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1.
Alexandra Lutz James M. Thomas Greg Pohll Mamadou Keita W. Alan McKay 《Environmental Geology》2009,58(7):1441-1450
The following paper describes the goals and some preliminary work in the Bani sustainability study, an ongoing project in
Mali, West Africa. Rural communities in Mali are increasingly relying on hand-pumps, which tap groundwater resources, as a
means of obtaining potable water. The long-term sustainable yield of groundwater resources is not known but can be evaluated
in sustainability study. In 2005, a groundwater sustainability study was established along the Bani River of Mali. The Bani
study collected groundwater levels that were used in a conceptual groundwater flow model—the Bani model—to develop an understanding
of current aquifer conditions and to make limited predictions of sustainability under various future scenarios. The Bani model
showed the climatic parameters of recharge (derived from precipitation) and evapotranspiration to influence simulated groundwater
levels and groundwater volume available, while increased pumping rates, due to population growth, showed little effect. When
considered in the context of the actual Bani sustainability study area, the change in groundwater levels resulting from climatic
parameters may have negative implications, especially during several consecutive years of decreased precipitation, such as
drought, or if downward trends anticipated for precipitation continue. 相似文献
2.
Comparing groundwater recharge and base flow in the Bukmoongol small-forested watershed,Korea 总被引:1,自引:0,他引:1
E. A. Combalicer S. H. Lee S. Ahn D. Y. Kim S. Im 《Journal of Earth System Science》2008,117(5):553-566
Groundwater recharge and base flow using different investigated methods are simulated in the 15-ha Bukmoongol small-forested
watershed located at the southern part of Korea. The WHAT system, PART, RORA, PULSE, BFI, and RAP software are used to estimate
groundwater recharge or base flow and base flow index from the measured streamflow. Results show that about 15–31 per cent
of annual rainfall might be contributed for base flow. The watershed groundwater recharge proportions are computed to about
10–21 per cent during the wet period and 23–32 per cent for the remainder periods. Mean annual base flow indices vary from
0.25 to 0.76 estimated using different methods. However, the study found out that all methods were significantly correlated
with each other. The similarity of various methods is expressed as a weighted relationship provided by the matrix product
from the principal component analysis. Overall, the BFI and WHAT software appeared consistent in estimating recharge or base
flow, and base flow index under Korea’s conditions. The case study recommends the application of different models to other
watersheds as well as in low-lying areas where most observation groundwater wells are located with available streamflow data. 相似文献
3.
作为低影响开发(Low Impact Developmet, LID)措施之一,城市雨水花园集中入渗雨水径流可增加对城区地下水的补给。根据一现场监测试验,研究了长期(监测期3年)及短期(降雨3天内)雨水花园入渗点及对照点地下水位与水质的变化,分析了集中入渗的效果和影响范围。结果表明:① 雨水花园对入渗区地下水位产生了显著影响(α=0.01);② 氨氮(NH4-N)在3年及雨后3日的观测值均显著小于对照值;总氮(TN)指标在短期增加显著,长期均值增加不显著。③ 硝态氮(NO3-N)浓度在降雨后有所升高,但不显著,几个观测点浓度有增有减;总磷(TP)浓度的短期值和长期均值有增有减。对于类似研究区地下水位在2~3 m的情况,集中入渗雨水径流可有效补给地下水,对氮素影响明显,对磷影响有限。 相似文献
4.
Numerical modeling the role of rubber dams on groundwater recharge and phreatic evaporation loss in riparian zones 总被引:1,自引:1,他引:0
Xi Chen Min-hua Ling Qiu Zhou Zhi-cai Zhang Qin-bo Cheng 《Environmental Earth Sciences》2012,65(1):345-352
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. 相似文献
5.
Groundwater is the main source of water supply for drinking and agriculture uses in Mazandaran province. In recent years,
the rapid growth of population and the increased need for water and food has put its land and water resources under severe
stress. The main objective of this study was to investigate the temporal trends in annual, seasonal and monthly groundwater
level using the Mann–Kendall test and the Sen’s slope estimator in the area during 1985–2007. The results indicated a mix
of negative and positive trends in the groundwater level series. However, the positive trends were much more than negative
ones. The statistical tests detected a significant increasing trend in more than 28% of the wells. The stronger increasing
trends were identified in the series in summer and spring compared with those in autumn and winter. Moreover, the highest
numbers of wells with significant positive trends occurred in August and July, respectively. The results of spatial analysis
showed that the significant positive trends were concentrated in the central parts of Mazandaran province where paddy fields
are the major water demanders. Analysis of climatic parameters revealed that decreasing trend of relative humidity and increasing
trends of minimum and maximum air temperature can be attributed to groundwater level fluctuations in the study region. The
research will be helpful for planners and policy makers to allocate groundwater resources in different sectors including agriculture,
drinking and industry. 相似文献
6.
