step-drawdown test pdf
Step-drawdown tests were introduced by Jacob 1947 in order to study how the discharge Q affects the drawdown s w of a well drilled in confined aquifers. PDF download and online access 4900 Details Check out Abstract A review of the literature and a study of a number of field tests shows that the presently used analysis and interpretation of step-drawdown tests can be misleading.
Pdf An Approach To Interpretation Of Step Drawdown Tests
The purpose of this paper is to.
. Analysing step-drawdown tests in heterogeneous aquifers G. From this one can derive a detailed physical. In the ideal case drawdown becomes.
The methods of analysis and the criteria for planning step drawdown tests are discussed and evaluated in order to produce an optimum test programme and a comprehensive test analysis. Various configurations of diagnostic plots are possible. This SOP provides a field procedure for the performance of a single well step-drawdown test only.
B is a numerical parameter which takes into account linear head losses of the aquifer C is the analogous parameter for non-linear quadratic. - The points form a horizontal line. The step-drawdown test involved.
This paper reports a new method for analysing step-drawdown data which not only takes heterogeneity into account but which also turns out to be simpler and more robust than existing methods even where the aquifer is relatively homogeneous. However some authors have used the step-drawdown test to evaluate drawdowns in unconfined heterogeneous and. This technical note describes the analysis for a step-drawdown pumping test which is used to estimate water level drawdown in water wells for the design production rate.
Calculate drawdown at a known pumping rate using the Graphical Method. Step-Drawdown Test Analysis by Computer. The methods of analysis and the criteria for planning step drawdown tests are discussed and evaluated in order to produce an optimum test programme and a comprehensive test analysis.
PDF Summary A step drawdown test is a pumping test in which the drawdown in a well is observed while the discharge rate from the well is increased in steps. A step drawdown test is a pumping test in which the drawdown in a well is observed while the discharge rate from the well is increased in steps. The first screen shows you the time-drawdown data plotted in semi-log for- mat during Step 1.
The efficiency of a well is defined. The new method is equally applicable to confined leaky and unconfined aquifers. The total depth of the well is 400 feet with an open-hole interval of 320 feet.
The analytical results of stepdrawdown test data from the study area in Bengal suggest that most test wells were not properly developed with adequate pumping prior to the test and that a significant amount of well development took place during the test exercise. The well is then pumped at a higher constant rate until a new QSS is achieved. 10 Step-drawdown analyses i files and select Jacobs method in the method selection form.
Discuss the theory of the step -drawdown test and methods of step -test data analysis. Step-drawdown tests are most often completed to aid in planning full-scale pump tests by determining a wells efficiency and providing an initial assessment of aquifer hydraulic properties. Groundwater Monitoring and Remediation.
A step-drawdown test is a single-well test that is frequently conducted after well development to determine well efficiency and correctly size the production pump. The step-drawdown test provides a means whereby at any time during the life of a well it should be possible to determine with considerable accuracy the two com- ponents of its specific drawdown ie. Step-drawdown pumping tests sometimes also called step-discharge or well-performance tests are a widely used method todeterminethemaximumallowablepumpingrateofawaterwell Batu1998KrusemananddeRidder 2000Kasenow 2010The well is successively pumped at several commonly three to six increasing pumping rates.
Coefficients B and C of the Jacob 1947 equation usually derived from step-drawdown tests are commonly attributed to aquifer losses and well losses respectively. The analysis of step-drawdown tests uses diagnostic plots in which values of sJQ versus Q are plotted on linear paper with s representing the stabilised drawdown at the end of each step. He proposed the following equation.
Those attributable to formation loss and to well loss. The step-drawdown test is the first step after a sequence of practical operations carried out for the construction of a new well. This implies that sJQ B.
This paper analyzes and separates the linear laminar nonlinear laminar and turbulent losses occurring during flow from an aquifer to a screened well. Review results of previous studies where step -drawdown tests were applied. Younger Environmental Science Quarterly Journal of Engineering Geology and Hydrogeology 2002 All existing methods for analysing step-drawdown test data assume that the aquifer is homogeneous whereas most real aquifers are heterogeneous.
No steady state developed during Step l. Stepdrawdown tests SDTs typically involve pumping a well at a constant rate until a quasisteady state QSS is observed in the drawdown response. A step-drawdown pumping test was conducted on an 8-inch diameter test well completed in siltstones and shales of the Triassic Passaic Formation in Central New Jersey.
This graph shows you that the drawdowns had not yet sta- bilised at the end of this step ie. The parameters defining well loss are presently obtained only by using the drawdown observed during a step drawdown test. Pumping rates are constant during steps which are of sufficient duration about 14 hours for water levels to change minimally at the end of each step Halford and Kuniansky 2002.
A step drawdown test consists of pumping at several successively higher rates and recording the drawdowns during each pumping stage which generally continues until nearly steady state is reached. Water level drawdown is necessary for the proper design of a submersible well pump and control system. Test data were analyzed by standard analytical methods and for a number of tests reasonable values of hydraulic properties were obtained.
Pdf A Generalised Solution For Step Drawdown Tests Including Flow Dimension And Elasticity
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