step-drawdown test pdf

8 Begin the step test. The pumping rate is successively increased for each of several time intervals the water level is measured during each interval and drawdown is calculated for each pumping rate.

Step Drawdown Testing

Step drawdown tests can be used to.

. That due to formation loss and that due to well loss. The step-drawdown in Kruseman and de Ridder 1990 which are stored in the Sheahan file. Knowing B and C we can predict the drawdown inside the well for any realistic discharge Q at a certain time t B is time-dependent.

The maximum design rate of the well. Convert water level measurements to drawdown s ft by subtracting the water level. 1 a pumping rate for a constant-rate test 2 specific capacity defined as the ratio of.

However some authors have used the step-drawdown test to evaluate drawdowns in unconfined hetero-geneous and anisotropic aquifers with good results Helweg 1994. It is a short-term test that can be used to determine. Are rarely encountered during a step-drawdown test and a factor of safety should be applied to the estimated sustainable yield.

Step drawdown test. Recommended steps for a step-drawdown test are based on the maximum design rate of the well and include. A step-drawdown test makes it possible to evaluate the parameters B and C and eventually P.

It is capped by a 45-m-thick clay layer and thus confined. Up to 10 cash back The third step-drawdown test comes from an experimental well that was equipped with a novel screen design made of compacted porous plastic granulate Tholen and Treskatis 1998. The first discharge rate is approximately 50 of the desired rate and each subsequent step increases the discharge between 20 and 25 above the previous.

An understanding of the various factors affecting well efficiency is important because savings in. Graphical solution of multiple step-drawdown test data permits an approximate determination of the two components of drawdown in a pumped well. A constant -rate test is run for 12 to 24 hours and recovery is measured for the same duration as pumping.

The Cretaceous Nubia sandstone aquifer is the main aquifer in East El-Oweinat area along the Egyptian-Sudanese borders and in NE Africa. A type of aquifer test in which the water level in a pumped well is measured while the well is pumped at a constant rate for a given period of time. Aquifer and the step-drawdown test.

It is located in the Horkesgath wellfield near the city of Krefeld Germany Table 1. 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. The pumping rate is then increased to a higher constant rate and the well is pumped until the drawdown stabilises once more Figure 51.

Dr Clark has presented an excellent review of the theory of the step drawdown test and its applications. The aquifer storage coefficient can also be estimated. This content is PDF only.

Please click on the PDF icon to access. The first screen immediately shows the diagnostic plot because only one drawdown value per step is available for this test. 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.

Until a steady state is reached. Multi-well test spreadsheets included in this report are. A short summary of this paper.

In addition to this controversy its application is hindered because the. The Theis method may be applied if the variable discharge rate is replaced by the average of the pumping rates. Usually the step-drawdown test is the first step after a sequence of practical operations carried out for the construc-tion of a new well.

We can then use the relationship between drawdown and discharge to choose empirically an optimum yield for the. A step -drawdown test is conducted for six hours consisting of 3 to 6 steps. 50 of the maximum design rate.

The efficiency of a well is defined. The test should be started at a defined time eg 1000 AM so. Recovery is measured for 12 hours before starting the next phase.

Step-Drawdown Pumping Test Example 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. Hantush-Jacob Leaky Aquifer Method and Distance-Drawdown Methods. If a step drawdown test is done the well should be rested between the step test and the constant-rate pumping test to allow for the water.

The purpose of this communication is to comment on the use of the recovery portion of a step drawdown test to calculate aquifer transmissivity. Generally a step-drawdown test comprises 3 to 5 steps of 60 minutes duration. This in turn permits an engineering estimate of the efficiency of a well.

East El-Oweinat project has been recently considered one of the main agricultural projects in the southwest of. Step drawdown tests can be used to determine the aquifer transmissivity and the well loss component of the drawdown in the pumped well. Full PDF Package Download Full PDF Package.

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. Test may determine if a step drawdown test is needed before the constant rate pumping test is conducted eg in situations where the aquifer conditions are not sufficiently understood. Step -test data are analyzed by Rorabaughs method 1953 and by a graphical method.

The step-drawdown test involved. Also referred to as a variable-rate test the step-drawdown test is one of the most useful assessment tools. Many geohydrologists believe that the step-drawdown test is useful in determining many important characteristics of a well whereas others altogether question its utility.

Select this file from the list of existing files and select Rorabaughs method in the method selection form. 75 of the maximum design rate. 5 Theory of step-drawdown test analysis In a step-drawdown test the well is initially pumped at a low constant rate until the drawdown within the well stabilises ie.

Calculate drawdown at a known pumping rate using the Graphical Method. Calculate elapsed time t min for each water level measurement during a given pumping rate. The distance-drawdown method is an equilibrium or steady-state method thus storage cannot be estimated.

Convert units to minutes and record values in a blank Excel spreadsheet Table 1 Col. The usefulness of the step-drawdown test is outlined and a hypothesis for reduction in specific capacity is offered. The total depth of the well is 400 feet with an open-hole interval of 320 feet.

Step Drawdown Tests Step Tests Aquifer Testing 101