INTERACTIONS BETWEEN TIDES, CURRENTS, AND WATER QUALITY IN THE DAMARISCOTTA ESTUARY

Brandon Lieberthal*, Kimberly Huguenard, and Kyah Lucky
 
University of Maine
Civil Engineering Department
5711 Boardman Hall
Orono, ME 04469
brandon.lieberthal@maine.edu

The Damariscotta estuary in downeast Maine houses over one hundred acres of American oyster aquaculture, as well as several acres of blue mussel and seaweed aquaculture, and it is of economic importance to the region. The ecosystem of Damariscotta could be significantly altered by climate change as increasing temperatures, increased precipitation, and rising sea levels affect the transport of particulate matter. This project explores the spatial and temporal variability of water level and current velocity cycles of the estuary, and how they are correlated to measures of water quality such as turbidity, salinity, pH, and oxygen concentration. Over a period of time from July to November 2016, pressure data were collected from twelve points along the river, which were used to compute the tidal elevation time series. In addition, velocity current, water quality, and wind were obtained from a network of buoys.

A statistical analysis was used to study tidal phase propagation and amplification along the river. It was found that constrictions near Fort Island and Clark Cove cause reflecting overtides that contribute to tidal asymmetry, and that bottom friction from shallow water in the northern region of the river is responsible for higher frequency resonance waves. The overtides result in a net volumetric flow

that distributes particulate matter throughout the river. The enclosed figure shows how these overtides become larger in amplitude near the head of the river.

The overtides and tidal asymmetry have an effect on measures of water quality in the river. For example, turbidity is highest during the low tide of the day and salinity is highest during high tide. Low water levels and slow currents near the head of the river result in greater subtidal variability of particulate concentration, with high and low frequency oscillations carrying equal magnitude. In addition, severe rainstorms have a flushing effect on the river, reducing turbidity and salinity but increasing acidity for several days after the storm event. A thorough understanding of Damariscotta's material transport cycle will enhance prediction of the effects of climate change on the health of the aquaculture industry.