

2009 ◽

Author(s):

Jian Zhang ◽

Weihua Lu ◽

Xiaodong Yu ◽

Yu Zheng

Keyword(s):

Water Level ◽

Influence Factors ◽

High Water ◽

Water Diversion ◽

Width Ratio ◽

Surge Tank ◽

Hydraulic Transients ◽

Length Width ◽

Water Conveyance ◽

Simulation Results

Since the length-width ratio of large long corridor surge tank is big, longitudinal flow appears obviously, which influences the safety of water diversion system. Based on the water conveyance system of hydropower station with long corridor surge tank, influence of longitudinal fluctuation on hydraulic transients is analyzed, which is contrasted with the results without consideration of longitudinal fluctuation, and corresponding model test is also carried out. It is shown that numerical simulation results, without consideration of longitudinal fluctuation, are more dangerous and those considering longitudinal fluctuation relatively conform to reality. Further more, influence factors on longitudinal fluctuation are studied, the bigger the length-width ratio of surge tank and the lower the operation water level, the severer the longitudinal fluctuation. In order to decrease longitudinal fluctuation, surge tank with small length-width ratio should be designed, and station should be operated on high water level as much as possible.

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