Impacts of small cascaded hydropower plants on river discharge in a basin in Southern China     

Xu Xiao  Xiaohong Chen  Lilan Zhang  Rouyi Lai  Jie Liu 《水文研究》2019,33(10):1420-1433

The run‐off volume altered by the construction of hydropower plants affects ecohydrological processes in catchments. Although the impacts of large hydropower plants have been well documented in the literature, few studies have been conducted on the impacts of small cascaded hydropower plants (SCHPs). To evaluate the impacts of SCHPs on river flow, we chose a representative basin affected by hydropower projects and, to a lesser degree, by other human activities, that is, the Qiuxiang River basin in Southern China. The observed river discharge and climate data during the period of 1958–2016 were investigated. The datasets were divided into a low‐impact period and a high‐impact period based on the number of SCHPs and the capacities of the reservoirs. The daily river discharge alteration was assessed by applying the Indicators of Hydrologic Alteration. To separate the impact of the SCHPs on the local river discharge from that of climate‐related precipitation, the back‐propagation neural network was used to simulate the monthly average river discharge process. An abnormal result was found: Unlike large reservoirs in large watersheds, the SCHPs regulated the flows during the flood season but were not able to mitigate the droughts during the dry season due to their limited storage and the commonly occurring inappropriate interregulations of the SCHPs. The SCHPs also reduced the annual average river discharge in the research basin. The contribution of the SCHPs to the river discharge changes was 85.37%, much higher than the contributions of climate change (13.43%) and other human activities (1.20%). The results demonstrated that the impacts of the SCHPs were different from those of large dams and reservoirs that regulate floods and relieve droughts. It is necessary to raise the awareness of the impacts of these river barriers.  相似文献   

New graphical methods for estimating aquifer hydraulic parameters using pumping tests with exponentially decreasing rates     

Chao Zhuang  Zhifang Zhou  Hongbin Zhan  Jinguo Wang  Yabing Li  Zhi Dou 《水文研究》2019,33(17):2314-2322

Actual pumping tests may involve continuously decreasing rates over a certain period of time, and the hydraulic conductivity (K) and specific storage (S_s) of the tested confined aquifer cannot be interpreted from the classical constant‐rate test model. In this study, we revisit the aquifer drawdown characteristics of a pumping test with an exponentially decreasing rate using the dimensionless analytical solution for such a variable‐rate model. The drawdown may decrease with time for a short period of time at intermediate pumping times for such pumping tests. A larger ratio of initial to final pumping rate and a smaller radial distance of the observation well will enhance the decreasing feature. A larger decay constant results in an earlier decrease, but it weakens the extent of such a decrease. Based on the proposed dimensionless transformation, we have proposed two graphical methods for estimating K and S_s of the tested aquifer. The first is a new type curve method that does not employ the well function as commonly done in standard type curve analysis. Another is a new analytic method that takes advantage of the decreasing features of aquifer drawdown during the intermediate pumping stage. We have demonstrated the applicability and robustness of the two new graphical methods for aquifer characterization through a synthetic pumping test.  相似文献   

Root‐zone moisture replenishment in a native vegetated catchment under Mediterranean climate     

Xiang Xu  Huade Guan  Grzegorz Skrzypek  Craig T. Simmons 《水文研究》2019,33(18):2394-2407

The root‐zone moisture replenishment mechanisms are key unknowns required to understand soil hydrological processes and water sources used by plants. Temporal patterns of root‐zone moisture replenishment reflect wetting events that contribute to plant growth and survival and to catchment water yield. In this study, stable oxygen and hydrogen isotopes of twigs and throughfall were continuously monitored to characterize the seasonal variations of the root‐zone moisture replenishment in a native vegetated catchment under Mediterranean climate in South Australia. The two studied hillslopes (the north‐facing slope [NFS] and the south‐facing slope [SFS]) had different environmental conditions with opposite aspects. The twig and throughfall samples were collected every ~20 days over 1 year on both hillslopes. The root‐zone moisture replenishment, defined as percentage of newly replenished root‐zone moisture as a complement to antecedent moisture for plant use, calculated by an isotope balance model, was about zero (±25% for the NFS and ± 15% for the SFS) at the end of the wet season (October), increased to almost 100% (±26% for the NFS and ± 29% for the SFS) after the dry season (April and May), then decreased close to zero (±24% for the NFS and ± 28% for the SFS) in the middle of the following wet season (August). This seasonal pattern of root‐zone moisture replenishment suggests that the very first rainfall events of the wet season were significant for soil moisture replenishment and supported the plants over wet and subsequent dry seasons, and that NFS completed replenishment over a longer time than SFS in the wet season and depleted the root zone moisture quicker in the dry season. The stable oxygen isotope composition of the intraevent samples and twigs further confirms that rain water in the late wet season contributed little to root‐zone moisture. This study highlights the significant role of the very first rain events in the early wet season for ecosystem and provides insights to understanding ecohydrological separation, catchment water yield, and vegetation response to climate changes.  相似文献   

