Alternative linearization of water table kinematic condition for unconfined aquifer pumping test modeling and its implications for specific yield estimates

2011 ◽  
Vol 399 (3-4) ◽  
pp. 141-147 ◽  
Author(s):  
Bwalya Malama
Keyword(s):  
Water Table ◽  
Pumping Test ◽  
Unconfined Aquifer ◽  
Specific Yield ◽  
Kinematic Condition

Drawdowns at the Free Water Table During Pumping Tests in Artesian and Semiartesian Aquifers

1980 ◽  
Vol 11 (3-4) ◽  
pp. 159-168 ◽  
Author(s):  
Henrik Kærgaard
Keyword(s):  
Water Table ◽  
Free Water ◽  
Pumping Test ◽  
Water Withdrawal ◽  
Specific Yield ◽  
Minor Role ◽  
Long Term Effects ◽  
Long Term Storage ◽  
Term Storage

In an earlier paper I have shown an example of how long term drawdowns can be used for the computation of long term storage in artesian and semiartesian areas. In most cases the long term storage is more or less equivalent to the specific yield at the water table; the storage mechanisms of consolidation playing a minor role in long term situations. The specific yield in artesian areas is a very important parameter in the prediction of long term effects of ground water withdrawal. Especially the stream depletion will often mainly be governed by draw-downs in upper nonpumped aquifers near the water table, and these drawdowns depend to a great extent on the specific yield at the water table. A determination of long term storage will often necessitate long term draw-down data, however, under certain circumstances a determination can be made on the basis of a pumping test of limited duration (3-5 weeks) provided drawdown observations at the water table can be made. In this paper some formulas dealing with water table drawdowns in different geohydrologic systems are reviewed, and two cases in which these formulas have been used in practice are presented.

Floodplain hydraulics in a glaciated bedrock river valley

2012 ◽  
Vol 43 (6) ◽  
pp. 870-889 ◽  
Author(s):  
David W. Ostendorf ◽  
Erich S. Hinlein ◽  
Aaron I. Judge
Keyword(s):  
Travel Time ◽  
Water Table ◽  
Unconfined Aquifer ◽  
Silty Sand ◽  
Specific Yield ◽  
Recharge Rate ◽  
One Dimensional ◽  
Sand Deposit ◽  
Diurnal Fluctuations ◽  
Eastern Massachusetts

Data and one dimensional, unsteady theory document the average, seasonal, and diurnal hydraulics of an unconfined aquifer in the surficial floodplain deposit of the Neponset River, which flows through a glaciated bedrock valley in eastern Massachusetts. The 20 m thick silty sand deposit has a permeability of 1.4 × 10−11 m2, a porosity of 0.37, a 600 m halfwidth, and an infiltration coefficient of 0.39. The steady water table is parabolic with a 0.60 m value at the valley wall that implies an average 33-year travel time across the floodplain in response to an average recharge rate of 7.0 × 10−9 m/s. Seasonal hydraulics are governed by the floodplain porosity and marked by periodicity of the river (0.48 m amplitude) and recharge (1.9 × 10−8 m/s amplitude), which maintain flow from the floodplain into the river year round. Attenuation of the diurnal fluctuations suggests that the specific yield ranges from 0.05 to 0.14, and yields horizontal flow excursions of 1 m scale near the riverbank.

scholarly journals Optimal estimation of unconfined aquifer parameters in uncertain environment based on fuzzy transformation method

2018 ◽  
Vol 19 (2) ◽  
pp. 444-450
Author(s):  
Atefeh Delnaz ◽  
Gholamreza Rakhshandehroo ◽  
Mohammad Reza Nikoo
Keyword(s):  
Test Data ◽  
Statistical Error ◽  
Optimal Estimation ◽  
Pumping Test ◽  
Transformation Method ◽  
Unconfined Aquifer ◽  
Uncertain Variable ◽  
Specific Yield ◽  
Pumping Rate ◽  
Fuzzy Transformation

Abstract In this paper, a fuzzy simulation–optimization model coupled with the genetic algorithm based on Boulton's equation is presented to estimate transmissibility (T), storage coefficient (S), specific yield (Sy) and leakage factor (Dt) of an unconfined aquifer. This model is capable of minimizing the deviation between observed and calculated drawdowns of pumping test data. To assess the applicability of the model, its results are compared with the graphically obtained solutions from Boulton's equation. To this end, real pumping test data obtained from an unconfined aquifer in Dayton, Ohio, are considered as the case problem to evaluate the efficacy of the model. In the fuzzy approach, pumping rate is considered as an uncertain variable. For evaluation of the model, several statistical error indices are utilized. Results show better matches for the model as evidenced by much smaller errors. As an example, mean absolute relative error for the proposed model and graphical Boulton's solution is 2.52% and 4.98%, respectively. It is concluded that the model is accurate and may replace the graphical Boulton's solution. T and Sy were found to be more sensitive to uncertainty in the pumping rate measurement, when compared with S and r/Dt.

