Seepage meter errors

Abstract

Although the seepage meter has been widely used in limnology, measurement errors are commonly ignored. These errors result in the need for meter correction factors due to flow field deflection and frictional resistance and head losses within the meter and prefilled bags to avoid short‐term influx of water caused by the pulling action of deformed bags. Tank‐test data indicate a ratio of measured to actual inseepage of 0.77 (at inseepage rates <20 mm h−1), with a ratio of meter to interstitial seepage flux of 0.50. Provided these precautions are observed and the adjustment factor is applied, field test “point estimates” of seepage inflow with replicate seepage meters generally have relative root‐mean‐square error(s) <20%. Data from measurements at single locations in tank tests indicate a constant bias and show that, once installed, the actual instrument error is even less (∼5%). These errors are small compared to spatial and temporal components of sampling error typically encountered in the field.

An automated dye‐dilution based seepage meter for the time‐series measurement of submarine groundwater discharge

“…Specifically, bag-derived flow rates may be biased by constriction of flow by the bag and/or by wave-induced motion of the water inside the bag. Bags, partially prefilled with water prior to deployment, yielded more accurate results than empty bags (Belanger and Montgomery 1992). Moreover, the intensive labor involved in the bag method does not lend itself to time series studies on the scale of lunar tidal cycles and seasons.…”

“…As discussed in numerous articles, the volumetric measurement of a seepage rate using a bag on the end of a seepage housing is prone to artifacts (Shaw and Prepas 1989;Belanger and Montgomery 1992;Isiorho and Meyer 1999;Shinn et al 2002). Specifically, bag-derived flow rates may be biased by constriction of flow by the bag and/or by wave-induced motion of the water inside the bag.…”

“…Our comparison was not meant to be a systematic and rigorous study of the two flow methods. This is best carried out in a test tank (Belanger and Montgomery 1992;Isiorho and Meyer 1999). Given the controversy surrounding the interpretation of seepage using bags (see Discussion), we can only speculate that a bag attached downstream of our mixing chamber affected the dye dilution curve by transforming our instrument's design from an open to a closed system.…”

Assessment of submarine groundwater discharge by handheld aerial infrared imagery: case study of Kaloko fishpond and bay, Hawai'i

“…However, seepage meters are labor intensive, problematic when flows are small (Belanger andMontgomery 1992, Shinn et al 2002), and unsuitable for installation on steep, rocky, heterogeneous, and rough coastlines as exist at our study site.…”

Development and deployment of an ultrasonic groundwater seepage meter: a reliable way to measure groundwater seepage

“…This conventional bag method has been successfully applied in various hydrogeologic settings, including lakes, reservoirs, rivers, estuaries, and coasts. Subsequent studies have shown that this method has several limitations [9,10,11,12,13,14]. First, it is cumulative and therefore cannot provide information on the temporal evolution of seepage.…”