Apparent permeability variation of underground water aquifer induced by an earthquake:A case of the Zhouzhi well and the 2008 Wenchuan earthquake

t Taking the M2 wave as calibration signals, we extract the phase shifts of the water level relative to the Earth tide in the Zhouzhi well by utilizing the cross-correlation function. And we further obtain the apparent permeability variation in the aquifer of the Zhouzhi well in 2008. Comparison with the commonly used tidal analysis software Baytap-G shows that phase shifts obtained by cross-correlation function are more stable. The resulting apparent permeability of the Zhouzhi well aquifer fluctuates with time, indicating it is a dynamically controlled parameter. The 2008 Wenchuan earthquake caused the apparent permeability increasing drastically, which is interpreted as the combination effects of effective stress changes and the barriers removing in the flow channel due to seismic wave pressure pulse. After the Wenchuan earthquake, the effective stress began to recover and the impurities deposited gradually, causing the apparent permeability to decrease a month later and almost recover to the pre-earthquake level in six months.

Characteristics of Underground Water Flow at Different Water Levels in Tianshengan Karst Area, Yunnan, China

Three tracing tests from the same injection point executed at low, medium, and high water levels in the karst aquifer near Tianshengan village, Lunan Stone Forest, Yunnan Province, China, have revealed the basic properties of underground water flow. They showed the general directions of water flows; tracer concentrations were observed at six successive points allowing for the calculation of apparent dominant flow velocities at these sections towards the Dalongtan karst spring. For the high water level, the discharge between single sections was between two and 10 times greater than that at low water level. For the medium water level, the flow velocity at different sections was between 1.4 and 3.7 times faster than that at low water level; and for high water level, it was between 1.3 and 2.7 times faster than that at medium water level. The fastest water flow appeared at the first section （23 cm/s at medium water level）; and the slowest （0.6 cm/s at low water level） appeared where water flow must cross the Tianshengan fault （north-south direction）, and later, a layer of 20-30 m thickness of quartz sandstone and shale clay-stones. It was also possible to calculate the recovery of the tracer for point 4, Dakenyan, where discharge was measured. At the medium water level, 50% of the injected tracer was detected a half-day after its first appearance and at low water level after more than 3 days. The previously published research illustrates the transport velocities of possible contaminants and their solubilities in water at different hydrological conditions.

Exploring effective policies for underground water management in artificial oasis: a system dynamics analysis of a case study of Yaoba Oasis

The development of oasis along the edge of the Tengerli Desert, where underground water is available, is one of the major strategies to reallocate 'ecological refuges' from their seriously degraded grasslands to agriculturally cultivable land. Yet, underground water resources, the major constraint, hate not been fully integrated in the development process. Therefore, the decline of water resources and deterioration of water quality caused by over-consumption of water resources has begun to hinder further development and has even fed to the abandonment of some oasis. A system dynamics modeling approach is applied to analyze the water use and water management structures in Yaoba Oasis as a case study. The study attempts to identify the characteristics of major feedback loops, which dominate the over-use of underground water resources leading to the deterioration of water resources in quantity and quality.

Discussion on applying an analytical method to optimize the anti-freeze design parameters for underground water pipelines in seasonally frozen areas

Adopting the quasi-three-dimensional （Quasi-3D） numerical method to optimize the anti-freeze design parameters of an underground pipeline usually involves heavy numerical calculations. Here, the fitting formulae between the safe con-veyance distance （SCD） of a water pipeline and six influencing factors are established based on the lowest water temper-ature （LWT） along the pipeline axis direction. With reference to the current widely used anti-freeze design approaches for underground pipelines in seasonally frozen areas, this paper first analyzes the feasibility of applying the maximum frozen penetration （MFP） instead of the mean annual ground surface temperature （MAGST） and soil water content （SWC） to calculate the SCD. The results show that the SCD depends on the buried depth if the MFP is fixed and the variation of the MAGST and SWC combination does not significantly change the SCD. A comprehensive formula for the SCD is estab-lished based on the relationships between the SCD and several primary influencing factors and the interaction among them. This formula involves five easy-to-access parameters： the MFP, buried depth, pipeline diameter, flow velocity, and inlet water temperature. A comparison between the analytical method and the numerical results based on the Quasi-3D method indicates that the two methods are in good agreement overall. The analytic method can be used to optimize the anti-freeze design parameters of underground water pipelines in seasonally frozen areas under the condition of a 1.5 safety coefficient.