Groundwater recharge in arid areas induced by tropical cyclones: lessons learned from Gonu 2007 in Sultanate of Oman 总被引:4,自引:1,他引:3
Younger groundwater found in some Omani aquifers is a result of recent recharge from cyclonic and storm events [Weyhenmeyer
et al. (Science 287:842–845, 2000); Young et al. (J Appl Geophys 57:43–61, 2004)]. The analysis of the meteorological data in Oman indicates an anomalous rainfall on a decadal interval whereas cyclones
frequency is expected to increase due to global climatic changes. The cyclone Gonu has severely struck the eastern Omani coasts
in 2007 resulting in devastating floods. Huge volume of water (3,672 mm3) spread over the coastal plain calling for an assessment of potential groundwater recharge subsequent to this event. The
present study evaluates groundwater recharge with respect to Gonu 2007 to assess the potential of recharge induced by such
cyclones in the arid zones. The hydrographs of several piezometers sited along the coastal plain in Muscat Province have been
studied and variation in water table rise has been analyzed. Significant water table rise is indicated for areas with geological
and structural settings favoring rapid infiltration of water yielding considerable groundwater mound, whereas piezometers
located in less favorable zones show minimum rise of water table. However, soon after the floods the aquifer hydrodynamics
has readjusted to attain equilibrium and the groundwater mound dissipated. The cumulative rise of the water table on an areal
extent does not exceed a few centimeters indicating lesser volume of recharge. Comparatively, recharge from frequent precipitation
along favorable zones produces more significant recharge compared with cyclonic events where surface water residence time
is shorter to allow for efficient infiltration. 相似文献
7.
B. J. M. Goes 《Hydrogeology Journal》1999,7(3):294-304
The Hadejia–Nguru Wetlands are annually inundated flood plains in semi-arid northeastern Nigeria. The area has a unique ecosystem
that forms a natural barrier against the encroachment of the Sahara desert. Both the rich wetland vegetation and local farmers
using shallow tube wells depend on a groundwater mound (with a water table less than 6 m below the surface) that is present
in the unconfined aquifer under the flood-plain area. Using well records (1991–97) and a hydrogeologic profile based on piezometers
that were monitored for two years, it is shown that recharge through the annually inundated flood plains is the source of
the groundwater mound. Maintenance of the groundwater-recharge function of the flood plains depends on wet-season releases
from two large upstream dams. On the basis of a water-budget method, the mean (1991–97) wet-season unconfined groundwater
recharge in the flood-plain area between Hadejia and Nguru and in the immediate vicinity (1250 km2) is estimated to be 132 mm (range, 73–197 mm). Outflow from the unconfined flood-plain aquifer to the unconfined upland aquifer
is approximately 10% of the wet-season flood-plain recharge. The unconfined groundwater outflow from the flood-plain area
can provide a significant contribution to the present-day rural water supply in the surrounding uplands, but it does not offer
much potential for additional groundwater abstraction. In addition to outflow to the upland aquifer (∼14 mm), the distribution
of the annually recharged water volume of the shallow flood-plain aquifer is (1) domestic uses (3 mm), (2) small-scale irrigation
(∼15 mm), and (3) evapotranspiration ( 1 100 mm). Along the hydrogeologic profile, the recharge in the upland (i.e., outflow
from the unconfined flood-plain aquifer and possibly diffuse rain-fed recharge) is in balance with the water uses (i.e., domestic
uses, groundwater outflow, and evapotranspiration). The absence of a seasonal water-level trend in the two piezometers in
the upland indicates that no rain-fed recharge occurs through preferential path-way (macropore) flow.
Received, June 1998 / Revised, November 1998, January 1999 / Accepted, January 1999 相似文献
8.
