Integrating hydrological, landscape ecological, and economic assessment during hydropower exploitation in the upper Yangtze River

Prediction of water level at Huayuankou station based on rating curve

The construction of large reservoirs has modified the process of water and sediment transport downstream, resulting in changes in the morphology of the river cross-section. Changes in water and sand transport and cross-sectional morphology are reflected in the rating curve at the cross-section. This study analyzed the variations in the rating curve at the Huayuankou (HYK) section and their influencing factors, and conducted water level predictions based on this relationship. The findings revealed that while the annual mean water level has shown a declining tendency over the past 20 years, the annual mean discharge has shown a constant pattern. The rating curve at this stretch narrowed from a rope-loop type curve in its natural condition to a more stable single curve as a result of the construction of the dam upstream of the HYK section. The effect of pre-flood section morphology and the water-sediment process on the scattering degree of the rating curve is inverse; increasing roughness and hydraulic radius decreases scattering degree, while increasing sand content and sand transport rate increases scattering degree. Using the measured data from 2020 as an example, the feasibility of predicting cross-sectional water levels using the rating curve was verified. The prediction results were accurate when the flow was between 1000 and 2800 m3/s; However, when the flow was between 2800 and 4000 m3/s, the forecast results were typically slightly lower than the measured values. Overall, the method demonstrates good predictive accuracy. Insight from the method can be used to predict water levels to better inform decision making about water resources management, and flood emergency response in the lower Yellow River.

Impacts of cascade hydropower development on aquatic environment in middle and lower reaches of Jinsha River, China: a review

The middle and lower reaches of the Jinsha River, which is the upper reach of the Yangtze River in China, play crucial roles in the water security of people living in the middle and lower reaches of the Yangtze River. The construction of 11 dams in this region has significantly altered the aquatic environment. Although researchers have investigated the effects of cascade hydropower station development in the middle and lower reaches of the Jinsha River based on factors such as flow, sediment, and fish, the overall impact of this station on the aquatic environment remains unclear. Therefore, the purpose of this study is to comprehensively investigate the effects of cascade hydropower station development on the aquatic environment based on three factors: river, aquatic organism, and ecosystem factors. In terms of river factors, the development of cascade hydropower stations increases runoff in the dry season and decreases it in the flood season, leading to sediment deposition and water temperature stratification in cascade reservoirs, and changes in water quality. In terms of aquatic organism factors, cascade hydropower development not only changes the species composition but also reduces biodiversity. Effects of ecosystem factors including the ecological flow, value, and landscape as well as sustainability are summarized, with results indicating positive and negative impacts on river ecosystems. Finally, recommendations for future research on the effects of cascade hydropower development on the aquatic environment of rivers are provided.

Research on Town Ecological Landscape Planning and Governance Based on Fuzzy Optimization Method of Internet of Things Technology

The current town ecological landscape planning and governance methods are mainly based on the high quality, high energy-saving, and environmental protection effect of the town ecological landscape. How to innovate the town ecological landscape planning and governance process with the help of Internet of things technology and fuzzy optimization method is the current development trend. Based on this, this paper studies the application of Internet of things technology in town ecological landscape planning and management. Firstly, a small town ecological landscape evaluation model based on fuzzy optimization algorithm is proposed. Combined with multivariate matrix transformation function, the authenticity data of ecological landscape are simulated. The original analysis of different types of small town ecological landscape is realized by selecting the multivariate extremum of autocorrelation function curve in the process of planning and governance. Secondly, in the simulation evaluation link, the fuzzy evaluation method is adopted and improved. At the same time, the improved three-dimensional original planning governance model is used to comprehensively analyze the simulation results of three-dimensional landscape planning governance. Finally, by designing fuzzy simulation experiments, the application effects of different Internet of things technologies in town ecological landscape planning and governance are analyzed. The experimental results show that the correlation data indicators of fuzzy optimization methods corresponding to different Internet of things technologies are very different. The application effect of different types of Internet of things technology in ecological landscape planning and governance of small towns is targeted and shows strong regularity.

