A Stream‐Based Methane Monitoring Approach for Evaluating Groundwater Impacts Associated with Unconventional Gas Development. Issue 4 (11th June 2013)

• Record Type: Journal Article
• Authors: Heilweil, Victor M.; Stolp, Bert J.; Kimball, Briant A.; Susong, David D.; Marston, Thomas M.; Gardner, Philip M.
• Is Part Of: Ground water. Volume 51:Issue 4(2013:Jul./Aug.)
• Page Start: 511
• Page End: 524
• Publication Date: 2013-06-11
• Subjects: Groundwater -- Periodicals; Wells -- Periodicals; Eau souterraine -- Périodiques; Puits -- Périodiques; Grondwater; Eau souterraine; Puits; Electronic journals; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); 551.49
• DOI: 10.1111/gwat.12079
• Languages: English
• ISSNs: 0017-467X

Abstract

<abstract abstract-type="main" id="gwat12079-abs-0001"> <title>Abstract</title> <p id="gwat12079-para-0001">Gaining streams can provide an integrated signal of relatively large groundwater capture areas. In contrast to the point‐specific nature of monitoring wells, gaining streams coalesce multiple flow paths. Impacts on groundwater quality from unconventional gas development may be evaluated at the watershed scale by the sampling of dissolved methane (CH<sub>4</sub>) along such streams. This paper describes a method for using stream CH<sub>4</sub> concentrations, along with measurements of groundwater inflow and gas transfer velocity interpreted by 1‐D stream transport modeling, to determine groundwater methane fluxes. While dissolved ionic tracers remain in the stream for long distances, the persistence of methane is not well documented. To test this method and evaluate CH<sub>4</sub> persistence in a stream, a combined bromide (Br) and CH<sub>4</sub> tracer injection was conducted on Nine‐Mile Creek, a gaining stream in a gas development area in central Utah. A 35% gain in streamflow was determined from dilution of the Br tracer. The injected CH<sub>4</sub> resulted in a fivefold increase in stream CH<sub>4</sub> immediately below the injection site. CH<sub>4</sub> and δ<sup>13</sup>C<sub>CH4</sub> sampling showed it was not immediately lost to the atmosphere, but remained in the stream for more than 2000 m. A 1‐D stream transport model simulating the decline in CH<sub>4</sub> yielded an apparent gas transfer velocity of 4.5 m/d, describing the rate of loss to the atmosphere (possibly including some microbial consumption). The transport model was then calibrated to background stream CH<sub>4</sub> in Nine‐Mile Creek (prior to CH<sub>4</sub> injection) in order to evaluate groundwater CH<sub>4</sub> contributions. The total estimated CH<sub>4</sub> load discharging to the stream along the study reach was 190 g/d, although using geochemical fingerprinting to determine its source was beyond the scope of the current study. This demonstrates the utility of stream‐gas sampling as a reconnaissance tool for evaluating both natural and anthropogenic CH<sub>4</sub> leakage from gas reservoirs into groundwater and surface water.</p> </abstract>