Hydrogeological and hydrochemical framework of regional aquifer system in Kali-Ganga sub-basin, India

 The central Ganga Basin is one of the major groundwater reservoirs in India. The Kali-Ganga sub-basin is a micro watershed of the central Ganga Basin, containing a number of productive aquifers. A detailed hydrogeological investigation was carried out, which reveals the occurrence of a single-tier aquifer system down to 163 m bgl (metres below ground level), but at places it is interleaved with clay layers; thus imparting it a two-to three-tier aquifer system. These aquifers are unconfined to confined in disposition. The transmissivity, storage coefficient and hydraulic conductivity are determined as 2178 m²/day, 1.12×10^–5 and 120 m/day, respectively. The groundwater of the basin is fresh, of an alkali-bicarbonate type and is suitable for irrigation and domestic use. However, in certain areas, extensive agricultural activities, and domestic and industrial effluents have caused some deterioration of groundwater quality. This study contains data of where the concentration of Fe, Pb, Cd, Cr and Ni are higher than the permissible limits, which may be hazardous to public health. Received: 2 March 2000 · Accepted: 3 July 2000     

Increase in thermal groundwater due to a flowing well near the Songshan hot spring in Beijing,China

The Songshan hot spring occurs in granite in Yanqing County in northwestern Beijing, China. TDS of the hot water ranges from 459 to 475 mg/L and pH varies between 8.6 and 9.13. The water is of Na–SO₄ type. Isotopic analyses indicate that the hot spring is meteoric in origin and receives recharge from precipitation in the northern and northwestern granite mountain with elevation of about 1,600–1,800 m. The depth of circulation of the thermal groundwater is estimated to be 2,240 m below the spring’s threshold and the temperature of the geothermal reservoir, 76°C. The residence time of the thermal groundwater is estimated to be about 52 years. A flowing well near the spring has chemical compositions and formation conditions similar to the spring. The discharge of the flowing well is approximately eighteen times larger than that of the spring and the residence time of the former (about 15.4 years) is about three times smaller than that of the latter. Although the well and spring are close to each other, the well’s larger flow rates, indicated residence time and high hydraulic head suggest that the well taps a separate, but genetically similar flow system.     

Effect of oil pollution on fresh groundwater in Kuwait

Massive oil fires in Kuwait were the aftermath of the Gulf War. This resulted in the pollution of air, water, and soil, the magnitude of which is unparalleled in the history of mankind. Oil fires damaged several oil well heads, resulting in the flow of oil, forming large oil lakes. Products of combustion from oil well fires deposited over large areas. Infiltrating rainwater, leaching out contaminants from oil lakes and products of combustion at ground surface, can reach the water table and contaminate the groundwater. Field investigations, supported by laboratory studies and mathematical models, show that infiltration of oil from oil lakes will be limited to a depth of about 2 m from ground surface. Preliminary mathematical models showed that contaminated rainwater can infiltrate and reach the water table within a period of three to four days, particularly at the Raudhatain and Umm Al-Aish regions. These are the only regions in Kuwait where fresh groundwater exists. After reaching the water table, the lateral movement of contaminants is expected to be very slow under prevailing hydraulic gradients. Groundwater monitoring at the above regions during 1992 showed minor levels of vanadium, nickel, and total hydrocarbons at certain wells. Since average annual rainfall in the region is only 120 mm/yr, groundwater contamination due to the infiltration of contaminated rainwater is expected to be a long-term one.     

江汉平原第四系弱透水层渗透系数求算方法

弱透水层的渗透系数是区域地下水流系统划分和关键带水-土-生作用的重要参数.结合江汉平原关键带调查采集1:5万杨林尾-陆溪口图幅钻孔52组不同深度、不同岩性的原状土样,利用改进的渗透仪进行室内渗透实验,对粘性土样的渗透系数和粒度特征参数进行经验公式修正.发现研究区沉积物渗透系数与含水岩组埋深和岩性有关.浅层孔隙潜水含水岩组以粉质粘土、粘土为主,沉积环境稳定,渗透系数约10-9 m/s,变异系数为1.56;中深层承压含水岩组夹有多层粘土和粉砂,呈现多旋回分布的典型河湖交互作用的沉积环境,渗透系数为10-10~10-6 m/s,变异系数为2.04,变异性较大.利用有效孔隙比e_u与黏粒含量P的显著二项式关系,修正预测粘性土渗透系数的太沙基经验公式,预测值与室内实测数据基本吻合,二者比值均小于10,验证了太沙基修正公式在河湖相平原区的适用性.      

