Influence of flooding on groundwater flow in central Cambodia

Cambodia is affected by flooding from the Mekong, Tonle Sap and Bassac rivers every year, which harms human populations and damages property, as well as alters the water quality in aquifer systems. The objective of this paper is to highlight the effects of river flooding on groundwater flow using numerical simulation. A two-dimensional groundwater flow model coupled with a groundwater recharge model was applied to the research area in central Cambodia. River level variation was included in model processes, and flood areas and periods were assigned. The results showed that during flooding periods, floodwater from the three rivers played an important role in recharging groundwater. During the dry season, Tonle Sap River received groundwater supply from the northwest, and levels in the Bassac and Mekong River dropped to lower than the groundwater level. This study improves understanding of the surface water and groundwater flow system in the study area.     

Groundwater potential for irrigation in the East Oweinat area,Western Desert Egypt

The Nubia Sandstone aquifer system is one of the most extensive groundwater systems in North Africa, covering an area of about 2,000,000 km², including parts of Egypt, Libya, Sudan, and Chad. In the Western Desert of Egypt, the Nubian formation has a thermal gradient of 1.1–5°C 100 m^–1 with the exception of the East Oweinat area, located in the southern part of the Western Desert. This is the only part of this huge system where ground-water occurs under unconfmed conditions in an area where the Nubian sandstone crops out and is underlain by shallow basement rocks; in this area groundwater has no thermal characteristics. The aquifer system in the East Oweinat area attains a relatively high hydraulic conductivity. The direction of groundwater flow is generally northeastwards but is distorted at faults and fracture zones. Chemical analyses of groundwater in the area indicate a low salt content and suitability for irrigation purposes. As the estimated recharge to the area is low compared with the foreseen irrigation water requirement, the development of groundwater in the East Oweinat should be based on groundwater mining. Although the evaluation of the groundwater resources in East Oweinat has indicated that groundwater can be extracted at a rate of 4.7×10⁶ m³ d^–1, the long-term economics of extraction that can sustain large-scale development projects has to be assessed.     

Variability of the metal content of flood deposits

Fresh flood deposits were sampled in the flood-plains of two river systems, the River Meuse, with a catchment area of 33,000 km² and the River Geul, with a catchment area of 3,000 km². As a result of industrial and mining activities, both rivers have a history of severe metal pollution, especially with zinc, lead, and cadmium. The flood deposits of both rivers are heterogeneous mixtures of contaminated bottom sediments (with relatively long residence times in the river) and clean sediments derived from soil erosion on agricultural cropland (with very short residence times). An additional source of sediment is formed by erosion of older, locally highly contaminated streambank deposits. These older sediments are polluted as a result of solid waste disposal containing metalliferous ore and tailings in the sand fraction. This is especially the case in the River Geul, which drains an old zinc and lead mining area. The metal content of the Meuse sediments, however, originates largely from liquid industrial wastes and occurs mainly in the clay fraction. For this reason, the positive correlation between textural composition, organic matter content, and heavy metal concentration, which is often reported, was not observed, and normalization of the metal content was not possible. Nevertheless, a clear decrease of contamination was noticed along the River Geul; this trend was absent along the River Meuse. An attempt has been made to model the longitudinal decay pattern for each of the investigated havey metals.     

挠力河流域三维地下水流数值模拟

在分析概化挠力河流域地质及水文地质条件的基础上,建立了研究区地下水流系统的三维数学模拟模型,运用Visual MODFLOW软件进行求解,并对研究区未来7年的地下水流场进行了预报。模型预报过程中用迭代逼近方法预报二类边界,用频谱分析法预报年降水量和地下水开采量,实现了随机模型与确定性模型相耦合。结果表明,研究区地下水多年平均补给量为20.9×10⁸ m³/a。从预报的等水位线图看出,按照预测的开采量进行开采,研究区的地下水位在预报期间略有下降,每年平均下降0.329 m。     

Is groundwater in the Tarkwa gold mining district of Ghana potable?

