Step testing
The test starts with pumping at a low rate with measurement of water levels in the pumping bore. After a set amount of time the pumping rate is increased by an incremental amount and the water level decline is measured for the same amount of time or until the draw down level stabilizes. The test continues with the pumping rate increased by an incremental amount after a set period of time. The test should include measurements from at least three different pumping rates (steps) to provide a minimum degree of accuracy. It is common for the test to be undertaken in 1 day and comprise 4 5 steps.
constant rate tests
It is good practice for the pumping rate used in the test to closely reflect the design pumping rate required by the project. The pumping test will often reach an equilibrium condition in which the water level decline in the aquifer becomes negligible over time. This is caused by the balancing of aquifer inflows such as recharge with aquifer outflows including the water removed during test pumping and referred to by hydrogeologists as the steady-state condition. In the case of a private water supply that may only be run intermittently, a test pumping rate of 1 10l/s may be sufficient to provide meaningful results. The relatively small pumping rate has a small impact on the aquifer and often results in stabilization of water levels within several hours. In the case of large irrigation bores, individual bores may be required to pump at rates in excess of 200l/s and have a large impact on aquifer water levels. Consequently it may take many days for the aquifer to reach steady-state therefore a longer test is advised. The maximum pumping rate is limited by the hydrogeology of the aquifer and may not be known until initial test pumping investigations are undertaken.