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1.
Dorothy J. Vesper Rachel V. Grand Kristen Ward Joseph J. Donovan 《Environmental Geology》2009,58(3):667-678
The distribution and chemistry of the springs in the Tuscarora Creek watershed is controlled by both geologic structure and
karst dissolution. The watershed is located in eastern West Virginia in the structurally complex Great Valley of the Appalachian
Valley and Ridge province. The upper portion of the stream parallels strike along a mapped fault zone and is bordered by clastic
rocks that comprise North Mountain. The lower reaches of the stream flow cross-strike through Cambro-Ordovician carbonates.
The controlling chemical signature in the spring water is carbonate dissolution. Little evidence was seen for the recharge
from adjacent clastic rocks although differences in the Ca/Mg molar ratio between springs indicated the presence of localized
spring basins in headwater reaches. Na, Cl and Ca generally increased from upstream to downstream in the cross-strike reaches.
Comparison of stream and cumulative spring discharge was consistent with significant groundwater base-flow contribution directly
to the creek, particularly in the strike-parallel region. The largest spring in the watershed (>162 L/s) was sampled during
and after a large storm event along with the adjacent creek. The creek displayed a typical dilution response with each flood
pulse, whereas the spring had only a limited or delayed response. The overall chemical and thermal stability of the spring,
relative to the creek, indicated the lack of significant direct hydraulic connection between the two. The conceptual model
for the area includes localized flowpaths in the headwater region where the stream flow is parallel to strike and a thrust
fault. In addition to the shallow localized flowpaths, a deeper, more regional flowpath likely exists for a large spring further
downstream. 相似文献
2.
Yucca Mountain, Nevada is the site of the proposed US geologic repository for spent nuclear fuel and high-level radioactive waste. The repository is to be a mine, sited approximately 300 m below the crest of the mountain, in a sequence of variably welded and fractured mid-Miocene rhylolite tuffs, in the unsaturated zone, approximately 300 m above the water table. Beneath the proposed repository, at a depth of 2 km, is a thick sequence of Paleozoic carbonate rocks that contain the highly transmissive Lower Carbonate Aquifer. In the area of Yucca Mountain the Carbonate Aquifer integrates groundwater flow from north of the mountain, through the Amargosa Valley, through the Funeral Mountains to Furnace Creek in Death Valley, California where the groundwater discharges in a set of large springs. Data that describe the Carbonate Aquifer suggest a concept for flow through the aquifer, and based upon the conceptual model, a one-layer numerical model was constructed to simulate groundwater flow in the Carbonate Aquifer. Advective transport analyses suggest that the predicted travel time of a particle from Yucca Mountain to Death Valley through the Carbonate Aquifer might be as short as 100 years to as long 2,000 years, depending upon the porosity. 相似文献
3.
Regional recharge estimation using multiple methods: an application in the Annapolis Valley, Nova Scotia (Canada) 总被引：1，自引：0，他引：1
Recharge is a key parameter in groundwater resources management, and a reliable estimate of recharge is required for their sustainable development. Several methods are available to evaluate recharge; however, selecting the appropriate one is made difficult because each method has its advantages and drawbacks, and results can vary greatly from one method to another. Recharge methods can actually refer to different processes. This paper compares and discusses the results obtained from five regional-scale recharge assessment approaches applied to a fractured rock aquifer in a region with a temperate and humid climate (Annapolis Valley, Nova Scotia, Canada). These methods are distinguished between those providing estimates of the net infiltration (I) into the subsurface (river hydrograph separation and soil moisture balance) from those considering the net recharge (W) to the regional bedrock aquifer (river 7-day low-flows, the corrected soil moisture balance, a numerical groundwater flow model developed with FEFLOW and an infiltration model developed with HELP). The estimated net infiltration ranges from 160 to 250 mm/year, whereas the net recharge estimates range from 80 to 175 mm/year for the entire study area. Although different assessment methods were used, the estimated recharge range is still quite large, demonstrating the importance of using several methods. This case study should provide guidance on choices to be made in the development of a strategy for assessing representative values of aquifer recharge at the regional scale under similar geological and climatic conditions. The use of multiple complementary approaches should lead to a better understanding of the system dynamics and to better defined a representative range of recharge estimates. 相似文献
4.
