Water Level Difference Research Articles

Mapping of Maximum and Minimum Inundation Extents in the Amazon Basin 2014–2017 with ALOS-2 PALSAR-2 ScanSAR Time-Series Data

Seasonal inundation is an important effect that governs the distribution of ecosystems in the tropics. In the Amazon Basin, the seasonal flood pulse causes a difference in high and low water levels that can exceed 15 m. The associated flood duration and extent play an important role in land-atmosphere carbon exchange and affect the ecosystem’s carbon pool that originates from organic matter transported from upland and flooded forests. Studies of wetlands inundation across the Amazon Basin have utilized dual season mosaics from JERS-1 and wide-swath ScanSAR data from ALOS PALSAR to characterize inundation across the basin. This study builds upon past efforts with JERS-1 and ALOS PALSAR and uses ALOS-2 PALSAR-2 ScanSAR data to generate annual maximum and minimum inundation extent maps over the full Amazon Basin for the period spanning November 2014–October 2017. The study uses decision tree classification to create a maximum and a minimum inundation extent map for each year over this time period. The results show that a generalized algorithm that fits the entire basin has an 86% overall accuracy compared with a classification made for a local region from the same PALSAR-2 datasets. Comparisons with previous full-basin inundation maps by other L-band radars shows similar results for inundated areas during maximum inundation. The maps derived previously from JERS-1 and ALOS PALSAR show 7.3% and 6.9% inundated vegetation, respectively, and this study using PALSAR-2 shows values ranging between 5.5% and 7.0% across the three study years. Comparisons between the stage data across the basin and acquisition dates/periods for JERS-1 and PALSAR-2 show that the sensors capture the nature of the maximum and minimum flooding across the basins but have not successfully captured the exact maximum and minimum flood levels that have been recorded in the stage data. The inundation maps are publicly available under a Creative Commons (CC BY 4.0) licensefrom the Alaska Satellite Facility.

Performance Investigation of the Immersed Depth Effects on a Water Wheel Using Experimental and Numerical Analyses

The purpose of this research is to study the effect of different immersed depths on water wheel performance and flow characteristics using numerical simulations. The results indicate that the simulation methods are consistent with experiments with a maximum error less than 5%. Under the same rotational speeds, the efficiency is much higher and the fluctuation amplitude of the torque is much smaller as the immersed radius ratio increases, and until an immersed radius ratio of 82.76%, the wheel shows the best performance, achieving a maximum efficiency of 18.05% at a tip-speed ratio (TSR) of 0.1984. The average difference in water level increases as the immersed radius ratio increases until 82.76%. The water area is much wider and the water volume fraction shows more intense change at the inlet stage at a deep immersed depth. At an immersed radius ratio of 82.76%, some air intrudes into the water at the inlet stage, coupled with a dramatic change in the water volume fraction that would make the flow more complex. Furthermore, eddies are found to gradually generate in a single flow channel nearly at the same time, except for an immersed depth of 1.2 m. However, eddies generate in two flow channels and can develop initial vortexes earlier than other cases because of the elevation of the upstream water level at an immersed radius ratio of 82.76%.

Water Level Fluctuation under the Impact of Lake Regulation and Ecological Implication in Huayang Lakes, China

Water level fluctuation (WLF) in shallow lakes in the middle and lower reaches of the Yangtze River has been a concern of many researchers. This work aims to investigate the effects of climate change and regulation of floodgates and the Three Gorges Dam (TGD) on WLF and lake volume in Huayang Lakes during the past 52 years. The results revealed that precipitation is the dominant factor that leads to seasonal variation of lake levels, whereas regulation of floodgates and TGD are the key drivers of hydrology regime change in the past 20 years. Natural lake regime has higher water level when there is more precipitation and less lake volume. Floodgates and TGD regulations have changed this pattern since 2003, causing less difference in water level in spite of more precipitation and lake recession. Under the combined impacts of floodgates and TGD regulations, Huayang Lakes have experienced a prolonged outflow time since 2003 and the contribution rate caused by the floodgates and TGD regulations has increased by 19.90%. Additionally, the water level of Huayang Lakes decreased by approximately 0.3~0.5 m from September to November, but it showed no alteration from January to March in the past two decades. This indicated that floodgate regulations used for agricultural irrigation and fishery culture dominate the hydrology regime in winter and early spring. This study is beneficial for aquatic ecosystem protection in floodgate-controlled lakes under the circumstance of climate change and vigorous anthropology activities.