Hand-pump wells in the Tarkwa gold mining district and the geologically similar Bui area were chemically analysed and compared in an effort to determine whether groundwaters in the Tarkwa area have been affected by mining. Significant chemical differences attributed to mine water discharges have been observed in streams in the Tarkwa area. Groundwater chemistry from hand-pump wells in Tarkwa and Bui areas reveal similar hydrochemical facies, predominantly Ca–Na–Mg–HCO₃–Cl. However, except for SO₄^2–, ionic concentrations of groundwaters from Bui are greater than those from Tarkwa probably due to differences in (1) water availability during sedimentation (2) water-rock interactions and/or residence times for water. No demonstrable impact of mining on groundwaters from hand-pumped wells in the Tarkwa area has been noted. Hydrogeological inference suggests that the main streams which receive mine water discharges are both gaining and are groundwater divides. The overwhelming majority of population centres and mining operations are located on opposite sides of these groundwater divides, therefore, it is unlikely aquifers tapped for drinking by these communities would be affected by mining.     

Assessment of factors influencing groundwater-level change using groundwater flow simulation,considering vertical infiltration from rice-planted and crop-rotated paddy fields in Japan

Assessing factors that influence groundwater levels such as land use and pumping strategy, is essential to adequately manage groundwater resources. A transient numerical model for groundwater flow with infiltration was developed for the Tedori River alluvial fan (140 km²), Japan. The main water input into the groundwater body in this area is irrigation water, which is significantly influenced by land use, namely paddy and upland fields. The proposed model consists of two models, a one-dimensional (1-D) unsaturated-zone water flow model (HYDRUS-1D) for estimating groundwater recharge and a 3-D groundwater flow model (MODFLOW). Numerical simulation of groundwater flow from October 1975 to November 2009 was performed to validate the model. Simulation revealed seasonal groundwater level fluctuations, affected by paddy irrigation management. However, computational accuracy was limited by the spatiotemporal data resolution of the groundwater use. Both annual groundwater levels and recharge during the irrigation periods from 1975 to 2009 showed long-term decreasing trends. With the decline in rice-planted paddy field area, groundwater recharge cumulatively decreased to 61 % of the peak in 1977. A paddy-upland crop-rotation system could decrease groundwater recharge to 73–98 % relative to no crop rotation.     

Performance of a mixed-waste landfill amid geologic uncertainty—learning from a case study: Altamont Hills,California, U.S.A.

The Jharia coalfield is the most important and active minig region; it experiences groundwater inflow and affects groundwater levels in overlying aquifers, and it provides the basis for a conceptual model of the hydrogeological impacts of coal mining. The several sandstone aquifers of the overburden are separated by aquitards that limit vertical hydraulic connection, but the inflow responds to seasonal events and seems to be linked to shallow groundwater behavior. The mine drainage behavior suggests a hydraulic connection between the mine and the shallower groundwater system. The greatest declines are directly above the panels, with an immediate response to coal mining. The inflow is localized by natural and induced fracture zones and is mostly into recent workings. The groundwater behavior is controlled by hydraulic property changes caused by mine-induced fracturing. The hydrological and chemical qualities of the shallow groundwater regime in 13 mining collieries in Mukunda Block have been investigated. Water samples collected from 30 shallow monitoring dug wells were chosen for the study. Rainfall, runoff, and infiltration rates have been calculated in the area. The water-quality plottings were used to interpret the distribution of individual chemical parameters and in predicting the water quality. The underground mine water has been classified as: (1) unconfined groundwater in the calcareous siltstone and sandstone—its composition is Na, Ca, SO₄ and Na-MgHCO₃ with moderate total dissolved solids (TDS) 200–1480 ppm; (2) the deep groundwater originating from the coal seams and associated sediments in the near-surface environments—this is a Na-HCO₃ water with higher TDS; and (3) spoil dump waters are essentially Na-HCO₃ with high TDS. This article presents some hydrologic results and conclusions relating to the hydrogeological and environmental impacts of the coal mining in the Jharia coalfield.     

