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521.
Daily Bank Erosion Rates in the Lower Yellow River Before and After Dam Construction 总被引:1,自引:0,他引:1
Junqiang Xia Tao Li Xiaojuan Li Xiaolei Zhang Quanli Zong 《Journal of the American Water Resources Association》2014,50(5):1325-1337
During the period of water impoundment and sediment detention of the Sanmenxia Reservoir, riverbank erosion processes played a key role in the channel evolution of the Lower Yellow River (LYR). However, research into bank erosion rates of the LYR has been neglected due to the lack of direct field monitoring. In this study, an indirect method is proposed to determine bank erosion rates at daily time scales by outlining a detailed calculation procedure using measured hydrological data. A total of 810 data points of daily bank erosion rates before and after the construction of Sanmenxia Dam was calculated at seven hydrometric sections along the LYR, with the corresponding values of the bank stability coefficient and the width‐to‐depth ratio also being calculated. Empirical relations were then developed to estimate the daily bank erosion rates, using these parameters at the sections. Temporal and spatial variability in daily bank erosion rates in the LYR before and after dam construction were also investigated, revealing that: (1) the bank erosion rates had a mean value of 16.7‐29.1 m/day in the braided reach, with a maximum value of 290.0 m/day, while they were relatively low in the meandering reach, with a mean value of 2.5 m/day; (2) the erosion rates before dam construction were slightly greater than those after dam construction, with the difference reaching 5‐10 m/day in the braided reach, decreasing in the transitional reach gradually, and being slight in the meandering reach. 相似文献
522.
淮河流域新型城镇化水平的空间差异及其影响因素分析 总被引:1,自引:0,他引:1
以淮河流域31个地级市为研究对象,从人口、经济、生活和环境四个方面构建了新型城镇化水平的综合评价指标体系,利用熵值法对其综合城镇化水平及其子系统水平进行评价.结果表明,淮河流域地区新型城镇化发展水平存在较强的空间依赖性,即一个地区城镇化水平的提高通过空间溢出促进周边地区的城镇化发展,地区产业结构的变化是决定其新型城镇化水平的主要因素,尤其是第三产业发展对其影响极大. 相似文献
523.
524.
Groundwater is the essential resource for various uses and have a great economic importance especially in the areas like Mekong Delta, which is the home for some 18 million people and produces a half of Vietnam’s rice and contributes substantial part of the country’s gross domestic product (GDP). Sustainable use of the groundwater resource is threatened by its uncontrolled abstraction and climate change. This study assesses groundwater resources in Mekong Delta aquifer system in the context of climate change. A set of models are used for the purpose. Groundwater recharge and its spatial variation are estimated using WETSPASS model, groundwater level and storage are estimated using MODFLOW and future climatic conditions in the area are developed by downscaling the data of five General Circulation Models (GCMs) retrieved from CMIP5 data portal. Two representative concentration pathways (RCPs) scenarios (RCP4.5 and RCP8.5) are considered for projecting future conditions of groundwater resources. Results reveal that the future average annual temperature is projected to increase by 1.5 °C and 4.9 °C by the end of the 21st century under RCP4.5 and RCP8.5 scenarios, respectively. Future rainfall is projected to increase in wet season and decrease in dry season. Groundwater recharge is projected to decline in short-, medium-, and long-terms. As a result, groundwater levels and storage are also projected to decline in future. These findings may help decision-makers and stakeholders for devising sustainable groundwater management strategies in Mekong Delta. 相似文献
525.
