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1.
Pollution and overexploitation of scarce groundwater resources is a serious problem in the Zarqa River catchment, Jordan. To estimate this resource’s potential, the amount and spatial distribution of groundwater recharge was calculated by applying the hydrological model J2000. The simulation period is composed of daily values gathered over a 30-year period (July 1977 to June 2007). The figure finally obtained for estimated groundwater recharge of the Zarqa River catchment is 105 × 106 m3 per year (21 mm a?1). This is 19 % higher than the value previously assumed to be correct by most Jordanian authorities. The average ratio of precipitation to groundwater recharge is 9.5 %. To directly validate modelled groundwater recharge, two independent methods were applied in spring catchments: (1) alteration of stable isotope signatures (δ18O, δ2H) between precipitation and groundwater and (2) the chloride mass balance method. Recharge rates determined by isotopic investigations are 25 % higher, and recharge rates determined by chloride mass balance are 9 % higher than the modelled results for the corresponding headwater catchments. This suggests a reasonably modelled safe yield estimation of groundwater resources.  相似文献   

2.
Figeh watershed spring is one of the important groundwater aquifer, which is considered a major source for drinking waters of Damascus city and countryside. The origin identification and recharge estimates of groundwater are significant components of sustainable groundwater development in this Mountain karst aquifer of Figeh spring. During the period 2001–2009, monthly groundwater and precipitation samples were taken and the isotopic compositions of δ18O, δ2H, and chloride contents were analyzed to identify groundwater origins and to estimate recharge rates. The δ18O, δ2H of the groundwater show that the groundwater recharge is of meteoric origin. The chloride mass balance (CMB) method was used to quantify recharge rates of groundwater in the Mountain karst aquifer of Figeh spring. The recharge rate varies from 192 to 826 mm/year, which corresponds to 43 and 67% of the total annual rainfall. Recharge rates estimated by CMB were compared with values obtained from other methods and were found to be in good agreement. This study can be used to develop effective programs for groundwater management and development.  相似文献   

3.
The major ion hydrochemistry, sodium absorption ratio (SAR), sodium percentage, and isotopic signatures of Hammamet-Nabeul groundwaters were used to identify the processes that control the mineralization, irrigation suitability, and origin of different water bodies. This investigation highlights that groundwater mineralization is mainly influenced by water-rock interaction and pollution by the return flow of irrigation water. The comparison of groundwater quality with irrigation suitability standards proves that most parts of groundwater are unacceptable for irrigation and this long-term practice may result in a significant increase of the salinity and alkalinity in the soils. Based on isotopic signatures, the shallow aquifer groundwater samples were classified into (i) waters with depleted δ18O and δ2H contents, highlighting recharge by modern precipitation, and (ii) waters with enriched stable isotope contents, reflecting the significance of recharge by contaminated water derived from the return flow of evaporated irrigation waters. The deep-aquifer groundwater samples were also classified into (i) waters with relatively enriched isotope contents derived from modern recharge and mixed with shallow-aquifer groundwater and (ii) waters with depleted stable isotope contents reflecting a paleoclimatic origin. Tritium data permit to identify three origins of recharge, i.e., contemporaneous, post-nuclear, and pre-nuclear. Carbon-14 activities demonstrate the existence of old paleoclimatic recharge related to the Holocene and Late Pleistocene humid periods.  相似文献   

4.
The stable isotopes of oxygen and hydrogen were used to determine the seasonal contributions of precipitation to groundwater recharge at a forested catchment area in the upper North Han River basin, Korea. A comparison of the stable isotopic signatures of groundwater and precipitation indicates that the precipitations which occurred during both the dry and rainy seasons are the important source of groundwater recharge in this region. A stable isotopic signature shown in the stream waters at the upstream reaches is similar to that of groundwaters, indicating that stream waters are mostly fed by groundwater discharge. Reservoir waters in the downstream flood control dams have lower deuterium excess values or d-values compared with those of the upstream waters, indicating a secondary evaporative enrichment. These results can provide a basis for the effective management of groundwater and stream water resources in the North Han River basin.  相似文献   

