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991.
马莲河全新世古洪水沉积学和水文学研究 总被引:3,自引:2,他引:1
通过对马莲河中下游的深入考察,在甘肃省合水县河段发现全新世古洪水滞流沉积剖面,对采集的沉积物样品进行粒度成分、石英砂表面结构等分析,证明为典型的古洪水滞流沉积物。通过地层学年代对比分析,确定马莲河在全新世中晚期发生特大洪水,年代大致为4200-4000a B.R之间。根据该组古洪水滞流沉积物所指示的洪峰水位,采用比降法恢复洪峰流量在16400~16900m^3/s之间。同时对该断面2003年和2005年洪水的洪痕进行了流量恢复计算,计算结果与实测洪水误差小于5%,证明古洪水水文学计算结果合理可靠,从而为马莲河水利工程建设及沿岸城镇的防洪减灾提供了科学依据。 相似文献
992.
Evaporation loss from the saturated soil beneath drip irrigation emitters highly influences the irrigation efficiency of drip irrigation (DI). Subsurface drip irrigation (SDI) is one good approach to curb this inefficiency, but in a new irrigation method, straight tube irrigation (STI), the irrigation tubes do not need to be buried and thus STI is recommended to increase the irrigation efficiency under normal surface-applied DI. STI consists of only connectors and water-transference tubes that can directly transfer irrigation water from the lateral emitters in the drip line to the root zone of plants. Five-month field experiments were carried out in Aeolian sand soil in the forest-belts of the Taklimakan Desert, which have poor water storage capacity, to compare the potential water saving between STI and DI. The preliminary results showed that, compared with DI, STI (1) improved the soil water content in soil depths from 40 to 100 cm under the soil surface; (2) achieved the same irrigation effects in relatively shorter irrigation durations; (3) had very little water loss due to deep seepage; and (4) formed a layer of dry sand about 10 to 30 cm thick immediately below the soil surface, which lessened evaporation loss of soil water beneath the emitters on the soil surface. This demonstrates that STI can maximize the water-saving potential of DI through the reduction of wetted soil perimeters on the soil surface. This is valuable information for water-saving engineering applications and projects with STI in arid and semiarid regions. 相似文献
993.
BAOHai-jun XUBao-gen WUCi-fang ZHOUWang-yue 《中国地理科学(英文版)》2004,14(4):304-307
Sustainable farmland consolidation covers ecology, economy and society, which means, its only goal is to protect eco-environment, in accordance with public benefits and economic laws. China is still a developing country, facing capital-lacking, an important but difficult problem, while sustainable farmland consolidation will need more money than common farmland consolidation. To solve the problem, this paper put forward and designed a new financing mode for farmland consolidation: BOT(Build-Operate-Transfer), which can effectively solve the financing problem and investment reclamation by the way of concession, and make sustainable farmland consolidation be realized in China. 相似文献
994.
995.
萧山—富阳一带的前震旦系,分别由中元古代陆缘岛弧型双溪坞群火山岩、新元古代青白口纪河上镇群弧后盆地沉积和双峰式陆相火山岩组成。中元古代末的神功运动表现强烈,青白口纪末的晋宁运动叠加褶皱明显。剖面连续完整,地质现象丰富.是华南重要的层型剖面。 相似文献
996.
Xing-Ming Bao Hong-Qi ZhangNational Astronomical Observatories Chinese Academy of Sciences Beijing baoxm@sunlO.bao.ac.cn 《中国天文和天体物理学报》2003,3(1):87-97
We observed the line-of-sight magnetic field in the chromosphereand photosphere of a large quiescent filament on the solar disk on September 6, 2001 using the Solar Magnetic Field Telescope in Huairou Solar Observing Station. The chromospheric and photospheric magnetograms together with Hβ filtergrams of the filament were examined. The filament was located on the neutral line of the large scale longitudinal magnetic field in the photosphere and the chromosphere. The lateral feet of the filament were found to be related to magnetic structures with opposite polarities. Two small lateral feet are linked to weak parasitic polarity. There is a negative magnetic structure in the photosphere under a break of the filament. At the location corresponding to the filament in the chromospheric magnetograms, the magnetic strength is found to be about 40-70 Gauss (measuring error about 39 Gauss). The magnetic signal indicates the amplitude and orientation of the internal magnetic field in the filament. We discuss several possible causes which may produce such a measured signal. A twisted magnetic configuration inside the filament is suggested . 相似文献
997.