Severe Weather-Induced Exchange Flows through a Narrow Tidal Channel of Calcasieu Lake Estuary

Exchange flows between estuaries and the coastal ocean are important for land-ocean interactions and ecosystem health. This study is aimed at resolving severe weather-induced exchange flows between the Calcasieu Lake Estuary and Gulf of Mexico. For that purpose, we use data from a long-term deployment of side-looking acoustic Doppler current profilers (ADCPs) and conductivity-temperature-depth sensors (CTDs) as well as flow velocity data from a boat operated survey. Regression between the transport measured from a boat mounted ADCP and the velocity data from a fixed side-looking ADCP is done to calculate a long-term transport along the Calcasieu Pass. Analyses have been done for the hydrodynamic response to 16 cold fronts passing the study area. Effects of six strongest cold fronts are discussed in more detail. Results have confirmed that the hydrodynamics is highly correlated with the frequent cold fronts. The highest correlation coefficient is r ~0.75 between the north wind and along channel transport. In general, winds from the southern quadrants push water into the estuary before each frontal passage; after the passage of the front, a rapid change of wind direction to the northern quadrants produces strong outward flows. A quasi-steady state balance between the wind stress and water level difference proposed in recent studies for different systems is further confirmed and discussed in this system. The quasi-steady state balance leads to a relatively high R2 value of greater than 0.8 between the modeled water level gradient and actual observed gradient. We have also applied a regression model, derived from the momentum balance requirement, for the subtidal exchange flow as a function of wind components and their squares which yield an R2 value greater than 0.7. With a confidence in the regression model, we further implement it for twelve years from 26 February 2007 to 10 April 2019. Four extreme events during this 12-year period of time are discussed–they include the Hurricane Ike (2008), Tropical Storm Lee (2011), a warm front, and a cold front. This hindcast of the exchange flows over multiple years can provide a useful tool for coastal management and research for estuarine channels where continuous observations of velocity are not always available.

Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone

Earth slopes stability analysis is important in the design and construction of earth dams under different loading conditions. Several factors such as difference in water level or rapid drawdown in the reservoir, right after construction, and steady - state seepage may result in instability of Earth Dams for all possible combinations. In this study, three scenarios were evaluated for the Gbeni Earth Dam (GB3) at Sierra Rutile Mining Company in Sierra Leone. It is a zoned earth-filled embankment dam with respective upstream and downstream slopes of 1:3 and 1:2, having a horizontal sand blanket downstream. The upstream slope was subjected to both rapid drawdown in the reservoir of the earth dam and end of construction condition when there is no water present in the reservoir, whilst the downstream slope was assessed for steady seepage and end of construction conditions. The shape of the critical slip surface of both slopes was evaluated using a circular failure surface. The objective of this study was to assess the stability of these slopes under the above conditions using traditional analysis according to the theory of limit states and safety factor in GEO 5 software and its subprograms. The level of water on the upstream and downstream banks, the geotechnical properties of soil materials and boundary conditions of the dam were used as contribution variables and safety factors as the desired output. The study found out that the factor of safety against sliding of the upstream slope marginally drops within the short period after the start of rapid drawdown of water in the reservoir of the dam. Also, the downstream slope was found to be more stable under steady seepage. This accounts for the uncertainties involved in the strength of material, pore pressures in impervious clay core material, and long-term loading condition.

ДВУХПРУДОВОЙ НАГУЛЬНО-ВЫРОСТНОЙ РЫБОВОДНЫЙ КОМПЛЕКС

Purpose: development and description of the layout and design solution for a two-pond feeding nursery fish-breeding complex, which characterizes by compact placement of its constituent structures and their adaptation to the topographic conditions of the territory. Materials and methods. The theoretical and empirical basis for the development was made up of well-known recommendations on design and construction of pond complexes and survey data of operating fish-breeding facilities and their structures. During the development, the technologies of search design of engineering projects in compliance with fish breeding requirements and restrictions were used. Results. The fish-breeding complex includes: two fish-breeding ponds with a common dividing dam and a water supply system including a pumping station; water supply pipe system; a system of devices and structures that ensure the release of fish grown in ponds into a fish trap; spillway devices for discharging water from ponds and a fish trap with a set of regulating elements. Fish ponds are located on the floodplain lands of the river Don and are formed by protecting dikes. The bed of the reservoirs is planned with sections with longitudinal and transverse slopes to the water-fish collecting and-transporting ditches arranged in their bottom, allowing them to be emptied and the fish grown in the ponds to be directed to the outlet structures. The release of fish from the ponds is carried out by two tower water outlets. The design of the fish trap provides for the accumulation and seine fishing, it is equipped with means for regulating water discharge and maintaining conditions for fish. Conclusions. The developed layout and design solution for a two-pond fish-breeding complex with one fish trap is adapted to the local relief and the difference in water levels in ponds and in water intake. The implemented layout and design solutions can be used in the development of similar objects

