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1.
Using time series analysis to assess tidal effect on coastal groundwater level in Southern Laizhou Bay,China 
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下载免费PDF全文 Chen She-ming Liu Hong-wei Liu Fu-tian Miao Jin-jie Guo Xu Zhang Zhou Jiang Wan-jun 《地下水科学与工程》2022,10(3):292-301
Sea water intrusion is an environmental problem cause by the irrational exploitation of coastal groundwater resources and has attracted the attention of many coastal countries. In this study, we used time series monitoring data of groundwater levels and tidal waves to analyze the influence of tide flow on groundwater dynamics in the southern Laizhou Bay. The auto-correlation and cross-correlation coefficients between groundwater level and tidal wave level were calculated specifically to measure the boundary conditions along the coastline. In addition, spectrum analysis was employed to assess the periodicity and hysteresis of various tide and groundwater level fluctuations. The results of time series analysis show that groundwater level fluctuation is noticeably influenced by tides, but the influence is limited to a certain distance and cannot reach the saltwater-freshwater interface in the southern Laizhou Bay. There are three main periodic components of groundwater level in tidal effect range (i.e. 23.804 h, 12.500 h and 12.046 h), the pattern of which is the same as the tides. The affected groundwater level fluctuations lag behind the tides. The dynamic analysis of groundwater indicates that the coastal aquifer has a hydraulic connection with seawater but not in a direct way. Owing to the existence of the groundwater mound between the salty groundwater (brine) and fresh groundwater, the maximum influencing distance of the tide on the groundwater is 8.85 km. Considering that the fresh-saline groundwater interface is about 30 km away from the coastline, modern seawater has a limited contribution to sea-salt water intrusion in Laizhou Bay. The results of this study are expected to provide a reference for the study on sea water intrusion. 相似文献
2.
Freshwater discharge into Albemarle Sound and many other large estuaries can have a major impact on the physical and biological properties of the estuary. Earlywood (EW) and latewood (LW) width tree ring chronologies recently developed from ancient trees and sub-fossil logs found at Devil’s Gut of the Roanoke River, North Carolina, were used with new EW and LW width data from Blackwater River, Virginia, to reconstruct the July Palmer Hydrological Drought Index (PHDI) over the drainage basin of Albemarle Sound from 934 to 2005. This reconstruction is based on a principal component regression using millennium-long chronologies of both EW and LW widths, calibrated and verified against instrumental July PHDI from 1895 to 1985. The reconstruction provides a lengthy representation of inter-annual to multi-decadal growing season moisture variability that directly affects water quality in the Albemarle Sound estuarine ecosystem. Single-year drought and wetness extremes were more common in the modern instrumental period (1895–2005), but prolonged droughts reconstructed during the Medieval and Early Colonial eras were more severe and sustained than the reconstructed or observed droughts during the twentieth century. Several abrupt transitions between decadal drought and wetness regimes are reconstructed, especially during the Medieval Era. Composite analysis of lower-magnitude sub-decadal regime shifts in the instrumental record during the twentieth century indicates that major changes in mid-latitude circulation over the Northern Hemisphere may have been involved in these longer decadal transitions between moisture regimes over Albemarle Sound in prehistory. 相似文献
3.
Kuo-Chuin Wong 《Estuaries and Coasts》1990,13(4):362-372
Sea level variability in Long Island Sound is examined at both tidal and subtidal frequencies over a 1-yr period. The sound is found to be decoupled effectively from the lower Hudson Estuary at tidal frequencies. The predominantly semidiurnal tides in the sound are forced by the oceanic tides transmitted from the mouth. There is a near fourfold amplification of the semi-diurnal tides within the sound due to resonance. Diurnal tides are much weaker in the sound, and there is also no evidence of significant amplification in the interior. At subtidal frequencies, the pressure-adjusted sea level in the interior of the sound is forced by a combination of co-oscillation with coastal sea level at the mouth and direct setup induced by local wind forcing over the surface of the sound. Because the longitudinal axis of Long Island Sound is roughly aligned with the open coast from Montauk Point to Sandy Hook, these two mechanisms work in concert to produce larger subtidal sea level fluctuations in the western sound relative to those in the eastern sound. A linearized, frequency-dependent analytical model is developed to aid the interpretation of field observations. 相似文献
4.
