Yufeng Li

Water diversion projects have proven to be effective interventions to improve water quality in irrigation ditches. This study focused on quantifying the water quality improvement by utilizing a hydrodynamic water quality model in Funing County, Yancheng City. The model performed a spatial analysis of pollution concentrations across the study area. Various optimization scenarios were designed based on the diversion project and hydrological structure connectivity. The model was used to simulate changes in nutrient concentrations under different scenarios. The findings of this study were as follows: (1) Rural areas had lower nutrient concentrations and superior hydrological connectivity than urban areas. (2) The effect of water quality improvement correlated positively with increased flow rates introduced by the diversion project. Specifically, when the flow rate increased by 50%, the average reductions were 20% for NH₄⁺, 5.2% for TN, and 5.1% for TP. Furthermore, introduced clean water led to more pronounced improvements in the overall regional water quality. (3) Although increasing the number of ditches improved water pollution concentration, the impact was not significant. (4) Model simulation results showed that 18 to 45% water diversion intensity effectively improved water quality, and the optimal water diversion intensity was 27 to 30%. The optimal water diversion intensities offered valuable insights for managing this region. The study’s methods contributed to the promotion of sustainable development in regional water resources and the integrated management of the water environment.

In the coastal zone, there exists a close interrelationship between hydrology, geomorphology, and vegetation, which collectively shape the coastal ecosystem. Hydrological processes significantly influence the formation and evolution of coastal landfo...

The ecological changes have attracted extensive international attention at Jiangsu Yancheng coastal wetland on the west coast of the Pacific Ocean in recent decades. Tidal creek is an important channel for material exchange between sea and land and plays an important role in the connectivity of water in coastal wetlands. The tidal flats from Sheyang Port to Liangduo Estuary in Jiangsu Province were selected and divided into five sub-study areas using each port as a split point. Based on the remote sensing image data from 1987 to 2020, this study used seven parameters (grade, number, length, density, curvature, bifurcation ratio, and drainage efficiency) to analyze the spatio-temporal divergence patterns and hydrological connectivity of tidal creek network. The results showed that (1) the area of tidal flat was reduced from 1024.87 to 352.05 km², the total length of the tidal creek was directly reduced from 1061.27 to 640.74 km, the average density increased from 1.00 to 1.82 km/km², and the total number increased by 33% in 1987–2020, indicating the tidal creeks tended to be “short, fragmented, and parallelized.” (2) The development degree of tidal creek networks showed a trend of gradually increasing from north to south, in which the γ index in areas II and V were closer to 1/3 of tree shape after 2002, indicating that the development of tidal creeks in these two areas was better. (3) The spatial heterogeneity of hydrological connectivity levels of tidal creeks in the study area was obvious, which gradually increased from north to south. In 2020, Area I was the lowest, and IC_min was 0.14, and Area V was the highest, and IC_max was 0.90. (4) Reclamation was the main factor leading to the shrinkage and degradation of tidal creeks, but it also increased tidal creek density and hydrological connectivity per unit area; the expansion of Spartina alterniflora had a certain influence on the development of tidal creeks. The results of this study are expected to provide data support for understanding and predicting the evolution of the morphological characteristics of tidal creeks under the influence of human and natural activities and provide scientific reference for the protection and restoration of hydrological connectivity in coastal wetlands.

As a transition zone between the terrestrial ecosystem and the marine ecosystem, coastal intertidal wetland provides an important place for material circulation and energy exchange, and it is nature’s most precious resource. The ecological health of intertidal wetlands is an important prerequisite for sustainable green development. The material exchange function objectively and accurately reflects the material balance and ecological health of intertidal wetlands in the coastal zone. This paper uses remote sensing, geographic information technology, and model methods to objectively and accurately assess the temporal and spatial changes in the material exchange function of intertidal wetlands, providing a feasible method for studying the material exchange function of coastal wetlands. The material exchange capacity of wetlands in intertidal zones is affected by many factors, such as vegetation, topography, and base soil. After the invasion of the alien species Spartina alterniflora Lois., the elevation of the Suaeda salsa beach increased by 0.3 m. The elevation of the Phragmites australis beach rose by 0.14 m. The average elevation of S. alterniflora increased by 1.24 m. The material exchange capacity of the intertidal zone decreased by 25%. The functioning of the material exchange between sea and land changed significantly, and the area with a high level of material exchange function capacity was reduced by 71%.

As an important indicator of wetland hydrology, hydrogeomorphic conditions clearly indicate the coupling relationships between hydrology, landscape, and habitat. Aiming at problems of small-scale recovery and lack of systematic guidance in current coastal wetland restoration research, this study put forward a coastal wetland restoration system based on the hydrogeomorphic spatial unit. The spatial units of the hydrogeomorphic model were defined according to the regional background in Yancheng coastal wetland, and the changes in land cover patterns from 1980 to 2019 were analyzed. Then, based on the importance and potential for restoration, the key restoration areas were determined and then the dynamics change characteristic of S. salsa salt marsh boundary at the natural state was summarized. It showed that the ecosystem function in the region was basically stable from 1980 to 1998, and the boundary of the S. salsa salt marsh in each key restoration area showed dynamic stability or expansion to the sea. By 2019, with the construction of reclamation and coastal engineering, the hydrogeomorphic conditions in the region changed significantly. In addition to the continuous expansion of S. alterniflora marshes, other natural wetland types almost disappeared and transformed into aquaculture ponds or farmland. Based on those above, the study discusses the overall restoration modes of different hydrogeomorphic spatial units from two aspects of active restoration and passive restoration and puts forward systematic restoration measures in combination with the current characteristics of key restoration areas, forming a technical framework for coastal wetland restoration with practical guiding significance.