Long‐term streamflow trends in Hawai'i and implications for native stream fauna     

Hannah M. Clilverd  Yin‐Phan Tsang  Dana M. Infante  Abigail J. Lynch  Ayron M. Strauch 《水文研究》2019,33(5):699-719

Climate change has fundamentally altered the water cycle in tropical islands, which is a critical driver of freshwater ecosystems. To examine how changes in streamflow regime have impacted habitat quality for native migratory aquatic species, we present a 50‐year (1967–2016) analysis of hydrologic records in 23 unregulated streams across the five largest Hawaiian Islands. For each stream, flow was separated into direct run‐off and baseflow and high‐ and low‐flow statistics (i.e., Q10 and Q90) with ecologically important hydrologic indices (e.g., frequency of flooding and low flow duration) derived. Using Mann–Kendall tests with a running trend analysis, we determined the persistence of streamflow trends through time. We analysed native stream fauna from ~400 sites, sampled from 1992 to 2007, to assess species richness among islands and streams. Declines in streamflow metrics indicated a general drying across the islands. In particular, significant declines in low flow conditions (baseflows), were experienced in 57% of streams, compared with a significant decline in storm flow conditions for 22% of streams. The running trend analysis indicated that many of the significant downward trends were not persistent through time but were only significant if recent decades (1987–2016) were included, with an average decline in baseflow and run‐off of 10.90% and 8.28% per decade, respectively. Streams that supported higher native species diversity were associated with moderate discharge and baseflow index, short duration of low flows, and negligible downward trends in flow. A significant decline in dry season flows (May–October) has led to an increase in the number of no‐flow days in drier areas, indicating that more streams may become intermittent, which has important implications for mauka to makai (mountain to ocean) hydrological connectivity and management of Hawai'i's native migratory freshwater fauna.  相似文献   

浙江省测震观测台网井下地震计方位角检测与校正     

张明  陈军辉  严俊峰  尹晶飞  戴陈兵 《地震地磁观测与研究》2019,40(4):125-129

选取浙江省测震台网景宁、北仑、南麂岛地震台井下地震计观测数据，采用地震数据波形相关性分析法，与地表地震计同步观测数据进行相关性分析，检测并校正井下地震计方位角，结果发现，3个地震台井下地震计方位角实际偏差分别为82.2°、-22.8°、32.2°。分析认为，井下地震计安装易受线缆应力影响，导致方位角与实际偏差过大，应在应力释放完成后固定地震计，并架设地表地震计进行数据相关性分析，以确定方位角可靠性。  相似文献   

胶州湾沉积物中石油降解菌的降解能力及多样性研究     

高伟  高祥兴  米铁柱  韩彬  张毅然  李馨子  尹晓斐  孙承君  李倩  崔志松  栾晓  于志刚  郑立 《海洋学报(英文版)》2019,38(6):54-64

2013年青岛输油管道爆炸，大量石油污染了附近海岸。课题组采集了污染的沉积物样品，以原油为唯一碳源和能源，富集了四个石油降解菌群。生物多样性和群落分析表明，Luteibacter、Parvibaculum 和属于食烷菌科的一个属是降解菌群的主要优势菌，都属于变形菌门。从石油降解菌群中分离筛选，获得了9株具有不同16S rRNA基因序列的降解菌，分别属于8个属。重量法测定降解菌的石油降解率，其中5株的石油降解率大于30%。GC-MS分析结果表明，石油降解菌多倾向于降解烷烃，对多环芳烃的降解能力较差，其中5株细菌的烷烃降解率较大，仅1株菌D2对多环芳烃的降解率较大，其降解率在34.9%到77.5%。通过对高通量数据的分析，表明食烷菌属是菌群A和菌群E的主要降解菌群，其中筛选获得的菌株E4可能是菌群E的一株优势降解菌。本研究所筛选菌株证明了其石油降解潜力，为油污染海滩生物修复提供了菌株资源。  相似文献   

A method for the extraction of partition lines from long and narrow patches that account for structural features     

Chengming Li  Zhaoxin Dai  Yong Yin  Pengda Wu 《Transactions in GIS》2019,23(2):349-364