受大气降水、黄河水位断流、风暴潮和人类工程活动等因素影响,现代黄河三角洲滨海湿地生态水文环境极其脆弱和敏感。本文运用地下水数值模拟方法,通过构建滨海湿地水文模型,以氯离子作为模拟因子,预测滨海湿地地下水趋势性变化。计算结果显示,湿地水位和盐度对湿地生长和发育起控制作用;黄河持续断流和强烈风暴潮对湿地水质影响明显;当风暴潮引起增水幅度超过正常潮高的2.4m,会造成沿海低地特别是北部未受防潮大坝保护的滨海湿地淹没。 相似文献
5.
Judith Wolf 《Natural Hazards》2009,49(2):241-260
Wind waves and elevated water levels together can cause flooding in low-lying coastal areas, where the water level may be
a combination of mean sea level, tides and surges generated by storm events. In areas with a wide continental shelf a travelling
external surge may combine with the locally generated surge and waves and there can be significant interaction between the
propagation of the tide and surge. Wave height at the coast is controlled largely by water depth. So the effect of tides and
surges on waves must also be considered, while waves contribute to the total water level by means of wave setup through radiation
stress. These processes are well understood and accurately predicted by models, assuming good bathymetry and wind forcing
is available. Other interactions between surges and waves include the processes of surface wind-stress and bottom friction
as well as depth and current refraction of waves by surge water levels and currents, and some of the details of these processes
are still not well understood. The recent coastal flooding in Myanmar (May 2008) in the Irrawaddy River Delta is an example
of the severity of such events, with a surge of over 3 m exacerbated by heavy precipitation. Here, we review the existing
capability for combined modelling of tides, surges and waves, their interactions and the development of coupled models. 相似文献
6.
A high-resolution coastal ocean model is used to investigate salinity variability and water exchange in a complex coastal system off the southern U.S. characterized by three adjacent sounds that are interconnected by a network of channels, creeks, and intertidal areas. Model results are generally highly correlated with observations from the Georgia Coastal Ecosystem Long Term Ecological Research (GCE-LTER) program, revealing a high degree of salinity variability at the Altamaha River and Doboy Sound, decreasing sharply toward Sapelo Sound. A Lagrangian particle tracking method is used to investigate local residence time and connectivity in the system. Local residence time is highly variable, increasing with distance from the Altamaha River and decreasing with river flow, revealing that discharge plays a dominant role on transport processes and estuary-shelf exchange. The Altamaha River and Doboy Sound are connected to each other in all seasons, with exchange occurring both via coastal and estuarine pathways. While particles released at the Altamaha and Doboy rarely reach Sapelo Sound, particles released at Sapelo Sound and the creeks surrounding its main channel can reach the entire estuarine system. 相似文献
7.
Tim Beach Sheryl Luzzadder-Beach Nicholas Dunning John Jones Jon Lohse Tom Guderjan Steve Bozarth Sarah Millspaugh Tripti Bhattacharya 《Quaternary Science Reviews》2009,28(17-18):1710-1724
In the Maya Lowlands of Mexico, Belize, and Guatemala two main types of wetlands have played important roles in human history: bajos or intermittently wet environments of the upland, interior Yucatán and perennial wetlands of the coastal plains. Many of the most important Maya sites encircle the bajos, though our growing evidence for human–wetland interactions is still sparse. The deposits of these wetlands record two main eras of slope instability and wetland aggradation: the Pleistocene–Holocene transition as rainfall increased and forests eclipsed savannas and the Maya Preclassic to Classic as deforestation, land-use intensity, and drying increased. The ancient Maya adapted with terraces around these bajo margins but retracted in the Late Preclassic in some areas. The perennial wetlands of the coastal plains have different histories, and the first conceptual model of human–wetland interaction described intensive wetland agriculture in the Preclassic through Classic based on raised fields and canals. But a second model arose that interpreted the wetland stratigraphy and canals as more indicative of natural aggradation by accelerated erosion and gypsum precipitation that buried Archaic and Preclassic fields and there was little Classic era use. We present new data on a third and fourth model in this study. The third is a hybrid of the models one and two, including the Archaic to Preclassic aggradation of the second model, and the first model's Classic period fields and canals as piecemeal attempts by the Maya to adapt to these and other environmental changes. The fourth conceptual model describes a very Late/Terminal Classic, preplanned project on a floodplain. These wetland fields were short-lived, aggraded rapidly but with some reoccupation in the Postclassic. All of these new models display the burgeoning evidence for intricate Maya interactions with wetlands, and the diversity of evidence from the relatively few studies underscores the infancy of our understanding of Maya interaction with tropical wetlands. 相似文献
8.
