Safeguarding water resources, aquatic habitats, and ecosystems is paramount for the well-being of the populace, the future of the nation, and the sustainable development of China. With the relentless progression of ecological and environmental protection and the establishment of an ecological civilization, China’s aquatic ecological environment protection has undergone five decades of exploration. The water environment protection paradigm has gradually transitioned from emphasizing pollutant emission concentration control and total pollutant emission control to prioritizing water environment quality improvement. Particularly in the past decade, regions nationwide have conducted proactive explorations and practices in source control, emission abatement, and quality enhancement. This paper systematically reviews the achievements in China’s water environmental quality improvement and the characteristics of water environment management at various stages over the past half-century. Considering the deployment of “three waters” coordination (water resources, water environment, and water ecology), green development, pollution, carbon reduction, and so forth, this paper analyzes the challenges confronted by China’s aquatic ecological environment protection. Finally, future directions are prospected from six aspects: green development, climate change response, water resource allocation optimization, collaborative governance of multiple pollutants, aquatic ecological protection strengthening, and intelligent management improvement.
The presence, abundance, and distribution of aquatic macrophytes and their growth forms in the river Krka in Slovenia were studied. The studied slow-flowing lowland River Krka is also called a »green river« since it is overgrown with macrophytes from its source to its outflow to the river Sava. The environmental parameters of the river ecosystem were also assessed using the modified version of the RCE (Riparian, Channel, and Environmental Inventory) method. Within 24 sections reaching from 100 to 250 m, 23 taxa of macrophytes were found. Sections were distributed noncontinuously from the source to the outflow more or less equally along the river course. The invasive alien species Elodea canadensis reached the highest relative abundance, followed by Ranunculus trichophyllus, Potamogeton crispus, Myriophyllum spicatum, Ceratophyllum demersum, and Potamogeton nodosus. Potamogeton crispus was present in most of the studied sections followed by Nasturtium officinale and M. spicatum. The river offers suitable conditions for the high diversity of macrophytes regarding the type of substrate, low flow velocity, heterogeneity of habitats, and relatively high concentrations of nutrients. In comparison to the survey performed in 2003, when the river Krka was surveyed continuously from the source to the outflow, we found that seven of the submerged and natant macrophytes were not detected in 2020. Macrophytes, growing in the river Krka, indicated meso- to eutrophic conditions. Five species recorded in the river Krka are listed on the Red list of endangered species in Slovenia, indicating the need to conserve the river ecosystem.
Bedload studies at the particle scale may help grasp the essence of the problem. Existing studies suffer from short filming durations, limited data volume, and a narrow range of sediment transport intensity variations. This paper employs the high-speed photography technology and conducts experimental studies on bedload particle motion under 8 different sediment transport intensities. Using the latest image processing technology, over 6 million sediment particle coordinate points and nearly 400,000 particle motion trajectory curves were automatically obtained and used to compare the motion characteristics of bedload particles under different sediment transport intensities. The results show that under low sediment transport intensity, both the number of moving particles and particle motion velocity contribute to the bedload sediment transport rate, while under high-intensity conditions, the transport rate mainly depends on the number of moving particles. The probability density distribution of sediment transport rate is concentrated and varies within a small range under low-intensity conditions, exhibiting a tailing phenomenon. In contrast, under high-intensity conditions, the range of sediment transport rate values increases, and the probability density curve tends to be symmetric, more closely approximating a normal distribution. Additionally, the paper compares the longitudinal and transverse motion velocities of particles and the coefficient of variation of the bedload sediment transport rate.
The Navasota River Basin, itself a tributary of the Brazos River in Texas, is a dynamic watershed undergoing many natural and anthropogenic changes. Local stakeholder involvement in this watershed is quite high, and many landowners in the southern portion of the watershed have concerns regarding the increasing frequency and duration of flooding on private property adjacent to the river, often attributing these impacts to the construction of the Lake Limestone dam. In this study, we examine historical flow data, channel morphology, land use/land cover, and precipitation. Our findings indicate that while there appears to be increasing flow in the northern portion of the watershed, temporal data gaps near the watershed outfall prevent the indication of such a trend in the southern portion of the watershed. Nevertheless, other natural and anthropogenic factors are evident in the watershed that may have a significant influence on downstream flooding. Overall river sinuosity (meandering) declined over the study period, with some river segments encountering significant straightening. Total river length declined by 4.3 km from 1972 to 2020. The number and length of offtake channels also decreased substantially during this period. Land use/land cover use shifted dramatically, with a 39.2% increase in impervious cover and a 12.5% decrease in herbaceous cover since 1972. Finally, yearly precipitation increased, with the change point occurring in 1972. Our findings suggest that the shortening and straightening of the river has reduced its volumetric capacity over time. Coupled with increasing impervious surface cover and precipitation, more water is being delivered downstream at a rate exceeding the watershed’s ability to discharge it, thereby contributing to flooding issues expressed by stakeholders. We recommend that bathymetric data and supplemental flow monitoring and modeling within the watershed is needed to fully understand how anthropogenic and natural forces may further affect streamflow in the future.