5.
Groundwater and surface water samples were collected to improve understanding of the Senegal River Lower Valley and Delta system, which is prone to salinization. Inorganic ion concentrations and environmental isotopes (18O, 2H and 3H) in groundwater, river, lake and precipitation were investigated to gain insight into the functioning of the system with regard to recharge sources and process, groundwater renewability, hydraulic interconnection and geochemical evolution. The geochemical characteristics of the system display mainly cation (Ca2+ and/or Na+) bicarbonated waters, which evolve to chloride water type; this occurs during groundwater flow in the less mineralized part of the aquifer. In contrast, saline intrusion and secondary brines together with halite dissolution are likely to contaminate the groundwater to Na–Cl type. Halite, gypsum and calcite dissolution determine the major ion (Na+, Cl−, Ca2+, Mg2+, SO4 2− and HCO3 −) chemistry, but other processes such as evaporation, salt deposition, ion exchange and reverse exchange reactions also control the groundwater chemistry. Both surface water and groundwater in the system show an evaporation effect, but high evaporated signatures in the groundwater may be due to direct evaporation from the ground, infiltration of evaporated water or enriched rainwater in this region. The stable isotopes also reveal two types of groundwater in this system, which geomorphologically are distributed in the sand dunes (depleted isotopes) and in the flood plain (enriched isotopes). Consideration of the 3H content reinforces this grouping and suggests two mechanisms of recharge: contribution of enriched surface water in recharging the flood plain groundwater and, in the sand dunes area where water table is at depth between 8 and 13 m, slow recharge process characterized the submodern to mixed water.  相似文献   

6.
On the basis of the hydrogeology of the Dousitu River drainage basin, the changes of water flow rate, δ18O and δD along the Dousitu River are discussed according to measured and analytical results. Changes of flow rate along the Dousitu River agree well with groundwater level contours and the recharge and discharge of groundwater to the river. When compared with other types of water in the area, it is obvious that the 18O and D of river waters have experienced evaporation. The changes of δ18O and δD along the Dousitu River are mainly caused by combined effects of groundwater recharge and river water evaporation. The recharge of groundwater makes δ18O and δD of the river water decrease. Evaporation makes δ18O and δD of the river water increase. The evaporation fractions of the river water are calculated using the kinetic fractionation theory. Results showed as much as 10–30% of water was evaporated in different segments of Dousitu River.  相似文献   

7.
长期超采地下水形成的华北平原浅层含水层疏干空间是利用河道进行地下调蓄增加地下水补给的有利场所。在野外调查基础上,根据水文地质条件、地下水动态资料和地表水观测统计分析得出:华北平原主要水系永定河、大清河、子牙河和漳卫南运河等河段具有良好的人工地下调蓄潜力;在相同地下水水位埋深条件下,干涸河道的渗漏率明显大于有底水条件的渗漏率,河道在无底水条件下,当地下水埋深大时,渗漏率较大;山前平原主要水系的砂层裸露及浅埋型可调蓄区面积4 703.13 km2,现状可利用调蓄库容66.28×108m3;以不引起陆表生态环境负效应为原则,拟定上限约束深度4 m,计算得出大型冲洪积扇区主要河道带现状可利用地下调蓄库容42.59×108m3,可供调节水量22.83×108m3/a,地下水补给量增加14.82×108m3/a。  相似文献   

8.
 Acidification of groundwater lags behind acid deposition due to the relatively long water residence time in conjunction with various buffering processes in the soil zone and deeper aquifer (chemical weathering, cation exchange, sulfate sorption, and N uptake by the biomass). Extensive field data from eight forested catchments in the Bunter Sandstone of the Black Forest, including results from water budget studies and hydrochemical analysis of stream and spring waters, were used to simulate the future evolution of ground-water acidification with the MAGIC model. The present acid deposition exceeds the “critical load” (here meaning buffering due to chemical weathering and protonation of organic acids) in six of eight catchments. Two catchments are well buffered because they contain carbonate-bearing layers in the Upper Bunter sandstone. Transient buffering (i.e., cation exchange, N uptake, the sulfate sorption) thus far prevents worse acidification, but this effect will decline in the future. For one of the poorly buffered catchments (Seebach), a two-layer simulation was carried out, based on extensive data from 10 years of measurements. Validation of the long-term simulations by hydrochemical and soil data was hampered by strong annual variations but generally supported by paleolimnological studies. In the future, reductions in the S deposition by 20% and the N deposition by 10% up to the year 2030 are assumed as the most probable scenario. N uptake through soil and vegetation will come to an end as suggested by decreasing C/N ratios of the organic matter. This process is arbitrarily included in the simulations. In the periglacial soil layer, acidification will decrease until the year 2030 and then approach a steady-state condition. In the fractured aquifer, acidification will also proceed at a decreasing rate; however, sulfate desorption up to the year 2130, the end of simulated period, will prevent earlier remediation. Despite a significant reduction in S deposition since the mid-1980s, further efforts are necessary to reduce the emission of acidifying substances. Liming in the recharge area is partially effective to ameliorate “shallow” groundwater but largely fails to ameliorate “deeper” groundwater in the sandstone aquifer. Received: 30 July 1996/Accepted: 23 January 1997  相似文献   

