Pumping test of a water table aquifer is carried out to estimate the aquifer parameters, the obtained data were analysed through the solution of both Neuman(1975) and Jacob(1946) methods through AQTESOLV and Spreadshe...Pumping test of a water table aquifer is carried out to estimate the aquifer parameters, the obtained data were analysed through the solution of both Neuman(1975) and Jacob(1946) methods through AQTESOLV and Spreadsheet programs, the results of each methods are compared to evaluate the applicability and accuracy of the solution theoretically and practically. In the paper an example is presented, which is conducted for a constant rate pumping test from Ohio, in Fairborn(near Dayton), and it supplied by S.E. Norris(U.S. Geological Survey, Columbus, Ohio). The main objective of this study is to introduce both program and the way of the applications, and compare the results and the hand on of both programs in the field.展开更多
The Diizce Plain has a multi-aquifer system, which consists of a near surface unconfined aquifer, along with first and second deeper confined aquifers. Hydrochemical evolution and water quality are related to infiltra...The Diizce Plain has a multi-aquifer system, which consists of a near surface unconfined aquifer, along with first and second deeper confined aquifers. Hydrochemical evolution and water quality are related to infiltration of the precipitation, recharge from the formations surrounding the plain, flow path of groundwater and the relationship between surface and groundwater. The groundwater in the unconfined aquifer flows towards the Efteni Lake and the Biiyiik Melen River. Surface waters are divided into two main hydrochemical facies in the study area： （a） Ca2＋-HCO3-; and （b） Ca2＋, Mg2＋-HCOc-, SO4^2-. The groundwater has generally three main hydrochemical facies： （a） Ca2＋-HCO3-; （b） Ca2＋, Mg2＋-HCO3-; and （c） Ca2＋, Mg2＋-HCO3-, Cl-. The hydrochemical facies ＂a＂ and ＂b＂ dominate within shallow depths in recharge areas under rapid flow conditions, while hydrochemical facies ＂c＂ characterizes shallow and mixed groundwater, which dominate intermediate or discharge areas （near Efteni Lake and Biiyiik Melen River） during low flow conditions and agricultural contamination. Calcium and bicarbonate ions, total hardness and electrical conductivity of total dissolved solids （EC-TDS） values increase along the groundwater flow path; but these parameters remain within the limits specified by the standards set for industrial and agricultural usages.展开更多
Dispersion parameter is an important parameter for the establishment of groundwater solute transport model.The dispersion test uses sodium chloride as a tracer,which was conducted in a site in Jilin City.The standard ...Dispersion parameter is an important parameter for the establishment of groundwater solute transport model.The dispersion test uses sodium chloride as a tracer,which was conducted in a site in Jilin City.The standard curve comparison method was used to solve the dispersion parameters of the aquifer under the natural flow field.The test results show that under the natural flow field,the longitudinal dispersion of unconfined aquifer in Jilin City is 0.400m,and the transverse dispersion is 1.933×10-5~6.557×10-3m;while the longitudinal dispersion coefficient is 0.246m2/d,the transverse dispersion coefficient is 1.191×10-5~4.039×10-3m2/d.The above results can provide an important parameter basis for the establishment of groundwater solute transport model,the accurate prediction of temporal and spatial variation of pollutant concentration in groundwater and the formulation of groundwater pollution prevention and control scheme.展开更多
Most studies on solute transport in coastal aquifers affected by tides focus on the transport of instantaneous released solute,and there are few studies on continuously released solute affected by tides.In this study,...Most studies on solute transport in coastal aquifers affected by tides focus on the transport of instantaneous released solute,and there are few studies on continuously released solute affected by tides.In this study,the image monitoring method is used to establish the quantitative relationship between the concentration of the colored tracer and the hue value of the image,and the digital image is used to determine the tracer concentration distribution.Using image monitoring method laboratory experiments,quantitative analysis of the characteristics of continuously released solute transport in coastal unconfined aquifers under the tidal influence.Experiments show that the high tide inhibits the increase in the