Confined groundwater near the rockhead in igneous rocks in the Mid-Levels area, Hong Kong, China

It is customary in Hong Kong to assume that the hydraulic conductivity of weathered igneous rocks decreases with depth or as the rock mass becomes less weathered. Such a hydraulic conductivity pattern can only lead to an unconfined aquifer. This paper presents a case study in the regions in and around the Mid-Levels area in Hong Kong regarding a possible relatively high hydraulic conductivity (K) zone and confined groundwater along the rockhead. The Mid-Levels area is located at the lower part of the north-facing slopes of Victoria Peak on Hong Kong Island and is prone to landslides. Although this site has a long history of geotechnical studies because of extensive urban development along the coast and public concern on slope stability, hydrogeology of the site remains poorly understood. This paper reexamined the hydraulic conductivity data in 7 boreholes conducted in the 1970s and found that 4 of them indicate an increase in K at the rockhead. Groundwater conditions revealed by tunnel construction at the coast suggest that K close to the rockhead is about 10 times greater than above rockhead. A careful analysis of storm response of a piezometer group with tips in different depths indicates that there was an upward flow from the bedrock to the colluvium. A field study of two overflow standpipes conducted by the authors showed that the water level can be 0.64 and 3.73 m above the ground surface, which illustrates that the deep groundwater is significantly artesian. A search of the archived site investigation reports from the government and private companies has led to an identification of about 24 sites with overflow boreholes, which suggests that overflow phenomenon is quite common in the study area. The paper then concludes that in the study area there is a relatively high K zone along the rockhead and the groundwater in the zone is confined. It is recommended that geotechnical engineers should carry out a more careful field study on an overflow borehole because such a borehole indicates a confined groundwater condition important for slope stability study and foundation design.     

The relationship between the water table and the surface flow of a losing stream, lower Medano Creek, Great Sand Dunes National Monument, Colorado

 Proposed groundwater withdrawals in the San Luis Valley of Colorado may lower the water table in Great Sand Dunes National Monument. In response, the National Park Service initiated a study that has produced a generalized conceptual model of the hydrologic system in order to assess whether a lowering of the water table might decrease the surface flow of lower Medano Creek. Based upon information obtained during the drilling of several boreholes, there appear to be five important hydrostratigraphic units underlying lower Medano Creek within the upper 30 m of the ground surface: 1. a perched aquifer overlying an aquitard located between about 5 and 6 m below the ground surface; 2. the aquitard itself; 3. an unconfined aquifer located between the upper and lower aquitards; 4. an aquitard located between about 27 and 29 m below the ground surface; and 5. a confined underlying the lower aquitard. Because the areal extent of the aquitards cannot be determined from the borehole data, a detailed conceptual model of the hydrogeologic system underlying lower Medano Creek cannot be developed. However, a generalized conceptual model can be envisioned that consists of a complex system of interlayered aquifers and leaky aquitards, with each aquifer having a unique hydraulic head. Water levels in the perched aquifer rise rapidly to their annual maximum levels in response to the arrival of the flow terminus of Medano Creek during the spring runoff event, and the location of the flow terminus is directly dependent upon the discharge of the creek. Water levels in the deeper, non-perched aquifers do not appear to fluctuate significantly in response to the arrival of the flow terminus, demonstrating that it is unlikely that the proposed groundwater withdrawals will decrease the surface flow of lower Medano Creek. Received: 27 December 1995 · Accepted: 20 February 1996     

Evaluation of heterogeneity and field-scale groundwater flow regime in a leaky till aquitard