The Wingate Field, Blocks 44/23b, 44/24b and 44/19f, UK North Sea

Abstract The Wingate gas field was discovered in August 2008 by Wintershall's exploration well 44/24b-7, which targeted a Base Permian closure with subcropping reservoirs of the Late Carboniferous Lower Ketch Formation. Pre-drill, significant upside was identified as a result of ConocoPhillips’ nearby 44/23b-13 well (2006), where the Westoe Coal Formation provides a seat seal to the Lower Ketch Formation. Because of the significant difference in free water level between the two wells, the volumetric uncertainty of undrilled compartments with reservoirs in the Lower Ketch, as well as the Caister Coal Formation, remained relatively high. To manage development risk and uncertainty without further appraisal expenditure, and to allow for early gas production, a phased field development was planned: that is, to appraise through development and production. Gas production, through a six-slot platform and export to the Dutch D15-A platform, commenced in October 2011, only 3 years after discovery. Initial development comprised the tieback of the exploration well and drilling of the second compartment with well 44/24b-A2Y. Subsequently, three more compartments were drilled as soon as production dropped off plateau. During the appraisal/development and 7 years of production, knowledge of the reservoirs increased significantly, improving the understanding of the challenging Westphalian gas play.

Morphological Characteristics of Cambodia Mekong Delta and Tonle Sap Lake and Its Response to River-Lake Water Exchange Pattern

Tonle Sap Lake is the largest river-connected lake, buffer area and ecological zone of Mekong River, which plays a huge role in dispelling flood peak and compensating water, and the conservation of biological diversity. The river-lake relationship between Mekong River and Tonle Sap Lake is unique and has always been a major focus in the international community. The land terrain and under-water topography were used to analyze the morphological characteristics of Cambodia Mekong Delta and Tonle Sap Lake. Long series of hydrological data of river-lake controlling stations were used to analyze the water level variation characteristics and water volume exchange pattern between Mekong River and Tonle Sap Lake, and the response relationship to river-lake morphological characteristics were also researched. The results show that: Cambodia Mekong Delta and Tonle Sap Lake Area is low-lying and flat with gentle channel gradient and water surface gradient, making the relationship between water level and area (or volume) smooth. The channel storage capacity of Mekong River and Tonle Sap River is not enough compared to the inflow, so vast flooding plain is extremely prone to be inundated, making the flood relationships between the left and right banks become very complicated. Tonle Sap Lake is a seasonal freshwater lake with water flowing in and flowing out, and the timing and intensity of water exchange with Mekong River are closely related to the water flow resistance at the exit section of Tonle Sap Lake and the cross-sectional area of Tonle Sap River, which can be reflected by the river-lake water level difference and the water level of Tonle Sap River. Affected by the river-lake morphological characteristics, the water exchange intensity between Mekong River and Tonle Sap Lake is great. Tonle Sap Lake not only stores 14.4% of flood volume (39.7 billion m3) from the Mekong River every year, but also supplies 29.7% of dry water (69.4 billion m3) to the Mekong River. Influenced by the adjustment of the floodplain, the water level fluctuation of Mekong River and Tonle Sap Lake is slow, and the rising and droop rates of water level are positively correlated with the floodplain storage area. The research results will help to understand the relationship mechanism between Mekong River and Tonle Sap Lake and provide a scientific basis for the comprehensive governance of Cambodia Mekong Delta and Tonle Sap Lake Area.

