Study On Responses Of Saline Intrusion To Combined External Effects In Riverine Estuary

Behind the rapid transformations of ages and the economic development in estuary and surrounding cities,the water environment and water safety issues in the estuary have become increasingly prominent.The intrusion of the saline water in the estuarine area has been exacerbated by human activities and global climate change,which affects many aspects of human production and living as well as the ecological environment.Saline water intrusion in estuarine areas has always been the focus of attention.Many predecessors and scholars congruously argue that runoff and tide are the two major factors affecting salt water intrusion,and they have also adopted different research methods on each impact of external environmental factors on saline intrusion..However,there is still some value for further research and discussion on the response of saline water movement under the combined action of the runoff and tide,the influence of the relative change of the runoff and tide on the saline and the mechanism of action on the saltwater under the main external effects.With the preliminary analysis of some observed data,this paper uses the numerical model to generalize the real river channel under the background that Modaomen is a representative of riverine estuary.Firstly,this paper start with the understand of the equilibrium processes,setting a combination of multiple flow and tidal ranges to explore the mechanism of saline water intrusion under the cooperation of the runoff and tide.Secondly,the main tidal constituents were used as the boundary conditions,and the main external factors such as wind were used for simulation calculations,this paper expects to obtain the effect of the relative changes of the main factors such as the runoff and tide on the movement of saline water.After successive layers of research and analysis,the main results of this paper are as follows: The laws of saltwater intrusion can be more fully showed under the numerical simulation of a variety of changes and combinations of external conditions.Firstly,according to the change of saltwater intrusion under the action of constant tidal ranges,the saltwater can reach the quasi-equilibrium and stable intrusion state due to the density current,in addition to the fact that the regular pattern about saltwater intrusion reproduces the critical tidal ranges as same as previous conclusions who has obtained by physical model experiments,the results of numerical simulation also show that this physical state is not influenced by the change of runoff.tidal range has a direct effect on the vertical transportation of salt,combined with different runoff changes,they both affect saltwater intrusion and have a different regularity of intrusion curve clusters due to the relative change of runoff and tide.Secondly,the curve of the non-equilibrium saltwater intrusion response to the relative change of runoff and tide was obtained by means of using neap-spring cycle to drive calculations,this intrusion rule is a self-adjustment of "rope-wrapping" and the curve changes periodically and repeatedly in the same flow conditions,after being affected by different runoff conditions,it's shape will change,but it will always be guided by quasi-equilibrium intrusion curves,it is considered that the dominating of the common influence on the variation of the saltwater in riverine estuary is the unity of opposites of stratification and mixing,extending the conclusion to engineering application,based on the change of adjustment scale,research also shows that the choice of saltwater tide control is before neap tide will be better,though the study of the combined action of runoff,tidal and wind,it is believed that the response of saltwater to external main effects during the neap tide is more obvious than the spring tide.This paper focuses on the response mechanism of the upstream of saline water under the main control factors.Based on the research results of this article,this paper hope to provide a reference for the actual salt suppression project and prediction of saltwater intrusion,and use the obtained universal rules to offers some help for approaching scientific research.