Drought-induced recharge promotes long-term storage of porewater salinity beneath a prairie wetland

Journal of Hydrology
By: , and 



Subsurface storage of sulfate salts allows closed-basin wetlands in the semiarid Prairie Pothole Region (PPR) of North America to maintain moderate surface water salinity (total dissolved solids [TDS] from 1 to 10 g L−1), which provides critical habitat for communities of aquatic biota. However, it is unclear how the salinity of wetland ponds will respond to a recent shift in mid-continental climate to wetter conditions. To understand better the mechanisms that control surface-subsurface salinity exchanges during regional dry-wet climate cycles, we made a detailed geoelectrical study of a closed-basin prairie wetland (P1 in the Cottonwood Lake Study Area, North Dakota) that is currently experiencing record wet conditions. We found saline lenses of sulfate-rich porewater (TDS > 10 g L−1) contained in fine-grained wetland sediments 2–4 m beneath the bathymetric low of the wetland and within the currently ponded area along the shoreline of a prior pond stand (c. 1983). During the most recent drought (1988–1993), the wetland switched from a groundwater discharge to recharge function, allowing salts dissolved in surface runoff to move into wetland sediments beneath the bathymetric low of the basin. However, groundwater levels during this time did not decline to the elevation of the saline lenses, suggesting these features formed during more extended paleo-droughts and are stable in the subsurface on at least centennial timescales. We hypothesize a “drought-induced recharge” mechanism that allows wetland ponds to maintain moderate salinity under semiarid climate. Discharge of drought-derived saline groundwater has the potential to increase the salinity of wetland ponds during wet climate.

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Publication type Article
Publication Subtype Journal Article
Title Drought-induced recharge promotes long-term storage of porewater salinity beneath a prairie wetland
Series title Journal of Hydrology
DOI 10.1016/j.jhydrol.2017.12.005
Volume 557
Year Published 2018
Language English
Publisher Elsevier
Contributing office(s) Northern Prairie Wildlife Research Center, WMA - Earth System Processes Division
Description 19 p.
First page 391
Last page 409
Country United States
State North Dakota
Other Geospatial Cottonwood Lake Study Area
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