Economic development and increasing population density along the lower reaches of the Yellow river have challenged the river’s ability to meet human and ecological demand. The evaluation of the sustainability of water resources in the lower reaches of the Yellow River is of great significance for the achievement of high-quality development in the region. Based on an improved ecological footprint method considering soil water, the spatial and temporal evolution of the water resources ecological footprint and water resources carrying capacity and evaluates the utilization of water resources in the lower Yellow River are comprehensively evaluated. The results show that agricultural water consumption in the urban agglomerations in the lower reaches of the Yellow River occupies a major position in water consumption, accounting for more than 70%. In 2013–2017, the per capita water resources ecological footprint of the cities along the lower reaches of the Yellow River decreases every year, while the water resources carrying capacity is slightly fluctuating, but remains in a relatively stable state. The deficit situation has eased, falling by 54.52% in the past five years. The water use efficiency of the lower reaches of the Yellow River has increased every year, and the water resources conflict improved significantly, after the implementation of the new environmental policy in 2015. In terms of space, the cities with the smallest per capita ecological deficits include Zibo, Zhengzhou, and Laiwu City, and Dezhou, and Kaifeng and Binzhou City have the largest. Strict water resources management measures and water pollution prevention and control regulations should be formulated to improve the water use efficiency in these areas in order to solve the problem of water shortage.

Riverbank erosion is a natural process in rivers that can become exacerbated by direct and indirect human impacts. Unfortunately, riverbank degradation can cause societal impacts such as property loss and sedimentation of in-stream structures, as well as environmental impacts such as water quality impact. The frequency, magnitude, and impact of riverbank collapse events in China and worldwide are forecasted to increase under climate change. To understand and mitigate the risk of riverbank collapse, experimental/field data in real conditions are required to provide robust calibration and validation of hydraulic and mathematical models. This paper presents an experimental set of tests conducted to characterize riverbank erosion and sediment transport for banks with slopes of 45°, 60°, 75°, and 90° and quantify the amount of sediments transported by the river, deposited within the bank toe or settled in the riverbed after having been removed due to erosion. The results showed interesting comprehension about the characterization of riverbank erosion and sediment transport along the river. These insights can be used for calibration and validation of new and existing numerical models.

With the development of industrial and agricultural production and the social economy, the demand for water resources has gradually increased. In this paper, based on the principles of system dynamics, a sustainable water resources utilization model with coupled water quality and quantity is established using STELLA software to assess the sustainable use of water resources. The model includes two modules: a water supply module and a water quality module. The water supply module includes four sub-systems: economy, population, water supply, and water demand. The water quality module consists of an environmental sub-system. The model is suitable for Tianjin, where water resources are scarce. Calibration is performed using data from 2013–2016, and verification is performed using data from 2017. The simulation results are good. In order to compare the sustainable use of water resources in different development scenarios in Tianjin for 2025, a sensitivity analysis is performed for each variable, and four decision variables are selected to establish four water resources use scenarios (Scenarios 1–4). The results show that, compared with scenario 1, water shortages in scenarios 2 and 3 are delayed. Scenario 4, with stable economic growth and environmental consideration, can effectively resolve the contradiction between water supply and demand in the future, and is more conducive to the improvement of water quality. Finally, based on the above research, measures to solve water resources problems are proposed, in order to provide a reference for the sustainable use of water resources and optimization of water resources allocation in Tianjin.

By offering natural protection along offshore wetlands, mangroves play a crucial role in providing great ecological and economic benefits to local communities. However, mangroves are currently facing an increasing threat of decline worldwide due to widespread human activities and climate change. Recently, eco-friendly wooden fences have been deployed along eroded coasts for mangrove restoration projects, and these fences have the capability to attenuate incoming waves and strengthen sediment deposition in new habitats for mangrove colonization and persistence. However, the design and performance of the fences used can differ substantially among different projects; therefore, it is necessary to study the major factors affecting the wave dissipation performance of these fences and find out a more effective structural design. Thus, we focus on two distinct types of fences with and without porous infill to study the function of infill porosity and frame density, and physical experiments of waves transmission through the fences were carried out in a wave flume, in which nine wooden fences with varied infill porosities (0.60–0.90) and frame densities (0.40 and 0.70) were predetermined to measure the wave transmission, reflection, and wave dissipation. In total, 180 experimental runs were conducted under 18 wave conditions with different wave steepness. The results showed that the fence with a lower infill porosity appears to increase wave transmission coefficient that comes at a cost of a higher reflection coefficient and less wave-energy dissipation inside the fence, and the fence with the highest porosity infills (90%) is nearly equivalent to the fence without any infills but a dense frame in terms of wave damping performance. Moreover, the wave transmission through both fences with and without infill can be remarkably affected by incoming wave steepness. The outcome of the research is not only indicating the importance of the appropriate infill porosity in attenuating incoming waves but also guiding the design of mangrove restoration project in offshore wetlands.

Artificial reefs are effective measures to improve the marine ecological environment and increase fishery production. However, there are several geometries being investigated nowadays and their setup, including the spacing between groups of them, can provide dissimilar effects on hydrodynamics. To enhance the understanding of this topic, in this paper, the focus is mainly on M-Type artificial reefs that will be adopted in Juehua Island, Liaodong Bay, China. An experimental campaign was carried out in order to simulate the influence that M-Type unit reef groups may have on the local flow field and the Particle Image Velocimetry (PIV) technique has been implemented to provide velocity maps. The results showed that with the increase of velocity’s current approaching the artificial reef, the height, length and area of the upwelling and the back vortex rise with the increase of spacing between the artificial reefs. Furthermore, when comparing different geometrical configurations with similar currents approaching the artificial reef, the maximum values of both upwelling and back vortex were obtained when the spacing between unit reefs was 1.25 L. Finally, the entropy method was used to evaluate the effects on the flow field under four kinds of spacing based on the hydrodynamic characteristics and the economic cost. The comprehensive score obtained for all the configurations followed the order 1.25 L > 1.50 L > 0.75 L > 1.00 L. Therefore, it is suggested that the original design spacing should be increased by 25% when the M-type unit reef is put into practice. Additionally, after having completed a comparative analysis, it is recommended to further change the reef group into four reef monocases. By executing this adjustment, the unit reef cost was reduced by 10%, and the influence range on the flow field increased by 10%, and this result can consequently achieve greater ecological benefits with less economic input. The results of this study provide a preliminary reference for the construction of artificial reefs M-Type from the perspective of theory and practice.