Spring and Snake valleys, western USA, are scheduled for development and groundwater export to Las Vegas, Nevada (USA). New work, compared to published studies, illustrates the critical role of conceptual models to underpin water withdrawals in arid regions. Interbasin flow studies suggest that 30–55?% of recharge to Snake Valley arrives from adjacent Spring Valley. This study, however, suggest little or no interbasin flow; rather, Spring and Snake valleys comprise separate systems. Contrary to expectation, δD and δ18O contours are perpendicular to proposed interbasin flow paths. 14C age gradients up to 10?ka along interbasin flow paths indicate that old waters are not displaced by such fluxes. 14C and 3H patterns indicate local recharge occurs in adjacent mountain ranges and is transferred to basin-fill by losing streams, mountain front recharge, and upward leakage from carbonate bedrock beneath basins. The choice of conceptual models is critical for groundwater development. Simple analyses of water withdrawals indicate that monitoring discharges at desert springs is an inadequate protective measure. Once flows decline, recovery is lengthy even if pumping is stopped. The conceptual framework behind quantitative evaluations of sustainable yield is critical to determine the ability of a groundwater system to deliver sustained withdrawals. 相似文献
5.
Urban karst systems are typically considered more vulnerable to contamination and excess storm discharge because of potential
source areas, increased sediment loading, and focusing of water from impervious surfaces. However, urban hydrology can lead
to unexpected patterns, such as pirating of recharge into man-made storm systems. Valley Creek Basin in southeastern Pennsylvania,
presents such an urban karst system. Four springs were monitored for suspended sediment, water chemistry, and storm response
for an 18-month period. The baseflow suspended sediment concentrations were low, less than 4.0 mg/l. Furthermore, trace metal
analysis of baseflow water samples and spring mouth sediment showed only low concentrations. The response to storms within
the system was rapid, on the order of 1–3 h. The maximum water stage increases at the urban springs were typically less than
15 cm, with springs from more commercialized areas showing <2 cm increase. A nearby retention basin, in contrast, had water
level rises of 100 cm, suggesting that pirating of recharge into stormwater systems occurs. Thus, the concept of an urban
karst system as a contaminant conduit is not the only one that applies. In Valley Creek Basin, reduced infiltration due to
paving led to smaller storm response and less contaminant input, and the smaller capture area due to diversion of stormwater
led to short flow paths and rapid storm response. Although contaminant levels have not increased due to urbanization, the
springs may be at risk for future contamination. Short flow paths may reduce flushing, which means that the system will not
cleanse itself if contamination occurs. 相似文献
6.
Jakub T. Szmigielski S. Lee Barbour Sean K. Carey John Kurylo A. F. McClymont M. Jim Hendry 《Hydrogeology Journal》2018,26(7):2341-2356
Steelmaking-coal waste rock placed in mountain catchments in the Elk Valley, British Columbia, Canada, drain constituents of interest (CIs) to surface water downgradient of the waste rock dumps. The role of groundwater in transporting CIs in the headwaters of mountain catchments is not well understood. This study characterizes the physical hydrogeology of a portion of a 10-km2 headwater catchment (West Line Creek) downgradient of a 2.7-km2 waste rock dump placed over a natural headwater valley-bottom groundwater system. The study site was instrumented with 13 monitoring wells. Drill core samples were collected to determine subsurface lithology and geotechnical properties. The groundwater system was characterized using field testing and water-level monitoring. The valley-bottom sediments were composed of unconsolidated glacial and meltwater successions (<64 m thick) deposited as a series of cut and fill structures overlying shale bedrock. An unconfined basal alluvial aquifer located above fractured bedrock was identified as the primary conduit for groundwater flow toward Line Creek (650 m from the toe of the dump). Discharge through the basal alluvial aquifer was estimated using the geometric mean hydraulic conductivity (±1 standard deviation). These calculations suggest groundwater discharge could account for approximately 15% (ranging from 2 to 60%) of the total water discharged from the watershed. The residence time from the base of the waste rock dump to Line Creek was estimated at <3 years. The groundwater system was defined as a snowmelt (i.e., nival) regime dominated by direct recharge (percolation of precipitation) across the catchment. 相似文献
7.
