A cone of depression is formed in the aquifer around the pumping well as the water level declines due to pumping. Pumping tests can be performed within an aquifer to collect information relative to the aquifer in which the pumped well and observation wells are located. In practice, it is said that steadystate flow is attained if the changes in the water level in the well and piezometers have become so small with time that they can be neglected. The slug test is simpler and quicker than the theis pumping test because observation wells and pumping the well are not. Aquifer testing is a common tool that hydrogeologists use to characterize a system of aquifers, aquitards and flow system boundaries a slug test is a variation on the typical aquifer test where an. Theis 1935 pumping test solution for unconfined aquifers. Airflow induced by pumping tests in unconfined aquifer with a lowpermeability cap jiu jimmy jiao1 and haipeng guo1,2 received 21 january 2009. A slug test for determining hydraulic conductivity of unconfined aquifers. If the pumping test involves pumping a large volume of water for a long duration e. Analysis of unconfined flow induced by constant rate pumping.
Neuman developed a solution method for pumping tests performed in unconfined aquifers, which can be used for both fully or partially penetrating wells. Introduction extensive research has been conducted to accurately characterize unconfined aquifers in the field of groundwater. Aquifer testing is a common tool that hydrogeologists use to characterize a system of aquifers, aquitards and flow system boundaries. The aquifer is unconfined this assumption is only applicable to latetime drawdown data. The idea of a pump test is to stress the aquifer by pumping or injecting water and to note the drawdown over space and time. General pumping test is the examination of aquifer response, under controlled conditions, to the abstraction of water. The impact of airflow on drawdown of hydraulic heads in the aquifer was also explored. In general pumping test is still until pseudosteady state flow is attained or low fluctuation in dynamic water is occur. Hydrogeologists determine the hydraulic characteristics of waterbearing formations, by conducting pumping tests.
Consider that the recharge to the aquifer within the influence zone of the pumped well equals the rate of discharge of the well so that the drawdown remains stabilised and therefore steady state exists. Recovery method a after exactly one day of pumping, the pump was shut off and residual drawdown was measured in the 30 m observation well. The principle of a pumping test is that if we pump water from a well and measure the discharge of the well and the drawdown in the well and in piezometers at known distances from the well, we can substitute these measurements into an appropriate well flow equation and can calculate the hydraulic characteristics of the aquifer fig ure 2. Analysis of data from a correctly executed pumping test can be one of the most reliable methods of determining the mass permeability of. A pumping test should also measure the changes in water level after the pump stops see figure 2. Learn both the fundamentals and advances in pumping test interpretation from pumping well and observation well storage and the role it plays in unconfined aquifer hydraulics. Radial flow to a well in an confined unconfined aquifer.
With the slug test the hydraulic conductivity or transmissibility of an aquifer is determined from the rate of rise of the water level in a well after a certain volume or slug of water is suddenly removed from the well. Jun 10, 2015 pumping test analysis part1 jacob duration. Jacob is attributed with a procedure jacob 1944 that corrects drawdown data for the reduction in an unconfined aquifer s saturated thickness resulting from groundwater withdrawal by a pumping well and thereby enables pumping tests in watertable aquifers to be interpreted by methods for nonleaky confined aquifers such as the theis 1935 solution. Confined and unconfined aquifers respond differently to pumping. Diagrammatic representation of an unconfined aquifer discharging through a beach system. This study finds that the unconfined confined conversion is quite sensitive to. Pumping test procedures for water withdrawal applications. Mod01 lec14 unsteady radial flow in confined and unconfined aquifers. During the middle part of the test the rate of drawdown starts to level off. The limitations and advantages of the model approach are also discussed in the paper.
This study finds that the unconfinedconfined conversion is quite sensitive to. The test is made by observing groundwater flow that is produced by known hydraulic. Suggested operating procedures for aquifer pumping tests. Pumping test to determine k solve equation 6 for k. The paper presents the results of a pumping test at a constant flow rate.
Unsaturated and saturated flow in response to pumping of. View the article pdf and any associated supplements and figures for a period of 48 hours. Three major nearshore flow processes are illustrated. Pumping tests in a pumping test, groundwater is extracted from a pumping well with water level measurements observed in the pumping well and in one or more observation wells. Calculation of discharge in confined and unconfined aquifer. Read this article to learn about the calculation of discharge in confined and unconfined aquifer using theims formula for steady flow. An aquifer in which the water table forms the upper boundary. Its difficult to determine how many hours that pumping test required because period of pumping depends on the type and natural materials of the aquifer. Demonstration with a physical model covers unconfined and confined aquifers using a physical model. Joint interpretation of sequential pumping tests in. Usually measured relative to static non pumping conditions. Data were collected primarily from test pumping reports and files kept at regional environment agency offices, with some additional data from water companies and bgs records.
