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1.
Studies on groundwater recharge are essential for sustainable exploitation of groundwater resources, especially in areas of extensive groundwater exploitation such as the Anyanghe River alluvial fan (ARAF) in the North China Plain (NCP). However, the recharge sources and processes and the contribution of each recharge flow component remain unclear. This study used hydrochemistry, stable isotopes, and tritium to investigate sources and underlying processes of groundwater recharge, along with the steady flow Mixing Cell Model (MCMsf) to quantify the proportion of each source flow for the shallow confined groundwater system in the medial fan. The results showed that groundwater mainly originates from precipitation occurring on the eastern Taihang Mountain area with average elevation estimated at 700–1,000 m above sea level during the East Asia summer monsoon period since 1952. Recharge mechanisms are: (1) river water seepage for the unconfined aquifers of the proximal and medial fan; (2) lateral flow for the confined aquifers of the medial and distal fan; and (3) precipitation infiltration for the phreatic water system. The MCMsf simulation showed that the shallow confined groundwater system in the central zone of the medial fan mainly recharged by the lateral flow from the proximal fan, a constant and considerable recharge flow from the southwestern and southern hills, and river water seepage in the medial fan; the lateral recharge flow from the Zhanghe alluvial aquifer was insignificant by comparison. The results of this study can act as a valuable reference for sustainable groundwater management in the ARAF. 相似文献
2.
通过恢复巴丹吉林沙漠及其周边地区大气降水氚值，并结合区域稳定同位素组合特征，揭示了区域地下水氚年龄的多解性与地下水稳定同位素的温度效应。恢复的1963年核试验期氚高峰值达到2 100 TU，进入90年代平均为60 TU。1960年以来降水补给的地下水氚值都应大于15 TU，而1963年的高峰氚衰变至今应在200 TU左右。地下水实测氚值较低，表明由现代少量降水补给的地下水与大量的古水进行了混合。影响降水中δ18O和δ2H分布的主要影响因子是月平均空气温度，对δ18O与δ2H的影响权重分别占到59.9%和57.0%。巴丹吉林沙漠及其周边地区地下水较低的稳定同位素组成表明，其补给主要是晚更新世较冷环境下形成的，来源于东南部的雅布赖山区，部分浅层地下水接受现代降水与河流的补给。
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3.
利用地下水水化学和同位素测试分析成果,结合区域地质、水文地质条件研究了平谷北山山区侧向补给情况和中桥水源地地区第四系松散孔隙水和下伏岩溶水关系。结果表明：研究区第四系松散孔隙水和基岩岩溶地下水均来源于大气降水,地下水化学类型均为HCO-3-Ca2+?Mg2+ 型;平谷北山山前基岩岩溶水侧向补给平原区第四系松散孔隙水和下伏岩溶地下水;通过D值估算得到中桥水源地第四系浅层地下水的山区岩溶水侧向补给和垂向降水入渗补给比例为57：43;中桥水源地基岩岩溶水接受山区岩溶水侧向补给和第四系孔隙水垂向越流补给比例为87：13。研究成果为平谷地区地下水资源量评价和地下水动力场数值模型的建设提供了关键参数,为区域地下水的合理开采和有序回补涵养提供了科学依据。 相似文献
4.
The Najd, Oman, is located in one of the most arid environments in the world. The groundwater in this region is occurring in four different aquifers A to D of the Hadhramaut Group consisting mainly of different types of limestone and dolomite. The quality of the groundwater is dominated by the major ions sodium, calcium, magnesium, sulphate, and chloride, but the hydrochemical character is varying among the four aquifers. Mineralization within the separate aquifers increases along the groundwater flow direction from south to north-northeast up to high saline sodium-chloride water in aquifer D in the northeast area of the Najd. Environmental isotope analyses of hydrogen and oxygen were conducted to monitor the groundwater dynamics and to evaluate the recharge conditions of groundwater into the Najd aquifers. Results suggest an earlier recharge into these aquifers as well as ongoing recharge takes place in the region down to present day. Mixing of modern and submodern waters was detected by water isotopes in aquifer D in the mountain chain (Jabal) area and along the northern side of the mountain range. In addition, δ 2H and δ 18O variations suggest that aquifers A, B, and C are assumed to be connected by faults and fractures, and interaction between the aquifers may occur. Low tritium concentrations support the mixing assumption in the recharge area. The knowledge about the groundwater development is an important factor for the sustainable use of water resources in the Dhofar region. 相似文献
5.
