Using thermal infrared sensing from a UAV/UAS to identify groundwater inflows and guide freshwater wetland restoration

Abstract:

Groundwater-dependent ecosystems depend on groundwater for saturation, ecosystems for wetland plants and creatures, maintenance of wetland soils, and thermal buffering. These ecosystems critically require significant, predictable, and resilient inputs of groundwater in order to persist into the future. Identifying specific locations where groundwater enters a site provides critical information for restoration design, enabling practitioners to maximize the capture and residence time of groundwater inputs to sustain the future wetland.

Many cranberry farms across Massachusetts were created atop historic peat bogs, which have been manipulated and simplified from their natural peatland surface for farming. Specific hydraulic modifications to peatlands include: surface flattening, application of sand layers, construction of large berms to break up farms into manageable chunks, construction of dams, ponds and other water control structures, installation of networks of irrigation piping, digging vast networks of ditches around the perimeters and throughout the bogs for rapid delivery and removal of water, and channel widening and straightening where channels existed. Ultimately, in order to return these farms to a wetland system, all of these human modifications must be undone, or overcome, to restore dominantly wet conditions to the land such that a wetland once again thrives. Step one is to identify the location of groundwater inputs.

One method used to identify the source of water on the surface is analyzing the water isotopes. Where springs and seeps express on the surface, samples are categorized as ground- or surface water, and mapped. Another method used to locate groundwater inputs in the restoration of Foothills Preserve is thermal imaging: Thermal infrared data collected from an unmanned aerial vehicle (UAV; or sensor, UAS) assist researchers mapping the locations of groundwater inputs across the 60-acre site, allowing for site-wide assessment and restoration design for minimal cost. The path of a designed constructed stream channel can easily incorporate these identified points of groundwater input to ensure constant consistent flows through time and resilience of the wetland system. Isotopic and thermal tracers of groundwater locations are consistent across the site.