Date of Award

2005

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

P.J. Gerla

Abstract

Pigeon Point lies along the Sheyenne River in the west-central part of the Sheyenne Delta Aquifer, southeastern North Dakota. Groundwater discharges along a north-facing bluff at Pigeon Point and forms springs, seeps, and fens 'hosting atypical boreal species. The Nature Conservancy owns 231 ha at Pigeon Point, a tract that also includes the largest and least disturbed spring-fed stream in the region as well as some of the finest riparian forest in the state. In response to possible future groundwater diversion, the objectives of this study are: 1) to characterize the Sheyenne Delta Aquifer up-gradient from Pigeon Point, 2) to define the recharge capture zone for the springs and seeps, and 3) to estimate the wetland water budget.

Nineteen new and existing water table wells were used to map the configuration of the water table above Pigeon Point. The capture zone is about 3.5 km at its widest and extends southward with decreasing hydraulic gradient to an indeterminate distance. Flow net analysis indicates that 16,000 to 17,000 m3/day of water flow into the Pigeon Point area. Discharge occurs along nearly the entire length of the bluff (1.5 km) from a seepage face with up to 5 m of relief. These springs and seeps coalesce to form four surface water tributaries that were gauged for this study. Discharge to the streams accounts for 25 to 60% of groundwater flow estimated by flow net analysis, suggesting that groundwater movement through the terrace and evapotranspiration account for the remainder. Closure on the water budget is attained when measurement uncertainty is considered.

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