北京五里营井流体异常原因及解决办法

2010年7月3日延庆地震台五里营井流体测项均出现大幅波动现象。本文台站人员通过科学系统分析,确定此异常变化是由于该井泄流管最高端憋气造成,并采用类似暖气跑风的原理,对泄流管进行了改造,使所有流体测项恢复正常观测。     

延庆地震台地电阻率改造影响的分析研究

对延庆地震台地电阻率的观测系统进行改造后的变化特征进行了初步研究,介绍了电极和外线路改造技术环节,并通过改造前后观测资料的对比分析对改造后的观测系统情况进行了评价。     

嘉山地震台地电阻率数字化改造

地球科学是一门观测科学,地震观测是研究与应用的基础。地电阻率作为地震前兆观测手段之一,发挥着日益重要的作用,而良好的观测系统是产出连续、可靠、高质量数据的前提。因此,对观测系统的数字化改造工作必须予以高度重视。本文对嘉山台地电阻率数字化改造工作进行了简要介绍,并就一些技术问题进行了论述。     

福建省闽清梅埔井的水位大幅突降变化常调查分析

针对闽清梅埔观测井在2009年8月出现的水位大幅突降以及波动现象,通过观测仪器检查和水位值校测、降水和气压资料分析,以及周边抽水等环境干扰因素的排查等,没有找出可能的影响因素.但最后通过对测点附近的深入调查,寻找出是由于观测围墙下的暗沟内出现裂缝导致井水泄露引起水位下降的原因.本项工作表明,深入细致的调查研究是落实观测...     

福建省闽清梅埔井水位固体潮畸变成因探讨

对闽清梅埔观测井在2008年3月出现的水位固体潮畸变和大幅波动,进行了成因探讨。通过实地落实和对周边影响环境的因素进行综合分析,认为此井水位的固体潮畸变主要受附近库区日平均出库流量,及坝下发电排水量改变而造成,对今后的观测提出一些建议。     

浅谈延庆地震台地电阻率观测系统改造

分析了延庆地震台地电阻率观测中存在的干扰因素，以此说明观测系统进行改造的必要性，介绍了电极和外线路改造的过程和技术环节，通过改造前后观测资料的对比分析对改造的效果进行了评价。     

2016年衡水冀16井水位变化分析

衡水冀16井水位2016年经常出现有规律的大幅度异常波动变化,具有小幅下降—持续上升—小幅上升—持续下降变化形态,日变最大幅度0.73 m。通过现场核实,发现观测仪器工作正常,附近鱼场地下水开采量增加。增加辅助观测仪器同井对比水位观测,并对鱼场2口冷水井进行抽水试验,分析衡水冀16井水位异常变化原因。结果显示,衡水冀16井水位大幅波动异常变化可能因冷水井1抽水所致,冷水井2无影响。     

泉点改造对山西定襄七岩泉水氡影响

2014年定襄七岩泉泉点改造后,水氡含量大幅下降,通过分析排除各类干扰因素,进行对比观测认为,此次定襄七岩泉水氡浓度下降可能因泉点改造后取样口不密封所致。     

临汾中心地震台体应变大幅变化的异常分析

为明确临汾中心地震台体应变大幅变化的原因,按照中国地震局异常核实要求,山西省地震局进行异常落实。通过对体应变观测系统、观测环境等情况和钻孔辅助观测资料进行分析,重点利用固体潮振幅比和频谱分析方法对异常数据进行对比,认为引起体应变大幅变化的原因是传感器故障,属于非地震前兆异常。     

高邮车逻井水位大幅波动异常分析

2016—2019年高邮车逻井水位出现多次大幅波动变化。结合周边自然环境和农业活动的调查工作,对异常成因和影响水位变化的因素进行了跟踪分析。研究认为,该井水位出现的大幅波动变化异常是高邮湖水位短期大幅波动产生的荷载影响所致,与水利部门对高邮湖水位调控间关系密切,而非地震地球物理异常。     

福建闽江水口库区飘浮植物覆盖对水体环境的影响

为了探索城市富营养化湖泊生态修复技术,2000年9月在南京市莫愁湖物理生态工程试验区内,开展了隔离外源污染、覆盖底泥和种植水生植物对湖泊水质平均水平和水体脉动强度影响的比较研究．试验结果表明,通过围隔隔离外源污染可在较短时间内迅速改善湖泊TN的平均水平,但难以提高湖泊生态系统的稳定性;通过覆盖底泥控制内源污染难以改善湖泊水质的平均水平,并且难以提高湖泊生态系统的稳定程度;种植水生植物不仅能够全面改善湖泊水质的平均水平,而且可以提高湖泊生态系统的稳定性．此外,富营养化湖泊中,藻类生长与湖水营养盐浓度并不存在正相关的关系．因此,对城市湖泊富营养化的防治,在控制外源污染降低营养盐浓度的同时,应恢复湖泊原有的以水生高等植物为主的生态系统．     

New Understanding of Variation Characteristics of Well Water Level in Majiagou Mine, Tangshan City, Hebei, China

Based on the well water level data in Majiagou Mine in Tangshan City since 2000, it is suggested that the water level rise from 2008-2014 is possibly associated with reduced infiltration caused by less precipitation, together with the effect of less groundwater exploitation. However, the water level rise from 1992-1998 cannot be interpreted properly if we extend the data source back to 1991. After comparing the data with long-term water level data of five wells with different hydro-geological units in Tangshan and Qinhuangdao, the study indicates that the long-term water level variation cannot be only attributed to the effect of less precipitation and the control of groundwater exploitation, but also with the influence of regional stress field change. With the support of regional geological and tectonic information, combined with the comprehensive analysis of CBM data obtained from the coal field, new understandings of the dynamic characteristics of annual variation are obtained.     