concentration of each point in the aquifer.Under the influence of tides,the solute plume retreats towards the land.During the low tide period,the solute plume migrates toward the sea again.And the solute plume will maintain a relatively stable shape after entering the aquifer for a long enough time.Ignoring the tidal effect seems to have little effect on the estimation of the position of the solute plume,but ignoring the tidal effect has a certain influence on the estimation of the dispersion range of the solute plume.No matter whether considering the tidal action,the final dispersion range of the solute plume is almost the same.But before the solute plume reaches a stable state,ignoring the tidal effect will lead to a smaller dispersion range of the solute plume.展开更多
Lab experiment and mathematical simulation Modular three dimensional finite difference groundwater （MODFLOW） were performed in a soil tank to simulate the hydrogeochemical interaction between lake and typical unconf...Lab experiment and mathematical simulation Modular three dimensional finite difference groundwater （MODFLOW） were performed in a soil tank to simulate the hydrogeochemical interaction between lake and typical unconfined aquifer. Results show that the velocity decreases exponentially with the transect distance on seepage face. The maximal velocity occurs at the top point of seepage face. The obliquity of seepage face has a great influence on the maximum and distribution of seepage velocity. With the increase of the obliquity of seepage face, the maximal velocity decreases quickly and the velocity distribution becomes much more even. Most of groundwater flow and pollutant flux discharges through a narrow portion near the top of seepage face. The flow and mass concentrated in the narrow portion increase with the decrease of the obliquity of seepage face. These will benefit to design a reasonable and economical scenario to manage lakeshore and to control the pollution of lake water near lakeshore.展开更多
The airflow in unsaturated soils is an issue of great importance in various fields such as in agricultural, nuclear, environmental engineering. However, up to now, little attention was paid to the generation of the ai...The airflow in unsaturated soils is an issue of great importance in various fields such as in agricultural, nuclear, environmental engineering. However, up to now, little attention was paid to the generation of the airflow induced by a pumping test in an unconfined aquifer with a low-permeability cap and its influence on the pumping test. In this paper, pumping tests were carried out experimentally in the aquifer with a low-permeability cap in order to study the influence of the airflow induced by the pumping on the drawdown of the tests. It is shown that： （1） there is an airflow with negative pressure generated by the pumping tests, （2） the Negative air Pressure （NP） is increased with the pumping rate but decreased with the radial distance, and （3） the NP also changes with the initial water table. The results provide a good basis for further theoretical study of the airflow induced by pumping.展开更多
In the management of unconfined aquifer systems, if the thickness of the aquifer is very small and the drawdown is relatively big, errors may arise when the superposition principle is adopted. directly. In allusion to...In the management of unconfined aquifer systems, if the thickness of the aquifer is very small and the drawdown is relatively big, errors may arise when the superposition principle is adopted. directly. In allusion to this limitation, a new management model for the management of unconfined aquifer systems called two-level response matrix method is put forward. This method is applied in groundwater resources management in Shenyang city. The managing results show that this method can, in some degree, increase the efficiency of management and decrease the risk of management.展开更多
