Methane emissions from groundwater pumping in the USA

Abstract

Atmospheric methane accumulation contributes to climate change, hence quantifying methane emissions is essential to assess and model the impacts. Here, we estimate methane emissions from groundwater pumping in the Los Angeles Basin (LAB), northeastern Pennsylvania, and the Principal aquifers of the USA using the average concentrations of methane in groundwater and annual groundwater pumping volumes. High average methane concentrations, 44.1 mg/L, and extensive groundwater pumping,~3.1 × 10 11 L/a in the LAB, result in the annual emission of~2.9 × 10 −3 Tg of microbial methane. Ethane emissions in the LAB were 3.5 × 10 −6 Tg/a. Lower methane emissions estimated for NE Pennsylvania,~3.0 × 10 −6 Tg/a, reflect lower methane concentrations and groundwater pumping, 0.7 mg/L and 4.27 × 10 9 L/a, respectively. Methane concentrations and groundwater withdrawals, 1.06 × 10 14 L/a, across the USA enabled the estimation of the total emissions of methane from Principal aquifers (92% of total pumping) of 0.044 Tg/a in the year 2000, which represents a small percentage (~0.2%) of the total annual US methane emissions, but a previously unquantified flux in the global methane budget. Globally, groundwater-pumping methane emissions were estimated to be 0.53 Tg/a, 0.2% of global methane emissions, by adopting a global estimate for groundwater extraction, and an average methane concentration in older groundwater of 0.44 mg/L.

A Structured Approach for the Mitigation of Natural Methane Emissions—Lessons Learned from Anthropogenic Emissions

“…If not properly addressed, this may result in (1) overlooked emissions. Some examples are emissions from groundwater pumping with approximated 0.53 Tg CH 4 per year [59] and from drainage ditches, ponds and reservoirs often used for agricultural irrigation [60][61][62]. Another is the recently discovered subglacial methane production and release through the ice sheet bed with meltwater [63].…”

Free‐PhaseGas Detection in Groundwater Wells via Water Pressure and Continuous Field Parameters

“…The occurrence of free‐phase gas (FPG) in groundwater wells can have significant implications in hydrogeological studies, such as affecting measurements of aquifer in situ dissolved gas concentrations (Roy and Ryan 2010), influencing the transfer of greenhouse gases to the atmosphere (Waddington et al 2009; Kulongoski and McMahon 2019), and triggering geyser eruptions (Ladd and Ryan 2016; Hurwitz and Manga 2017). Although not reported in the published literature, gas‐locking of domestic and municipal water wells can also be an issue in areas with abundant groundwater gases (Agriculture and Rural Development 2006).…”

Microbial and Biogeochemical Indicators of Methane in Groundwater Aquifers of the Denver Basin, Colorado

“…13 Furthermore, methane released from groundwater wells presents a small but potentially important local source of methane that contributes to atmospheric greenhouse gas concentrations and degraded air quality. 14 However, the presence of methane in groundwater does not by itself demonstrate stray gas migration, as microbes also generate methane naturally in the subsurface across the globe. 15 Thus, it is critical to properly identify the mechanisms of methane generation and accumulation in groundwater when assessing potential impacts from oil and gas development.…”