Temporal trends in concentrations of DBCP and nitrate in groundwater in the eastern San Joaquin Valley,California, USA

Temporal monitoring of the pesticide 1,2-dibromo-3-chloropropane (DBCP) and nitrate and indicators of mean groundwater age were used to evaluate the transport and fate of agricultural chemicals in groundwater and to predict the long-term effects in the regional aquifer system in the eastern San Joaquin Valley, California. Twenty monitoring wells were installed on a transect along an approximate groundwater flow path. Concentrations of DBCP and nitrate in the wells were compared to concentrations in regional areal monitoring networks. DBCP persists at concentrations above the US Environmental Protection Agency’s maximum contaminant level (MCL) at depths of nearly 40 m below the water table, more than 25 years after it was banned. Nitrate concentrations above the MCL reached depths of more than 20 m below the water table. Because of the intensive pumping and irrigation recharge, vertical flow paths are dominant. High concentrations (above MCLs) in the shallow part of the regional aquifer system will likely move deeper in the system, affecting both domestic and public-supply wells. The large fraction of old water (unaffected by agricultural chemicals) in deep monitoring wells suggests that it could take decades for concentrations to reach MCLs in deep, long-screened public-supply wells, however.     

北京地区不同介质的土柱淋滤水质试验研究

为探讨冲洪积平原地带地下水水质劣变机理及过程,开展了不同的水土样品组合的16组淋滤试验,以期揭示不同源水在土柱入渗过程阴阳离子、硬度和TDS的变化规律以及地下水类型的演化特征。试验结果表明:淋出液中,阴离子浓度的变幅由大到小依次为HCO_3~-、NO_3~-、SO_4~(2-)、Cl~-和F~-,阳离子的变幅则依次为Na~++K~+、Ca~(2+)和Mg~(2+)。淋出液的硬度、TDS和水化学类型均呈现出有规律的变化,先期主要受控于源水,尔后则主要受土柱介质的影响。除了以垃圾作为淋滤介质的试验外,其他组合的试验都出现了初期TDS和硬度升高的过程,之后与源水趋于一致,揭示了淋滤中浸泡—水岩相互作用—吸附解析—淋洗等复杂过程。     

Development of a numerical groundwater flow model using SRTM elevations

Remotely-sensed elevation data are potentially useful for constructing regional scale groundwater models, particularly in regions where ground-based data are poor or sparse. Surface-water elevations measured by the Shuttle Radar Topography Mission (SRTM) were used to develop a regional-groundwater flow model by assuming that frozen surface waters reflect local hydraulic head (or groundwater potential). Drainage lakes (fed primarily by surface water) are designated as boundary conditions and seepage lakes and isolated wetlands (fed primarily by groundwater) are used as observation points to calibrate a numerical flow model of the 900 km² study area in the Northern Highland Lakes Region of Wisconsin, USA. Elevation data were utilized in a geographic information system (GIS) based groundwater-modeling package that employs the analytic element method (AEM). Calibration statistics indicate that lakes and wetlands had similar influence on the parameter estimation, suggesting that wetlands might be used as observations where open water elevations are unreliable or not available. Open water elevations are often difficult to resolve in radar interferometry because unfrozen water does not return off-nadir radar signals.     

Primary study on evaluation index system for groundwater exploitation potentiality based on the niche theories

This paper presents a method combining single-indicator comprehensive evaluation and influence factor identification to measure groundwater quality. This method not only reflects groundwater quality classification with clear physical significance, but also divides the possibilities of man-made pollution in regional groundwater. The paper selects 6 063 representative groundwater wells in the North China Plain to evaluate 49 groundwater inorganic and organic index and comes to a conclusion: Controlled by geological environment and hydrogeological conditions, the groundwater quality in the North China Plain deteriorates from the bottom of maintain to coastal area, with Class I to III groundwater decreasing from 49% to 3.9% while Class V groundwater increasing from 21% to 86.9%; the quality of deep groundwater is better than that of shallow groundwater; the contribution rate of manganese, total hardness, total dissolved solids and iodide in shallow groundwater to over-III type water exceeds 50%; the contribution rate of nitrite in pollution index reaches 20%; while heavy metal and organic indexes have limited impact on regional groundwater quality. The North China Plain is an important economic area in China. Over decades, it has witnessed intense human activities, and water resource quantity demanded has been far greater than quantity supplied. Due to scarce surface water resource, groundwater becomes the pillar supporting regional economic development. This has led to increasing groundwater exploitation and development. According to statistics, the exploitation degree of shallow groundwater reaches 105% in the North China Plain and 118% in the Hebei Plain; the exploitation degree of deep groundwater reaches 143% in the North China Plain and 163% in the Hebei Plain. The serious over-exploitation of groundwater brings various geological environmental problems, with the worsening of groundwater quality being a typical one. Besides impact brought by human activities, the poor quality of natural water in the North China Plain is also an important factor. Therefore, to understand the current regional groundwater quality situation and to master influence factors and influence degree can provide reliable scientific protection for regional economic development.     