8.
高放废物地质处置库北山预选区地下水的形成和分布 总被引：1，自引：0，他引：1
本文论述北山地区不同类型地下水的形成和赋存规律。松散岩类孔隙水主要分布于沟谷和洼地，主要为潜水。沟谷潜水的形成以基岩裂隙水的侧向补给及洪流渗漏补给为主，洼地潜水可由沟谷潜水、断裂带或基岩裂隙水、古洪积扇潜水侧向补给，也可由地表洪流渗入补给；碎屑岩类孔隙-裂隙水主要分布在由自垩系或第三系砂砾石构成的山间沉积盆地中，以承压水为主，洪水下渗和盆地周围基岩裂隙水的侧向径流是此类地下水的主要补给来源；基岩裂隙水主要赋存于变质岩、岩浆岩、碎屑岩、碳酸盐岩节理、裂隙中，以潜水为主。降水垂直渗入、侧向补给或洪流渗漏补给为其主要来源。 相似文献
9.
Brendan M. Mulligan M. Cathryn Ryan Tom��s Padilla C��mbara 《Hydrogeology Journal》2011,19(7):1335-1347
Relative recharge areas are evaluated using geochemical and isotopic tools, and inverse modeling. Geochemistry and water quality in springs discharging from a volcanic aquifer system in Guatemala are related to relative recharge area elevations and land use. Plagioclase feldspar and olivine react with volcanically derived CO2 to produce Ca-montmorillonite, chalcedony and goethite in the groundwater. Alkalinity, Mg, Ca, Na, and SiO2(aq) are produced, along with minor increases in Cl and SO4 concentrations. Variations in groundwater δD and δ18O values are attributed to recharge elevation and used in concert with geochemical evolution to distinguish local, intermediate, and regional flow systems. Springs with geochemically inferred short flow paths provided useful proxies to estimate an isotopic gradient for precipitation (??.67 δ18O/100?m). No correlation between spring discharge and relative flow-path length or interpreted recharge elevation was observed. The conceptual model was consistent with evidence of anthropogenic impacts (sewage and manure) in springs recharged in the lower watershed where livestock and humans reside. Spring sampling is a low-budget approach that can be used to develop a useful conceptual model of the relative scale of groundwater flow (and appropriate watershed protection areas), particularly in volcanic terrain where wells and boreholes are scarce. 相似文献
10.
Methods of estimating recharge in arid basin aquifers (such as the 1 % rule, Maxey-Eakin method, storm-runoff infiltration and others) overlook the potential contribution of direct recharge on the basin floors. In the Trans-Pecos region of west Texas, USA, this has resulted in potential recharge and solute flux to basin aquifers being ignored. Observed trends in groundwater nitrate (NO3 ?) concentrations and the presence of young (<70 years old) water in the basins indicate that recharge is occurring through the basin floors. A spatially variable net infiltration model (INFIL 3.0.1) was used to estimate the volume and spatial distribution of potential recharge to two basins: Red Light Draw and Eagle Flats. The INFIL model provides insight into the mechanisms by which recharge and solute flux occurs in arid basin systems. This method demonstrated that recharge is widespread; it is not limited to the mountainous areas and mountain-front recharge mechanisms, and up to 15 % of total potential recharge in these basins occurs across widespread areas of the basin floors. Models such as this should improve scientific understanding and sustainable management of arid basin aquifers in Texas and elsewhere. 相似文献
11.
The city of Scarborough lies on the eastern margin of the Greater Toronto Area of southern Ontario, Canada, along the northern
coastline of Lake Ontario. The City has a population of 500,000 and is presently one of the fastest growing communities in
Canada. The City is expanding northwards onto rural land on the south slope of the large Pleistocene glacial Oak Ridges Moraine
system. The moraine system is underlain by a thick (150 m) succession of tills, sands and gravels and is a regionally-significant
recharge area for three principle aquifer systems that discharge to numerous watercourses that flow to Lake Ontario. Protection
of deeper aquifers from surface-generated urban contaminants is a particular concern.