《环境科学学报(英文版)》2023,35(2):712-722
The temporal variation of greenhouse gas concentrations in China during the COVID-19 lockdown in China is analyzed in this work using high resolution measurements of near surface △CO2, △CH4 and △CO concentrations above the background conditions at Lin'an station (LAN), a regional background station in the Yangtze River Delta region. During the pre-lockdown observational period (IOP-1), both △CO2 and △CH4 exhibited a significant increasing trend relative to the 2011-2019 climatological mean. The reduction of △CO2, △CH4 and △CO during the lockdown observational period (IOP-2) (which also coincided with the Chinese New Year Holiday) reached up to 15.0 ppm, 14.2 ppb and 146.8 ppb, respectively, and a reduction of △CO2/△CO probably due to a dramatic reduction from industrial emissions. △CO2, △CH4 and △CO were observed to keep declining during the post-lockdown easing phase (IOP-3), which is the synthetic result of lower than normal CO2 emissions from rural regions around LAN coupled with strong uptake of the terrestrial ecosystem. Interestingly, the trend reversed to gradual increase for all species during the later easing phase (IOP-4), with △CO2/△CO constantly increasing from IOP-2 to IOP-3 and finally IOP-4, consistent with recovery in industrial emissions associated with the staged resumption of economic activity. On average, △CO2 declined sharply throughout the days during IOP-2 but increased gradually throughout the days during IOP-4. The findings showcase the significant role of emission reduction in accounting for the dramatic changes in measured atmospheric △CO2 and △CH4 associated with the COVID-19 lockdown and recovery. 相似文献
526.
527.
ABSTRACT: As part of a basinwide water-quality study, nitrogen and phosphorus data for the Upper Colorado River Basin from the Colorado-Utah State line to the Continental Divide were analyzed for spatial distributions, concentrations associated with various land uses, and temporal trends. Nitrogen and phosphorus concentrations generally increased in a downstream direction. Some nutrient concentrations were elevated at some sites in the upper parts of the basin in areas influenced by increasing urbanization. Sites were grouped according to land use and site type, and median nutrient concentrations were compared among groups. Sites within the agricultural areas of the basin generally had the highest concentrations of nitrogen and phosphorus; concentrations for main-stem, tributary, and urbanization sites were slightly lower than for the agricultural sites. Background sites, or sites with minimal land-use impacts, had very low median nutrient concentrations. Several sites with long-term data were analyzed for temporal trends in concentrations. Several statistically significant downward trends of low and moderate magnitude were observed for nitrogen and phosphorus species. No upward trends were observed in the data at any site. 相似文献
528.
Dai Ming Qin Jian Dai Xie’er. Research Centre for Regional Urban Development Jinan University Guangzhou Guangdong China . Faculty of Mathematics Sun Yat-sen University Guangzhou Guangdong 《中国人口.资源与环境(英文版)》2008,6(1):72-78
There is an obvious departure from the regional equilibrium of developments between the upper and lower reaches of the Pearl River in Guangdong, which resulted in "the effects of contra-geography-grads development". It is mainly because the upriver mountainous areas have been deeply stuck in industrialization delay and marginalization plights, so that nearly 40 million local people have conceived a dream to get rid of "the vicious circle of poverty" by speeding up industrial development. But the problem is that such industrialization efforts on a large scale in mountainous areas are encountering the bottleneck of environmental capacity that strictly limits industrial emissions along the upper reaches of any water system. As a solution, an institutional arrangement called "the Local Area Quotas for Industrial Emissions along the Pearl River" is put forward supposed to give corresponding compensation to the rights of industrial development yielded by some areas with lower environmental capacity through the distribution and trading of IDQs. 相似文献
529.
珠江上游少数民族县域经济活动的累积环境效应研究--以贵州三都水族自治县为例 总被引:1,自引:0,他引:1
为了探索珠江上游少数民族区域经济活动的累积环境效应与生态安全,我们选择三都水族自治县作为定位研究基地.对建国以来区域内经济活动变迁进行历史、现状研究和综合评估,揭示历史时期发展政策、发展模式、重大经济活动等人为扰动因素在区域生态环境系统退化过程中的作用.评估少数民族经济活动的累积环境效应与生态安全。 相似文献
530.
19世纪是我国特大暴雨洪水发生期 总被引:1,自引:0,他引:1
本文用大量资料,论述了我国七个江河历史首位洪水均发生在19世纪。而且,洪水泛滥使得平原地区的水系迁移、湖泊淤缩极为严重。同时,存洪水年前后,伴随着一系列寒冷、干旱的气候异常现象。 相似文献