辽河三角洲地区地下水动态监测研究

辽河三角洲处于陆地和海洋的结合部,蕴含丰富的资源,具有十分重要的战略地位。项目通过三年的时间,查明了辽河三角洲地区主要含水层结构:第四系含水层系统(Q)、明化镇组含水层系统(Nm)、馆陶组含水层系统(Ng)。通过设立动态监测网,建立、完善地下水动态监测体系,实现地下水位和水质的实时监测;地下水水位动态:第四系松散岩类孔隙水较为稳定,水位动态变化不大;上新近系明化镇组和馆陶组地下水,受人类活动影响较大,由于多年连续大量开采,地下水位逐年下降,已形成了2个区域性地下水降落漏斗。地下水水质动态:第四系上更新统(Q3)浅层水Cl-、SO42-、Na+及矿化度持续升高,高矿化度水分布面积扩大,水化学类型复杂化,氯化物型和钠型水分布面积增大,向周边扩散;明化镇组和馆陶组地下水,水质优良,变化不大。针对地下水超采,注重水资源合理配置,适当减少新近系地下水资源的开采,充分利用地表水资源的对策。     

Effects of intraborehole flow on groundwater age distribution

Environmental tracers are used to estimate groundwater ages and travel times, but the strongly heterogeneous nature of many subsurface environments can cause mixing between waters of highly disparate ages, adding additional complexity to the age-estimation process. Mixing may be exacerbated by the presence of wells because long open intervals or long screens with openings at multiple depths can transport water and solutes rapidly over a large vertical distance. The effect of intraborehole flow on groundwater age was examined numerically using direct age transport simulation coupled with the Multi-Node Well Package of MODFLOW. Ages in a homogeneous, anisotropic aquifer reached a predevelopment steady state possessing strong depth dependence. A nonpumping multi-node well was then introduced in one of three locations within the system. In all three cases, vertical transport along the well resulted in substantial changes in age distributions within the system. After a pumping well was added near the nonpumping multi-node well, ages were further perturbed by a flow reversal in the nonpumping multi-node well. Results indicated that intraborehole flow can substantially alter groundwater ages, but the effects are highly dependent on local or regional flow conditions and may change with time.     

冀东铁矿田的开发对区域地下水环境的影响

冀东铁矿田赋存在太古界单塔子群白庙子组中,资源量（332＋333）为25亿 t,平均品位〉30%,是我国重要的铁矿基地。矿区位于滦河冲洪积扇中上部,矿体上覆第四系砂砾卵石含水层富水性强,水量丰富,属于大水矿床,矿床疏干排水困难,疏干排水将破坏地下水环境。本文在分析矿区水文地质条件的基础上,提出了具有密切水力联系的多层含水层系统的水文地质概念模型,并建立了刻画多层含水层系统的数值仿真模拟模型,基于预留隔水顶板井下充填法采矿,预测矿山开采地下水流场演变,评价了矿山开采对区域地下水环境的影响,提出了环境保护措施,对今后矿山开发过程中的地下水环境影响评价方法、地下水资源开发利用及环保管理决策具有重要意义。     

南水北调进京后怀柔应急水源地地下水资源涵养研究

怀柔应急水源地作为北京最大的应急地下水源地,在连续10多年的干旱期间,为保障城市供水安全做出了巨大贡献。文章在总结怀柔应急水源地10年供水历程的基础上,评价了连续干旱和应急开采条件下区域水资源的变化;结合南水北调进京的契机,从"资源人工回补"和供水系统"热备运行"两方面开展当地地下水资源涵养研究工作,以保障怀柔应急水源地可持续"应急供水"能力,为应对南水北调供水过程中的突发事件,做好水资源战备储备。     

