Groundwater Pumping Is a Significant Unrecognized Contributor to Global Anthropogenic Element Cycles

Abstract

Quantifying anthropogenic contributions to elemental cycles provides useful information regarding the flow of elements important to industrial and agricultural development and is key to understanding the environmental impacts of human activity. In particular, when anthropogenic fluxes reach levels large enough to influence an element's overall cycle the risk of adverse environmental impacts rises. While intensive groundwater pumping has been observed to affect a wide-range of environmental processes, the role of intensive groundwater extraction on global anthropogenic element cycles has not yet been characterized. Relying on comprehensive datasets of groundwater and produced water (groundwater pumped during oil/gas extraction) chemistry from the U.S. Geological Survey along with estimates of global groundwater usage, I estimate elemental fluxes from global pumping, consumptive use, and depletion of groundwater. I find that groundwater fluxes appreciably contribute to a number of elements overall cycles and thus these cycles were underestimated in prior studies, which did not recognize groundwater pumping's role. I also estimate elemental loadings to agricultural soils in the United States and find that in some regions, groundwater may provide a significant portion (more than 10%) of crop requirements of key nutrients (K, N). With nearly 40% of globally irrigated land under groundwater irrigation, characterizing nutrient and toxic element fluxes to these soils, which ultimately influence crop yields, is important to our understanding of agricultural production. Thus, this study improves our basic understanding of anthropogenic elemental cycles and demonstrates that quantification of groundwater pumping elemental fluxes provides valuable information about the potential for environmental impacts from groundwater pumping.

Global Groundwater Sustainability, Resources, and Systems in the Anthropocene

“…Despite this large volume of groundwater, the fluxes between groundwater and other compartments of the hydrologic cycle are relatively small compared to those on and above the Earth's surface.. While these fluxes are often small, they can be of critical local importance in nutrient (Hayashi & Rosenberry, 2002) and elemental cycling Stahl, 2019), regulation of temperature (Powers, 1999) and maintaining streamflow during low flow periods (Winter, 2007). The various inputs, outputs, boundaries and stores described above interact with each other in a dynamic and non-linear way, creating globally diverse, complex and dynamic groundwater systems, with multiple feedbacks with other parts of the Earth System.…”

Reply to Comment on “Groundwater Pumping Is a Significant and Unrecognized Contributor to Global Anthropogenic Elemental Cycles”

“…I appreciate the interest and discussion stimulated by my paper (Stahl ). The comment by Ferguson and McIntosh is thought provoking and suggests the opportunity for additional research.…”

Drivers of nitrogen and phosphorus dynamics in a groundwater-fed urban catchment revealed by high-frequency monitoring

“…Investment in high-frequency monitoring would greatly benefit the management of urban lowlands with substantial groundwater seepage by elucidating the principle biogeochemical processes and nutrient temporal patterns for realizing efficient mitigation and control of eutrophication. For example, redirecting the drain water effluent into constructed wetlands could be considered a mitigation measure in low-lying areas with artificial water systems that resemble the Amsterdam region, e.g., in cities such as New Orleans, Shanghai, and Dhaka (Li et al, 2009;Nahar et al, 2014;Jones et al, 2016;Stahl, 2019). Centralizing the treatment of discharge water is also recommended, e.g., by harvesting N as phytoplankton from the discharge during spring or filtrating P at the pumping station during winter.…”