安徽马鞍山高村采场矿坑地下水疏干预测

根据马鞍山高村铁矿露天采场矿区地质及水文地质特征,对矿区的基岩裂隙地下水系统进行概化。结合高村采矿场历史疏干资料和观测孔的地下水动态观测资料,建立了矿区地下水水流模型。然后按照露天采场的开采计划,论证矿坑地下水疏干对策,分别对2个开采规划期进行地下水疏干预测,为安全开采和经济有效地防治地下水提供设计依据。     

青岛大沽河下游地下咸水体变化的数值模拟

采用Visual-MODFLOW软件中SEAWAT模块建立变密度地下水流与溶质运移数值模型,对青岛大沽河地下水库南端残留咸水运移情况进行模拟。采用2001-2002年的降雨、蒸发、开采等资料,识别和验证模型,并在现有的开采条件下模拟研究区地下咸水未来10年的运移情况进行预测。研究发现,研究区内地下咸水总面积略有减小,靠近大沽河一侧咸水浓度降低,而魏家屯附近咸水浓度升高。     

Late Quaternary activity of the Feldbiss Fault Zone, Roer Valley Rift System, the Netherlands, based on displaced fluvial terrace fragments

The Meuse River crosses the Feldbiss Fault Zone, one of the main border fault zones of the Roer Valley Graben in the southern part of the Netherlands. Uplift of the area south of the Feldbiss Fault Zone forced the Meuse River to incise and, as a result, a flight of terraces was formed. Faults of the Feldbiss Fault Zone have displaced the Middle and Late Pleistocene terrace deposits. In this study, an extensive geomorphological survey was carried out to locate the faults of the Feldbiss Fault Zone and to determine the displacement history of terrace deposits.The Feldbiss Fault Zone is characterized by an average displacement rate of 0.041–0.047 mm a⁻¹ during the Late Pleistocene. Individual faults show an average displacement rate ranging between 0.010 and 0.034 mm a⁻¹. The spatial variation in displacement rates along the individual faults reveals a system of overstepping faults. These normal faults developed by reactivation of Paleozoic strike-slip faults.As fault displacements at the bases of the younger terrace deposits are apparently similar to the tops of the adjacent older terrace, the age of these horizons is the same within thousands of years. This implies that the model of terrace development by rapid fluvial incision followed by slow aggradation does apply for this area.     

Patterns in groundwater chemistry resulting from groundwater flow

 Groundwater flow influences hydrochemical patterns because flow reduces mixing by diffusion, carries the chemical imprints of biological and anthropogenic changes in the recharge area, and leaches the aquifer system. Global patterns are mainly dictated by differences in the flux of meteoric water passing through the subsoil. Within individual hydrosomes (water bodies with a specific origin), the following prograde evolution lines (facies sequence) normally develop in the direction of groundwater flow: from strong to no fluctuations in water quality, from polluted to unpolluted, from acidic to basic, from oxic to anoxic–methanogenic, from no to significant base exchange, and from fresh to brackish. This is demonstrated for fresh coastal-dune groundwater in the Netherlands. In this hydrosome, the leaching of calcium carbonate as much as 15 m and of adsorbed marine cations (Na⁺, K⁺, and Mg²⁺) as much as 2500 m in the flow direction is shown to correspond with about 5000 yr of flushing since the beach barrier with dunes developed. Recharge focus areas in the dunes are evidenced by groundwater displaying a lower prograde quality evolution than the surrounding dune groundwater. Artificially recharged Rhine River water in the dunes provides distinct hydrochemical patterns, which display groundwater flow, mixing, and groundwater ages. Received, May 1998 · Revised, August 1998 · Accepted, October 1998     

Numerical modeling the role of rubber dams on groundwater recharge and phreatic evaporation loss in riparian zones

