Simulated Ground-Water-Flow Responses to Geohydrologic Characteristics, Corinna, Maine

Ground-water-flow simulations of an idealization of surficial and bedrock aquifers of the East Branch Sebasticook River Valley, in Corinna, Maine, were done to test the effects of known or hypothesized geohydrologic characteristics on the local and regional ground-water-flow system. The purpose of the simulations was to develop a better understanding of the aquifer system to aid in planning for the eventual removal of contaminants.

The effects of eight individual geohydrologic characteristics on simulated ground-water flow were compared with a base simulation. The eight geohydrologic characteristics simulated were (1) a northeast-southwest transmissive bedding- plane fracture system, (2) a northwest-southeast valley floor transmissive fracture zone, (3) an upper weathered bedrock transmissive zone, (4) river- and pond-stage changes, (5) river- and pondbottom conductivity changes, (6) multiple withdrawals, (7) a combination of some of these characteristics, and (8) relocation of a pond-outlet stream.

The effects of many of the analyzed characteristics are slight or relatively minor with respect to a simulated bedrock aquifer. The simulated ground-water flow through the bedrock aquifer is a small percentage (about 1 percent) of the total flow to the system; therefore, the effects of most geohydrologic characteristics simulated are minimal in the aquifer. Some characteristics, for example, anisotropy imparted on the bedrock system by a northeast-southwest transmissive bedding-plane fracture system, strongly affect flow patterns in the bedrock aquifer but not in the surficial aquifer. Individually, most of the geohydrologic characteristics evaluated only slightly affect the groundwater flow in the bedrock; however, in combination, these characteristics significantly affected the entire simulated ground-water-flow system. Domestic or remedial withdrawal wells generally had little effect on the regional ground-water-flow system but did affect the local ground-water-flow patterns, which could affect the extent and movement of contaminants.