Groundwater Connectivity between Douglas Lake and Carp Creek Based on Fluorescein Dye Studies

Abstract

ABSTRACT Sandy-gravelly deposits are highly permeable and allow groundwater to seep from one lake to another in glacial lake districts such as occur throughout much of Michigan. The springs that form the headwaters of Carp Creek were assumed to have their origins as groundwater seepage from Douglas Lake. A tracer test using a concentrated fluorescein dye solution was conducted during the summer of 2011 to confirm the velocity of groundwater flow from Douglas Lake to a series of springs in Carp Creek. Five springs were monitored from 28 June to 21 September 2011. Dilution of the dye by groundwater was nine orders of magnitude (g−L to ng−L) by the time it reached the springs. The fastest travel times of the dye were ≤ 10 days to all except one spring giving an average observed linear velocity of approximately 100 m d−1 to travel an average distance of 1036 m. Dye was not detectable in the springs after 19 August (day 53 of the experiment). Observed seepage velocities were faster than those predicted from Darcy's Law using hydraulic conductivities for gravel and sand. Douglas Lake and Carp Creek are connected hydrologically through the sand-gravel aquifer and much of the groundwater seepage most likely originates in the deep hole in South Fishtail Bay. This study contributes to our understanding of subsurface connectivity and drainage patterns between glacial lakes of northern Lower Michigan.