Thermal hydraulic characteristics of two-phase natural circulation for secondary side passive residual heat removal system

Abstract The Secondary Circuit Passive Residual Heat Removal System (PRHRS) is designed for advanced nuclear power system. A research on thermal hydraulic characteristics of two-phase natural circulation process for secondary circuit PRHRS has been carried out using the RELAP5 code. For this, the natural circulation steam generator (SG) and the PRHRS are modeled. Five thermal boundary conditions are set to verify the function of PRHRS. The phenomenon of flow instability in the two-phase natural circulation process is of great significance for system operation, as well as the performance of SG and condenser. Therefore, the focus is on the natural circulation flowrate oscillation of steam and condensed water. The mixed water level difference between descending pipe of PRHRS and secondary side of natural circulation SG is found to be the meaningful parameter to characterize the flow instability of natural circulation. The comparative analysis is also performed by considering the effects of height between the SG and condenser, as well as system resistance, which can provide support for PRHRS design and optimization.

Effects of Water Intake Layout along the Wharf Shoreline on Ships

Abstract The construction of a water intake along the wharf shoreline can realise the intensive and comprehensive utilisation of the shoreline. However, since the water intake will increase the lateral flow at the wharf and also the hydrodynamic forces on ships, it will bring risks to ships mooring and leaving. The effects of the water intake on ships are studied using a physical model, numerical model and standard formulas. The results show that it leads to an increase of the hydrodynamic forces acting on the ship when the standard formulas are used to calculate the forces without considering the water level difference between the two sides of the ship. The results of the physical model are closer to the real situation. Measures that can effectively reduce the influence of the water intake on ships are proposed by increasing the distance between the wharf front and the front of the water intake as well as the depth of the water inlet windows.

Development and Numerical Performance Analysis of a Pump Directly Driven by a Hydrokinetic Turbine

Marine and hydrokinetics (MHK) represent an emerging industry with hundreds of potentially viable technologies, such as potential extractable energy from plain area rivers where the water level differences are very small and the traditional water turbine pump (WTP) cannot be used. A suitable WTP, composed of a tubular turbine directly driving a centrifugal pump, was designed and developed based on computational fluid dynamics (CFD) and model tests. Two general design schemes of such river-current (RC)-driven WTP are presented here, obtaining the desired operating parameters of discharge and pump head. A CFD analysis of Scheme B, which employs a radial outlet, allowing additional degrees of freedom for the dimensions of the centrifugal pump, was carried out and verified experimentally by model tests. The minimum deviation of pump head is within ±5%, and the trend of other working conditions is consistent, so the results of the numerical simulation and model tests show good agreement, demonstrating the feasibility of the CFD method for practical applications. Then, using the CFD method, the optimum rotational speed for the turbine was determined, and the turbine draft tube was improved further. With a turbine runner diameter of 0.5 m, the results show best performance at n = 350 r/min. The straight conical draft tube was changed to an elbow draft tube with multiple exits. Additionally, four different cross-sectional shapes were designed for the pump volute, and their effects on the performance of the WTP were analyzed. Finally, the round shape was selected, because of its best performance. The turbine unit has the highest efficiency of 81.2%, at an inlet velocity v = 2.4 m/s, while the pump exhibits the best efficiency of 90.2% at the design discharge and head of 30 l/s and 4.45 m respectively. Overall, the RC-driven WTP makes good use of the kinetic energy of the river current as a power source, solving the inapplicability of traditional WTP in plain areas.

FEM Analysis of Stress Charecteristics of Cut-off Wall in Rushan River Groundwater Reservoir

In order to evaluate the safety of stress intensity of the plastic concrete cut-off wall in Rushan River underground reservoir, the most dangerous section of the cut-off wall was selected, the stress distribution characteristics of the cut-off wall were analyzed by ABAQUS finite element analysis method, the safety strength was rechecked, and the calculation results are compared with the stress calculation results of the elastic foundation beam method. The following conclusions are drawn. The calculation results of the two methods show that the water level difference between the two sides of the cut-off wall has a great influence on the stress of the cut-off wall. The maximum compressive stress of cut-off wall is less than 3 Mpa and the maximum tensile stress is less than 0.65 Mpa, which meets the design strength of plastic concrete cut-off wall. ABAQUS finite element analysis method is feasible in the stress analysis of cut-off wall. Compared with the results of elastic foundation beam method, the finite element method can better reflect the stress distribution and displacement deformation on both sides of cut-off wall. ABAQUS finite element analysis method has certain advantages in stress analysis of cut-off wall.

