INVESTIGATION OF TUFA ON THE SPRING RIVER IN NORTHERN ARKANSAS

In the summer of 2018, an accident involving a recreational boater on the Spring River near Hardy, Arkansas, led to a review of naturally occurring dams in the river. This review of the dams showed that there are over 2 dozen of these structures present, and initial fieldwork suggests these structures may be tufa deposits (tufa dams). The Spring River is fed by Mammoth Spring, a large spring that produces roughly 9 million gallons of water per hour (⁓230 MGD), and is located on the state line of Missouri and Arkansas. Although the appearance of tufa deposits on a spring-fed river coming from a karst region is not unusual, preliminary reviews suggest these tufa deposits may be more common farther away from Mammoth Spring (rather than close to the spring mouth).

Little to nothing is known about the naturally occurring dams in the Spring River. In this study of the dams we aim to answer three questions: (1) Why do we see the tufa dams on the Spring River while they are not found elsewhere in the same karst region? (2) What is controlling the deposition of the tufa at the locations? And (3) Why do they become more frequent further downriver? To answer these questions, a study has been designed to investigate potential structural factors which might lead to water chemistry changes downriver..

A preliminary review of aerial photography done on Google Earth and ArcGIS have shown that the dams continue downriver for several miles past Hardy, AK. Efforts are being made to obtain access to conduct more detailed mapping, perhaps including coring some of the dams, and to collect other data which may indicate possible causes of these tufa dams.