Kuang Wenhui Zhang Shuwen Du Guoming Yan Changzhen Wu Shixin Li Rendong Lu Dengsheng Pan Tao Ning Jing Guo Changqing Dong Jinwei Bao Yuhai Chi Wenfeng Dou Yinyin Hou Yali Yin Zherui Chang Liping Yang Jiuchun Xie Jiali Qiu Juan Zhang Hansong Zhang Yubo Yang Shiqi Sa Rigai Liu Jiyuan 《地理学报(英文版)》2022,32(9):1705-1723
Journal of Geographical Sciences - High-resolution mapping and monitoring of national land use/cover changes contribute significantly to the knowledge of the interaction between human activities... 相似文献
998.
In the new era of the rapid development of economic globalization and the community of human destiny, the implementation of the “One Belt and One Road” (OBOR) construction model is designed to coordinate environmental protection and economic development. Most of the countries along the Silk Road in the 21st century are developing countries, and the majority of them are facing the same ecological and developmental difficulties as China. In this paper, under the background of the “OBOR” strategy and on the basis of the distribution of global climate types, we selected Central Asia and Northwest China, which have temperate continental climates, as the research objects. We sorted out and summarized the main ecological problems faced by Western China and Central Asia during the development of the “Belt and Road” initiative. At the same time, in combination with the major ecological governance projects implemented in recent years, we proposed key ecological governance technologies that have a certain degree of scalability, such as key technologies for water resource utilization and protection, sand prevention and control, and saline-alkali land governance. The aim was to offer the experiences and a reference for providing technological models for the “one belt along the road” region and the country to build an effective ecological governance system. Two suggestions are then proposed for improving the feasibility and rationality of ecological governance technology in the construction of the “One Belt, One Road”. 1) With the implementation of the strategy of “OBOR” construction, the ecological threats the OBOR countries are facing cannot be ignored. Every country needs to jointly act to build an “OBOR” ecological civilization. 2) The participants must pay attention to the spatial heterogeneity and temporal dynamics of ecological carrying capacity, and provide data reference and support for the reasonable allocation of ecological governance technology. 相似文献
999.
Wang Yuan Niu Shengjie Lu Chunsong Lv Jingjing Zhang Jing Zhang Hongwei Zhang Sirui Shao Naifu Sun Wei Jin Yuchen Song Qinghai 《中国科学:地球科学(英文版)》2021,64(11):1982-1995
Science China Earth Sciences - We conducted a three-month field experiment focusing on the physical and chemical characteristics of fog in a tropical rainforest in Xishuangbanna, Southwest China,... 相似文献
1000.
Jinlin Li Xiubin He Jie Wei Yuhai Bao Qiang Tang Jean de Dieu Nambajimana Gratien Nsabimana Dil Khurram 《国际泥沙研究》2021,36(4):489-500
The Three Gorges Reservoir(TGR)in China is the largest hydroelectric project in the world,but the threat of sediment affecting ecological sustainability of the reservoir is a topic of concern.Sediment particlesize distribution(PSD)is informative in understanding sediment transport dynamics and biochemical functions.It is,therefore,important to quantitatively characterize the distribution of sediment particles.In the current study,fractal theory is applied to determine the PSD of suspended sediment in the TGR.The results show that the volumetric fractal dimension(D_v)exhibits a significant seasonal difference(p<0.05),reflecting sediment source and hydrodynamic sorting control the granularity of suspended sediment in the TGR.More specifically,suspended sediment particles are coarser in the wet season than in the dry season for the Yangtze River,and the opposite is true for the Ruxi River,an important tributary.The generalized dimension spectrum,D(q)-q,and multifractal singularity spectrum,f[α(q)]-α(q),were calculated for each suspended sediment sample.Thereafter,the parameters,D(0),D(1),D(2),α(0),Δα(q),andΔf[α(q)],were determined to characterize the PSD.As a result,the coarser suspended sediment during the wet season is characterised by a more complex PSD pattern,with a wider range of particle sizes,greater heterogeneity,and greater homogeneity of distribution over the measurement interval.However,the multifractal structure of the PSD of suspended sediment is more complex during the dry season than during the wet season,with higher local dispersion and variability.The findings of the current study highlight that multifractal analysis provides important insight for understanding the PSD of suspended sediment in the TGR. 相似文献