The present paper provides evidence of the possible impact of shale-limestone-mudstone successions aquifers on groundwater chemistry by assessing the different hydrogeochemical processes. This was done by considering ...The present paper provides evidence of the possible impact of shale-limestone-mudstone successions aquifers on groundwater chemistry by assessing the different hydrogeochemical processes. This was done by considering a sedimentary aquifer basin, namely the Hantebet sub basin (24.4 km<sup>2</sup>), Tekeze basin, northern Ethiopia. Groundwater is the main source of water supply in the sub basin extracted using hand dug wells, for domestic, irrigation and livestock uses. The sub basin is dominated by Paleozoic-Mesozoic sedimentary successions. Twenty groundwater samples were collected from hand dug wells using depth-integrated sampling techniques from both confined and unconfined aquifers. The major water bearing formations are gravely sand, weathered shale and weathered and fractured limestone, and intercalated weathered and fractured limestone and mudstone. The results indicate that groundwater is acidic to neutral, fresh, and hard to very hard. Ca<sup>2+</sup>, Na<sup>+</sup>, HCO<sup>-</sup>3</sub> and SO<sup>2-</sup>4</sub> are dominant ions compared to Mg<sup>2+</sup>, K<sup>+</sup>, and Cl<sup>-</sup> ions which show low to very low concentrations. Among eight hydrochemical facies identified, Ca-Na-HCO<sub>3</sub> (40%), Ca-HCO<sub>3</sub> (20%), Ca-Mg-Na-HCO<sub>3</sub> (10%) and Ca-Na-HCO<sub>3</sub>-SO<sub>4</sub> (10%) types dominate water chemistry. Dissolution of calcite and gypsum, and hydrolysis of feldspars, plagioclase, biotite and pyroxene are the major geochemical processes that control the chemistry of groundwater in the area. The intercalated shale beds are the source of sodium and chloride ions. Since, this study is based on groundwater from hand dug wells, the conclusions of this study should be further verified using groundwater from deep wells that are drilled in these successions.展开更多
A simple estimation model of groundwater discharge and nutrient flux from nearshore unconfined aquifer to lake was studied. It was supposed that the aquifer was permeable isotropic homogeneously and its thickness appr...A simple estimation model of groundwater discharge and nutrient flux from nearshore unconfined aquifer to lake was studied. It was supposed that the aquifer was permeable isotropic homogeneously and its thickness approximated to the depth of lake. Distribution of the hydraulic gradient and the specific discharge along the transect of the discharge zone were discussed. Results show that the groundwater discharge patterns vary with the inclination angle of lakeshore bottom. For a shallow lake with gentle slope bottom, the rate of discharge of groundwater to lake is not constant across a discharge zone, but the discharge is concentrated in a narrow portion of the littoral zone where the Dupuit assumptions are invalid. The width of the discharge zone is correlative with aquifer thickness and slope of the lake bottom. The distribution functions of hydraulic gradient and groundwater discharge rates accord exponentially with offshore distance.展开更多
文摘Pumping test of a water table aquifer is carried out to estimate the aquifer parameters, the obtained data were analysed through the solution of both Neuman(1975) and Jacob(1946) methods through AQTESOLV and Spreadsheet programs, the results of each methods are compared to evaluate the applicability and accuracy of the solution theoretically and practically. In the paper an example is presented, which is conducted for a constant rate pumping test from Ohio, in Fairborn(near Dayton), and it supplied by S.E. Norris(U.S. Geological Survey, Columbus, Ohio). The main objective of this study is to introduce both program and the way of the applications, and compare the results and the hand on of both programs in the field.
文摘The Diizce Plain has a multi-aquifer system, which consists of a near surface unconfined aquifer, along with first and second deeper confined aquifers. Hydrochemical evolution and water quality are related to infiltration of the precipitation, recharge from the formations surrounding the plain, flow path of groundwater and the relationship between surface and groundwater. The groundwater in the unconfined aquifer flows towards the Efteni Lake and the Biiyiik Melen River. Surface waters are divided into two main hydrochemical facies in the study area： （a） Ca2＋-HCO3-; and （b） Ca2＋, Mg2＋-HCOc-, SO4^2-. The groundwater has generally three main hydrochemical facies： （a） Ca2＋-HCO3-; （b） Ca2＋, Mg2＋-HCO3-; and （c） Ca2＋, Mg2＋-HCO3-, Cl-. The hydrochemical facies ＂a＂ and ＂b＂ dominate within shallow depths in recharge areas under rapid flow conditions, while hydrochemical facies ＂c＂ characterizes shallow and mixed groundwater, which dominate intermediate or discharge areas （near Efteni Lake and Biiyiik Melen River） during low flow conditions and agricultural contamination. Calcium and bicarbonate ions, total hardness and electrical conductivity of total dissolved solids （EC-TDS） values increase along the groundwater flow path; but these parameters remain within the limits specified by the standards set for industrial and agricultural usages.