CFCs法在鄂尔多斯白垩系地下水盆地浅层地下水年龄研究中的应用

鄂尔多斯白垩系地下水盆地是中国重要的能源基地,利用CFCS方法对鄂尔多斯白垩系地下水盆地年轻地下水年龄进行测定,取得了比较准确的结果。结果表明,盆地地下水系统可以分为局部地下水系统、中间地下水系统和区域地下水系统。地下水盆地内局部地下水系统地下水循环更替快,年龄为20 a左右,地下水年龄随深度增加而增加;中间地下水系统和区域地下水系统地下水循环更替相对较慢,年龄大于70 a,可以寻求14C等其他同位素方法确定准确年龄。     

Numerical simulation of response of groundwater flow system in inland basin to density changes

The developmental characteristics of groundwater flow system are not only controlled by formation lithology and groundwater recharge conditions, but also influenced by the physical properties of fluids. Numerical simulation is an effective way to study groundwater flow system. In this paper, the ideal model is generalized according to the fundamental characteristics of groundwater system in inland basins of Western China. The simulation method of variable density flow on the development of groundwater system in inland basins is established by using EOS9 module in TOUGHREACT numerical simulation software. In accordance with the groundwater streamline, the groundwater flow system is divided into three levels, which are regional groundwater flow system, intermediate groundwater flow system and local groundwater flow system. Based on the calculation of the renewal rate of groundwater, the analysis shows that the increase of fluid density in the central part of the basin will restrain the development of regional groundwater flow system, resulting in a decrease of the circulation rate from 32.28% to 17.62% and a certain enhancement to the local groundwater flow system, which increased from 37.29% to 51.94%.     

The development and control of the land subsidence in the Yangtze Delta,China

Land subsidence in China occurs predominantly in 17 provinces (cities) situated in the eastern and middle regions of the country, including Shanghai, Tianjin and Jiangsu, and Hebei provinces. It is primarily caused by groundwater overpumping. One of the areas most severely affected by land subsidence is the Yangtze Delta, most of which consists of Shanghai City, the Su-Xi-Chang area (Suzhou, Wuxi and Changzhou cities) of Jiangsu Province, and the Hang-Jia-Hu area (Hangzhou, Jiaxing and Huzhou cities) of Zhejiang Province. The excessive exploitation of groundwater forms in a large regional cone of depression and, consequently, land subsidence is also regional, currently centered in the Shanghai and Su-Xi-Chang areas. In 2002, the maximum cumulative subsidence of Shanghai, Su-Xi-Chang and Hang-Jia-Hu were 2.63 m, 2.00 and 1.06 m, respectively. The land subsidence area is continuing to expand throughout the Yangtze Delta. To study the characteristics and the pattern of this land subsidence, the government has implemented a monitoring system involving the placement of 37 groups of extensometers (layers marks) and drilling of more than 1000 observation wells. These provide an invaluable historical record of deformation and pore water pressure and facilitate studies on the special features of soil deformation when the groundwater level changes due to pumping. Several measures have been taken in recent years to control the development of the land subsidence in the different areas; these include groundwater injection, prohibition of pumping deep confined groundwater, and an adjustment of the pumping depth and magnitude of the groundwater withdrawn. At present, although the subsidence area is still increasing slowly, the subsidence rate is controlled.     

http://www.sciencedirect.com/science/article/pii/S1674987112000400

Monitoring of regional groundwater levels provides important information for quantifying groundwater depletion and assessing impacts on the environment Historically,groundwater level monitoring wells in Beijing Plain,China,were installed for assessing groundwater resources and for monitoring the cone of depression.Monitoring wells are clustered around well fields and urban areas.There is urgent need to upgrade the existing monitoring wells to a regional groundwater level monitoring network to acquire information for integrated water resources management.A new method was proposed for designing a regional groundwater level monitoring network.The method is based on groundwater regime zone mapping.Groundwater regime zone map delineates distinct areas of possible different groundwater level variations and is useful for locating groundwater monitoring wells.This method was applied to Beijing Plain to upgrade a regional groundwater level monitoring network.     