Case 21 water level and strain changes preceding and following the August 4, 1985 Kettleman Hills, California, earthquake

Two of the four wells monitored near Parkfield, California, during 1985 showed water level rises beginning three days before theM _w 6.1 Kettleman Hills earthquake. In one of these wells, the 3.0 cm rise was nearly unique in five years of water level data. However, in the other well, which showed a 3.8 cm rise, many other changes of comparable size have been observed. Both wells that did not display pre-earthquake rises tap partially confined aquifers that cannot sustain pressure changes due to tectonic strain having periods longer than several days. We evaluate the effect of partial aquifer confinement on the ability of these four wells to display water level changes in response to aquifer strain. Although the vertical hydraulic diffusivities cannot be determined uniquely, we can find a value of diffusivity for each site that is consistent with the site's tidal and barometric responses as well as with the rate of partial recovery of the coseismic water level drops. Furthermore, the diffusivity for one well is high enough to explain why the preseismic rise could not have been detected there. For the fourth well, the diffusivity is high enough to have reduced the size of the preseismic signal as much as 50%, although it should still have been detectable. Imperfect confinement cannot explain the persistent water level changes in the two partially confined aquifers, but it does show that they were not due to volume strain. The pre-earthquake water level rises may have been precursors to the Kettleman Hills earthquake. If so, they probably were not caused by accelerating slip over the part of the fault plane that ruptured in that earthquake because they are of opposite sign to the observed coseismic water level drops.     

霍山皖33井水位与"霍山窗"小震活动关系的初步研究

分析了霍山皖33井水位变化与"霍山窗"地震活动的关系:首先采用差分法和从属函数等方法对水位数据进行处理,提取了水位的短期异常,结果表明该井水位异常对霍山以及周边地区的中小地震有较好的反映;其次,通过对该井水位与"霍山窗"小震活动性的对比研究,发现该地区小地震在水位低值时活跃.参考该地区的环境剪应力,我们认为霍山皖33井...     

鲁—14井井径变化试验的解释

对鲁－14井井径变化试验的井水位潮汐资源进行了反复调和分析，结果表明试验前后井水位对气压和固体潮的响应改变较小。根据多孔介质渗流理论和弹性理论，对这一现象进行了解释，认为井径变化相当于改变了井水柱的有效高度，从而影响了水井含水层系统的固有振动周期。分析了井孔变径对潮汐信号响应的周期特征，认为在含水层水体很大（含水层水平面积比井孔面积大得多），且含水层的渗透系数也很大的条件下，井径变化对井水位畦体潮响应幅度影响很小。     

广西桂平西山井水位同震特征和机理初探

收集了2008~2016年广西桂平西山井水位观测数据及全球5级以上地震资料,分析井孔记录水震波的能力、水震波形态特征及影响因素,初步探讨了西山井同震的机理,获得以下认识:桂平西山井对全球M_S≥7地震具有较好的同震响应能力,水震波的形态主要为振荡型,少数呈现阶升型。井-含水层观测系统、地震震级、井震距是影响井孔记录水震波能力的主要因素。含水层介质受瑞利面波作用会发生体积变化,导致水位振荡,是形成振荡型水震波的可能机理。阶变型水震波的形成与区域应力场增强、介质变化及构造活动等因素有关。西山井水位阶升与周边中强地震活动存在较好对应关系,该认识可为地震预测研究提供参考。     

Characterizing replenishment water,lake water and groundwater interactions by numerical modelling in arid regions: a case study of Shahu Lake

In order to maintain the scenic and eco-environmental values of a lake, we need to characterize its water interactions. Shahu Lake was used as a case study to show the interactions among replenishment water, lake water and groundwater in an arid region. Shahu Lake is located in the Ningxia Hui Autonomous Region of northwest China and has an area of 13.96 km² and an average depth of 2.2 m. The groundwater modelling software MODFLOW was used. The analysis results show that hydraulic connectivity among replenishment water, lake water and groundwater is the crucial driving factor that affects the water level in Shahu Lake. The lake water level is highly sensitive to the volume of replenishment water. The groundwater is of great importance in balancing the water level in the lake and preventing it from drying up. It was determined that 13.8 × 10⁶ m³/yr is the optimal volume of replenishment water for Shahu Lake in order to maintain the lake level at its normal state and also to make the best use of available water resources on a long-term basis. Understanding of the water interactions can promote effective management of water resources in Shahu Lake.