Design and operation problems related to water curtain system forunderground water-sealed oil storage caverns

The underground water-sealed storage technique is critically important and generally accepted for the national energy strategy in China. Although several small underground water-sealed oil storage caverns have been built in China since the 1970s, there is still a lack of experience for large-volume underground storage in complicated geological conditions. The current design concept of water curtain system and the technical instruction for system operation have limitations in maintaining the stability of surrounding rock mass during the construction of the main storage caverns, as well as the long-term stability. Although several large-scale underground oil storage projects are under construction at present in China, the design concepts and construction methods, especially for the water curtain system, are mainly based on the ideal porosity medium flow theory and the experiences gained from the similar projects overseas. The storage projects currently constructed in China have the specific features such as huge scale, large depth, multiple-level arrangement, high seepage pressure, complicated geological conditions, and high in situ stresses, which are the challenging issues for the stability of the storage caverns. Based on years’ experiences obtained from the first large-scale （millions of cubic meters） underground water-sealed oil storage project in China, some design and operation problems related to water curtain system during project construction are discussed. The drawbacks and merits of the water curtain system are also presented. As an example, the conventional concept of “filling joints with water” is widely used in many cases, as a basic concept for the design of the water curtain system, but it is immature. In this paper, the advantages and disadvantages of the conventional concept are pointed out, with respect to the long-term stability as well as the safety of construction of storage caverns. Finally, new concepts and principles for design and construction of the underground water-sealed oil storage caverns are proposed.

Underground water stress release models

The accumulation of tectonic stress may cause earthquakes at some epochs. However, in most cases, it leads to crustal deformations. Underground water level is a sensitive indication of the crustal deformations. We incorporate the information of the underground water level into the stress release models （SRM）, and obtain the underground water stress release model （USRM）. We apply USRM to the earthquakes occurred at Tangshan region. The analysis shows that the underground water stress release model outperforms both Poisson model and stress release model. Monte Carlo simulation shows that the simulated seismicity by USRM is very close to the real seismicity.

The Underground Water Level Simulation in Imamzadeh Jafar Plateau by the Use of Mudflow Software

The most secure method in providing water in the dry and semi-dry regions is the use of underground water sources and due to over consumption of water aquifers capacities, most of fields and specially Imamzadeh Jafar are faced with negative performance and balance, which threatens the land subsiding. The plateau with the annual raining of 438 millimeters has 169 deep and semi-deep wells with annual 36.68 million consumption and this issue has increased the research signification, in order to protect and relive the required water aquifers, there is a need to predict the underground water level accurately in different condition. In this research, by the use of balance equation and modflow software in Imamzadeh Jafar, water aquifer was analyzed within seven scenario. The underground water level evaluation for the short run periods for 2 years and middle term of 4 years and 12 years of long term was performed;and the results showed that the performance and balance of the plateau was increased due to increase of water consumption compared to the water aquifer quantity in the region that was negative. To the point that the 1, 3, 4, 5, 7 scenarios (minimum 0.17 and maximum -11.34) and 2, 6 scenarios in different timely periods show that the underground water saving volume is positive (minimum 3.64 and maximum 19.83).