基金National Joint Foundation for Natural Science Focus(Project No.:U 19A20107).
文摘Dispersion parameter is an important parameter for the establishment of groundwater solute transport model.The dispersion test uses sodium chloride as a tracer,which was conducted in a site in Jilin City.The standard curve comparison method was used to solve the dispersion parameters of the aquifer under the natural flow field.The test results show that under the natural flow field,the longitudinal dispersion of unconfined aquifer in Jilin City is 0.400m,and the transverse dispersion is 1.933×10-5~6.557×10-3m;while the longitudinal dispersion coefficient is 0.246m2/d,the transverse dispersion coefficient is 1.191×10-5~4.039×10-3m2/d.The above results can provide an important parameter basis for the establishment of groundwater solute transport model,the accurate prediction of temporal and spatial variation of pollutant concentration in groundwater and the formulation of groundwater pollution prevention and control scheme.
基金supported by the National Natural Science Foundation of China(No.42172281)the Opening Fund of the State Key Laboratory of China University of Geosciences(Wuhan)(No.SKJ2018055)。
文摘Most studies on solute transport in coastal aquifers affected by tides focus on the transport of instantaneous released solute,and there are few studies on continuously released solute affected by tides.In this study,the image monitoring method is used to establish the quantitative relationship between the concentration of the colored tracer and the hue value of the image,and the digital image is used to determine the tracer concentration distribution.Using image monitoring method laboratory experiments,quantitative analysis of the characteristics of continuously released solute transport in coastal unconfined aquifers under the tidal influence.Experiments show that the high tide inhibits the increase in the concentration of each point in the aquifer.Under the influence of tides,the solute plume retreats towards the land.During the low tide period,the solute plume migrates toward the sea again.And the solute plume will maintain a relatively stable shape after entering the aquifer for a long enough time.Ignoring the tidal effect seems to have little effect on the estimation of the position of the solute plume,but ignoring the tidal effect has a certain influence on the estimation of the dispersion range of the solute plume.No matter whether considering the tidal action,the final dispersion range of the solute plume is almost the same.But before the solute plume reaches a stable state,ignoring the tidal effect will lead to a smaller dispersion range of the solute plume.
基金the National Natural Science Foundation of China (Grant No. 40601050)the National Basic Research Program of China (973 Program, Grant No. 2002CB412303)the Jiangsu Province Qinglan Project (2006).
文摘Lab experiment and mathematical simulation Modular three dimensional finite difference groundwater （MODFLOW） were performed in a soil tank to simulate the hydrogeochemical interaction between lake and typical unconfined aquifer. Results show that the velocity decreases exponentially with the transect distance on seepage face. The maximal velocity occurs at the top point of seepage face. The obliquity of seepage face has a great influence on the maximum and distribution of seepage velocity. With the increase of the obliquity of seepage face, the maximal velocity decreases quickly and the velocity distribution becomes much more even. Most of groundwater flow and pollutant flux discharges through a narrow portion near the top of seepage face. The flow and mass concentrated in the narrow portion increase with the decrease of the obliquity of seepage face. These will benefit to design a reasonable and economical scenario to manage lakeshore and to control the pollution of lake water near lakeshore.
