3 Pumping Tests

Question 1

Why perform hydraulic tests?

Answer 1

To learn about aquifer (and aquitard) characteristics:
•permeability (transmissivity)
•storage coefficient
•spatial extent of aquifer
•boundary conditions

🡺 data are required for many planning purposes

Question 2

Preparation of pumping tests

Before pumping:

Answer 2

• measure water levels in pumped well and observation wells

* water level fluctuations? (natural or induced by other wells?)

Question 3

Preparation of pumping tests

Measurements during pumping:

Answer 3

•pumping rate (several times)

•water levels in well and observation wells
measuring interval:
-more often in initial phase
-when to stop? steady-state (no more drawdown)

Question 4

Measuring the discharge of the pump

Answer 4

Possible techniques:
•“bucket and stop watch“ (low Q only)

• differential pressure(e.g. venturi, orifice)
• steady pressure (irrigation nozzle)
• overflow(weir, flume)
• current meters (impeller)

•other methods
(e.g. ultrasonic Doppler effect)

Question 5

Measuring of water levels in wells

using deep meter and water level gauges

Answer 5

Measuring techniques
-water level meter(water contact closes electrical circuit)

• float
• pressure transducer
• air bubble line

-velocity sounding
(ultrasonic, radar)

Question 6

Mathematics of transient (sementara) pumping test evaluation

Answer 6

Boundary conditions:
•aquifer is unlimited in size

• aquifer is homogeneous and isotropic (thickness, porosity, permeability)
• groundwater surface before pumping is horizontal
• well completely screened over whole aquifer thickness
• diameter of well is small (amount of water stored inside well is small)
• pumping rate remains constant during pumping test

🡺 rotational symmetry of cone of depression

Question 7

Recovery test after THEIS & JACOB

Answer 7

Water level in well rises again after pump has been turned off
🡺residual drawdown after shutdown of pump is measured

Question 8

Recovery test after THEIS & JACOB

Advantage

Answer 8

•uses average pumping rate (Q = Qaverage)
🡺not influenced by discontinuous pump operation

•data from pumped well can be used

Question 9

Recovery test after THEIS & JACOB

Disadvantage

Answer 9

calculation of storage coefficient S

not possible

Question 10

Infiltration (slug) tests

Source: Domenico

Answer 10

Especially useful in low permeability rocks ! (where pumping tests are not suitable)

Raising of the well water level through fast injection of water

Measure decreasing water level over time
(until original water level is reached again)

Evaluation methods:
•type curves
-COOPER, BREDEHOEFT &PAPADOPULOS

•semilog straight line methods

• HVORSLEV
• BOUWER & RICE

Question 11

Slug and bail-tests

Source: Sanders

Answer 11

Sudden raise/lowering of well water level through sudden insertion/recovery of a probe

Measuring of decrease/recovery of the well water level over time

Advantage:
•quick and easy execution
Disadvantage:
•limited aerial influence
•influence of well screen and gravel pack

Other methods:
Drill-stem-test, oszillation method etc. ……

Question 12

Step discharge tests

Answer 12

Assessment of well capacity

Usually several successively increasing pumping rates