Recent work in southern Ontario, Canada, demonstrates anomalously high vertical groundwater flow velocities (>1 m/year) through a thick (as much as 60 m), sandy silt till aquitard (Northern till), previously assumed to be of very low permeability (hydraulic conductivity <10^–10 m/s). Rapid recharge is attributed to the presence of fractures and sedimentary heterogeneities within the till, but the field-scale flow regime is poorly understood. This study identifies the nature of physical groundwater pathways through the till and provides estimates of the associated groundwater fluxes. The aquitard groundwater flow system is characterized by integrating details of the outcrop and subsurface sedimentary characteristics of the till with field-based hydrogeologic investigation and numerical modeling. Outcrop and subsurface data identify a composite internal aquitard stratigraphy consisting of tabular till beds (till elements) separated by laterally continuous sheet-like sands and gravels (interbeds) and boulder pavements. Individual till elements contain sedimentary heterogeneities, including discontinuous sand and gravel lenses, vertical sand dikes, and zones of horizontal and vertical fractures. Hydrogeologic field investigations indicate a three-layer aquitard flow system, consisting of upper and lower zones of more hydraulically active and heterogeneous till separated by a middle unit of relatively lower hydraulic conductivity. Groundwater pathways and fluxes in the till were evaluated using a two-dimensional aquitard/aquifer flow model which indicates a step-wise flow mechanism whereby groundwater moves alternately downward along vertical pathways (fractures, sedimentary dikes) and laterally along horizontal sand interbeds within the till. This model is consistent with observed hydraulic-head and isotope profiles, and the presence of tritiated pore waters at various depths throughout the till. Simulations suggest that a bulk aquitard vertical hydraulic conductivity on the order of 1×10^–9 m/s is required to reproduce observed hydraulic-head and tritium profiles. Electronic Publication     

Hydrogeological framework and water balance studies in parts of Krishni–Yamuna interstream area, Western Uttar Pradesh, India

The Krishni–Yamuna interstream area is a micro-watershed in the Central Ganga Plain and a highly fertile track of Western Uttar Pradesh. The Sugarcane and wheat are the major crops of the area. Aquifers of Quaternary age form the major source of Irrigation and municipal water supplies. A detailed hydrogeological investigation was carried out in the study area with an objective to assess aquifer framework, groundwater quality and its resource potential. The hydrogeological cross section reveals occurrence of alternate layers of clay and sand. Aquifer broadly behaves as a single bodied aquifer down to the depth of 100 m bgl (metre below ground level) as the clay layers laterally pinch out. The depth to water in the area varies between 5 and 16.5 m bgl. The general groundwater flow direction is from NE to SW with few local variations. An attempt has been made to evaluate groundwater resources of the area. The water budget method focuses on the various components contributing to groundwater flow and groundwater storage changes. Changes in ground water storage can be attributed to rainfall recharge, irrigation return flow and ground water inflow to the basin minus baseflow (ground water discharge to streams or springs), evapotranspiration from ground water, pumping and ground water outflow from the basin. The recharge is obtained in the study area using Water table fluctuation and Tritium methods. The results of water balance study show that the total recharge in to the interstream region is of the order of 185.25 million m³ and discharge from the study area is of the order of 203.24 million m³, leaving a deficit balance of −17.99 million m³. Therefore, the present status of groundwater development in the present study area has acquired the declining trend. Thus, the hydrogeological analysis and water balance studies shows that the groundwater development has attained a critical state in the region.     

沈阳市阳光港湾建筑群基坑降水施工研究

沈阳市阳光港湾建筑群高层建筑采用筏板基础,多层建筑采用人工挖孔灌注桩基础,在基础施工时,均需进行相应的降水工作。采用了分期降水的施工方法,首期降水施工是在分析场地水文地质条件的基础上,利用稳定流"大井法"预算基坑的涌水量,布置了9口井,使基坑周边的1#、2#、3#、4#观测孔水位均下降至5.11m,基本上达到了首期的降水的目的;第二期降水是利用首期降水观测的水位资料,采用稳定流干扰井群计算公式对场区地下水位进行了预报,重新设计了3口井。12口井全部投放使用后,测得稳定排水量为43 000m3/d,并形成了以基坑为中心的地下水降落漏斗,降水效果明显。此经验值得同类工程借鉴。     

Assessment of in situ permeability with emphasis on packer testing in Kuwait

This paper discusses in situ permeability testing performed at two sites in bore holes drilled in an extensive hydrogeological exploration program in Kuwait. The testing program, comprising packer, falling and rising head tests, was carried out in calcareous and variedly textured cemented sand formed during post-depositional diagenetic processes with the colloquial name ‘Gatch’. The program was undertaken to assist in the design and construction of a pilot drainage scheme aimed at lowering of the groundwater table in Kuwait City and suburbs.