The extraction of partition lines for long and narrow patches (LN patches) is an important yet difficult problem in the generalization of thematic data. When current methods are used to process polygons with irregular shapes or complex branch convergence zones, the extracted line structural features tend to be inaccurate and topologically erroneous. In this article, we propose an improved partition lines extraction algorithm of constrained Delaunay triangulation to counter these issues. The proposed method aims to maintain consistency between the extracted line structure characteristics and the actual object structure, especially for complex branch convergence zones. First, we describe three types of aggregation patterns (Type A, B, and C aggregation zones) that occur in partition line extractions for LN patches of complex branch convergence zones using Delaunay triangulation. Then, a partition line extraction algorithm that accounts for the direction between the edges of triangles and the distance of nodes in aggregation zones is proposed. Finally, we test our method for a dataset relating to Guizhou Province, China. Compared with the current method that uses quantitative indicators and visualization, the results indicate that our method not only has applicability for simple situations but also is superior for preserving structural features of complex branch convergence zones.  相似文献   

Groundwater recharge in an arid grassland as indicated by soil chloride profile and multiple tracers          下载免费PDF全文

Tianming Huang  Zhonghe Pang  Jilai Liu  Lihe Yin  W. Mike Edmunds 《水文研究》2017,31(5):1047-1057

Previous studies have shown that shallow groundwater in arid regions is often not in equilibrium with near‐surface boundary conditions due to human activities and climate change. This is especially the case where the unsaturated zone is thick and recharge rate is limited. Under this nonequilibrium condition, the unsaturated zone solute profile plays an important role in estimating recent diffuse recharge in arid environments. This paper combines evaluation of the thick unsaturated zone with the saturated zone to investigate the groundwater recharge of a grassland in the arid western Ordos Basin, NW China, using the soil chloride profiles and multiple tracers (²H, ¹⁸O, ¹³C, ¹⁴C, and water chemistry) of groundwater. Whereas conventional water balance and Darcy flux measurements usually involve large errors in recharge estimations for arid areas, chloride mass balance has been widely and generally successfully used. The results show that the present diffuse recharge beneath the grassland is 0.11–0.32 mm/year, based on the chloride mass balance of seven soil profiles. The chloride accumulation age is approximately 2,500 years at a depth of 13 m in the unsaturated zone. The average Cl content in soil moisture in the upper 13 m of the unsaturated zone ranges from 2,842 to 7,856 mg/L, whereas the shallow groundwater Cl content ranges from 95 to 351 mg/L. The corrected ¹⁴C age of shallow groundwater ranges from 4,327 to 29,708 years. Stable isotopes show that the shallow groundwater is unrelated to modern precipitation. The shallow groundwater was recharged during the cold and wet phases of the Late Pleistocene and Holocene humid phase based on palaeoclimate, and consequently, the groundwater resources are nonrenewable. Due to the limited recharge rate and thick unsaturated zone, the present shallow groundwater has not been in hydraulic equilibrium with near‐surface boundary conditions in the past 2,500 years.  相似文献   

A biodiversity evaluation framework for restoration of aquatic macrophyte communities in shallow lakes driven by hydrological process management     

Shuhan Li  Tao Sun  Wei Yang  Baoshan Cui  Xinan Yin 《水文研究》2021,35(1):e13983

Macrophyte community diversity and composition respond to ecosystem conservation and local environmental factors. In this study, we developed a multidimensional diversity framework for macrophyte communities, including the taxonomic and functional alpha and beta diversity. We used the framework to explore the relationships among water level regimes and these diversity parameters in a case study of China's Baiyangdian Lake. Analysis of indicators of hydrologic alteration divided the water level from 1959 to 2019 into four regimes (dry, <6.42 m; low, 6.42–7.23 m; medium, 7.23–8.19 m; high, >8.19 m). Alpha and beta diversity were significantly higher in the medium regime than in the low and high regimes. Redundancy analysis indicated that the maximum water depth significantly affected taxonomic alpha diversity, and total nitrogen (TN) and chemical oxygen demand (COD) concentration significantly affected functional alpha diversity, respectively. Mantel tests showed that TN, Secchi depth (SD), and water depth in the high water level regime significantly increased the total beta diversity and turnover components. TN was the main factor that increased total taxonomic beta diversity. Water level regime mainly influenced interspecific relationships by changing the TN and COD concentration. The water level should be maintained between the medium and high water level regimes to promote restoration of the macrophyte community and improve ecosystem stability. The biodiversity evaluation framework would provide a deeper insight into the hydrological process management for restoration of aquatic macrophyte communities in shallow lakes.  相似文献   