Rubber dams have been widely built for their advantages in increase of flooding resources utilization in the north arid and semiarid plain regions of China. Rise in river water stage by the dams, particularly during the drought periods, increases lateral seepage of river water into groundwater, and thus groundwater table and phreatic evaporation loss in the riparian zones. In this study, a riparian area of the Baihe River in Nanyang of Henan Province, China was selected for investigation of influences of the river dams on the groundwater recharge and evaporation loss. A hydraulic model, HEC-RAS, was used for simulation of the river stage variations along the Baihe River, and a numerical groundwater model, MODFLOW, was applied for simulation of groundwater dynamics and estimation of river flow seepage into aquifer and evaporation loss. The results show that the dams increase river stages of 2–3 m during January 2000–December 2002. The increase in the captured groundwater recharge was 7.15–34.06 million m³/a and the increased phreatic evaporation loss occupies 10% of the increased recharge when four rubber dams were built.     

试论武汉地区构造演化与岩溶发育史

为了更全面地揭示岩溶发育特点,运用历史比较法,研究了武汉地区构造演化和岩溶发育史。古生代—中生代早期,武汉及周边地区地壳运动以整体升降为特点,各时代地层之间为平行不整合接触。晚古生代和中生代早期发生的两次大的海进—海退作用分别形成了石炭—二叠系和下三叠统两套碳酸盐岩系,为武汉地区岩溶发育提供了物质条件。中三叠世期末的印支运动产生的强大的NNE—SSW向挤压应力,形成NWW—SEE走向的线状褶皱,控制了碳酸盐岩的平面分布格局。晚三叠世—侏罗纪,武汉以西及北部等地隆起,东部及东南部的梁子湖地区在襄樊—广济等断裂的控制下逐步开始凹陷。这一时期内,地表、地下水总体向东部梁子湖凹陷汇集,控制了武汉地区第一期地下岩溶的发育。白垩—古近纪,武汉及周边地区地壳活动表现为差异性沉降,接受沉积,岩溶作用停止。新近纪—早更新世,武汉以西的潜江凹陷继续发展,而武汉地区则总体隆升。该时期内古地势东高西低,地表、地下水由东向西流动,第二期地下岩溶也自东向西发育。中、晚更新世时期,武汉及周边地区总体下沉,广泛形成厚10～30 m不等的老粘性土层覆盖于前二期岩溶之上。由于相对不透水层的阻隔,这一时期内岩溶作用基本停止发生。全新世时期,地表水的侵蚀作用部分地破坏了老粘土盖层的连续性。由于碳酸盐岩分布于现长江水体以下10～20 m,侵蚀基准面远高于碳酸盐岩的分布高程,地下水活动很弱,岩溶作用很弱或未发生。      

广西平南某矿区岩溶地下水连通试验研究

广西平南某矿区在人工疏水过程中地下水位持续下降,形成以采区为降落漏斗、周边地下水向采区径流排泄的地下水流场。位于矿区东侧的秦川河成为危及矿区施工安全的最大隐患。为了查明矿区岩溶地下水径流途径、径流特征,进而了解矿区采矿排水的主要来源及周边地表河的影响,在矿区周围进行了地下水连通试验。试验结果表明:矿区岩溶含水介质渗透性差异较大,含水层各向异性明显;矿区北部、东南部存在连通性较好的地下水径流带,北部流速为0.3 ~ 20 m/h,东南部流速为3.72 ~ 98 m/h;矿区南部、西南部与周边地下水连通性较差,与矿区以南的浔江存在地下分水岭;矿区东部一采区矿坑排水主要来自东侧秦川河渗漏补给及北部地下水侧向径流补给,矿区西部二采区矿坑排水补给来源为北部地下水侧向径流及大气降水。因此,采矿疏水过程中应及时掌握秦川河水位变化情况,采取帷幕等有效手段对水害进行治理,以确保生产安全。      

Aquifers in the benin formation (miocene—recent), eastern Niger delta,Nigeria: Lithostratigraphy,hydraulics, and water quality