EDITOR D. Koutsoyiannis

ASSOCIATE EDITOR D. Hughes     

Interactive influence of water level,sediment heterogeneity,and plant density on the growth performance and root characteristics of Carex brevicuspis

Water level, sediment heterogeneity, and plant density are important factors that determine plant growth, distribution, and community structure. In the present study, we investigated the effects of these factors on the growth and root characteristics of Carex brevicuspis. We conducted an outdoor experiment to monitor biomass accumulation and allocation, relative root distribution mass ratio, longest root length, and total N and P contents of C. brevicuspis plants. We used a factorial design with two water levels (0 cm and −15 cm relative to the soil surface, named high and low water level treatments, respectively), three sediment types (sand/clay sediment with 0–15 cm of sand and 15–30 cm of clay; mixed sediment with 0–30 cm mixture of sand and clay with 1:1 volumw ratio; and clay/sand sediment with 0–15 cm of clay and 15–30 cm of sand), and three plant densities (88 plants per m², 354 plants per m², and 708 plants per m²). Biomass accumulation decreased with increasing plant density and was significantly higher in the low water level and the clay/sand sediment than in the high water level and the other two sediment types. The shoot:root ratio was markedly higher in the high water level than in the low water level and decreased with increasing plant density; further, in the high water level, it was significantly lower in the sand/clay sediment than in the other two sediment types. The relative root distribution mass ratio was markedly higher in the high water level treatments than in the low water level treatments. Further, in the high water level treatments, the relative root distribution mass ratio increased with increasing plant density in the clay/sand sediment and was lower in the sand/clay sediment than in the other two sediment types. The longest root length was significantly lower in the high water level than in the low water level and increased with increasing plant density in the sand/clay sediment in the high water level. Total N content in the plants was influenced only by sediment type; on the other hand, total P content was markedly higher in the high water level than in the low water level. Our data indicate that growth of C. brevicuspis was limited by higher water level, higher density and sand/clay sediment. Plants can increase shoot:root ratio and develop shallow root system to acclimate to high water level and thus could adjust shoot:root ratio and root characteristics, e.g. decrease their shoot:root ratio and allocating more root and increasing root length to the nutrient rich layer to acclimate to conditions of higher density and sediment heterogeneity.     

Evaluation of long-term groundwater level data in regular monitoring wells,Barka, Sultanate of Oman

A detailed investigation was carried out to evaluate long-term groundwater level fluctuation in regular monitoring wells constructed by the Ministry of Water Resources in Barka, Sultanate of Oman. For this study, groundwater level data for 71 wells and rainfall data from six stations were collected from 1984 to 2003 and analysed. Based on long-term water level fluctuation, groundwater wells are classified into three groups. In group 1, water level shows a long-term cyclic trend without yearly fluctuation whereas in group 2 the water level declined continuously until 1995 followed by a constant water level. In group 3, water level decreases continuously throughout the study periods with rapid annual cyclic variation. Group 1 wells show high water-level fluctuations (5 to 10 m) and seem to be regulated by discharge (lateral flow) from this aquifer and recharge from the adjacent Jabal Akhdar mountainous region. Constant trend in water level after 1995 in group 2 wells illustrates the advancement of saline–fresh water interface to the inland due to heavy pumping which is justified by higher electrical conductivity and Cl/HCO₃ ratio. In group 3 wells, the water level dropped continuously due to overabstraction by agricultural farms and human settlements. In addition, wells existing near the recharge dams express the influences of recharge dams and rainfall, and exhibit high water-level fluctuations during heavy rainfall periods. The long-term regional variation indicates that water level drops continuously in the coastal and central parts of the study region. Linear regression analysis revealed that the decline in water level is 0·3–0·4 m year⁻¹ near the coastal and central parts of the study area and is almost constant in the remaining area. We conclude that the contribution of man-made activities on groundwater level is well compared with natural factors. Copyright © 2007 John Wiley & Sons, Ltd.     

SEEPAGE, a new MODFLOW DRAIN package

The prediction of the location of ground water discharge areas is a key aspect for the protection and (re)development of ground water-dependent wetlands. Ground water discharge areas can be simulated with MODFLOW using the DRAIN package by setting the drain level equal to the topography, while the conductance is mostly set to an arbitrary high value. However, conceptual and practical problems arise in the calculation of the ground water discharge by the DRAIN package as calculated water tables above the land surface, difficult parameterization of the conductance, and large water balance errors. To overcome these problems, a new SEEPAGE package for MODFLOW is proposed. The basic idea of this package is an adaptable constant head cell. It has a variable head, unless the ground water rises above the seepage level, in which case it has a constant head cell. The estimation of the ground water discharge location along a homogeneous, isotropic, linear sloping profile is used to verify the model and to compare it to the DRAIN solution. In an application to three basins in Belgium, it is shown that the SEEPAGE package can be used in combination with the DRAIN package in situations where an upper boundary for a free water table and additional resistance for drainage is required. It is clearly demonstrated that the identification and delineation of regional ground water discharge areas is more accurate using the SEEPAGE package.