Quality evaluation of groundwater in the North China Plain

This paper presents a method combining single-indicator comprehensive evaluation and influence factor identification to measure groundwater quality. This method not only reflects groundwater quality classification with clear physical significance, but also divides the possibilities of man-made pollution in regional groundwater. The paper selects 6 063 representative groundwater wells in the North China Plain to evaluate 49 groundwater inorganic and organic index and comes to a conclusion: Controlled by geological environment and hydrogeological conditions, the groundwater quality in the North China Plain deteriorates from the bottom of maintain to coastal area, with Class I to III groundwater decreasing from 49% to 3.9% while Class V groundwater increasing from 21% to 86.9%; the quality of deep groundwater is better than that of shallow groundwater; the contribution rate of manganese, total hardness, total dissolved solids and iodide in shallow groundwater to over-III type water exceeds 50%; the contribution rate of nitrite in pollution index reaches 20%; while heavy metal and organic indexes have limited impact on regional groundwater quality. The North China Plain is an important economic area in China. Over decades, it has witnessed intense human activities, and water resource quantity demanded has been far greater than quantity supplied. Due to scarce surface water resource, groundwater becomes the pillar supporting regional economic development. This has led to increasing groundwater exploitation and development. According to statistics, the exploitation degree of shallow groundwater reaches 105% in the North China Plain and 118% in the Hebei Plain; the exploitation degree of deep groundwater reaches 143% in the North China Plain and 163% in the Hebei Plain. The serious over-exploitation of groundwater brings various geological environmental problems, with the worsening of groundwater quality being a typical one. Besides impact brought by human activities, the poor quality of natural water in the North China Plain is also an important factor. Therefore, to understand the current regional groundwater quality situation and to master influence factors and influence degree can provide reliable scientific protection for regional economic development.     

Groundwater recharge: an overview of processes and challenges

Since the mid-1980s, a relative explosion of groundwater-recharge studies has been reported in the literature. It is therefore relevant to assess what is now known and to offer further guidance to practitioners involved in water-resource development. The paper summarizes current understanding of recharge processes, identifies recurring recharge-evaluation problems, and reports on some recent advances in estimation techniques. Emphasis is accorded to (semi-)arid regions because the need for information is greatest in those areas – groundwater is often the only water source, is vulnerable to contamination, and is prone to depletion. Few studies deal explicitly with groundwater recharge in temperate and humid zones, because recharge is normally included in regional groundwater investigations as one component of the water balance. The resolution of regional water-balance studies in (semi-)arid areas is, in contrast, often too low to quantify the limited recharge component with sufficient precision. Despite the numerous studies, determination of recharge fluxes in (semi-)arid regions remains fraught with uncertainty. Multiple tracer approaches probably offer the best potential for reliable results in local studies that require 'at-point' information. However, many investigations indicate that these approaches are not straightforward, because in some cases preferential flow contributes as much as 90% of the estimated total recharge. Tracer results (e.g. Cl^–, ³H) must therefore be interpreted with care in areas with multi-modal flow in the vadose zone. Moreover, accurate estimation of total chloride deposition is essential, and tritium may be influenced by vapour transport at low flux rates. In addition, paleoclimatic and paleohydrological conditions may cause discrepancies between measured actual processes and calculated long-term averages. The frequently studied issues of localized recharge and spatial variability need not be a problem if concern is with regional estimates. The key for practitioners is the project objective, which dictates whether 'at-point' or area-/groundwater-based estimation methods are appropriate. Many indirect (wadi) recharge studies reported in the literature are site specific; the relationship between 'at point' hydraulic properties and channel-reach losses demands further investigation. Electronic Publication     

Groundwater recharge of carbonate aquifers of the Silesian-Cracow Triassic (southern Poland) under human impact

A Triassic carbonate unit has been intensively drained by zinc and lead ore mines and numerous borehole fields since the nineteenth century. Its groundwater recharge has increased due to: pumping of water from boreholes, mining activity, and urbanization. An approach to determine the amounts of the recharge at a variety of spatial scales is presented in the paper. Different methods were used to identify and quantify recharge components on a regional and local scale: mathematical modelling was performed for four aquifers included in an aquifer system, an analytical estimation based on the assumption that an average recharge is equal to the average discharge of the hydrogeological system—for six man-made drainage centres, and the method of water level fluctuation (WLF) was applied in one observation borehole. Results of modelling have been supplemented by observation of environmental tracers (δ¹⁸O, δ²H, ³H), noble gases temperatures, and ⁴He_exc in groundwater. The regional aquifer’s current recharge according to estimations performed by means of modelling varies from 39 to 101 mm/year on average. Depending on the aquifer site the average precipitation ranges from 779 to 864 mm/year. In the confined part of the aquifer average recharge ranges from 26 to 61 mm/year. Within outcrops average recharge varies from 96 to 370 mm/year. Current recharge estimated by the analytical method for man-made drainage centres varies from 158 up to 440 mm/year. High values are caused by different recharge sources like precipitation, induced leakage from shallow aquifers, and water losses from streams, water mains and sewer systems. Pumping of water, mining and municipal activities constitute additional factors accounting for the intensified recharge.     