Assessment on Changes of Ecosystem Carbon Storage in Reservoir Area due to Hydroproject

Hydropower offers significant value for global carbon peak and carbon neutrality. However, the construction of hydropower stations leads to significant changes in land use and cover structure in reservoir areas, which affect ecosystem services including carbon balance. Furthermore, the development and operation of hydropower project require vast investment. However, the reservoir ecosystem's carbon storage and carbon emission reduction caused by hydropower could offer economic benefits when the official carbon market trading in China was launched in 2021. Therefore, it is necessary to assess comprehensively the changes in carbon storage and its value to the ecosystem in reservoir areas. The evaluation is of great importance for carbon loss reduction, land management, and hydropower development. This study provides a comprehensive and effective framework for evaluating changes in carbon storage and has its value to the reservoir ecosystem. It combines land utilization classification data obtained from remote sensing image interpretation and the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) carbon storage model. Based on the case study of the Xiluodu reservoir area, they were evaluated from two aspects: physical quantity and value quantity. The results show that the carbon storage in the Xiluodu reservoir area increased by 8,504.42 Mg from 2000 to 2018. The spatial distribution of the carbon storage shows a trend of high in the north and west, but low in the south and east. The construction of hydropower stations and the rise of reservoir water level covered a large amount of land, which led to the loss of carbon storage in reservoir areas. By implementing soil and water conservation and vegetation protection policies, parts of the cultivated land and grassland were converted into forestland, which was the main source for increasing the ecosystem's carbon storage. Moreover, carbon emission reduction was achieved by hydropower. In terms of the monetary value, the carbon storage value of the reservoir ecosystem increased to 19 million RMB during the construction period (2005–2015). The carbon storage value of the reservoir ecosystem increased to 611 million RMB during the operation period (2015–2018). The latter was greater than the maintenance cost of the hydropower station and exceeded the amortized cost of hydropower development, indicating the feasibility and economic benefits of hydropower development. These findings provide guidance for future hydropower development decisions in Jinsha River Basin and also others.

Hydrological Response of the Kunhar River Basin in Pakistan to Climate Change and Anthropogenic Impacts on Runoff Characteristics

Pakistan is amongst the most water-stressed countries in the world, with changes in the frequency of extreme events, notably droughts, under climate change expected to further increase water scarcity. This study examines the impacts of climate change and anthropogenic activities on the runoff of the Kunhar River Basin (KRB) in Pakistan. The Mann Kendall (MK) test detected statistically significant increasing trends in both precipitation and evapotranspiration during the period 1971–2010 over the basin, but with the lack of a statistically significant trend in runoff over the same time-period. Then, a change-point analysis identified changes in the temporal behavior of the annual runoff time series in 1996. Hence, the time series was divided into two time periods, i.e., prior to and after that change: 1971–1996 and 1997–2010, respectively. For the time-period prior to the change point, the analysis revealed a statistically significant increasing trend in precipitation, which is also reflected in the runoff time series, and a decreasing trend in evapotranspiration, albeit lacking statistical significance, was observed. After 1996, however, increasing trends in precipitation and runoff were detected, but the former lacked statistical significance, while no trend in evapotranspiration was noted. Through a hydrological modelling approach reconstructing the natural runoff of the KRB, a 16.1 m3/s (or 15.3%) reduction in the mean flow in the KRB was simulated for the period 1997–2010 in comparison to the period 1971–1996. The trend analyses and modeling study suggest the importance of anthropogenic activities on the variability of runoff over KRB since 1996. The changes in streamflow caused by irrigation, urbanization, and recreational activities, in addition to climate change, have influenced the regional water resources, and there is consequently an urgent need to adapt existing practices for the water requirements of the domestic, agricultural and energy sector to continue being met in the future.

Impacts of high-speed rail on urban smog pollution in China: A spatial difference-in-difference approach

Smog pollution poses a severe threat to residents' health and economic development in China. High-speed rail (HSR) is a new and efficient infrastructure that is expected to provide economic and environmental benefits. Based on the STIRPAT model and the environment Kuznets curve (EKC) hypothesis, this study employs a spatial difference-in-difference approach using 284 prefecture-level cities' panel data from 2007 to 2016 to explore the impacts of HSR on urban smog pollution. The results demonstrate that urban smog pollution shows strong spatial correlations and that HSR can significantly reduce smog pollution. Causal mediation analysis is used to test two mechanisms related to HSR: sector structure upgrading, which can reduce smog pollution, and real estate market development, which tends to increase smog pollution. After controlling for the two opposite mechanisms, HSR is proven to have positive environmental benefits. Besides HSR, the impacts of per capita GDP and population on smog pollution are further discussed. The relationship between per capita GDP and urban smog pollution follows an N-shaped curve, and smog is proved to reduce to a certain extent as per capita GDP increases. The relationship between population and smog pollution shows a U-shaped curve, provided with a new interpretation relating to economies of scale. The findings have implications for policy-making, as they enrich the EKC hypothesis and provide evidence for the environmental benefits of HSR.