A groundwater flow model using Visual MODFLOW was developed for the 350-km2 Rouge River–Highland Creek (RRHC) drainage basin using an extensive GIS-based collection of subsurface geological, geophysical
and hydrogeological data, maps of land use and surficial geology. The RRHC model was calibrated against point water level
data, known potentiometric surfaces of the principal aquifers and baseflow measurements from streamflow gauging stations and
determined to be within acceptable limits. Water balance calculations indicate that 70% of the basin recharge (106,000 m3/day) enters the Upper Aquifer along the crest and immediate flanks of the Oak Ridges Moraine. To the south, Upper Aquifer
water moving through fractured till aquitards accounts for more than 75% of recharge to deeper aquifers. Water quality data
confirm previous observations that urban- and rural-sourced contaminants (chlorides and nitrates) present in Upper Aquifer
waters are moving rapidly into deeper aquifers. Some 83% of total RRHC recharge water is ultimately discharged as baseflow
to creeks draining to Lake Ontario; the remainder discharges to springs and along eroding lakeshore bluffs. Model results
demonstrate that deeper aquifers are poorly protected from urban contaminants and that long-term protection of ground and
surface water quality has to be a priority of municipal planners if the resource is not to be severely degraded.
Electronic Publication 相似文献
12.
Xiaobin Zhu Jichun Wu Huijun Nie Fei Guo Jianfeng Wu Kouping Chen Penghui Liao Hongxia Xu Xiankui Zeng 《Hydrogeology Journal》2018,26(5):1475-1485
Inter-basin water transfer projects (IBWTPs) can involve basins as water donors and water receivers. In contrast to most studies on IBWTPs, which mainly impact the surface-water eco-environment, this study focuses on the impacts of an IBWTP on groundwater and its eco-environment in a water donor basin in an arid area, where surface water and groundwater are exchanged. Surface water is assumed to recharge groundwater and a groundwater numerical simulation model was constructed using MODFLOW. The model was used to quantitatively evaluate the impact of an IBWTP located in the upstream portion of Nalenggele River (the biggest river in the Qaidam basin, Northwest China). The impact involved decrease in spring flow, drawdown of groundwater, reduction in oasis area, and an increase in species replacement of oasis vegetation in the midstream and downstream of the river. Results show that the emergence sites of springs at the front of the oasis will move 2–5 km downstream, and the outflow of springs will decrease by 42 million m3/a. The maximum drawdown of groundwater level at the front of the oasis will be 3.6 m and the area across which groundwater drawdown exceeds 2.0 m will be about 59.02 km2, accounting for 2.71% of the total area of the oasis. Under such conditions, reeds will gradually be replaced by Tamarix, shrubs, and other alternative plant species. These findings have important implications for the optimization of water resource allocation and protection of the eco-environment in arid regions. 相似文献
13.
Irene M. Farnham Klaus J. Stetzenbach Ashok K. Singh Kevin H. Johannesson 《Mathematical Geology》2000,32(8):943-968
The origin of groundwater discharging via evapotranspiration and from springs within Oasis Valley, Nevada, is of concern owing to the close proximity of the Nevada Test Site (NTS) and the possible contamination of groundwater as a result of underground nuclear testing. Principal components analysis, cluster analysis, and population partitioning, along with a Geographical Information System, were used to decipher groundwater flow patterns in Oasis Valley, Nevada. These multivariate statistical techniques were applied to the trace element chemistry of groundwater samples collected from 26 springs and wells within Oasis Valley, the NTS, and the Nellis Air Force Range. The results of all statistical analyses showed similar geographical trends in the trace element chemistry of the groundwaters included in this study. Differences are observed between the groundwaters from the NTS and those of Oasis Valley based on the concentrations of the elements Li, Ge, Mo, Rb, Ba, U, and Ru. A concentration gradient is observed from lower concentrations in the NTS to increasing concentrations toward Oasis Valley suggesting groundwater flow in an overall southwestward direction from the NTS. Also, a different trace element signature is observed for the waters collected in the northern and western region of Oasis Valley, suggesting another source of groundwater to this area. 相似文献
14.