For example, at a distance of 10,000 feet about 2 miles from the pumping well, the drawdown in the unconfined mineral grains pore water well discharge original. Confined and unconfined aquifers respond differently to. Schematic diagram for the conceptual model of an unconfined aquifer under constantrate pumping temporal dimensionless drawdown sd for a 0qd. In the last expression the term in the parenthesis on the right hand side is the annulus area of the vertical leakage and the ratio is the hydraulic gradient that causes vertical groundwater flow from the unconfined aquifer into the confined layer. Calculate the radial flow to a well in a confined unconfined aquifer system. The pumping well is of infinitesimal diameter, and fully penetrates the aquifer.
A pumping test is a field experiment in which a well is pumped at a controlled rate and waterlevel response is measured in one or more surrounding observation wells and optionally in the pumped well control well itself. Duration of pumping test its difficult to determine how many hours that pumping test required because period of pumping depends on the type and natural materials of the aquifer. Introducing novel methods of pumping test interpretation discover key differences how unconfined and. A map, showing the location of the investigateda map, showing the location of the investigated site, pumping and observation wells. When analyzing pumping test data from unconfined aquifers, one often finds that the drawdown response fails to follow the classical theis 1935 solution. Pdf analysis and evaluation of pumping test data second. Sand bar in the wisconsin river showing confined flow changing to unconfined flow.
Click here full article airflow induced by pumping tests in. Jan 12, 2016 this second segment of understanding aquifers. As pumping continues, the cone expands and deepens, and the flow towards the well has clear vertical components. Neuman 1975 developed a solution method for pumping tests performed in unconfined aquifers, which can be used for both fully or partially penetrating wells. This indicates that well 299w15225 will impose a hydrologic area of influence of greater than 690 m at similar pumping rates i. An aquifer whose upper and lower boundaries are defined by aquicludes. Analysis of noflow boundaries in steady state unconfined. A pumping test involves pumping from a test well at a controlled rate and monitoring the flow rate from the well and the drawdown in an array of observation wells at varying radial distances from the test well. Pdf analysis of unconfined flow induced by constant rate. Introduction 2 pumping tests have proved to be one of the most effective ways of obtaining aquifer parameters. Theanalyticalnatureofthemodel forced them to ignore unsaturated flow induced by lowering the water table during the pumping test and to assume that the unsaturated hydraulicconductivity andmoisture. A test interpretation can be made using various analytical models based on simplified assumptions. Pumping 21 test data are presented as timedrawdown or distancedrawdown curves, which are.
The principle of a pumping test is that if we pump water from a well and measure the discharge of the well and the drawdown in the well and in piezometers at known distances from the well, we can substitute these measurements into an appropriate wellflow equation and can calculate the hydraulic characteristics of the aquifer fig ure 2. A slug test for determining hydraulic conductivity of. During the first ten minutes of the unconfined aquifer test, the drawdown is similar to that of a confined aquifer with groundwater mainly being sourced by horizontal flow. Note that drawdown in the observation well is much less than in the pumping well. Pumping test procedures for water withdrawal permit. Time of year the pumping test of unconfined sand andor gravel aquifer wells must be conducted during a time of average or below average seasonal stream flow conditions. Pumping test is conducted to examine the aquifer response, under controlled conditions, to the abstraction of water. A revisit of drawdown behavior during pumping in unconfined. An aquifer test or a pumping test is conducted to evaluate an aquifer by stimulating the aquifer through constant pumping, and observing the aquifers response in observation wells.
The equation for unsteady state flow toward a well in a confined aquifer was established by theis. Suggested operating procedures for aquifer pumping tests it is intended for use by those professionals involved in characterizing sites which require corrective action as well as those which are proposed for ground water development, agricultural development, industrial development, or disposal activities. The aquifer is a sand deposit overlying a thick nonfissured layer of champlain sea clay. Guide to conducting pumping tests 2 wa ter dept h below origina l pr e pu mping static wa ter. As pumping continues, the cone expands and deepens, and the. Typically, this eliminates the months of march, april, and may. Use of these neighbouring wells during the pumping test could affect. Airflow induced by pumping tests in unconfined aquifer. Guide to conducting pumping tests british columbia. Mod01 lec14 unsteady radial flow in confined and unconfined aquifers duration. The pump ing causes a dewatering of the aquifer and creates a cone of depression in the water table. A revisit of drawdown behavior during pumping in unconfined aquifers deqiang mao,1,2 li wan,1 tian.
1237 888 369 45 645 1263 615 752 605 1087 1107 491 225 684 161 188 407 108 1259 1121 219 332 154 1164 1229 398 51 1432 1088 495 202 866 585 1223 249 31 451 40 82