Numeric Study on the Influence of Sluice-Gate Operation on Salinity, Nutrients and Organisms in the Jiaojiang River Estuary, China

Abstract

The estuary—located in the joint zone between river and ocean—has created unique ecosystems and rich biodiversity due to its complex habitat conditions. As the critical period for the growth and reproduction of estuarine organisms, the flood season is also crucial for estuary sluice to play a role in flood control and drainage. This study aims at proposing an ecological scheduling scheme that comprehensively considers the adverse factors brought by draining of the estuarine sluice to maintain different ecological functions of the Jiaojiang River estuary. A two-dimensional mathematical model in MIKE 21 was used to ascertain the change of salinity and nutrients in the study area, and results were analyzed to understand the impact of draining on estuarine organisms. Based on an analysis of the change and redistribution of salinity and nutrients, the sea area could be divided into three parts during the operation of the estuarine sluice: nearshore area with low-salt and high eutrophication, medium mixed salinity under nitrogen limitation area and high-salt under phosphorus limitation area. The aquaculture area was alternately situated in the mesohaline (>5.0‰–18.0‰) and polyhaline (>18.0‰) zones. The after-effects of salinity change—including the lowest value and the sharp change of salinity, especially the sharp change of salinity (11.8‰–12‰) caused by large-volume discharge—would affect the growth of organisms to a certain extent, but would not be lethal. Moreover, a high-incidence red tide area was determined to be formed within 8–14 km away from the estuarine sluice after the sluice opening, and the area of this zone was firmly related to the opening schemes. The study suggested that the proposed sluice should choose the mode of draining frequent with the small flow at neap tide in order to reduce the stress of sluice construction and operation on mariculture organisms and phytoplankton in Jiaojiang River estuary on the strength of the ecological restoration measures for estuary and riparian zones.

Mathematical Modeling of the Phytoplankton Populations Geographic Dynamics for Possible Scenarios of Changes in the Azov Sea Hydrological Regime

“…The three-dimensional mathematical model of biogeochemical cycles, combined with the model of hydrodynamics, used in this work, makes it possible to predict the spatialtemporal dynamics of the main phytoplankton populations more accurately compared to the two-dimensional models discussed above [12,13,15,16], taking into account the changing hydrological regime, their consumption of nutrients, the transition of nutrients from one form to another. In contrast to the two-dimensional model used in [14], the three-dimensional model of hydrodynamics makes it possible to more accurately model wave processes under conditions of a complex, dynamically changing the geometry of the reservoir, friction on the bottom and wind stress on the free surface, turbulent and advective heat and mass transfer in three coordinate directions, Coriolis forces, river flows, precipitation and evaporation, heat and salt transportation.…”

“…In work [12], the estuary-located in the joint zone between the Jiaojiang River and ocean-was researched. A two-dimensional mathematical model MIKE 21 [13] was used to ascertain the dynamics of salinity and nutrients in the studied estuary and understand the influence of draining on hydrobionts in this area.…”

Environmental Flow Requirements of Estuaries: Providing Resilience to Current and Future Climate and Direct Anthropogenic Changes

“…For estuaries, process-based models have been proven to be particularly useful for exploring a range of flow regimes, including reference conditions, target hydrological conditions and extreme events (Beilfuss and Brown, 2010;Van Niekerk et al, 2019b). Most models focus on simulating the prevailing hydrodynamics and thermodynamics (Duarte et al, 2014;Biguino et al, 2021), fewer examine geomorphological evolution (Deng et al, 2017), and even fewer consider ecological states (Panda et al, 2015;Weng et al, 2020). As flow volumes to estuaries are naturally stochastic (Gillanders and Kingsford, 2002), model simulations need to include a range of relevant temporal variations that conform to the historical and future variance distribution in terms of flow exceedance likelihoods (Beilfuss and Brown, 2010;Van Niekerk et al, 2019b).…”

Hydraulic and Ecological Changes Under Drainage Gate Operations With Coupled Model Schism-Cosine in Saemangeum Basin, Korea

“…Jinqiong et al (2020) introduced the inside boundary condition of gate to reproduce the bidirectional flow. And Weng et al (2020) also presented a method applying the sluice control boundary considering the sea level. Therefore, the bi-directional flow through the drainage gates is reproduced with specific boundary condition using the field data such as operation time log of gates, the sea level and designated water surface elevation in this study.…”