Research on the Water Diversion Ratio Characteristics of the Plain River Network--A Case Study of the Channel in Zhangjiagang

This study combined numerical simulation with field observation, and this study took the classical bifurcated river of Zhangjiagang as an example and built a two- dimensional hydrodynamic model of the river course upon it. In addition, this project studied the influencing factors and the mechanism of the flow diversion ratio in the plain river network and established a formula to estimate the flow diversion ratios in plain river networks with ridge regression. The results show that: (1) the water diversion ratio in plain rivers has a positive correlation with the roughness, the ratio of the width of the tributary to that of the main channel and the water level differences. The water diversion ratio has a negative correlation with the mainstream discharge. (2)The mainstream discharge and the ratio of the width of a tributary to that of the main channel are two dominant factors ofthe flow diversion ratio.(3)By establishing an equation for the water diversion ratio, the water diversion ratio in the plain river network can be predicted.

Effects of tidal variations on storm waves: A case study of the radial sand ridges along China's Jiangsu coast during Typhoon Muifa

The radial sand ridges in China's southern Yellow Sea are famous for their fan-shaped pattern with complex channel-shoals. The area's large tidal range results in waves propagating onshore when most ridges are submerged at high tide, while that process is limited by the exposure of sand ridges at low tide. We investigated these processes using the WRF-ARW and MIKE21 models to assess the different spatiotemporal distributions of storm waves during normal spring tide (TSWR) and the tidal conditions present during the passage of Typhoon Muifa (TMWR) in August 2011. Spatial analysis showed that wave directions had few changes at high tide but changed significantly at low tide owing to the sheltering effects of sand ridges in the central and southern parts of the area. Differences in water level (WLD) and significant wave height (HsD) between TSWR and TMWR were high in the central and southern parts, where maximum values were twice those further north. Temporal analysis showed that WLD and HsD at twelve observation points within the sand ridges were significantly correlated. Our results show how employing WLD and HsD data can be used to improve the science-based prediction and prevention of storm disasters under similar conditions.

Research on the influence of diversion flow ratio on the water environment in Nanjing

AbstractIn this paper, we take the Qinhuai River Basin in Nanjing as an example to study the influence of diversion flow ratio on the water environment. The daily precipitation of 20 rainfall stations in the basin was collected from 1962 to 2006, and the rainfall under different assurance rates was calculated by P-III frequency curve to calculate the surface runoff in different typical years. In the meantime, according to the downstream furcated estuary water level in different typical years, the diversion flow ratio under different frequencies was calculated by using a mathematical model of the water environment. The results show that the diversion flow ratio of a branch channel increases with the increase of water level difference, and the growth rate decreases gradually. The other branch channel diversion flow ratio decreases with the increase of water level difference, and the decreasing rate decreases gradually. The pollutant concentrations in the bifurcated rivers are equal, but the concentration decreases exponentially with the increase of the upstream flow. Under different rainfall frequencies, the diversion pollutant ratio and diversion flow ratio are equal in different months of different years.

Pengaruh Perbedaan Elevasi Muka Air Tanah Pada Pondasi Telapak Berdasarkan Studi Numerik

The south Kalimantan Province has various soil characteristic, the difference of ground water level included . Experimental modeling of foot plate foundations in various ground water level is too difficult to be performed. There were so many variables that need to be evaluated in the modeling. The numerical model was based on finite element method such in Abaqus allowed the modeling of foot plate foundations with the various of ground water level. This study modeled the foot plate foundation structure where located on various ground water level by giving variations of the effect of water level to the elevation of the foundation. Water level variations are determined successively below the foundation elevation, the same as the foundation elevation and above the foundation elevation. The analysis performed is static structure analysis with idealization of 2D shell idealization. The result of the research showed that the ground water level effect the stress and deformation of soil closed to foundation elevation. The stress had been evaluated at the base of the foundation for each ground water level difference correspondently 16,53 MPa, 9.34 MPa and 3.59 MPa. The lowest stresses was occured in ground water elevation above the foundation elevation (78.28%).

Hydraulic Capacity and Efficiency of a Low-Speed Nonpressurized Coil Pump

The paper presents the results of an investigation on hydraulics of a low-speed coil pump for transport of liquids. One of the pump’s advantages is its wide range of potential inclination angles for its rotating shaft, from the horizontal to an almost vertical position. A simplified hydraulic model was developed based on kinematic and geometrical considerations to determine the pump capacity. The model was verified under laboratory conditions using a low-speed coil pump composed of transparent PVC tube (15 mm outer diameter) wound around a cylindrical drum (104 mm external diameter; 550 mm long). Laboratory tests were performed for three angles of inclination of the axis of rotation (20°, 40°, and 60°) and four rotational speeds (10, 20, 30, and 40 rpm). The results of the tests showed satisfactory agreement with the hydraulic model predictions. Energetic efficiency was estimated on the base of electric power measurements and difference of water levels in the two arms of rotating transparent torus, partly filled with water. The hydraulic efficiency of the coil pump is increasing with decreasing rotational speed.