Influence of underground water seepage flow on surrounding rock deformation of multi-arch tunnel

Based on a typical multi-arch tunnel in a freeway, the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) was used to calculate the surrounding rock deformation of the tunnel under which the effect of underground water seepage flow was taken into account or not. The distribution of displacement field around the multi-arch tunnel, which is influenced by the seepage field, was gained. The result indicates that the settlement values of the vault derived from coupling analysis are bigger when considering the seepage flow effect than that not considering. Through the contrast of arch subsidence quantities calculated by two kinds of computation situations, and the comparison between the calculated and measured value of tunnel vault settlement, it is found that the calculated value(5.7-6.0 mm) derived from considering the seepage effect is more close to the measured value(5.8-6.8 mm). Therefore, it is quite necessary to consider the seepage flow effect of the underground water in aquiferous stratum for multi-arch tunnel design.

Grey associated analysis of the underground water quality effected by the leaching water of dumping area or hillock of coal mine

The underground water has been contaminated seriously by the leaching water of dumping area or hillock. To determine the pollution limits of underground water, author took samples in the study area, analyzed samples for water quality, assessed the water quality of each monitoring point by the grey associated analysis method, and gave out the classifications of the underground water quality of the study area. Comparing with fuzzy comprehensive appraisal method, it is demonstrated that grey associated analysis method is applied easily, because of its clear concept, simple and convenient calculation and excellently operation.

A simulating experiment on the geochemical variation trend at the initial period of meteoric waters converting to underground waters and ore fluids

Experimental studies were undertaken on leaching of sedimentary rocks (dolomite and sandstone) and Hg, Sb ores by distilled water under the condition of a completely open system (room temperature and room pressure). The aim is to find whether the halogen elements or metal elements first enter the solution at the early stage of meteoric waters converting to groundwaters and ore fluids, and, at the same time, to understand how and when they enter distilled water solutions from the rocks. The experimental results have shown that F and Cl began to enter the fluids in the initial period of thirty days. With increasing leaching duration, the amounts of the elements that entered the fluids increased steadily. During the period from 120 days to 150 days the amounts increased more drastically, followed a slow increase. It is found that the capability of Cl entering the solutions is much greater than that of F. Hg and Sb were found not to have entered the solutions till 120 days later. During this period of time the pH value of the solutions began to drop. As for Hg and Sb ores, Hg and Sb began to enter the solutions on the 60th or 90th day, greatly ahead of schedule, but the two metallic elements in the rock samples began to enter the solutions 150 days later. Relatively speaking, Hg is more easily leached out than Sb from the rocks. In some rock samples, Sb could be detected in the solutions at the end of the experiment. However, Cu, Pb and Zn had not been detected in the leaching solutions from the beginning to the end of the experiment. In the whole leaching process the pH value of the solutions tend to decrease slowly from {7.1} at the beginning to {6.5} at the end. That is to say, in the interaction between pure water and rock the halogen elements in the rocks were preferentially leached out and then entered the fluids. With increasing water/rock reaction duration and amount of halogen-group elements in the solution and with decreasing pH value of the solution, some active metallic elements began to release in small amounts. This experimental result can explain the source and mechanism of volatile components and trace metals in underground waters. Meanwhile, as for those ore deposits produced by ore fluids derived from meteoric waters, the experimental result is also helpful to the understanding of the geochemical variation trend at the initial stage of conversion of meteoric waters to ore fluids.

Distribution and Origin of Underground Water Chemical Fields in Songliao Continental Oil-Bearing Sedimentary Basin