The results indicated that ‘Gatch’ is an almost impermeable soil. However, the hydraulic conductivity of the subsoils at the investigated sites is significantly influenced by the distribution and volume of macropores. These permeable zones act as preferential pathways for the movement of water bypassing the fine matrix and, thereby, improve markedly the overall drainage characteristics of the sites.

Various in situ test methods, including packer, compare results satisfactorily, to give the sites a variable hydraulic conductivity rating that straddles between very low and medium. The packer device, by faring well against other routine in situ tests, shows promises for use as a tool in the assessment of drainage parameters of cemented soils. Laboratory tests, performed in parallel, proved inadequate to characterize the permeability properties of the subsoils in Kuwait.     

Groundwater vulnerability map of the Chrzanów karst-fissured Triassic aquifer (Poland)

A map shows intrinsic vulnerability to pollution of the Chrzanów karst-fissured aquifer (273 km²) in the southern part of Poland. This aquifer is intensively drained by numerous intakes and Zn-Pb ore mines. A DRASTIC-type parametric system was applied for groundwater vulnerability evaluation. Vulnerability assessment is based on six factors (depth to groundwater table, lithology of the unsaturated zone, net recharge, hydraulic conductivity of the aquifer, groundwater flow velocity, aquifer thickness). For the final vulnerability map construction at the scale of 1:50,000, a combination of the aquifer simulation model (using MODFLOW) and a geographical information system was applied. Maps of the net recharge, hydraulic conductivity of the aquifer and groundwater flow velocity were derived by aquifer modelling. Based on the vulnerability index (21-182), six relative vulnerability classes were selected. Reliability of the map has been verified.     

Hydraulic parameters and solute velocities in triple-porosity karstic-fissured-porous carbonate aquifers: case studies in southern Poland

 Rock and flow parameters of three karstic-fissured-porous aquifers in the Krakow-Silesian Triassic formations were measured using various methods and compared. Though cavern and fissure porosities are shown to be very low (cavern porosity below 0.5% and fracture porosity below 0.2%), they contribute dominantly to the hydraulic conductivity (from about 1.3×10^–6 to about 11×10^–6 m/s). Matrix porosity (2–11%) is shown to be the main water reservoir for solute transport and the main or significant contributor to the specific yield (<2%). Though the matrix porosity is shown to be much larger than the sum of the cavern and fissure porosities, its contribution to the total hydraulic conductivity is practically negligible (hydraulic conductivity of the matrix is from about 5×10^–11 m/s to about 2×10^–8 m/s). On the other hand, the matrix porosity (for neglected cavern and fissure porosities) when combined with tracer ages (or mean travel times) is shown to yield proper values of the hydraulic conductivity (K) by applying the following formula: K≅(matrix porosity×mean travel distance)/(mean hydraulic gradient×mean tracer age). Confirming earlier findings of the authors, this equation is shown to be of great practical importance because matrix porosity is easily measured in the laboratory on rock samples, whereas cavern and fracture porosities usually remain unmeasurable. Received: 21 February 1997 · Accepted: 13 May 1997     

Evaluation of remedial alternatives for a petroleum contaminated unconfined aquifer with fluctuating groundwater level