基金National Natural Science Foundation of China (Grant Nos. 40872166, 51179042)the Research Grants Council of the Hong Kong Special Administrative Region, China (Grant No. HKU7019080P)the Innovative Projects of Hefei University of Technology (Grant No.2009HGCX0233)
文摘The airflow in unsaturated soils is an issue of great importance in various fields such as in agricultural, nuclear, environmental engineering. However, up to now, little attention was paid to the generation of the airflow induced by a pumping test in an unconfined aquifer with a low-permeability cap and its influence on the pumping test. In this paper, pumping tests were carried out experimentally in the aquifer with a low-permeability cap in order to study the influence of the airflow induced by the pumping on the drawdown of the tests. It is shown that： （1） there is an airflow with negative pressure generated by the pumping tests, （2） the Negative air Pressure （NP） is increased with the pumping rate but decreased with the radial distance, and （3） the NP also changes with the initial water table. The results provide a good basis for further theoretical study of the airflow induced by pumping.
基金This work was supported partly by the National Plan for Basic Studies of China under Grant G1999043606 and National Social Science Foundation under Grant 03CJL006
文摘In the management of unconfined aquifer systems, if the thickness of the aquifer is very small and the drawdown is relatively big, errors may arise when the superposition principle is adopted. directly. In allusion to this limitation, a new management model for the management of unconfined aquifer systems called two-level response matrix method is put forward. This method is applied in groundwater resources management in Shenyang city. The managing results show that this method can, in some degree, increase the efficiency of management and decrease the risk of management.
文摘The present paper provides evidence of the possible impact of shale-limestone-mudstone successions aquifers on groundwater chemistry by assessing the different hydrogeochemical processes. This was done by considering a sedimentary aquifer basin, namely the Hantebet sub basin (24.4 km<sup>2</sup>), Tekeze basin, northern Ethiopia. Groundwater is the main source of water supply in the sub basin extracted using hand dug wells, for domestic, irrigation and livestock uses. The sub basin is dominated by Paleozoic-Mesozoic sedimentary successions. Twenty groundwater samples were collected from hand dug wells using depth-integrated sampling techniques from both confined and unconfined aquifers. The major water bearing formations are gravely sand, weathered shale and weathered and fractured limestone, and intercalated weathered and fractured limestone and mudstone. The results indicate that groundwater is acidic to neutral, fresh, and hard to very hard. Ca<sup>2+</sup>, Na<sup>+</sup>, HCO<sup>-</sup>3</sub> and SO<sup>2-</sup>4</sub> are dominant ions compared to Mg<sup>2+</sup>, K<sup>+</sup>, and Cl<sup>-</sup> ions which show low to very low concentrations. Among eight hydrochemical facies identified, Ca-Na-HCO<sub>3</sub> (40%), Ca-HCO<sub>3</sub> (20%), Ca-Mg-Na-HCO<sub>3</sub> (10%) and Ca-Na-HCO<sub>3</sub>-SO<sub>4</sub> (10%) types dominate water chemistry. Dissolution of calcite and gypsum, and hydrolysis of feldspars, plagioclase, biotite and pyroxene are the major geochemical processes that control the chemistry of groundwater in the area. The intercalated shale beds are the source of sodium and chloride ions. Since, this study is based on groundwater from hand dug wells, the conclusions of this study should be further verified using groundwater from deep wells that are drilled in these successions.
基金Project supported by the National Basic Research Program of China (Grant No. 2002CB412303) the Graduate Innovation Project of Jiangsu Province, China.
文摘A simple estimation model of groundwater discharge and nutrient flux from nearshore unconfined aquifer to lake was studied. It was supposed that the aquifer was permeable isotropic homogeneously and its thickness approximated to the depth of lake. Distribution of the hydraulic gradient and the specific discharge along the transect of the discharge zone were discussed. Results show that the groundwater discharge patterns vary with the inclination angle of lakeshore bottom. For a shallow lake with gentle slope bottom, the rate of discharge of groundwater to lake is not constant across a discharge zone, but the discharge is concentrated in a narrow portion of the littoral zone where the Dupuit assumptions are invalid. The width of the discharge zone is correlative with aquifer thickness and slope of the lake bottom. The distribution functions of hydraulic gradient and groundwater discharge rates accord exponentially with offshore distance.