In seasonal frozen soil, freezing and thawing can change the physical and mechanical properties and affect slope stability. There are complex moisture conditions in the main water transfer canal. A study of the hydrothermal evolution of canals with different initial water contents under the action of freezing and thawing is of great importance for the prevention and control of canal slope slides. Hydrothermal coupling models are the key to revealing the canal’s hydrothermal evolution. As some of the modeling parameters in the current hydrothermal coupling model are based on empirical values, particularly those in the van Genuchten equation, which are not necessarily related to soil properties, they are not suitable for analyzing the hydrothermal evolution of canals. This paper determines the soil-water characteristic curve from the cumulative curve of particle gradation in the subsoil, and then determines the hydraulic parameters of the subsoil using the VG model, which then corrects the hydrothermal coupling model. The method of modifying the hydrothermal coupling model is original, which makes the model more realistically reflect drainage soil characteristics. During freezing and thawing of channel slopes with different initial water contents (21%, 25%, 29%, 33%, 37%, and 41%), temperature field, water field, and ice content distributions were investigated. Using the V-G model, the optimal parameters for canal subsoil were a = 0.06, n = 1.2, and m = 0.17, and temperature distribution trends between canals with different water contents were basically similar. Water will accumulate at the bottom as the liquid water content increases at the canal boundary.
Urban flooding is one of the significant issues that many cities are dealing with to ensure sustainable development. Upgrading the drainage systems is a standard measure that engineers have often used to reduce the risk of flooding. Because of climate change and urbanization, stormwater management systems may be inadequate to convey generated overflow in their catchment, which results in severe flooding in many cities worldwide. This research investigates climate change and urbanization’s influence on urban flooding by simulating the EPA Stormwater Management Model for drainage systems in an urban catchment in An Ha, Tam Ky, Quang Nam. The results showed that urbanization shortens the initial abstraction ability while climate change increases extreme rainfall and water levels of receiving sources. Additionally, the impacts are even more substantial when the high urbanization rate increases by more than 70%, together with climate change.
Under warming conditions and with increasing human perturbations, rivers across the globe are facing drastic shifts in their hydrologic regime, resulting in fragmentation and disconnection from the catchment. Subsequently, a dependency on in situ primary productivity as the source of organic matter increases and warrants detailed investigation of the nature of primary production in urbanized river systems. In this study, primary productivity was estimated at multiple locations along the continuum of an engineered (Sabarmati) and a free flowing (Mahi) river systems in India using 13C tracer incubation method. Significantly enhanced primary productivity in the riverfront (engineered construction along the Sabarmati that holds water supplied by a canal) and polluted downstream of the Sabarmati compared to free flowing Mahi was observed. It was also observed that water stagnancy, temperature, and nutrient availability were the key factors regulating the rates of primary productivity in the urban river system. The study highlights the salient features of riverine primary productivity associated with engineered modifications, which needs to be considered for future river development projects.
The problem of flooding in Central Vietnam in general and the lower Ba River in particular is one of the natural disasters that frequently threatens people’s lives and socioeconomic development in the region. Especially, climate change is becoming ever more prominent and hotter, making extreme natural disasters more unusual and unpredictable. In this research, MIKE-FLOOD—a model that connects a 1-dimensional (1-D) MIKE 11 Hydrodynamics (HD) model with a 2-dimensional (2-D) MIKE 21 HD model—was used to set up. The model was calculated for three floods: (1) flood in October 1993, (2) flood in November 2003, and (3) flood in November 2007; these are floods with high frequency and relatively large magnitude. The results show that the 1993 flood rose and receded quickly. The flood peak inundated an area of 22,600 ha, accounting for 52% of the natural area. The flooded areas deeper than 1, 2, 3, 4, and 5m were 16500, 11,000, 7000, 4200, and 2200 ha, respectively. In the center of Tuy Hoa city, the flooded area at the time of maximum water level was almost 100%.
We investigated the impacts of six major climate oscillations on river flow at three stations within the Humber catchments (located in Ontario, ON and Newfoundland and Labrador, NL) from 1970 to 2020 using sensitivity and wavelet analyses. Results indicate that the discharge at East Humber River near Pine (ON) exhibits the highest statistically significant sensitivity, with 0.304 and 0.394 monthly units to the Dipole Mode Index (DMI) and Tropical North Atlantic (TNA), respectively. Monthly significance analysis also highlights the diverse influence of large-scale climate oscillations on river flow across the three locations. Wavelet analysis reveals significant active multidecadal oscillations for the North Atlantic Oscillation (NAO) at East Humber River near Pine, with high spectral power. We confirmed that stations within ON demonstrate sensitivities in a similar direction to the large-scale climate oscillations, contrasting with those observed at NL. The observed inconsistency in the relationship between large-scale climate oscillations and, for instance, NAO at various locations suggests that the impacts of climate oscillations may manifest differently in different regions. Overall, while inland stations exhibit similar sensitivity patterns, the coastal station demonstrates distinct responses, highlighting the importance of geographical context in understanding the impacts of large-scale climate oscillations on river flow dynamics.