Chemical and isotopic data in atmospheric precipitation, surface water, and groundwater in arid Rasafeh area, northeast Syria, are used to clarify the status of groundwater quality, the interaction of water components, groundwater dating, and vulnerability to anthropogenic contamination. Interpretation of chemical data with thermodynamic calculation reveals that the dissolution of evaporate mineral is the main factor of high salinity. The δ 18O and δ 2H relationships indicate that the groundwater is fed by mixing water from Euphrates River and precipitation and the isotope balance equation were used to estimate the contribution of the Euphrates River to the aquifers recharge. High tritium content, together with high 14C activity in the majority of groundwater samples, indicate shorter residence times and consequently potentially greater recharge. The presence of high nitrate concentration associated with high tritium concentration in both shallow and deep aquifer units indicates the presence of high permeability, so that groundwater is highly susceptible to anthropogenic contamination. Nitrate seems to derive exclusively from the application of N fertilizers. The high nitrate values are characteristic of the areas with intensive agricultural activity, indicating the importance of irrigated return flow on the groundwater. 相似文献
6.
深层地下水的属性、深浅层地下水的水力联系(越流)是水文地质工作者一直研究和争论的问题。在对邯郸、邢台东部四县深、浅层地下水的氢、氧同位素样品的采集与测试中,发现该区地下水中氚同位素含量较高(15～30 TU,最高达51.1 TU)。本文利用区域大气降水中氚同位素衰减规律与特征,结合研究区地下水的水位和水质动态特征、含水层及隔水层的岩性特征,对特定水文地质条件下浅层地下水向深层地下水越流的可能性进行了分析研究,认为:本区存在浅层地下水越流至深层地下水的可能,在深层地下水中出现的高氚含量是其重要的证据。 相似文献
7.
Groundwater is the major source of water and a critical resource for socioeconomic development in semi-arid environments like the Johannesburg area. Environmental isotopes are employed in this study to characterise groundwater recharge and flow mechanisms in the bedrock aquifers of Johannesburg, which is known for polluted surface water. With the exception of boreholes near the Hartbeespoort Dam, groundwater in the study area was derived from meteoric water that has undergone some degree of evaporation before recharge, possibly via diffuse mechanisms. Boreholes that tap groundwater from the Transvaal Supergroup Formation show depletion in δ 18O and δ 2H values. This is attributed to diffuse recharge through weathering fractures at high elevation that are undergoing deep circulation or recharge from depleted rainfall from the high-latitude moisture sources. The influence of focused recharge from the Hartbeespoort Dam was observed in the boreholes north of the dam, possibly as a result of the north–south trending fault lines and the north-dipping fractures in the bedding planes of quartzites. This is also supported by a reservoir water budget method which indicated a mean annual net flux of 2,084,131 m 3 from Hartbeespoort Dam recharging groundwater per annum. Using tritium in the dam and boreholes located at 750 m and 5400 m downstream, average groundwater flow velocity was estimated as 202 m/year. An open system was observed in shale, andesite and granitic-gneiss aquifers indicating soil CO 2 as a dominant source of carbon (δ 13C) in groundwater. A closed system was also observed in dolomitic aquifers indicating carbonate dissolution as the predominant source of carbon. 相似文献
8.
The travel time of groundwater plays a major role in the understanding of hydrogeological systems; however, large data sets necessary for regional studies of groundwater age are rare. In this study, a unique large data set of groundwater samples analysed for tritium and helium isotopes collected over the last 20 years from Cenozoic aquifers of the North German Plain is explored. Hereby, the variety of natural and technical influences on the tritium-helium age, including screen depth and length, groundwater recharge rate and climatic effects, are investigated. To a sampling depth of ~40 m below ground level, the median tritium-helium age increases almost linearly with depth, reaching a maximum of 40 years. Below, the portion of older, tritium-free water rises. The tritium-helium ages of the tritium-bearing portion increase only slightly to a maximum of about 46 years. The depth distribution of the tritium-helium age shows a dependency on groundwater recharge rates. Considering the same depth level, younger ages are related to higher groundwater recharge rates as compared to groundwater that infiltrated in areas with lower recharge rates. This is especially observed for shallow depths. Tritium-helium ages younger than 40 years are reflected well in the atmospheric tritium input curves, while deviations from it can be related to anthropogenic influences such as input from nuclear power plants and irrigation with deep, tritium-poor groundwater. The regional distribution for shallow wells indicates increasing tritium-helium ages from west to east, corresponding to decreasing groundwater recharge rates due to the more continental climate in the east. 相似文献
9.