The water balance for the Basin of the Valley of Mexico and implications for future water consumption 总被引：2，自引：0，他引：2
The Basin of the Valley of Mexico is a closed basin of 9600?km2, where average annual precipitation (1980–85) is 746?mm (226.7?m3/s). Calculated actual evapotranspiration is 72–79% of the precipitation. The surrounding mountain ranges of the Sierra de Las Cruces, Sierra Nevada, and Sierra Chichinautzin are the main recharge areas for the enclosed Basin, in decreasing order. Calculated recharge rate is a maximum of 19?m3/s in the Metropolitan Zone, whereas a recent estimate of the groundwater exploitation rate indicates that 51.35?m3/s is being withdrawn from the Basin aquifer systems, resulting in a deficit of more than 30?m3/s. Taking into account infiltration processes by leaking water-supply systems, the calculated deficit is reduced to 20.5?m3/s. Overexploitation of the natural aquifer systems is also indicated by an average annual decline of 1?m of the potentiometric levels of the shallow groundwater systems. Possible solutions include: (1) the use of surface runoff water (unused amount in 1995?:?17.6?m3/s) for consumption purposes, which is currently pumped to areas outside the Basin; (2) an increased number and capacity of treatment plants; (3) the renovation of the leaky water-distribution network; (4) the reinjection of treated water; and (5) possible exploitation of deep regional aquifer systems. 相似文献
15.
Spring deposits reveal the timing and environment of past groundwater discharge. Herein, however, the potential for fossil spring deposits to infer water sources and palaeoflowpaths through trace elements and stable and radiogenic isotopes is examined. Past discharge (70 to 285 ka) in the Tecopa Basin in the Death Valley region of southeastern California is represented by tufa deposits, including mounds, pools, cemented ledges and rare calcite feeder veins. δ18O values indicate that spring discharge was a mixture of far‐travelled (regional) water with a significant, and perhaps dominant contribution of local recharge on a nearby range front and alluvial pediment, rather than simply representing an elevated regional water table. δ13C values indicate regional water had a high TDS, whereas solute data imply low overall solute contents, consistent with dilution by a large component of local recharge. Radiogenic isotope data (U‐series, 87Sr/86Sr) for tufa indicate that siliciclastic rocks (a regional aquitard) interacted with discharging water. To access this aquitard, regional flow was probably partitioned into a permeable north–south damage zone of a north–south range‐bounding fault along the foot of the Resting Spring Range, which ultimately controlled the location of groundwater discharge. Existing models for modern discharge in the Tecopa Basin, by contrast, call upon westward interbasin flow in carbonate rocks from the Spring Mountains through the intervening (and nearly perpendicular) Nopah and Resting Spring Ranges. Understanding the controls on regional groundwater flow is critical in this and other arid regions where water is, by definition, a scarce resource. Thus, although it is a case study, this report highlights a fruitful approach to palaeohydrology that can be widely applied. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
16.
Analysis of geothermal and hydrogeologic characteristics of Paleozoic interior basins of Brazil has identified an association between the geographic distribution of thermal springs and areas of occurrences of groundwater flow. Specifically, thermal springs are found to be absent in regions inferred to have lateral flows of groundwater. This trend is evident in the basins of the Amazon region, in the central parts of the Parnaíba basin and in the west-central parts of the Paraná basin. Model studies help to elucidate mutual exclusion of regions of thermal springs and sub-horizontal flows of groundwater. Numerical simulations indicate that groundwater flows with velocities ≥ 1 cm/year are capable of masking the occurrence of thermal anomalies. Also, down flow through distributed recharge zones can lead to development of large zones of relatively low temperature. The observational data sets of temperature gradients and Peclet numbers have been employed outlining advection-convection domains of subsurface strata in the sedimentary basins of the Amazon region, Parnaíba and Paraná. Results obtained indicate that thermal buoyancy forces are incapable of overcoming advective flows in basins of the Amazon region. Similar conditions are also found to prevail in the central parts of the Parnaíba and Paraná basins. 相似文献
17.
