Aerial Thermography of Groundwater Discharges into a River

This aerial mosaic of several thermorgraphic frames shows a suspected groundwater discharge into a river. Not far south of the river is a municipal water treatment plant. Coincidence? Perhaps...

On 3/28/11 we were simply out collecting thermographic aerials testing out ability to automate their delivery and simply stumbled across this subject. I'd like to ensure that everyone knows we're not charging the municipal wastewater treatment as the source of the discharge, nor are we presuming the discharge is violative. For that reason I have obscured identifying details of the treatment plant.

There is a small road leading north (toward the top of the image) to an older treatment plant. The discharge itself is evident as a warm (nearly white) plume along the south shore of the river. The effluent "hugs" the shore as the river is flowing rapidly at the entry point, but the thermal signature of the effluent persists for some distance downstream.

The coincidence of the rather voluminous discharge and both the old and new treatment plants is suggestive. The relative warmth of the effluent is also notable-it evidently is traveling via a buried conduit and is thus gathering heat from the ground (relative to the surface water in the river, which is some 20 miles from a reservoir replenished by snowmelt).

The following image is a higher resolution inset from the original mosaic:

Something very interesting about this imagery-and a testament to our very contemporary equipment-is the fact that the ambient air temperature was approximately 40°F-hardly an ideal situation for identifying these sorts of phenomena. Another oddity is that these images are actually video frames-we collect the imagery via videographic recording rather than fully radiometric still imaging. This facilitates the capture of thousands and thousands of images with a minimum of in-camera processing (which can interrupt other sequential sensing configurations).

Again-we're not presuming that any violative behavior is being indicated by these images, however, latitude, longitude, and ground elevation datums have been stripped to prevent association with any particular facility.

L