Groundwater recharge and agricultural contamination 总被引:21,自引:1,他引:20
John-Karl Böhlke 《Hydrogeology Journal》2002,10(1):153-179
Agriculture has had direct and indirect effects on the rates and compositions of groundwater recharge and aquifer biogeochemistry.
Direct effects include dissolution and transport of excess quantities of fertilizers and associated materials and hydrologic
alterations related to irrigation and drainage. Some indirect effects include changes in water–rock reactions in soils and
aquifers caused by increased concentrations of dissolved oxidants, protons, and major ions. Agricultural activities have directly
or indirectly affected the concentrations of a large number of inorganic chemicals in groundwater, for example NO3
–, N2, Cl, SO4
2–, H+, P, C, K, Mg, Ca, Sr, Ba, Ra, and As, as well as a wide variety of pesticides and other organic compounds. For reactive contaminants
like NO3
–, a combination of chemical, isotopic, and environmental-tracer analytical approaches might be required to resolve changing
inputs from subsequent alterations as causes of concentration gradients in groundwater. Groundwater records derived from multi-component
hydrostratigraphic data can be used to quantify recharge rates and residence times of water and dissolved contaminants, document
past variations in recharging contaminant loads, and identify natural contaminant-remediation processes. These data indicate
that many of the world's surficial aquifers contain transient records of changing agricultural contamination from the last
half of the 20th century. The transient agricultural groundwater signal has important implications for long-term trends and
spatial heterogeneity in discharge.
Electronic Publication 相似文献
9.
I. Engelhardt R. Rausch B. Keim M. Al-Saud C. Schüth 《Environmental Earth Sciences》2013,69(2):537-555
The water demand in arid regions is commonly covered by groundwater resources that date back to more humid periods of the Pleistocene and Holocene. Within the investigated arid part of SE Saudi-Arabia information about climate, groundwater levels, and pumping rates are only available for regions where groundwater extractions occur at present-day. For the prediction of the impact of long-term climate changes on groundwater resources an understanding of the hydrogeological and hydrological past and the development of the aquifers is necessary. Therefore, all available information about hydrology and hydrogeology for the past 10,000 years BP were collected and compiled to a conceptual model of the aquifer development on the Arabian Peninsula since the last Ice-Age. The climatic history was displayed by changes in precipitation, temperature and recharge during the mid-S and late Holocene. The hydrogeological development is described by groundwater ages, sea level fluctuations, movement of the coastline, and the development of sabkhas. The most sensitive parameter to describe the development of aquifer system is recharge. Present-day recharge was calculated with the hydrological model system HEC-HMS accounting for current precipitation, temperature, wind, soil types, and geomorphology. With respect to changes in precipitation and temperature over the past 10,000 years the temporal and spatial variability of groundwater recharge was calculated using empirical equations valid for semi-arid and arid settings. Further inflow into the groundwater system results from surface water infiltration in wadi beds, while natural outflow from the groundwater system occurs by discharge to the Gulf, evaporation from sabkhas, and spring discharge. Backward predictions can be verified by sedimentological observations of palaeo-river systems and lakes indicating that groundwater levels reached temporarily the surface under wetter climate conditions and 14C groundwater ages displaying groundwater residence times. 相似文献
10.
Wilson Yetoh Fantong Hiroshi Satake Festus T. Aka Samuel N. Ayonghe Kazuyoshi Asai Ajit K. Mandal Andrew A. Ako 《Environmental Earth Sciences》2010,60(1):107-120
Unplanned exploitation of groundwater constitutes emerging water-related threats to MayoTsanaga River Basin. Shallow groundwater
from crystalline and detrital sediment aquifers, together with rain, dams, springs, and rivers were chemically and isotopically
investigated to appraise its evolution, recharge source and mechanisms, flow direction, and age which were used to evaluate
the groundwater susceptibility to contamination and the basin’s stage of salinization. The groundwater which is Ca–Na–HCO3 type is a chemically evolved equivalent of surface waters and rain water with Ca–Mg–Cl–SO4 chemistry. The monsoon rain recharged the groundwater preferentially at an average rate of 74 mm/year, while surface waters
recharge upon evaporation. Altitude effect of rain and springs show a similar variation of −0.4‰ for δ18O/100 m, but the springs which were recharged at 452, 679, and 773 m asl show enrichment of δ18O through evaporation by 0.8‰ corresponding to 3% of water loss during recharge. The groundwater which shows both local and
regional flow regimes gets older towards the basins` margin with coeval enrichment in F− and depletion in NO3
−. Incidentally, younger groundwaters are susceptible to anthropogenic contamination and older groundwaters are sinks of lithologenic
fluoride. The basins salinization is still at an early stage. 相似文献
11.