基于砂槽模型研究不同水流密度下盆地地下水流系统

在干旱半干旱地区,沉积盆地是人类生产、生活用水的主要载体,为查明在水流自身密度改变条件下盆地地下水流系统的变化特征,需在变密度条件下对盆地地下水流系统进行模拟研究。本文采用砂槽物理模型,在改变区域性水流密度条件下模拟研究地下水流系统的变化规律。试验结果显示:随着区域性水流密度的增加,区域水流系统的渗流速度和循环量均减少,且流线径流距离和径流深度也随之减小;而局部水流系统的渗流速度和循环量均增加。结果表明区域性水流密度的增加会抑制区域水流系统的发育,对局部水流系统有一定增强作用。本研究着重强调了区域性水流自身密度变化对盆地地下水流系统所产生的影响,并通过物理试验模拟得出在改变区域性水流密度条件下盆地地下水流系统的变化规律。     

Asian Transboundary Aquifers Inventory and Mapping

Transboundary aquifer (TBA) is an aquifer system that exists in more than one state. As an important component of the groundwater system, proper management and rational utilization in trans-boundary aquifers are significantly important for promoting sustainable development and good-neighbor relationships. The Transboundary Aquifers will not implicate by the country’s political boundary as it follows the natural boundary lines. Within the frame work of the UNESCO''s International Hydrological Programme (IHP-VI & VII) activities for the International Shared Aquifer Resource Management (ISARM), the inventory on TBA in Asia both preliminary and detail has accomplished. Those TBAs are classified in to two types: regional and local grade. A of Asian Transboundary Aquifers Map has advanced. The updated map provides the situation of the regional TBAs identify as the actual shape. Countries with the TBAs should strengthen cooperation for coordination and joint management of groundwater resources in order to achieve sustainable use     

辽宁凌源——建昌一带基岩地下水主要特征

凌源—建昌一带是辽宁西部主要干旱少雨地区,研究这一地区基岩地下水的分布规律,具有重大经济意义。本文从综合分析辽宁西部水文地质调查资科入手,对该地区基岩地下水类型及岩石富水性和褶皱束、盆地、断裂及不整合接触带富水性以及该地区补给径流排泄条件等问题进行了讨论。特别是深入分析了碎屑岩类裂隙孔隙水、碳酸盐类岩石裂隙岩溶水、带状裂隙水、层状裂隙水的赋存特点。     

Influence of Sungun copper mine on groundwater quality,NW Iran

Sungun mine is the largest open-cast copper mine in northwest of Iran and is in the primary stages of extraction. The influence of mining activity on the quality of regional groundwater has been taken in to consideration in this study. Accordingly, sampling was done from 22 springs in the study area. The concentrations of major anions and cations as well as Al, Cu, Cd, Cr, Fe, Mn, and Zn were determined for all 22 spring samples in mid-August 2005. The results showed that the concentrations of most of these elements were below the USA Environmental Protection Agency (EPA) limits; however, Al and Fe concentrations are considered to be more than limits in a couple of samples. Despite the fact that geological formations are highly weathered and fractured, the dissolution of minerals within the study area is low. This may be justified by the relatively high alkalinity of local underground water which keeps metals in solid phase and does not let them enter dissolved phase. Additionally, this may be attributed to the high velocity of groundwater flows, which do not give enough time for minerals to dissolve. Correlation coefficients among water chemistry components were determined and the weighted-pair group method was chosen for cluster analysis. Accordingly, high correlation among Al, Fe and Cr, Cd ,and Cu, sodium absorption ratio (SAR) and Na as well as total hardness (TH), Ca, and Mg were observed. The chemical characteristics of water compositions on the basis of major ion concentrations were evaluated on a Schoeller and Piper diagram. Accordingly, the dominant type of water in the region is considered to be Ca-HCO₃ (calcium-bicarbonate type). However, this type of water is also rich in Na, K, and especially Mg. Regarding Schoeller diagram, the current status of local underground water is good for drinking purposes. By commencing mining excavation with designed capacity in near future, the minerals will come into contact with air and water resulting in dissolution, especially in ponds, which, in turn, will increase the concentration of toxic metals in groundwater. Considering future uses of this water including for drinking, irrigation, industrial purposes, etc., precautions must be taken in to consideration.