9.
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 δ18O 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   

10.
In Canada’s western Arctic, perennial discharge from permafrost watersheds is the surface manifestation of active groundwater flow systems with features including the occurrence of year-round open water and the formation of icings, yet understanding the mechanisms of groundwater recharge and flow in periglacial environments remains enigmatic. Stable isotopes (δ18O, δD, δ13CDIC), and noble gases have proved useful to study groundwater recharge and flow of groundwater which discharges along rivers in Canada’s western Arctic. In these studies of six catchments, groundwater recharge was determined to be a mix of snowmelt and precipitation. All systems investigated show that groundwater has recharged through organic soils with elevated PCO2, which suggests that recharge occurs largely during summer when biological activity is high. Noble gas concentrations show that the recharge temperature was between 0 and 5 °C, which when considered in the context of discharge temperatures, suggests that there is no significant imbalance of energy flux into the subsurface. Groundwater circulation times were found to be up to 31 years for non-thermal waters using the 3?H-3He method.  相似文献   

11.
The scarcity of surface water resources in arid and semi-arid regions from North African countries contributes to the considerable increase of groundwater exploitation, which leads to the development of hydrogeological studies. However, due to the lack of hydrodynamic data in these regions, these studies focus more and more on the geochemical and environmental isotope techniques to insure a better understanding of the hydrodynamic functioning of subsurface systems. In this study, which interests an important unconfined aquifer in central Tunisia, tritium data and chloride mass balance (CMB) method were applied in order to (1) understand the mode of recharge of this aquifer and (2) obtain a reliable estimation of its recharge amount as well as (3) estimate its annual renewal rate. It has been demonstrated that the shallow groundwaters are classified into two groups according to their tritium contents. The first group includes wells located mainly downstream and highlights the significant role of the post-nuclear lineal recharge through Wadis courses. The second group encloses wells located practically overall the rest of the basin and refers to relatively modern waters originated from areal recharge of present-day rainfall. Based on the CMB method, the recharge to this unconfined aquifer is estimated to 31.7 mm year−1, which corresponds to 10.5% of the total rainfall. The annual renewal rate of groundwater, evaluated based on the tritium contents, is up to 16%.  相似文献   

12.
河水入渗补给是傍河水源地的主要补给来源,确定河水补给强度对于促进水源地长期安全的开采具有十分重要的意义。以沈阳黄家水源地为研究区,通过对比研究区河水、地下水的水化学及氢氧稳定同位素特征,分析了水源地地下水的补给来源及强度。结果表明:傍河水源地地下水主要接受河水的入渗补给和区域地下水的侧向补给;受河床沉积物和含水介质的岩性及结构在空间上的差异影响,河水入渗补给后在向地下水位漏斗中心流动的过程中具有浅层和深层两条地下水流路径,深层地下水与河水的水力联系更为紧密;河水对地下水的补给强度具有明显的时空变化特点,表现为雨季河水入渗强度明显大于旱季,并且随着与辽河距离的增加,水源地地下水获得的河水补给量呈逐渐减小的趋势。  相似文献   

13.
Kong  Yanlong  Pu  Tao  Wang  Ke  Shi  Xiaoyi  Ren  Yaqian  Zhang  Weizun  Pang  Zhonghe  Cuntz  Matthias 《Hydrogeology Journal》2023,31(5):1259-1270

