Date of Award

Spring 2025

Project Type

Thesis

Program or Major

Earth Sciences

Degree Name

Master of Science

First Advisor

John Matthew Davis

Abstract

Artificial recharge (AR) is receiving increased attention as a means to manage water resources in the Northeast United States, as growing communities and increasing drought frequency increase demands on groundwater supplies. The water supply system serving the University of New Hampshire and the Town of Durham has implemented an AR system that recharges the small stratified-drift Spruce Hole Aquifer with surface water from the nearby Lamprey River. The system has been online since 2016, and the existing hydrogeological and system monitoring datasets provide the foundation to develop a numerical model capable of replicating dynamic responses to withdrawals and AR infiltration throughout the aquifer. Scenarios of theoretical operating rates are simulated to understand the impact that AR can have on groundwater availability to the production well and groundwater-fed surface water system.The model uses open-source programs that interpolate grid-independent source data files to the model discretization and execute MODFLOW6 groundwater flow simulations. Model calibration to a suite of long-term water level monitoring data is capable of simulating observed groundwater heads to within an average of 1.6 ft of nearly 26,000 observations. Simulations of theoretical operating scenarios suggest that AR can offset the impacts to groundwater availability when the current withdrawal rates are increased by 50%, maintaining heads in the production well and discharge to the nearby Chesley Brook that are similar to those observed at the current operating rates. Surface and groundwater samples are collected, and stable isotope analyses suggest that AR source water can be stored within the aquifer for months after infiltration.

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