Reproducibility of Flowmeter Data Clause Samples

Reproducibility of Flowmeter Data. A concern with any test is the reproducibility of the data. During a borehole flowmeter test, it is a good practice to repeat several flowmeter measurements without changing flowmeter position. If two measurements produce similar means and standard deviations, then the flowmeter system is assumed to be functioning properly. As standard practice, the flowmeter was considered to be performing adequately if two successive measurements produced mean values that overlapped in the range of their standard deviations. In developing a quality assurance plan for field testing, two types of duplicate measurements should be taken. The first type involves two successive measurements without moving the flowmeter. An assumption in comparing these values is that flow conditions in the aquifer have remained constant between measurements so that any differences reflect the uncertainties associated with the measurement technique. The second type involves measurements at the same location but at different times. Over periods of minutes and/or hours, the flow conditions in the aquifer may change. Differences in flow measurements would be primarily produced by variations in the saturated thickness of an unconfined aquifer in response to a pumping test, variations in the pumping rate caused by fluctuations in the performance of the pump, and inability to exactly reoccupy the same elevation in the well. The second type of duplicate measurement reflects the error associated with assuming that the flow conditions are at steady-state.