This study evaluated remedial alternatives for a petroleum-contaminated site where an unconfined aquifer composed of a sandy layer of about 3–3.5 m thickness is covered by alluvial deposits and reclaimed soil of about 1.5 m thickness. Precambrian gneiss, of low permeability, lies below the sandy layer. The shallow water table is about 3 m below the surface, but shows high fluctuations of up to 1.5 m in response to precipitation events. The unsaturated soil near the water table and the groundwater are highly contaminated with petroleum hydrocarbons, especially toluene, which have apparently leaked from storage tanks. Selection of the remedial alternatives required consideration of the relevant laws on soil and groundwater conservation in Korea, the results of risk analysis and the hydrogeological conditions. The contaminated area has been divided into zones in which different remediation goals are set based on risk analysis and the degree of natural attenuation. It is estimated that the clean-up goal can be achieved in two years by the combined use of a trench drain and well point pumping to collect the contaminated groundwater for treatment, and a dual air injection system for the contaminated soil.     

Characteristics of Piezometric heads and determination of fresh water–salt water interface in the coastal zone near Beihai,China

Changes in hydraulic heads with space and time and evolution of the location of fresh water–salt water interface are important for groundwater development in coastal aquifers. Measurements of piezometric heads at 11 well clusters consisting of three piezometric wells of different depths with a 5-day interval for 15 months show that the piezometric heads at nearly all the wells near the northwestern coast in Beihai decrease with increasing depth and increase with increasing distance from the coast. Changes in piezometric heads at the wells during the measurement period were caused by seasonal precipitation and induced by the tide. The depth of the sharp interface between fresh water–salt water can be estimated based on measurements of piezometric heads at a piezometric well tapping at a point in the salt water zone below the interface and measurements of the water table at the same well. The calculations of the interface for well H5 range from 40 to 80 m below sea level in the measurement period, which are believed to be more reasonable than those estimated with the Ghyben–Herzberg relation. An erratum to this article can be found at     

A modified DRASTIC model for Siting Confined Animal Feeding Operations in Williams County,Ohio, USA

Three of DRASTIC’s parameters (Depth to Water, Soil Media, and Topography) were modified and another parameter was added (land use/land cover) to the model to determine the potential impact on groundwater from Confined Animal Feeding Operations (CAFO) manure lagoon settings and manure application as fertilizer. Williams County is a mostly agricultural county located in northwest Ohio, USA. It currently has three CAFOs, all dairy, with the possibility of the construction of a multi-million chicken egg CAFO in the near future. A Geographic Information System (GIS) was utilized to modify the Ohio Department of Natural Resources (ODNR) DRASTIC map for the county to fully assess the county-wide pollution potential of CAFOs. The CAFO DRASTIC map indicates that almost half of Williams County has elevated groundwater pollution potential. The rest of the county, primarily the southeast corner, has lower CAFO groundwater pollution potential. Future CAFO development within the county should focus on the southeastern portion of the county where the groundwater table is deeper, and the aquifer is composed of shale substrate with low hydraulic conductivity. The CAFO DRASTIC results are intended to be used as a screening tool and are not to replace site-specific hydrogeologic investigations.     

渤海湾西岸滨海盐渍土的盐渍化特征分析

渤海湾西岸滨海盐渍土的盐渍化特征与滨海平原的地面高程、气候条件、盐渍土的理化性状、地下水的矿化度及人类活动等密切相关。就土盐渍化的程度而言,地面高程较高处的土高于地面高程较低处的土,上层土高于下层土。受蒸发和降水影响,地下水位以上土的盐渍化敏感深度为1 m左右。随着气候的变化,滨海盐渍土显现出春季蒸发,上层土积盐;夏季淋洗,土中盐分向下移动的盐渍化特征。随着深度的增加,土的含盐量逐渐减少,至地下水位附近出现轻微增长。从剖面上地表至地下水位间可划分为3个不同聚盐形态和含盐量的土盐渍化程度分区带,即土蒸发浓缩聚盐带、土盐化变动带和土饱水溶盐带;平面上向海岸线方向延伸,土逐渐由非盐渍土变为弱盐渍土、中盐渍土和强盐渍土,含盐量和盐渍化程度也越来越高。地下水位浅和地下水矿化度高,则上层土的盐渍化程度就愈高。     