基于人工地震波作用下大跨度悬索桥多点激励地震响应分析          下载免费PDF全文

易富  杜常博  王伟  孙悦  张智 《地震工程学报》2019,41(2):278-285

为研究大跨度悬索桥在多点激励作用下的地震响应规律,在已有的功率谱模型基础上提出了改进的功率谱模型,并将其应用到人工地震波合成过程中。以某水库上主跨720 m双塔单跨悬索桥为研究对象,用Midas civil建立全桥有限元模型,采用大质量法进行不同波速多点激励地震响应分析。结果表明:大跨度悬索桥在多点激励作用下的主塔内力响应、主塔位移响应及主梁位移响应均受行波效应、衰减效应、不相干效应及衰减后地震波叠加效应影响,且最终的响应值由衰减后地震波的叠加效应与衰减效应的共同作用决定;500 m/s多点激励下衰减后的地震波叠加加强效应与衰减效应共同作用后,对主塔轴力响应、主塔塔底顺桥向剪力响应、左塔上横梁处剪力和弯矩响应的加强效果最大;各波速多点激励下,主塔顶顺桥向位移响应相对变化率均大于零且几乎保持不变,主梁两端顺桥向位移响应相对变化率在1 000 m/s波速取得最大值,主梁竖向位移响应在500 m/s取得最大值并随波速的增加逐渐接近一致激励情况。  相似文献   

塘沽地电阻率观测轻轨干扰降噪处理     

王晓蕾  谷国梁  马义山  刘传军  徐小远  杨建思 《地震地磁观测与研究》2019,40(4):81-88

随着地铁轻轨的迅速发展，我国大多数地电阻率测项受到不同程度干扰，诸多学者为此提出采用小波方法进行滤波的建议。文中拟采用小波和HHT滤波方法，以受津滨轻轨干扰严重的塘沽地电阻率观测资料为例，进行降噪处理，对比2种方法的滤波效果，以获得更好的滤波方法。  相似文献   

宽频带流动地震台站中地震计浅井式安装研究     

刘政一  袁松湧  许卫卫  徐天龙 《地震地磁观测与研究》2019,40(4):130-137

在井下地震观测中，各种地表背景噪声具有显著衰减作用，针对中国地震科学台阵现有大量非专用浅井式设计的Guralp CMG系列地震计，以及目前多个新获批项目在高背景噪声区域的观测需求，设计一种野外实用浅井观测方式，在北京国家地球观象台进行不同深度、不同井壁材质的观测对比实验，分析研究观测数据的背景噪声功率谱密度，结果表明，随着浅井深度的增加，地震背景噪声在垂直、水平向得到改善，改善程度随频率变化有所不同。分析认为，在华北现有地质环境下，6 m浅井是较为经济的观测方式，性价比高、占地小、施工简便，可用于后续多个项目的宽频带流动地震台阵观测。  相似文献   

地震观测仪器自动监控软件设计与实现     

姜佳宁  吴利军  徐磊  赵祖虎  方宏 《地震地磁观测与研究》2019,40(4):167-175

结合地震地球物理观测台网台站监测工作实际，研制一款地震观测仪器自动监控软件。该软件适用于不同网络环境下IP类仪器设备的网络实时或定时自动监控，地球物理观测类仪器时钟、状态和观测数据的定时自动监控，能自动识别当日观测数据中的无效数据、变幅异常、干扰、地震和限幅等信息，无需借助其他硬件和软件即可将告警信息以短信方式发送给值班人员和管理人员，可实现对仪器原始观测数据的自动备份和手动恢复，及对仪器的一键重启和校正时钟等控制类操作，无需跨平台操作即可查看当日观测数据曲线及分析数据的完整性和有效性，从而实现对仪器的统一高效管理。  相似文献   