Water resources assessment in the Minqin Basin: an arid inland river basin under intensive irrigation in northwest China 总被引:1,自引:0,他引:1
Yanlin Zhang Jinhui Ma Xiaoli Chang Jan van Wonderen Lili Yan Jinhua Han 《Environmental Earth Sciences》2012,65(6):1831-1839
The Minqin Basin is at the lower reach of the Shiyang River of Gansu province in northwest China. Dramatic decline in groundwater
level has resulted from over-abstraction of groundwater since the late 1950s to satisfy increasing irrigation and other demands.
Severe water shortage led to environmental degradation. To better understand the spatial–temporal variation of groundwater
levels and to evaluate the groundwater resources in the region, a three-dimensional regional groundwater flow model was built
and calibrated under transient condition. The MODFLOW program was used and the research area was discretized as a square network
with cell size of 400 × 400 m. The model showed that the aquifer was under destructive stress, with a groundwater resource
deficit of 260 million cubic meters per year (Mm3/year) on average. Since the inflow of surface water from the upstream basin has declined to about 100–150 Mm3/year in recent decades, the irrigation return flow had become the main recharge and accounted for 60.6% of total recharge;
meanwhile, abstraction by pumping wells took 99.2% from the total groundwater discharge. 相似文献
12.
The Heretaunga Plains, Hawke's Bay, New Zealand, is underlain by Quaternary fluvial, estuarine-lagoonal, and marine deposits
infilling a subsiding syncline. Within the depositional sequence, river-channel gravels form one of the most important aquifer
systems in New Zealand. An interconnected unconfined–confined aquifer system contains groundwater recharged from the Ngaruroro
River bed at the inland margin of the plain, 20 km from the coast. At the coast, gravel aquifers extend to a depth of 250 m.
In 1994–95, 66 Mm3 of high quality groundwater was abstracted for city and rural water supply, agriculture, industry, and horticulture. Use
of groundwater, particularly for irrigation, has increased in the last 5 years. Concern as to the sustainability of the groundwater
resource led to a research programme (1991–96). This paper presents the results and recommends specific monitoring and research
work to refine the groundwater balance, and define and maintain the sustainable yield of the aquifer system. Three critical
management factors are identified. These are (1) to ensure maintenance of consistent, unimpeded groundwater recharge from
the Ngaruroro River; (2) to specifically monitor groundwater levels and quality at the margins of the aquifer system, where
transmissivity is <5000 m2/d and summer groundwater levels indicate that abstraction exceeds recharge; (3) to review groundwater-quality programs to
ensure that areas where contamination vulnerability is identified as being highest are covered by regular monitoring.
Received, January 1998 / Revised, August 1998, March 1999 / Accepted, April 1999 相似文献
13.
Hugo A. Loáiciga 《Mathematical Geosciences》2008,40(2):199-211
The equation of groundwater flow in marine island aquifers in which there is time-independent, spatially-variable recharge
and pumping is solved in closed form for rectangular, circular, and elliptical island geometries. The solution of the groundwater
flow equation is expressed in terms of the elevation of the phreatic surface within the flow domain. The depth of the seawater-freshwater
interface below mean sea level follows from the Dupuit–Ghyben–Herzberg relation. The method of solution presented in this
work relies on expanding the hydraulic head and forcing function (recharge and groundwater extraction) as Fourier series that
transforms the two-dimensional Poisson-type flow equations into second-order ordinary differential equations solvable using
classical theory. The important case of constant recharge (without groundwater extraction) leads to solutions in which the
hydraulic head is expressible as the product of a flow factor equal to the squared root of the ratio of recharge over hydraulic
conductivity times a geometric factor involving island shape parameters and flow boundary conditions. Estimability conditions
for the hydraulic conductivity are derived for the cases of constant recharge and spatially variable recharge with pumping. 相似文献
14.