A regional lithostratigraphic and hydraulic interpretation is presented for the upper 0–300 m of the Benin Formation where groundwater is abstracted in the Rivers State, Nigeria.The aquifers are predominantly sand beds with minor clays, lignite, and conglomerate intercalations. The sands are very fine to coarse grained, subangular to subrounded, poor to fairly well sorted and mostly lithic arenites. A maximum thickness greater than 50 m is developed in places and vertical stacking is common. Most of the conglomerate beds have a matrix support fabric and appear restricted to the east as the lignite beds. An east-west trending belt, about central to the state, seems to contain more clay interbeds.The transmissivity values for the aquifers range from 1.05 × 10^–2 to 11.3 × 10^–2 m²/sec, while the coefficient of storage varies between 1.07 × 10^–4 and 3.53 × 10^–4 and specific capacity values lie between 19.01 and 139.8 m³/h/m drawdown. These values suggest that the aquifers have very good capacity to transmit groundwater. The static water level map shows a north-to-south regional groundwater flow pattern except in the northeast (Imo River catchment area) where the flow is northeast to southwest. The groundwater quality is very good and compares favorably with WHO standards for drinking water. However, relatively high iron and chloride values are localized in time and space.Deposition of the aquifer materials is thought to have occurred in alluvial fan, fluvial channel, tidal channel, intertidal flat, beach, and related microenvironments.     

黄河支流汾河流域水资源开发利用现状及生态环境问题

【研究目的】汾河是黄河第二大支流,也是山西省的第一大河,流域内水资源供需矛盾突出,分析水资源开发利用现状及其生态环境问题是进行流域生态修复的前提。【研究方法】本文在分析汾河流域水资源特征及其开发利用现状的基础上,系统总结了汾河径流量衰减、岩溶大泉断流和水质恶化等生态环境问题,并对其成因进行了分析。【研究结果】研究表明：汾河流域多年平均水资源量为33.59亿m³,其中地下水资源是水资源的主要组成部分,约占72%;2005年以后由于跨流域调水、地下水压采等汾河流域综合治理措施的实施,水资源的供水结构发生了较大的变化,地表水的供水比例由最初的30%提高到55%,地下水供水比例由原来的62%降低到目前的37%。整体上,汾河流域的水资源开发利用程度高达80%以上,水资源的过度开发已导致汾河干流断流、入黄径流量大幅衰减、岩溶大泉断流等严重的生态环境问题。其中,汾河流入黄河径流量从1955至2018年衰减程度达63.5%,衰减的原因主要是降水量的减少和岩溶大泉的流量衰减;汾河流域内8个岩溶大泉的总流量从1956至2018年的衰减程度达69%,50%的岩溶大泉已在不同时期断流,岩溶大泉的水质恶化问题也非常严重,如晋祠泉和龙子祠泉的TDS和SO₄^2-呈逐年升高的趋势,煤矿开采是造成岩溶泉水SO₄^2-含量快速升高的主要原因。【结论】汾河流域的水资源供需矛盾十分突出,虽然通过跨流域调水等生态修复措施实现了汾河干流全年不断流、地下水位止降回升和地表水环境质量初步改善,但生态环境恶化的趋势依然严峻。创新点：分析了山西省汾河流域近15年的水资源特征及其供水结构的变化规律;系统总结了汾河流域的生态环境问题,并对其成因进行了探讨。     

Water resource accounting for an iron-ore mining area in India

A study has been conducted at the Bicholim iron-ore mine, North Goa, India to investigate the hydrogeological continuity between the mine's open pit and surrounding villages. Water resource accounting by demarcating different watersheds has also been carried out to analyse the major causes of groundwater scarcity in the region during dry periods. A resistivity survey and a ground penetrating radar survey were completed around the periphery of open pits, the surrounding village areas and Mayem Lake. The results of the two independent surveys and other related data confirm that there is no observable hydrogeological continuity between the pits, nearby villages and Mayem Lake. Hence, there may not be any significant effect on surrounding water resources due to mining or mine dewatering. Water resource accounting has revealed that only 15–20% of 3500 mm precipitation per annum becomes part of the groundwater resource. The remainder of the annual precipitation is lost as heavy runoff, evapotranspiration and subsurface capillary moisture. Closely spaced wells in the region have also aggravated the groundwater scarcity problem due to draw down effects. Therefore, an effective water resource conservation plan is required for the region to overcome the problem. Received: 18 January 1999 · Accepted: 17 May 1999     