Marcin Słowik 《Environmental Earth Sciences》2013,70(3):1277-1295
Ground penetrating radar (GPR) measurements have been conducted to retrace the natural course of the Obra River and changes of spatial extent of Obrzańskie Lake (western Poland). The Obra River valley was subjected to intensive anthropogenic transformation. Three artificial canals were constructed here in the beginning of the nineteenth century. The GPR surveys were done using a georadar MALA ProEx equipped with 250 MHz antenna. The measurement was verified by coring and analyses of historical maps, aerial photographs, and satellite images. The research has shown that there are at least three elongated depressions preserved in the modern land surface near the village of Solec, situated in the middle course of the valley. Several structures suggesting functioning of a multi-channel pattern in the past have been detected inside and in the vicinity of the depressions. Filling the channels with silts and peats might have been the effect of flow deceleration caused by the construction of the Obra Canals. Moreover, situation of two of the retraced depressions suggests that the landforms might be the remains of a river bed disappearing in wetlands. Further studies including groundwater flux measurements in the area between the depressions are needed to confirm such hypothesis. Furthermore, the study allowed retracing the spatial extent of Obrzańskie Lake. The sediment structures detected by the GPR measurements and calibrated with coring were interpreted to be the traces of the lake shoreline. The interpretation was supported by the findings inferred from aerial and satellite images. It was shown that Obrzańskie Lake had had at least three islands and had been directly connected with a network of braided channels before the anthropogenic intervention. The spatial extent of the lake was significantly altered by the construction of the North Obra Canal. Disconnecting the lake from the Canal resulted in more than 50 % decrease of the lake surface. 相似文献
9.
Freshwater–saline water interactions were evaluated in a coastal region influenced by external forces including tidal fluctuations and seasonal rainfall variations. Five different coastal zones were considered on Jeju Island, South Korea, and electrical conductivity (EC) profiles from the monitoring wells were examined to identify the configuration of the freshwater–saline water interface. There appeared to be discrepancies among EC profiles measured at different points in time. To analyze the dynamic behavior of freshwater–saline water interactions, groundwater level measurements and multi-depth EC and temperature probes were used to obtain time-series data; the data showed that water level, EC and temperature were influenced by both tidal fluctuations and heavy rainfall. The effects of oceanic tide on EC and temperature differed with depth due to hydraulic properties of geologic formations. A spectral filter was used to eliminate the effects of tidal forces and provide information on the influence of heavy rainfall on water level, EC and temperature. Heavy rainfall events caused different patterns and degrees of variation in EC and temperature with depth. The time-series data of EC and temperature in the subsurface at various depths enable greater understanding of the interaction processes between fresh and saline water. 相似文献
10.
海潮波动可以引起海岸带有越流的承压含水层地下水头发生波动。建立了基于有限差分法的滨海地区一维承压含水层地下水运动数值模型。通过将潮汐波动概化为正弦波,分别对初始水头水平及线性倾斜的承压含水层模拟了滨海地区有越流的承压含水层地下水头随潮汐波动的变化。通过对两种情形下的变化比较,结果表明,受海潮影响的滨海承压含水层地下水头与海潮有相似的波动特征,但变幅减小,受海潮的影响程度与离海岸的距离有关,随着离海岸距离的增加,地下水头的变幅及潮汐效率呈负指数函数衰减,水头倾斜情形下变幅更小,潮汐效率更小,滞后时间更短,地下水头对海潮的滞后时间随距离呈线性增加。 相似文献