Moisture samples obtained from unsaturated-zone profiles in sands from northern Nigeria were used to obtain recharge estimates
using the chloride (Cl) mass-balance method and to produce records of past recharge and climatic events. Recharge rates range
from 14–49 mm/year, on the basis of unsaturated-zone Cl values and rainfall chemistry measured over eight years at three local
stations. The unsaturated-zone results also provide a record of the changing recharge and climatic events of the past 80 years;
this record compares quite well with modelling results using precipitation data from Maiduguri, especially for the late 20th-century
period of drought. The best fit for the model is made, however, by using a lower mean rainfall Cl (0.65 mg/l) than that obtained
from the mean of the field results (1.77 mg/l Cl). This result implies that the measured rainfall Cl probably overestimates
the depositional flux of Cl, although the lower value is comparable to the minimum of the measured rainfall Cl values (0.6 mg/l
Cl). Recharge estimates made using these lower Cl values range from 16–30 mm/year. The spatial variability was then determined
using results from 360 regional shallow wells over 18,000 km2.
Using the revised rainfall estimate, the Cl balance indicates a value of 43 mm for the regional recharge, suggesting that
either additional preferential flow is taking place over and above that from the vadose one, or that the regional recharge
represents inputs from earlier wetter periods. These recharge estimates compare favourably with those from hydraulic modelling
in the same area and suggest that the recharge rates are much higher than values previously published for this area. High
nitrate (NO3) concentrations (NO3-N>Cl) preserved under aerobic conditions in the vadose zone reflect secondary enrichment from N-fixing vegetation, as occurs
elsewhere in the Sahel.
Electronic Publication 相似文献
15.
Hydrogeological and mixing process of waters in aquifers in arid regions: a case study in San Luis Potosi Valley,Mexico 总被引:1,自引:0,他引:1
J. A. Ramos-Leal V. J. Martínez-Ruiz J. R. Rangel-Mendez M. C. Alfaro de la Torre 《Environmental Geology》2007,53(2):325-337
The climatic conditions of arid regions are characterized by high temperatures, low precipitation and high evapotranspiration
rates that can explain the reduced recharge of aquifers. Thus, in these regions, there are some problems related to the groundwater
quality and recharge that makes worse the problem of groundwater supply. A model, taking into account ternary mixtures, is
presented and applied to a case study: the aquifer of San Luis Potosi valley located in the highlands of the central part
of Mexico. In this valley, four hydrochemical facies were identified that correspond to the Ca–Na + K–HCO3, Na + K–Ca–HCO3, Ca–HCO3 and Ca–SO4 types. From this characterization, it was found out that the recharge area (known as Bledos Graben) is located at the SE
of the valley; the deep water flow comes from there (Villa de Reyes and Alvarez Range) to the center of the valley. Mixture
fractions were obtained by using chlorides and fluorides as conservative elements, from which it was possible to quantify
the contribution of each member to the groundwater quality. According to these results, the contributions to the water extracted
from this aquifer are as follows: shallow flows 50%, deep flows from Villa de Reyes 27%, and flows coming from the Alvarez
Ranges about 15%. 相似文献
16.
The natural (electrical) potential (NP) method – also known as self-potential, spontaneous potential and streaming potential
(SP) – has been used to locate areas of groundwater flow in karst terrane. NP is the naturally occurring voltage at the ground
surface resulting from ambient electrical currents within the earth. The measurement of NP can be used to characterize groundwater
flow in karst terrane because electrical potential gradients are generated by the horizontal flow of water along fractures
or conduits and the vertical infiltration of water into fractures or shafts. NP data from a site on the Mitchell Plain of
southern Indiana, USA, revealed that NP data can be decomposed into three components: topographic effect, residual NP and
noise. At this site, NP was inversely proportional to elevation, but the correlation varied with time. The topographic correction
factor varied from –2.5 to –1.2 mV/m (NP change per unit elevation increase), with an average linear correlation coefficient
(R) of 0.95. Because the site slopes toward an adjacent creek that is the local groundwater discharge zone, one possible explanation
for this effect is a streaming-potential mechanism generated by groundwater movement toward the creek. The residual NP data
revealed three negative anomalies at the survey area. Two of them coincide with sinkholes. A part of the third anomaly is
coincident with a small valley, and concentrated infiltration does occur at this elevation in other valleys at the site, as
evidenced by the existence of sinkholes. However, the dispersed, low-magnitude nature of the third anomaly does not prove
the existence of concentrated groundwater recharge activity.
Received: 18 March 1998 · Accepted: 27 April 1998 相似文献
17.