Modelling of the construction of the Rhône alluvial plain since 15 000 years BP

A numerical model presented here develops a three-dimensional image of alluvial media on an elementary scale significant for groundwater flow modelling. The model was tested on the alluvial plain of the Rhône River (France), on a scale of several kilometres and, from geomorphological observations and dating, reproduced the construction of this alluvial plain from ≈15 000 years BP to the present. The history of the alluvial plain during the Late Glacial and Holocene periods is summarized. Through most of this time, the River Rhône has maintained a braided pattern, with the exception of two incising phases with a meander pattern. The model does not use any physically based equations or water representation. The main processes governing the construction of the plain are modelled by simple rules chosen according to geometrical or empirical laws taken from the literature or as modelling assumptions. Using multi-agent concepts of distribution and interaction of elementary entities, these sedimentary rules are applied to 'sediment' entities or to conceptual 'erosion' entities that simulate local deposition and erosion of sediments. The sedimentation model reproduces the various climatic periods during which the sediments were deposited by simulating genetic periods and associated modelled processes. For each period, the model was constrained by quantitative field data such as altitude of ancient channels and deposits or thickness of sediments. The general geometry of the alluvial deposits was satisfactorily reproduced. During the simulation, characteristic large-scale features emerge despite the use of local rules. The model results are discussed with reference to other approaches, such as geostatistical or Boolean models, and the applicability of the model to other less documented alluvial plains is outlined.     

The role of the Mississippi River in wetland loss in southeastern Louisiana,U.S.A.

The suspended load of the Lower Mississippi River has decreased almost 80 percent since 1850. The long-term suspended sediment record can be loosely subdivided into three phases: a historic interval prior to 1900, a predam period (1930–1952) and a postdam period (1963–1982). The suspended load decreased 43 percent from the historic to the predam period and 51 percent from the predam to the postdam period. The decreases in suspended load after 1952 coincide with the construction of reservoirs and dams on the Missouri and Arkansas rivers. Earlier decreases may be the result of changes in land use measurement practices. The decrease in suspended load and the elimination of overbank flow by the construction of artificial levees are considered to be major causes of coastal wetland loss in southeastern Louisiana. During the historic period sediment accumulation of the marsh surface was greater than the rate of water level rise. During the pre and postdam periods, the rate of water level rise exceeded sediment accretion on the marsh surface. Although the elimination of overbank sediment clearly exacerbated the wetlands loss, an accelerated rate of water level rise during the past 25 years has been a dominant factor. Based on estimates of available overbank sediment, it is suggested that the most viable management strategy for the wetlands would be the diversion of sediment into selected areas where the land loss is most critical.     

分布式“河道-沉陷区-地下水”水循环耦合模型——Ⅱ:模型应用

以淮南潘谢矿区2010年沉陷状况为背景,采用2001—2010年水文气象数据,应用构建的分布式"河道-沉陷区-地下水"耦合模拟模型对沉陷区水循环状况进行了模拟,并对模拟结果进行了检验。结果表明,河道汇流、水面降水、地下水和产流在沉陷区积水补给中所占比例分别为84.6%、8.8%、3.6%和3.0%,河道下泄、水面蒸发、渗漏和引水在沉陷区积水排泄中所占比例分别为80.6%、8.2%、1.3%和9.9%,沉陷区的自然水循环主要依赖于相连河道,其次为水面降水与蒸发,与地下水关联甚微。