A 3D dynamic visualization method coupled with an urban drainage model

The urban drainage model is an important tool for the management and decision-making around an urban drainage network. Owing to urban drainage networks’ complex distribution, existing model analysis methods have gradually exposed problems of insufficient utilization of spatial information, weak coupling and analytical capacity of multi-source heterogeneous data, and poor human-computer interaction. By coupling an urban drainage model with 3D GIS technology and 3D visualization technology, this study presents a 3D dynamic visualization method of an urban drainage model (3DDVM-UDM). A case study from Chaohu, China, is used to demonstrate the method. The environmental information and distributions of pipe network objects in 3D space were presented. The urban drainage model can be edited and simulated in the 3D environment, and a 2D flooding simulation method was also established. Multiple model results were dynamically and simultaneously visualized in the pipe network entity models. By coupling and comparing the model results under different rainfall return periods, various information was intuitively analyzed, such as the water level and water quality differences of each pipe and node, and the spatial distribution differences of fully filled pipes, overflowed nodes and buildings influenced by node overflow. The operation state of a drainage pipe network can be systematically analyzed by intuitively combining with the attribute information of a pipe network, 3D spatial information and other relevant data. This study provides a feasible theory and method to assist in environmental management and decision-making, to facilitate communication between different fields, and to promote a shift in analysis from 2D to the combination of 2D and 3D.

Effects of irrigation system alterations on the trophic position of a threatened top predator in rice‐field ecosystems

Abstract Rice fields serve as alternative habitats for wetland species, and their recent reduction in area due to land conversion is considered one of the main human drivers of wetland biodiversity loss. Even for existing rice fields, physico‐chemical disturbances, such as farmland consolidation and agrochemical application, also have negative effects on wetland biodiversity. For fish that inhabit rice fields for at least part of their life history, differences in water level between rice fields and irrigation ditches caused by irrigation system improvements are critical to their abundance by preventing their access. The ecological impact of differences in water level may extend to the foraging habits and trophic positions of the top predators in rice fields, resulting in the alteration of wetland food webs. Here, we investigated how physical disruptions to habitat networks affect food‐web properties in rice‐field ecosystems. We conducted stable nitrogen and carbon isotope analysis on a threatened giant water bug, Kirkaldyia deyrolli, to estimate its trophic position as an indicator of food‐chain length. Based on field observations, we found that fish that were at a high trophic position were only available to K. deyrolli in rice fields where there were no physical barriers blocking access to the network of habitats, and the diets of K. deyrolli included fish prey (18%, based on visual observation). The stable isotope analysis revealed that the trophic position of K. deyrolli was significantly lower in rice fields with physical barriers (no fish/10 dips by a dip net) than in those without physical barriers (5.6 fish) due to the absence of fish in locations with barriers. In conclusion, our study demonstrates that physical alterations are important to community composition and food‐web properties in rice‐field ecosystems because they can act as barriers to fish.

Analysis of earthquake-induced groundwater level change using self-organizing maps

For a better understanding of possible physical links between geophysical observables and earthquake characteristics, it is important to analyze statistical spatiotemporal patterns in nature related to such events. For this purpose, characteristic changes in groundwater level (GWL) were observed before and after the 2016 Kumamoto earthquake in Japan. Previous research has shown that self-organizing maps (SOM) can be used to classify complex patterns of GWL-change during different parts of the earthquake sequence. In this study, we used before and after earthquake GWL data as input vectors to SOM. In total, 64 observed GWLs were classified into 12 different clusters. Most shallow wells displayed GWL difference that was small during the foreshock (first earthquake) and large during the main-shock (second earthquake). Upstream deep wells showed relatively large difference in water level from 1 to 2 days after the earthquakes. The GWL rapidly increased just after the earthquake, then tended to gradually decrease from September. Most of the shallow wells in the unconfined aquifer rapidly recovered to initial GWLs within several hours to several days, because of hydrostatic pressure. However, most of the deep wells in the confined aquifer needed longer time to recover, in some cases several weeks to several months. These findings are important for the physical understanding of earthquake effects on the groundwater environment, disaster prevention, and possibility for development of earthquake precursors.