The altitude effect of isotopes in precipitation is not as significant on the leeward side of a mountain as it is on the windward side, which makes it difficult to use isotopes at leeward sites, especially if estimating elevation of groundwater recharge or reconstructing paleoelevations. Samples of precipitation were taken at three stations with different elevations—2,306–3,243 m above mean sea level (asl)—on the leeward side of the Meili Snow Mountains on the southeastern Tibetan Plateau from August 2017 to July 2018. The isotope vs. altitude gradients were calculated based on two adjacent stations at the daily, monthly, and annual scales. Most of the gradients are beyond the global ranges of –0.5 to –0.1‰ per 100 m for δ18O and –5 to –1‰ per 100 m for δ2H, and some of the gradients are even positive. Local processes of sub-cloud evaporation and mixing with recycled moisture are identified for the ambiguous altitude effect, while regional atmospheric circulation processes dominate the major patterns of stable isotope variation at the three stations. The groundwater recharge elevation is estimated to be in a very large range, 2,562–6,321 m asl, which could be caused by the differences in isotope vs. altitude gradient in the studied catchments. Considering the complex atmospheric processes affecting precipitation isotopes, sampling of event-based/monthly precipitation at more than two altitudes for at least one complete hydrological year is a minimum requirement to establish a reasonable isotope vs. altitude gradient.

  相似文献   

14.
The distribution of 18O and 2H in various water sources indicates that groundwater recharge is due to local rainfall occurring within the basins. Groundwater recharge takes place under a bypass flow mechanism and matrix diffuse flow and is 3% and 2% of the long-term mean annual rainfall of 550 mm for the Makutapora and Hombolo basins, respectively. Chloride mass balance indicates that 60% and 40% of the total groundwater recharge takes place through macropores and matrix flow, respectively. Sporadic variations in 18O, 2H and chloride among adjacent boreholes suggest existence of a discrete fractured aquifer and/or dominance of local recharge. The relationship between δ2H and chloride indicates that groundwater salinization is due to the leaching of surficial and soil salts during high intensity rainfall, which causes high surface runoff and flash floods. It has been concluded that the isotopic and chemical character of groundwater in fractured semi-arid areas may provide the most effective complementary means of groundwater recharge assessment and therefore is very useful in the management of the water resources.  相似文献   

15.
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, δ2H and δ18O 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   

16.
Groundwater discharge and non-point source (NPS) loading were evaluated along an urban reach of an eastern-slopes Rocky Mountains river (Bow River, Canada) to understand sources of water-quality impacts and baseflow. The discharge did not increase measurably over a 16-km reach. Groundwater in the river-connected alluvial aquifer was a mixture of river and prairie groundwater, with elevated chloride concentrations (average 379 mg L–1) from road salt. Alluvial groundwater was the major NPS of chloride discharging to the river. Although the mass-flux based estimates of groundwater discharge were small (mean 0.02 m3 s–1 km–1, SD = 0.04 m3 s–1 km–1, n?=?30), the associated chloride mass flux over 16 km was significant (equivalent to that discharged from the city’s largest wastewater-treatment-plant effluent). Although local groundwater baseflow was previously thought to contribute significantly to overwinter baseflow in this reach, little contribution was measured in this study. Low baseflow generation is consistent with long-term river discharge data that show almost all of the baseflow generation occurs in the Rocky Mountain reach. Thus, local watershed areas are important for water-quality protection, but climate change in the headwaters is most salient to long-term flow.  相似文献   

17.
Interactions between river water and groundwater have been used to help understand the movement of water and to evaluate water quality in the semi-arid area of the North China Plain (NCP). Stable isotopes, chlorofluorocarbons (CFCs) and hydrochemistry were used to study the influence of surface water from the Xiao River on regional groundwater. Using a mass balance approach based on chloride concentrations, hydrogen and oxygen isotope ratios, the average fraction of surface water recharging to groundwater was 50–60 %. CFC results indicated that the groundwater recharge age varied from 22.5 to 39.5 years. The vertical flow velocity of groundwater was estimated at about 1.8–3.5 m year?1. Nitrate concentrations in groundwater varied from 9.42 to 156.62 mg L?1, and exceeded 50 mg L?1 in most aquifers shallower than 80 m bordering the Xiao River. The δ 15N-NO3 data indicate that the major sources of nitrogen in groundwater are human sewage and animal excreta. Because groundwater is the main source of drinking water, there should be concern about public health related to the elevated nitrate concentrations in the NCP.  相似文献   