同位素技术是研究区域地下水循环规律的主要手段之一。本文对平原区地下水进行了取样分析,运用同位素技术并结合水文地质条件,研究了北京市平原区地下水循环演化规律。运用^3H和^14C的测年技术确定了地下水年龄;利用D和18^O关系曲线探讨了地下水的起源;按照是否积极参加了现代水循环的原则将第四系地下水划分为浅层水和深层水;对浅层水和深层水的更新状况进行了研究。研究表明,浅层水广泛分布于北京平原区,径流条件好,更新快;深层水主要分布于永定河、潮白河冲洪积扇下部及冲洪积平原的深部地区,补给条件相对差,与现代大气降水联系弱,径流条件差,更新慢。 相似文献
10.
An investigation was conducted in Beijing to identify the groundwater evolution and recharge in the quaternary aquifers. Water samples were collected from precipitation, rivers, wells, and springs for hydrochemical and isotopic measurements. The recharge and the origin of groundwater and its residence time were further studied. The groundwater in the upper aquifer is characterized by Ca-Mg-HCO 3 type in the upstream area and Na-HCO 3 type in the downstream area of the groundwater flow field. The groundwater in the lower aquifer is mainly characterized by Ca-Mg-HCO 3 type in the upstream area and Ca-Na-Mg-HCO 3 and Na-Ca-Mg-HCO 3 type in the downstream area. The δ D and δ 18O in precipitation are linearly correlated, which is similar to WMWL. The δ D and δ 18O values of river, well and spring water are within the same ranges as those found in the alluvial fan zone, and lay slightly above or below LMWL. The δ D and δ 18O values have a decreasing trend generally following the precipitation → surface water → shallow groundwater → spring water → deep groundwater direction. There is evidence of enrichment of heavy isotopes in groundwater due to evaporation. Tritium values of unconfined groundwater give evidence for ongoing recharge in modern times with mean residence times <50 a. It shows a clear renewal evolution along the groundwater flow paths and represents modern recharge locally from precipitation and surface water to the shallow aquifers (<150 m). In contrast, according to 14C ages in the confined aquifers and residence time of groundwater flow lines, the deep groundwater is approximately or older than 10 ka, and was recharged during a period when the climate was wetter and colder mainly from the piedmont surrounding the plain. The groundwater exploitation is considered to be “mined unsustainably” because more water is withdrawn than it is replenished. 相似文献
11.
为研究近几十年来佘太盆地地下水补给变化情况,通过现场调查分析,对佘太盆地浅层地下水开展同位素样品采集工作,并测定了其氢、氧稳定同位素的值。在分析同位素分布特征及变化规律的基础上,结合当地地质及水文地质条件识别了地下水补给来源和补给区并构建了浅层地下水的补给模式图,探讨了区域上浅层地下水的补给流动状况。通过分析研究区大气降水和地下水中的氢氧稳定同位素的变化特征发现:当地大气降水并不是地下水的主要补给来源,其补给源区为周边山区,补给来源主要是周边山区的大气降水,且地下水所经历的蒸发作用较明显;盆地的东、西部地下水的补给源区不尽相同,西部的补给区高程要高于东部的补给区高程,但两部分地下水所经历的蒸发强度基本相同。 相似文献
12.
An overview is presented of existing groundwater-age data and their implications for assessing rates and timescales of recharge in selected unconfined aquifer systems of the United States. Apparent age distributions in aquifers determined from chlorofluorocarbon, sulfur hexafluoride, tritium/helium-3, and radiocarbon measurements from 565 wells in 45 networks were used to calculate groundwater recharge rates. Timescales of recharge were defined by 1,873 distributed tritium measurements and 102 radiocarbon measurements from 27 well networks. Recharge rates ranged from?<?10 to 1,200?mm/yr in selected aquifers on the basis of measured vertical age distributions and assuming exponential age gradients. On a regional basis, recharge rates based on tracers of young groundwater exhibited a significant inverse correlation with mean annual air temperature and a significant positive correlation with mean annual precipitation. Comparison of recharge derived from groundwater ages with recharge derived from stream base-flow evaluation showed similar overall patterns but substantial local differences. Results from this compilation demonstrate that age-based recharge estimates can provide useful insights into spatial and temporal variability in recharge at a national scale and factors controlling that variability. Local age-based recharge estimates provide empirical data and process information that are needed for testing and improving more spatially complete model-based methods. 相似文献
13.
