Measurement of flux at sediment–water interface using a seepage meter under controlled flow conditions

The accuracy of groundwater flux measurement using a seepage meter was evaluated through a series of laboratory experiments under controlled flow conditions. Simulated groundwater influx and outflux rates were measured using a seepage meter, and the results were compared with the known water flux rates in our controlled tank flow system. Differences induced by the use of two different types of collection bag (Types 1 and 2) were also evaluated. The slopes of the trend lines between the controlled influx rate and influx as measured by the seepage meter were 0.6669 (for Type 1 bag) and 0.8563 (for Type 2 bag), suggesting that the groundwater influx rate as measured by the seepage meter may be less than the actual rate. This may be due to the resistance of the collection bags and head loss induced at the tubing orifice. With respect to outflux measurement, the slopes of the trend line were 1.3534 (for Type 1 bags) and 1.4748 (for Type 2 bags), suggesting that the outflux rate as measured by the seepage meter may be more than the actual rate. The size and wall thickness of the collection bag used affected the measured flux rates. This study suggests that, as long as errors can be identified, seepage meters can be a reliable means of studying groundwater–surface water interactions.