深基坑降水与沉降的非线性耦合计算

结合润扬长江公路大桥南锚基坑工程,基于不同水文地质层水流运动特征的差异,对基坑降水过程中的地下水流计算,提出了双层结构数学模型,由此可以同时求出各分层地下水位。在土层降水-固结过程中,考虑到渗透系数和贮水系数随土层物理力学参数的非线性变化,提出了深基坑降水与沉降的非线性耦合计算方法。这为基坑土体变形预测、控制,指导工程施工和设计提供了新的途经。     

基于现场双管试验确定弱透水层水力参数的方法

弱透水层水力参数对基础工程设计、建设和地下水资源评价、地下水污染预测具有重要意义。现提出一种现场确定含水层系统中弱透水层水力参数的钻孔双管试验方法。利用麻花钻钻孔,到达地下水位线以下揭露到目的层位后布设外管,以起到护壁防止土层塌孔的作用。在外管内通过锤击的方式将内管嵌入到目的层中,使其下部管中有一定厚度的土样作为现场固定试验土柱。待内外管中地下水位稳定后迅速加高内管水头,并通过马里奥特瓶装置保持定水头。建立钻孔双管试验土柱的数学模型,推导了土柱顶底面单位面积流量随时间变化的解析解,将其无量纲化后作出标准曲线。作为该方法应用的实例,在长江下游三角洲苏锡常冲积平原的常州天宁区德安医院附近的空旷场地进行了专门的钻孔试验。确定了该地区的细砂质粉土和粉质黏土的渗透系数和贮水率分别为：K=1.66×10?6 m/s,?s =8.21×10?3 m?1;K=6.06×10?7 m/s,?s =2.26×10?3 m?1。结果表明,该方法对于现场确定弱透水层的水力参数有较好的适用性。     

The hydraulic conductivity field and groundwater flow in the unconfined aquifer system of the Keta Strip,Ghana

This study investigates the hydraulic conductivity field and the groundwater flow pattern as predicted by a calibrated steady state groundwater flow model for the Keta Strip, southeastern Ghana. The hydraulic conductivity field is an important parameter in evaluating aquifer properties in space, and in general basin-wide groundwater resources evaluation and management. This study finds that the general hydraulic conductivity of the unconsolidated unconfined aquifer system of the Keta Strip ranges between 2 m/d and 20 m/d, with an average of 15 m/d. The spatial variation in horizontal hydraulic conductivity appears to take the trend in the variations in the nature of the material in space. Calibrated groundwater recharge suggests that 6.9–34% of annual precipitation recharges the shallow aquifer system. This amount of recharge is significant and suggests high fortunes in terms of groundwater resources development for agriculture and industrial activities in the area. A spatial distribution of groundwater recharge from precipitation is presented in this study. The spatial pattern appears to take the form of the distribution in horizontal hydraulic conductivity, and suggests that the vertical hydraulic conductivity takes the same pattern of spatial variation as the horizontal hydraulic conductivity. This is consistent with observations in other areas. The resulting groundwater flow is dominated by local flow systems as the unconfined system is quite shallow. A general northeast – southwest flow pattern has been observed in the study area.     

Evidence for deep groundwater flow and convective heat transport in mountainous terrain, Delta County, Colorado, USA

The Tongue Creek watershed lies on the south flank of Grand Mesa in western Colorado, USA and is a site with 1.5 km of topographic relief, heat flow of 100 mW/m², thermal conductivity of 3.3 W m^–1 °C^–1, hydraulic conductivity of 10^-8 m/s, a water table that closely follows surface topography, and groundwater temperatures 3–15°C above mean surface temperatures. These data suggest that convective heat transport by groundwater flow has modified the thermal regime of the site. Steady state three-dimensional numerical simulations of heat flow, groundwater flow, and convective transport were used to model these thermal and hydrological data. The simulations provided estimates for the scale of hydraulic conductivity and bedrock base flow discharge within the watershed. The numerical models show that (1) complex three-dimensional flow systems develop with a range of scales from tens of meters to tens of kilometers; (2) mapped springs are frequently found at locations where contours of hydraulic head indicate strong vertical flow at the water table, and; (3) the distribution of groundwater temperatures in water wells as a function of surface elevation is predicted by the model.