Articles | Volume 21, issue 12
https://doi.org/10.5194/hess-21-6031-2017
https://doi.org/10.5194/hess-21-6031-2017
Research article
 | 
30 Nov 2017
Research article |  | 30 Nov 2017

Hydrogeological controls on spatial patterns of groundwater discharge in peatlands

Danielle K. Hare, David F. Boutt, William P. Clement, Christine E. Hatch, Glorianna Davenport, and Alex Hackman

Abstract. Peatland environments provide important ecosystem services including water and carbon storage, nutrient processing and retention, and wildlife habitat. However, these systems and the services they provide have been degraded through historical anthropogenic agricultural conversion and dewatering practices. Effective wetland restoration requires incorporating site hydrology and understanding groundwater discharge spatial patterns. Groundwater discharge maintains wetland ecosystems by providing relatively stable hydrologic conditions, nutrient inputs, and thermal buffering important for ecological structure and function; however, a comprehensive site-specific evaluation is rarely feasible for such resource-constrained projects. An improved process-based understanding of groundwater discharge in peatlands may help guide ecological restoration design without the need for invasive methodologies and detailed site-specific investigation.

Here we examine a kettle-hole peatland in southeast Massachusetts historically modified for commercial cranberry farming. During the time of our investigation, a large process-based ecological restoration project was in the assessment and design phases. To gain insight into the drivers of site hydrology, we evaluated the spatial patterning of groundwater discharge and the subsurface structure of the peatland complex using heat-tracing methods and ground-penetrating radar. Our results illustrate that two groundwater discharge processes contribute to the peatland hydrologic system: diffuse lower-flux marginal matrix seepage and discrete higher-flux preferential-flow-path seepage. Both types of groundwater discharge develop through interactions with subsurface peatland basin structure, often where the basin slope is at a high angle to the regional groundwater gradient. These field observations indicate strong correlation between subsurface structures and surficial groundwater discharge. Understanding these general patterns may allow resource managers to more efficiently predict and locate groundwater seepage, confirm these using remote sensing technologies, and incorporate this information into restoration design for these critical ecosystems.

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Short summary
This research examines what processes drive the location and strength of groundwater springs within a peatland environment. Using temperature and geophysical methods, we demonstrate that the relationship between regional groundwater flow gradients and the basin shape below the peatland surface control where groundwater springs occur. Understanding this relationship will support effective restoration efforts, as groundwater spring locations are important to overall peatland function and ecology.