The Las Vegas Valley Water District in Nevada, USA, has operated an artificial recharge (AR) program since 1989. In summer 2001, observations of gas exsolving from tap water prompted a study that revealed total dissolved gas (TDG) pressures approaching 2?atm with a gas composition that it is predominantly air. Measurements of TDG pressure at well heads and in the distribution system indicated two potential mechanisms for elevated TDG pressures: (1) air entrainment during AR operations, and (2) temperature changes between the winter recharge season and the summer withdrawal season. Air entrainment during pumping was investigated by intentionally allowing the forebay (upstream reservoir) of a large pumping station to drawdown to the point of vortex formation. This resulted in up to a 0.7?atm increase in TDG pressure. In general, the solubility of gases in water decreases as the temperature increases. In the Las Vegas Valley, water that acquired a modest amount of dissolved gas during winter artificial recharge operations experienced an increase in dissolved gas pressure (0.04?atm/°C) as the water warmed in the subsurface. A combination of air entrainment during AR operations and its amplification by temperature increase after recharge can account for most of the observed amounts of excess gas at this site. 相似文献
18.
19.
S. J. Appleyard 《Environmental Geology》1993,21(4):227-236
Twelve bores were sunk adjacent to three stormwater infiltration basins in the Perth metropolitan area to examine the impact of runoff from a light industrial area, a medium-density residential area, and a major arterial road on groundwater quality, and to examine the hydrological response of the aquifer to runoff recharge. Automatic and manual water level monitoring between April and November 1990 indicated that groundwater levels responded within minutes to recharge from the infiltration basins. Peak water levels of up to 2.5 m above rest levels occurred 6–24 h after the commencement of ponding in the infiltration basins. There was a marked reduction in salinity and increase in dissolved oxygen concentrations in the upper part of the aquifer downgradient of the infiltration basins. Concentrations of toxic metals, nutrients, pesticides, and phenolic compounds in groundwater near the infiltration basins were low and generally well within Australian drinking water guidelines. However, sediment in the base of an infiltration basin draining a major road contained in excess of 3500 ppm of lead. Phthalates, which are US EPA priority pollutants, were detected in all but one bore near the infiltration basins. Their detection may be a sampling artifact, but they may also be derived from the plastic litter that accumulates in the infiltration basins. The concentration of iron in groundwater near the infiltration basins appears to be controlled by dissolved oxygen concentrations, with high iron concentrations occurring where dissolved oxygen concentrations are low. Pumping bores located near infiltration basins may suffer from iron encrustation problems caused by the mixing of shallow, oxygenated groundwater with water containing higher concentrations of iron from deeper in the aquifer. 相似文献
20.
Surface water bodies interact with underlying aquifer systems, creating a complex flow system and flow paths. In general, a surface water body may be classified as gaining, losing, or flow through on the basis of its interaction with the surrounding aquifer. In the Nile Valley, the quaternary aquifer system is in a direct hydraulic interaction with the River Nile, canals, and drains. In this study, a regional numerical model was developed and used to evaluate the interaction between surface water bodies and the quaternary aquifer system in the Nile Valley. The solution is considered for a quasi three-dimensional, steady-state groundwater flow. The model used simulates the interaction between surface water bodies and groundwater for saturated and unsaturated flow conditions. In addition, a hydrodynamic model was used to simulate different extreme (high and low) scenarios for Nile surface water levels along the distance between Old Aswan Dam and Delta Barrages. Model calibration shows close results, and the model was used to simulate surface water levels. Results indicate that the Nile River acts as a drain for the quaternary aquifer (gaining water from the aquifer), although in the reaches upstream of the main barrages, the Nile loses the water, recharging the aquifer. All other main canals are recharging the aquifer system. The seepage rate depends mainly on the difference in piezometric head between the aquifer system and surface water bodies, as well as the hydraulic conductance of the base layer sediments of the surface water body. The model was used to evaluate the regional water balance for the Nile Valley and to estimate the surface water bodies' gains and losses. 相似文献