Unusual drawdown curves for a pumping test in an unconfined aquifer at Lachenaie, Quebec: field data and numerical modeling

2005 ◽  
Vol 42 (4) ◽  
pp. 1133-1144 ◽  
Author(s):  
Robert P Chapuis ◽  
Djaouida Chenaf ◽  
Nelson Acevedo ◽  
Denis Marcotte ◽  
Michel Chouteau
Keyword(s):  
Numerical Modeling ◽  
Numerical Models ◽  
Field Tests ◽  
Pumping Test ◽  
Unconfined Aquifer ◽  
Specific Yield ◽  
Characteristic Functions ◽  
Constant Flow Rate ◽  
Monitoring Wells ◽  
Highly Nonlinear

An unconfined aquifer was instrumented with monitoring wells over a surface area of about 100 m × 100 m. The aquifer is a sand deposit overlying a thick nonfissured layer of Champlain Sea clay. The paper presents the results of a pumping test at a constant flow rate. None of the curves of drawdown versus time presented the S shape of current theories; however, all drawdowns indicated that the aquifer was homogeneous. The values for the specific yield were too low and varied with distance and time instead of being constant. The theories for steady and unsteady states provided different values for the saturated hydraulic conductivity. To understand the field behavior that differs from theoretical predictions, the pumping test conditions were modeled numerically using a finite element method. The transmissivity was derived from the Dupuit equation, and different curves for capillary retention and unsaturated permeability were examined. The numerical drawdowns agree with the experimental drawdowns. Several numerical models were investigated. All of them solved the inverse problem correctly for steady-state conditions and fairly well for transient conditions with highly nonlinear characteristic functions. The best solution to the transient problem was obtained using trial and error, by considering how the drawdown curves might be modified due to anisotropy and stratification. According to these field tests and the numerical analysis, the S shape is not the rule, and a different shape can be perfectly normal due to the complexity of unsaturated flow.Key words: pumping, unconfined aquifer, permeability, drawdown, numerical modeling.

scholarly journals Zonasi Potensi Airtanah Akuifer Bebas Di Cekungan Airtanah Majenang, Kabupaten Cilacap, Jawa Tengah

PROMINE ◽  
2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Mahira Anaqah Huwaina ◽  
Thomas Triadi Putranto ◽  
Narulita Santi
Keyword(s):  
Water Level ◽  
Water Table ◽  
Pumping Test ◽  
Unconfined Aquifer ◽  
Potential Zone ◽  
Central Java ◽  
A Value ◽  
Characteristic Data ◽  
Groundwater Basin ◽  
Medium Potential

Majenang Groundwater Basin is located in Cilacap Regency, Central Java. There is an increase of itsusage every year. Because of that, it is necessary to make groundwater zonation to get an overview ofthe potential zonation, specifically in unconfined aquifer. The methods used in this study is measuringwater table, sampling 17 samples of groundwater and pumping test to get the quantity of groundwater.Based on the measurement of known water table, it flows from the side of basin to the center of basin.It has a value of water level between 0.1-4.5 mbgl and water table 33.3-119.9 masl. Pumping test dataprocessing generates characteristic data aquifers, with value of transmisivity (T) is 2.9-11.3 m2/day,hidrolic conductivity (K) is 0.7-4.9 m/day, maximum debit is 2.3-3.6 L/day and optimum debit is 2.0-2.9L/day. Based on the result of quantity data, it has a medium potential zone for the unconfined aquifer.

Using groundwater levels and Specific Yield to Estimate the Recharge, South of Erbil, Kurdistan Region, Iraq

2018 ◽  
Vol 7 (4) ◽  
pp. 191
Author(s):  
Sherwan Sh. Qurtas
Keyword(s):  
Unconfined Aquifer ◽  
Middle Part ◽  
Water Levels ◽  
Specific Yield ◽  
Aquifer System ◽  
Groundwater Levels ◽  
Monitoring Wells ◽  
Water Table Fluctuation Method ◽  
Recharge Estimation ◽  
Fluctuation Method

