Research about Mt. Desert Island

USGS2005

Using hydrogeomorphic criteria to classify wetlands on Mt. Desert Island, Maine – Approach, classification system, and examples

A wetland classification system was designed for Mt. Desert Island, Maine, to help categorize the large number of wetlands (over 1,200 mapped units) as an aid to understanding their hydrologic functions. The classification system, developed by the U.S. Geological Survey (USGS), in cooperation with the National Park Service, uses a modified hydrogeomorphic (HGM) approach, and assigns categories based on position in the landscape, soils and surficial geologic setting, and source of water. A dichotomous key was developed to determine a preliminary HGM classification of wetlands on the island. This key is designed for use with USGS topographic maps and 1:24,000 geographic information system (GIS) coverages as an aid to the classification, but may also be used with field data. Hydrologic data collected from a wetland monitoring study were used to determine whether the preliminary classification of individual wetlands using the HGM approach yielded classes that were consistent with actual hydroperiod data. Preliminary HGM classifications of the 20 wetlands in the monitoring study were consistent with the field hydroperiod data. The modified HGM classification approach appears robust, although the method apparently works somewhat better with undisturbed wetlands than with disturbed wetlands. This wetland classification system could be applied to other hydrogeologically similar areas of northern New England.

Maine↗

USGS2002

Estimated quantity of water in fractured bedrock units on Mt. Desert Island, and estimated ground-water use, recharge, and dilution of nitrogen in septic waste in the Bar Harbor area, Maine

In 2002, the U.S. Geological Survey, in cooperation with the town of Bar Harbor, Maine, and the National Park Service, conducted a study to assess the quantity of water in the bedrock units underlying Mt. Desert Island, and to estimate water use, recharge, and dilution of nutrients from domestic septic systems overlying the bedrock units in several watersheds in rural Bar Harbor. Water quantity was calculated as the static volume of water in the top 600 feet of saturated thickness of the bedrock units. Volumes of water were estimated on the basis of effective fracture porosities for the five different rock types found on Mt. Desert Island. Values of porosities for the various bedrock units from the literature range more than five orders of magnitude, although the possible range in porosities for most individual rock types is on the order of three orders of magnitude. The static volume of water in the various units may range from a low of 4,000 gallons per acre for intrusive igneous rocks (primarily granites) to 20 million gallons per acre for the Cranberry Island Volcanics, but given the range in porosity estimates, these numbers can vary by orders of magnitude. Water-use data for the municipal water supply in the Town of Bar Harbor (1998-2000) indicate that residential usage averages 225 gallons per household per day. Recharge to the bedrock units in rural Bar Harbor was bracketed using low, medium, and high estimates, which were 3, 9, and 14 inches per year, respectively. Water use in 2001 was about 2.5 percent of the total estimated medium recharge (9 inches per year) in the study area. Dilution of nitrogen in septic effluent discharging to the bedrock aquifer was evaluated for the development density in 2001. On the basis of an assumed concentration of 47 mg/L of nitrogen in septic system discharge, dilution factors in populated rural Bar Harbor watersheds ranged from 4 to 151, for the housing density in 2001. Understanding that ground water in this fractured bedrock system mixes slowly, the fully mixed average nitrate-nitrogen concentrations in ground water estimated for the watersheds ranged from 0.1 to 11 mg/L.

Maine↗