2017年九寨沟MS 7.0地震震源深度测定     

郑国栋  梁姗姗  邹立晔  梁建宏  徐志国  安祥宇 《地震地磁观测与研究》2019,40(5):21-28

为了更好地确定2017年8月8日九寨沟M_(S )7.0地震震源深度其发震机理,利用四川、甘肃和青海区域地震台网的观测波形数据,采用多种方法研究了此次地震的震源深度。首先,采用gCAP方法反演了九寨沟M_(S )7.0地震的震源机制解和矩心深度,结果显示,节面Ⅰ走向243°/倾角87°/滑动角-158°,节面Ⅱ走向151°/倾角68°/滑动角-3°,矩震级为M_(W )6.5,矩心深度为8 km;然后,采用ISOLA近震全波形方法反演了此次地震的震源机制解,反演结果与gCAP方法结果相差不大,矩心深度为7 km;最后,通过sPn震相与Pn震相之间的走时差测定此次地震初始破裂震源深度,结果显示深度约为12 km。研究表明,九寨沟M_(S )7.0地震的矩心深度为7—8 km,初始破裂深度约为12 km。  相似文献   

不同水位和竞争模式对典型湿地植物生态化学计量特征的影响     

李旭  于洁  李峰  胡聪  曾静  侯志勇  谢永宏  陈心胜 《湖泊科学》2019,31(6):1651-1661

以洞庭湖典型湿地植物辣蓼为目标植物,短尖苔草为邻近植物,通过控制实验研究不同水位(30、0和-30 cm)和竞争(无竞争、全部竞争、地上竞争和地下竞争)模式下目标植物生长及生态化学计量特征的变化.结果表明:水位处理显著影响不同竞争模式下的生物量积累,辣蓼生物量随水位增加显著降低;-30 cm水位无竞争模式下生物量最大,为10.84±1.52 g.在30 cm和0 cm水位梯度下,不同竞争模式下的生物量间无显著差异.但-30 cm水位下,地下竞争模式下的辣蓼生物量积累较全竞争模式和地上竞争模式下显著增多,说明非胁迫条件下,辣蓼和苔草的竞争以地上竞争为主.水位处理对辣蓼叶片、茎和根的氮、磷含量影响显著,30 cm水位下,叶片氮、磷含量显著高于其他水位下的含量.在-30cm水位下,叶片C∶N和C∶P显著高于其他水位下的比值,分别为48.08±3.85、590.3±43.4.相比于对照处理(无竞争),竞争作用下的辣蓼总氮含量降低,而C∶N值增加,N∶P值降低,这可能是因为竞争作用导致辣蓼对氮的吸收减少所致.  相似文献   

Global Statistical Assessment and Cross-Calibration with Jason-2 for Reprocessed HY-2 A Altimeter Data     

Maofei Jiang  Ke Xu  Yalong Liu 《Marine Geodesy》2018,41(3):289-312

HY-2 A (Haiyang-2 A) satellite was launched on August 16, 2011 and radar altimeter is one of its main payloads. We reprocessed two years of HY-2 A altimeter sensor geophysical dataset records (SGDR) data. This paper presents the main results in terms of reprocessed HY-2 A altimeter data quality: verification of data availability and validity, monitoring several relevant altimeter parameters, and assessment of the HY-2 A altimeter system performances. A cross-calibration analysis of reprocessed HY-2 A altimeter data with Jason-2 was conducted. The reprocessed HY-2 A altimeter data show good quality and have a low level of noise with respect to Jason-2. The same geophysical correction methods were used to calculate the sea surface height (SSH) for the two missions. The mean standard deviations of the crossover differences for HY-2 A and Jason-2 are 5.24 cm and 5.34 cm, respectively. The mean standard deviation of the crossover differences between HY-2 A and Jason-2 is 5.37 cm. These show that HY-2 A can provide SSH measurements at almost the same level of accuracy as Jason-2. The relative SSH bias between HY-2 A and Jason-2 due to the Ultra Stable Oscillator (USO) drift is obviously observed, and it can affect the calculation of mean sea level and should be further studied and corrected.  相似文献