Recharge estimation accurately is crucial to proper groundwater resource management, for the groundwater is dynamic and replenished natural resource. Usually recharge estimation depends on the; the water balance, water levels, and precipitation. This paper is studying the south-middle part of Erbil basin, with the majority of Quaternary sediments, the unconfined aquifer system is dominant, and the unsaturated zone is ranging from 15 to 50 meters, which groundwater levels response is moderate. The purpose of this study is quantification the natural recharge from precipitation. The water table fluctuation method is applied; using groundwater levels data of selected monitoring wells, neighboring meteorological station of the wells, and the specific yield of the aquifers. This method is widely used for its simplicity, scientific, realistic, and direct measurement. The accuracy depends on the how much the determination of specific yield is accurate, accuracy of the data, and the extrapolations of recession of groundwater levels curves of no rain periods. The normal annual precipitation there is 420 mm, the average recharge is 89 mm, and the average specific yield is around 0.03. The data of one water year of 2009 and 2010 has taken for some technical and accuracy reasons.

scholarly journals Analysis of Groundwater Response to Oscillatory Pumping Test in Unconfined Aquifers: Consider the Effects of Initial Condition and Wellbore Storage

2018 ◽  
Author(s):  
Ching-Sheng Huang ◽  
Ya-Hsin Tsai ◽  
Hund-Der Yeh ◽  
Tao Yang
Keyword(s):  
Water Table ◽  
Integral Transform ◽  
Pumping Test ◽  
Hydraulic Head ◽  
Analytical Models ◽  
Hydraulic Parameters ◽  
Storage Effect ◽  
Initial Condition ◽  
Wellbore Storage ◽  
Present Solution

Abstract. Oscillatory pumping test (OPT) is an alternative to constant-head and constant-rate pumping tests for determining aquifer hydraulic parameters without water extraction. There is a large number of analytical models presented for the analyses of OPT. The combined effects of wellbore storage and initial condition regarding the hydraulic head prior to OPT are commonly neglected in the existing models. This study aims to develop a new model for describing the hydraulic head fluctuation induced by OPT in an unconfined aquifer. The model contains a typical flow equation with an initial condition of static water table, inner boundary condition specified at the rim of a finite-radius well for incorporating wellbore storage effect, and linearized free surface equation describing water table movement. The analytical solution of the model is derived by the Laplace transform and finite integral transform. Sensitivity analysis is carried out for exploring head response to the change in each of hydraulic parameters. Results suggest that head fluctuation due to OPT starts from the initial condition and gradually tends to simple harmonic motion (SHM) after a certain pumping time. A criterion for estimating the time to have SHM since OPT is graphically presented. The validity of assuming an infinitesimal well radius without wellbore storage effect is investigated. The present solution agrees well to head fluctuation data observed at the Boise hydrogeophysical research site in southwestern Idaho.

scholarly journals Approximate analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

2016 ◽  
Vol 20 (1) ◽  
pp. 55-71 ◽  
Author(s):  
C.-S. Huang ◽  
J.-J. Chen ◽  
H.-D. Yeh
Keyword(s):  
Groundwater Flow ◽  
Integral Transform ◽  
Three Dimensional ◽  
Vertical Component ◽  
Hydraulic Head ◽  
Unconfined Aquifer ◽  
Specific Yield ◽  
Specific Storage ◽  
Sink Term ◽  
Radial Collector Well

Abstract. This study develops a three-dimensional (3-D) mathematical model for describing transient hydraulic head distributions due to pumping at a radial collector well (RCW) in a rectangular confined or unconfined aquifer bounded by two parallel streams and no-flow boundaries. The streams with low-permeability streambeds fully penetrate the aquifer. The governing equation with a point-sink term is employed. A first-order free surface equation delineating the water table decline induced by the well is considered. Robin boundary conditions are adopted to describe fluxes across the streambeds. The head solution for the point sink is derived by applying the methods of finite integral transform and Laplace transform. The head solution for a RCW is obtained by integrating the point-sink solution along the laterals of the RCW and then dividing the integration result by the sum of lateral lengths. On the basis of Darcy's law and head distributions along the streams, the solution for the stream depletion rate (SDR) can also be developed. With the aid of the head and SDR solutions, the sensitivity analysis can then be performed to explore the response of the hydraulic head to the change in a specific parameter such as the horizontal and vertical hydraulic conductivities, streambed permeability, specific storage, specific yield, lateral length, and well depth. Spatial head distributions subject to the anisotropy of aquifer hydraulic conductivities are analyzed. A quantitative criterion is provided to identify whether groundwater flow at a specific region is 3-D or 2-D without the vertical component. In addition, another criterion is also given to allow for the neglect of vertical flow effect on SDR. Conventional 2-D flow models can be used to provide accurate head and SDR predictions if satisfying these two criteria.

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