A fractionation of uranium (U) series into parent–daughter pairs – 234U and 238U – always occurs in natural waters, and the disequilibria between these is commonly used as a tracer of groundwater flow.
We report here an interpretation of the U-content and U isotope disequilibria in groundwater sampled from the deep Complexe
Terminal and Continental Intercalaire aquifers of southern Tunisia. Variations in both the contents of these isotopes (0.006–2.4 ppb)
and 234U/238U activity ratios (ARs) (1.7–15.4) were observed. The data could be plotted in two distinct fields of reciprocal U concentration
versus 234U/238U AR according to groundwater flow and regional bedrock differences. An initial assessment aimed at verifying whether the
results of this investigation support those of previous hydrogeological and isotope studies, thereby suggesting that the disequilibrium
between U isotopes in groundwater may represent a useful tool for hydrogeological investigations of deep and fossil groundwater.
In addition, the disequilibrium can be used for quantifying the recharge or mixing rates between different formations with
the aim of delineating the preferential outflow pattern or determining residence times of waters. 相似文献
18.
Recharge rate estimation in the Mountain karst aquifer system of Figeh spring, Syria 总被引:3,自引:1,他引:2
A. Al-Charideh 《Environmental Earth Sciences》2012,65(4):1169-1178
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
19.
Xin Liu Xianfang Song Yinghua Zhang Jun Xia Xuecheng Zhang Jingjie Yu Di Long Fadong Li Bing Zhang 《Environmental Earth Sciences》2011,63(5):1105-1118
Groundwater is of utmost significance to socio-economic development and ecological recovery for the Loess Plateau. However,
studies regarding the mechanism governing groundwater recharge over this area appear to be inadequate. This study is to examine
the spatio-temporal variations of δ2H and δ18O in precipitation and shallow groundwater. On the basis of this, the mechanisms governing shallow groundwater recharge were
explored. Precipitation and groundwater were sampled monthly from May to October during the period 2004–2006 at 13 sites in
the Chabagou Catchment (187 km2). In the Caopingxigou Experimental Watershed (0.1 km2), meteorological variables were observed and rainfall larger than 5 mm was sampled immediately after each rain event. Across
the area, 90% of the precipitation occurred from May to September primarily in the form of heavy rains or rainstorms with
great spatial variability. There were about 30 localized rains in each year. It was indicated that there existed notable seasonality
and pronounced spatial variability in precipitation isotopic compositions. Contributing factors and indications of isotopic
compositions, as well as their climatic indications such as monsoon intensities and mixing processes of water vapor, were
investigated. The δ2H–δ18O relation of groundwater was found to be δ2H = 3.22 × δ18O − 38.1, deviating from the local meteoric water line δ2H = 7.57 × δ18O + 3.9. The range of δ values in groundwater is shrunken to be 15–21% of that in individual precipitations, and groundwater in the middle reaches
shows a wider range of δ values. Isotopic results showed that groundwater originates from precipitation with hydrogen and oxygen isotopic compositions
being −69 and −9.7‰, respectively, and most groundwater experiences serious evaporation and adequate mixing with old water
during infiltration or percolation in the aerated zone. It was also founded that obvious fluctuations of isotopic compositions
in groundwater mainly appear in the middle reaches especially at sites that are close to valleys, suggesting varying sources
of groundwater from precipitation, precipitation runoff, isotopically enriched surface water and/or lateral recharge of adjacent
groundwater. 相似文献
20.
A comparison of the d-excess values of precipitation and of spring water, streams, groundwater wells and submarine groundwater discharge indicated that the precipitation that occurred during winter season was an important source of groundwater recharge. Due to the steep slope of the island, most of the short duration and high intensity precipitation is lost through direct surface runoff. The comparison indicated that snowmelt is an important resource of groundwater recharge on Rishiri Island. Future climate change will continue to diminish the snowpack, and therefore, reduce groundwater recharge. It may cause the decline of the groundwater level in the coastal area and possibly shift the saline–freshwater boundary on the island. Chloride data indicated that saltwater intrusion is beginning to occur on the western flank of the island. A Piper diagram shows that the water samples are characterized by the dominance of the Ca–HCO3 and Na–Cl type. Their chemistry probably results from sea salt spray and the dissolution of minerals. These results support the need for the effective management of groundwater resources. 相似文献