There are many factors affecting underground water chemistry of an oil bearing sedimentary basin. The properties of underground water show variations in the vertical direction, giving rise to a vertical zonation with respect to underground water chemistry. Five zones could be divided downwards, including 1) the freshening zone due to meteoric water leaching (A); 2) the evaporation concentration zone near the surface (B); 3) the freshening zone due to stratum compaction released water(C\-1)—infiltration concentration zone during the mudstone compaction and water releasing (C\-2); 4) the freshening zone for clay mineral dehydration (D); and 5) the seepage concentration zone (E).\; The hydrodynamic fields in the Songliao Basin are obviously asymmetrical, with the characteristics of gravity induced centripetal flow recharged by meteoric water along the edge to the inner part of the basin mainly in its northern and eastern regions, centrifugal flow and cross formational flow in the center of the basin, as well as the cross formation flow evaporation discharge area in its southern area. Hydrodynamics controls the planar distribution of underground\|water chemical fields: 1) the freshening area due to penetrating meteoric water generally at the basin edges; 2) the freshening area for mudstone compaction released water at the center of the basin; 3) the cross formational area as the transitional area; and 4) the concentration area by cross formational flow and evaporation. The mineralization degree and the concentrations of Na\++ and Cl\+- and their salinity coefficients tend to increase, while the concentrations of (CO\+\{2-\}\-3+HCO\+-\-3) and SO\+\{2-\}\-4 and the metamorphism and desulfuration coefficients tend to decrease along the centrifugal flow direction caused by mudstone compaction in the depression area. But all of them tend to increase along the gravity induced centripetal flow direction.

Estimation of Natural-Technogeneous Pollution of Underground Waters in Horezm Region of Uzbekistan

Nowadays,the resources of underground water present itself as a valuable mineral and are to be the most important and in many regions one and only source of economic-drinking water-supply.For the past years,in connection with fast development of industry and agriculture,there occurred the tendency of increasing necessity in usage of underground water resources for production-technical needs,irrigation of

Hydrogeochemistry of karst underground waters at shallow depth in Guiyang City, Guizhou Province

The aim of this study is to shed light on the hydrogeochemical characteristics of karst underground waters at shallow depth in Guiyang City, Guizhou Province with an emphasis on the geochemistry of major elements. Guiyang City bears abundant underground waters and it is also an important representative of the karst areas throughout the world. Ca+{2+} and Mg+{2+} are the dominant cations, accounting for 81%-{99.7%} of the total, and HCO+--3 and SO+{2-}-4 are the dominant anions. Weathering of limestones and dolostones is the most important factor controlling the hydrogeochemistry of underground waters, and weathering of sulfate and evaporite rocks is less important. Moreover, the precipitation and human activities also have a definite influence on the hydrogeochemistry of underground waters in the region studied.

The Interpretation of Underground Water Physical Parameters of Housing in the Region of Asahan Indah Palm Oil Factory Area Rokan Hulu District

The research has been conducted to analyze the distribution of underground water physical parameters of the housing around Asahan Indah palm oil factory area Rokan Hulu District with radial method within ±300 meters radius from the factory location. The levels of underground water physical parameters include conductivity, resistivity, and salinity measured based on coordinate points amounted of 50 points. The data obtained from the measurement results were then inputted into “surfer 11” software to be processed in order to obtain the contour map of underground water physical parameters level. The results of this research indicated that the highest conductivity level came from the ring well type with 5 meter depth;it was 0.0964 (1/ohm·m) exceeded the standard threshold of underground water quality standard and the lowest conductivity was 0.00342 (1/ohm·m) which came from a ring well type with 10 meter depth. The lowest resistivity level was 10.37 ohm·m which came from the ring well type with 5 meter depth and the highest was 292.4 ohm·m which came from the ring well with 10 meter depth. The highest salinity level was 448 mg/l which exceeded the baseline threshold of underground water quality which came from the ring well type with 5 meter depth and the lowest was 175 mg/l from the ring well with 10 meter depth. The results of this research found that underground water in wells with 5 meters depth has been polluted with palm oil waste and at the depth of 10 meters, it has not been contaminated.

Underground water quality model inversion of genetic algorithm

The underground water quality model with non-linear inversion problem is ill-posed, and boils down to solving the minimum of nonlinear function. Genetic algorithms are adopted in a number of individuals of groups by iterative search to find the optimal solution of the problem, the encoding strings as its operational objective, and achieving the iterative calculations by the genetic operators. It is an effective method of inverse problems of groundwater, with incomparable advantages and practical significances.