Groundwater samples from 288 domestic wells in Barry County, Michigan, were analyzed for 33 inorganic chemical parameters. Variations in chemical composition were investigated by considering the possible effects of human impact, aquifer type (bedrock vs glacial drift), chemical evolution along groundwater flow paths, and glacial landform type (moraine vs outwash). Approximately 25 percent of the glacial drift wells were classified as degraded by human impact and were excluded from further analysis of chemical variation. Two-sample tests comparing individual concentrations from drift and bedrock aquifers suggest that groundwater in the Marshall Sandstone aquifer is derived from local recharge through the glacial drift. This conclusion is supported by generalized groundwater flow patterns recognized for the two aquifers.Concentrations in both aquifers were examined in relation to generalized flow paths derived from water level data and also by classification of wells as recharge, transition, and discharge. No spatial concentration trends in major ions were detected, although iron concentrations do appear to increase from recharge to discharge areas. Declining redox potential along groundwater flow paths may explain this trend.The possible influence of glacial landform type was investigated by comparing concentrations of wells in moraines with those in outwash deposits. Wells in moraines have significantly higher concentrations of most parameters, perhaps due to higher content of finer, more chemically reactive sediment grains. 相似文献
14.
In a typical winter season, approximately 471,000 tons of road salt are deposited along roadways in Illinois, USA. An estimated 45% of the deposited road salt will infiltrate through the soils and into shallow aquifers. Transported through shallow aquifers, chloride associated with the road salts has the potential to reside within groundwater for years based on the pathway, the geologic material, and the recharge rate of the aquifer system. Utilizing MODFLOW and MT3D, simulations employing various road-salt application rates were conducted to assess the net accumulation of chloride and the residence times of chloride in an agriculture-dominated watershed that originates in an urban area. A positive-linear relationship was observed between the application rate of chloride and both the maximum chloride concentration and total mass accumulated within the watershed. Simulated annual recharge rates along impacted surfaces ranged from 1,000 to 10,000 mg/L. After 60 years of application, simulated chloride concentrations in groundwater ranged from 197 to 1,900 mg/L. For all application rates, chloride concentrations within the groundwater rose at an annual rate of >3 mg/L. While concentrations increase throughout the system, the majority of chloride accumulation occurs near the roads and the urban areas. Model simulations reveal a positive relationship between application rate and residence time of chloride (1,123–1,288 days based on application rate). The models indicate that continued accumulation of chloride in shallow aquifers can be expected, and methods that apply less chloride effectively need to be examined. 相似文献
15.
There were three landforms ( i. e. desert, bedrock platform and loess gully) in deep-buried coalfield of northern Ordos Basin. Water inflow of working face in desert area was 1~2 orders of magnitude larger than that in other landform areas. In order to find out the key controlling factors of the directly water filled aquifers on the roof of the coal seam, we carried out research from the aspects of topography, landform and geological sedimentation. The results showed that desert landform provides abundant recharge water for underlying aquifers because of gentle topography, large precipitation infiltration coefficient, thick and water-rich quaternary system. While bedrock platform and loess gully landform were the water sources with weak recharge capacity of underlying aquifers. The sandstone-mudstone interbedding structure formed by continental deposits resulted in the absence of regional stable aquifers in Jurassic and Cretaceous strata on the roof of coal seams. Pumping tests of boreholes showed that all strata belong to weak to medium water-rich aquifers. The groundwater level of Cretaceous aquifer decreased by 20~130 m in three mines. There was a close hydraulic relationship between shallow and deep aquifers. The Mesozoic strata belonged to fluvial deposits. Qilizhen sandstone and Zhenwudong sandstone aquifers were mainly developed on the roof of the coal seam, which were characterized by thick medium-coarse sandstone sections. The geological and sedimentary conditions of direct water-filled aquifer were similar, but the amount of borehole water, cumulative pre-drainage water and water inflow from goaf in desert geomorphic area were much larger than those in bedrock platform and loess gully geomorphic area. The water-rich of the aquifer was mainly controlled by geomorphology, and the water sources of the deep aquifers were meteoric precipitation and Quaternary aquifer. In different mines with similar Quaternary conditions in Mu Us Desert, there were also great differences in the amount of borehole water, cumulative pre-drainage water and water inflow from goafs. The difference was related to the thickness and lithology of the aquifers. It reflected that the geological sedimentary conditions of the coal seam roof were also important factors to control the water-rich of the aquifers. Topography, landform and geological sedimentation were the key factors to control the water-rich of the aquifer directly and the water inflow from the working face. 相似文献
16.
