Standard Practice for (Analytical Procedure) Tests of Anisotropic Unconfined Aquifers by Neuman Method

Importancia y uso:

5.1 Assumptions: 

5.1.1 The control well discharges at a constant rate, Q.

5.1.2 The control well, observation wells, and piezometers are of infinitesimal diameter.

5.1.3 The unconfined aquifer is homogeneous and really extensive.

5.1.4 Discharge from the control well is derived initially from elastic storage in the aquifer, and later from gravity drainage from the water table.

5.1.5 The geometry of the aquifer, control well, observation wells, and piezometers is shown in Fig. 2. The geometry of the test wells should be adjusted depending on the parameters of interest.

FIG. 2 Cross Section Through a Discharging Well Screened in Part of an Unconfined Aquifer

5.2 Implications of Assumptions: 

5.2.1 Use of the Neuman (1) method assumes the control well is of infinitesimal diameter. The storage in the control well may adversely affect drawdown measurements obtained in the early part of the test. See 5.2.2 of Practice D4106 for assistance in determining the duration of the effects of well-bore storage on drawdown.

5.2.2 If drawdown is large compared with the initial saturated thickness of the aquifer, the late-time drawdown may need to be adjusted for the effect of the reduction in saturated thickness. Section 5.2.3 of Practice D4106 provides guidance in correcting for the reduction in saturated thickness. According to Neuman (1) such adjustments should be made only for late-time values.

5.3 Practice D3740 provides evaluation factors for the activities in this practice.

Note 1: The quality of the result produced by this practice is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this practice are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.

Subcomité:

D18.21

Volúmen:

04.09

Número ICS:

07.060 (Geology. Meteorology. Hydrology)

Palabras clave:

anisotropic aquifers; aquifers; aquifer tests; control wells; groundwater; hydraulic properties; observation wells; transmissivity; unconfined aquifers;