Origin of sulphate in the unsaturated zone and groundwater of a loess aquifer     

Yin Long  Tianming Huang  Fen Zhang  Zhenbin Li  Baoqiang Ma  Yiman Li  Zhonghe Pang 《水文研究》2021,35(4):e14166

The use of the sulphate mass balance (SMB) between precipitation and soil water as a supplementary method to estimate the diffuse recharge rate assumes that the sulphate in soil water originated entirely from atmospheric deposition; however, the origin of sulphate in soil and groundwater is often unclear, especially in loess aquifers. This study analysed the sulphur (δ³⁴S-SO₄) and oxygen (δ¹⁸O-SO₄) isotopes of sulphate in precipitation, water-extractable soil water, and shallow groundwater samples and used these data along with hydrochemical data to determine the sources of sulphate in the thick unsaturated zone and groundwater of a loess aquifer. The results suggest that sulphate in groundwater mainly originated from old precipitation. When precipitation percolates through the unsaturated zone to recharge groundwater, sulphates were rarely dissolved due to the formation of CaCO₃ film on the surface of sulphate minerals. The water-extractable sulphate in the deep unsaturated zone (>10 m) was mainly derived from the dissolution of evaporite minerals and there was no oxidation of sulphide minerals during the extraction of soil water by elutriating soil samples with deionized water. The water-extractable concentration of SO₄ was not representative of the actual SO₄ concentration in mobile soil water. Therefore, the recharge rate cannot be estimated by the SMB method using the water-extractable concentration of SO₄ in the loess areas. This study is important for identifying sulphate sources and clarifying the proper method for estimating the recharge rate in loess aquifers.  相似文献   

内蒙古分区地壳速度模型的建立及应用分析     

赵艳红  舒雷  刘永梅  张珂  尹占军 《中国地震》2018,34(4):731-744

内蒙古测震台网自"十五"数字化网络建成以来,一直使用华南速度模型。多年的大震速报和地震编目结果显示,华南速度模型不符合内蒙古地区的地质构造特征; 2016年开始使用的内蒙古2015速度模型也不能完全满足内蒙古各区域地震定位的需求。本文对内蒙古地区2009～2016年记录的所有M_L≥3.0地震震相数据利用速度拟合和折合走时方法,反演适合内蒙古西部、东部、中部各区域的分区地壳速度结构模型,并对西部速度模型、东部速度模型、中部速度模型进行应用对比分析。各分区的地壳速度模型定位误差较小,可靠性和稳定性优势明显。  相似文献   

地震台智能电源Android平台控制系统     

石磊  刘静  李凤  尹宏伟 《地震地磁观测与研究》2018,39(3):218-222

针对无人值守地震台因供电故障造成的观测数据质量问题，现阶段GPRS在地震台站的应用大多以手机短信呈现，无良好的可视化操作界面，设计开发一种底层基于STM32单片机，以GPRS为数据传输方式，Android手机APP为监控界面的智能电源控制系统。通过在河北省地震局石家庄中心台下属的深州郭家庄地震台进行应用，证明该电源控制系统能够保证观测设备的稳定运行，并为设备维护提供了保障和依据。  相似文献   

唐山马家沟矿井水位异常分析     

赵建明  李红超  赵亮  董祎玮  尹宝军 《地震地磁观测与研究》2018,39(5):150-156

地下水动态受水文因素影响较大，对地震和构造活动具有较灵敏的响应。判别并排除各种水文干扰，确认地下水在地震前的异常变化，对提高地震分析预报能力，具有重要作用。马家沟矿井水位动态观测层与地下水开采层为同一含水层，井水位于2010年出现破年变异常，加速持续上升，截至2015年，最大上升幅度约30 m。依据该井水文地质环境特征，根据唐山市区2001-2015年地下水位、降雨量、地下水开采量实测资料，建立合理多元回归模型和三维地下水流动模型，发现地下水开采量减少应为影响马家沟矿井水位动态的可能因素。文中采取的异常识别与分析方法，可为其他类似井孔的地下水动态异常识别及判定提供一定借鉴。  相似文献