A hydrochemical investigation was conducted in the Ejina Basin to identify the hydrochemical characteristics and the salinity
of groundwater. The results indicate that groundwater in the area is brackish and are significantly zonation in salinity and
water types from the recharge area to the discharge area. The ionic ration plot and saturation index (SI) calculation suggest
that the silicate rock weathering and evaporation deposition are the dominant processes that determine the major ionic composition
in the study area. Most of the stable isotope δ 18O and δD compositions in the groundwater is a meteoric water feature, indicating that the groundwater mainly sources from
meteoric water and most groundwater undergoes a long history of evaporation. Based on radioactive isotope tritium ( 3H) analysis, the groundwater ages were approximately estimated in different aquifers. The groundwater age ranges from less
than 5 years, between 5 years and 50 years, and more than 50 years. Within 1 km of the river water influence zone, the groundwater
recharges from recent Heihe river water and the groundwater age is about less than 5 years in shallow aquifer. From 1 km to
10 km of the river water influence zone, the groundwater sources from the mixture waters and the groundwater age is between
5 years and 50 years in shallow aquifer. The groundwater age is more than 50 years in deep confined aquifer. 相似文献
17.
通过环境同位素及其Tamers、IAEA模型应用研究表明,黑河流域水循环过程中地下水同位素特征与补给源属性和数量密切相关,具有非均一性;东部以山区降水通过出山地表径流补给为主,西部冰川雪融水和山区基岩裂隙水是主要补给源,下游区依赖中游区河水下泄状况,蒸发特征明显。东部同位素较新且地下水更新较快,西部同位素较老且地下水更新较慢;祁连山前戈壁带地下水同位素与山区河水相近,细土平原带地下水补给河水;高台一带受酒泉低氚值地下水补给影响而河水和地下水氚值都偏低;近河道带地下水年龄较新,远离河道则较老。因此,充分利用地下水与地表水之间转化规律,联合优化调控,有利于该区地下水资源可持续利用。 相似文献
18.
In order to improve understanding of the fate of septic tank or individual sewage disposal system (ISDS) effluent in regolith overlying fractured-rock aquifers, effluent from an ISDS in such a setting was tracked via geophysical, hydrological, and geochemical methods. Under typical precipitation conditions, the effluent entered the fractured bedrock within 5 m of the boundary of the constructed infiltration area. During a period of unusually high spring recharge, the plume migrated between 50 and 100 m within the regolith before infiltrating the fractured bedrock. The chemical signature of the effluent is similar to that required to account for the decline in water quality, suggesting a causative relationship (as estimated from mass-balance models of the surface-water chemistry near the mouth of the basin). The elevated salt content of the effluent during periods of high natural recharge to the infiltration area correlates with elevated salt concentrations in surface and groundwater at the basin scale, suggesting that some of the effluent salt load may be stored in the unsaturated zone during dry periods and flushed during periods of elevated natural recharge. 相似文献
19.
A study of environmental chloride, deuterium, oxygen-18, and tritium in deep sand profiles (35 m) has been carried out in order to estimate their relative value for measuring average groundwater recharge. The investigation was located at a 0.1-km 2 site in Quaternary sands near the northwestern coast of Senegal in a zone of rainfed agriculture. By using a steady-state model for duplicate unsaturated zone chloride profiles, the long-term average recharge at the site was estimated to be 30 mm yr –1 or around 10% of the average precipitation (290 mm). The chloride concentration of adjacent shallow groundwater was relatively uniform and comparable to the unsaturated zone average, while the spatial variability in the depth distribution of Cl – in the unsaturated zone was considerable. Stable isotope (deuterium and oxygen-18) data show that there is some isotopic enrichment due to direct evaporation through the soil surface. The degree of heavy isotope enrichment is proportional to the extent of evaporative loss and there is good correspondance with the chloride enrichment. Nevertheless, stable isotopes cannot be used quantitatively to estimate the recharge. The excellent preservation of the peak in thermonuclear tritium in precipitation in the unsaturated zone at depths between 12 and 20 m enables an estimated annual recharge of 24 mm yr –1 in this area to be calculated, using the piston flow model. Agreement therefore between Cl and 3H as tools for recharge measurement is reasonable over the site. 相似文献
20.
大量野外调查研究表明，气候变化和人类活动对黑河流域地下水循环和更新演变具有重要影响；平原区浅层地下水主要是现代水补给，35％来自祁连山区基岩裂隙水通过地表径流转化补给，其他是降水和冰雪融水在山前戈壁带入渗补给，具有较强的更新能力；深层承压水主要形成于地质历史时期区域性补给，与现代水循环有联系；中游区人类活动是造成下游区地下水补给能力减弱、地下水水位持续下降和生态环境退化的重要因素。因此强化中游区人类活动的科学调控，是实现黑河流域地下水可持续利用和下游区生态环境有效保护的关键。 相似文献
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