18.
Assessing groundwater recharge characteristics (recharge rate, history, mechanisms (piston and preferential flow)) and groundwater age in arid and semi-arid environments remains a difficult but important research frontier. Such assessments are particularly important when the unsaturated zone (UZ) is thick and the recharge rate is limited. This study combined evaluations of the thick UZ with those of the saturated zone and used multiple tracers, such as Cl, NO3, Br, 2H, 18O, 13C, 3H and 14C, to study groundwater recharge characteristics in an integrated loess tableland in the Loess Plateau, China, where precipitation infiltration is the only recharge source for shallow groundwater. The results indicate that diffuse recharge beneath crops, as the main land use of the study area, is 55–71 mm yr?1 based on the chloride mass balance of soil profiles. The length of time required for annual precipitation to reach the water table is 160–400 yrs. The groundwater is all pre-modern water and paleowater, with corrected 14C age ranging from 136 to 23,412 yrs. Most of the water that eventually becomes recharge originally infiltrated in July–September. The Cl and NO3 contents in the upper UZ are considerably higher than those in the deep UZ and shallow groundwater because of recent human activities. The shallow groundwater has not been in hydraulic equilibrium with present near-surface boundary conditions. The homogeneous material of the UZ and relatively old groundwater age imply that piston flow is the dominant recharge mechanism for the shallow groundwater in the tableland.  相似文献   

19.
Despite its extreme aridity, the Ordos Basin in northern China is rich in groundwater. Many artesian wells or springs with large fluxes are utilized for drinking, irrigation and industrial production. In a search for the origin of the groundwater, a detailed investigation of the stable isotopes of oxygen and hydrogen in the local precipitation, the river water, the springs, the well water, as well as the soil water extracted from six soil profiles in the Ordos Basin, was carried out. The data show that δD, δ18O and TDS values of the river water are similar to those of groundwater, while the TDS values of the soil water are about ten times greater than those of groundwater. Furthermore, the mean isotopic compositions of the local precipitation are significantly higher than those of river water and groundwater. Based on the chloride mass balance method, the estimated recharge rates range from 5.2 to 17.2 mm/year, with a mean value of 10.5 mm/year. The results show that the main source of recharge of the groundwater in the Ordos Basin is not the local precipitation, but must come from a region where the precipitation is characterized by much lower δD and δ18O values. In addition, the groundwater in the Ordos Basin contains a component of mantle-derived 3He and crust-derived 4He suggesting that the groundwater may partly derive from flows through basement faults beneath the Ordos Basin.  相似文献   

20.
Seven large catchments, cleared progressively from 1912 to 1985, were studied to determine the groundwater conditions for salinization of both the pristine and disturbed environments. Detailed drilling was conducted to provide information on the nature and didtribution of the physical and chemical properties of these groundwater systems. First-order estimates of recharge and discharge rates were derived from the groundwater balance, chloride mass balance, and specific yield techniques. Recharge rates under pristine conditions estimated from the groundwater balance method were of the order of 0.02–0.14 mm/yr and 0.05–3.0 mm/yr using the chloride method. Recharge was greatest in the deep sandplain and arkosic-outcrop soil associations and least in the heavy textured midslope and valley soils. Higher rates were obtained from the specific yield technique, where recharge under current agricultural conditions was considered to be between 6 and 10 mm/yr. Recharge rates of up to 30 mm/yr were noted when flooding of the sandy-textured, valley floor soils occured. Clearing of the native vegatation for agriculture is estimated to have increased groundwater recharge by between one and three orders of magnitude. Equilibrium groundwater balance estimates suggest that discharge rates have only increased ten-fold. As a result of the changes to the water balance, 5–30% of particular catchments may need to become discharge areas to balance increased recharge of 6–10 mm/yr. Native woodlands and halophyte communities are considered to have played an important role in providing a complex discharge mechanism before clearing. The management of catchments to contain soil salinity should include improved recharge control systems using specialized crop rotations. To date, however, little evidence of the success of this method exists. Therefore, discharge enhancemnet should also become a part of catchment management systems. Discharge can be manipulated by planting phreatophytic vegetation and by pumping groundwater from basement aquifers to improve agricultural water supplies. The results presented in this paper suggest that discharge enhancement has an important role to play and, as a part of integrated catchment water management, has the potential to control and eventually reduce dryland salinity  相似文献   

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