Date of Award

5-2001

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Biological Engineering

Advisor

Warren E. Hedstrom

Second Committee Member

Willem F. Brutsaert

Third Committee Member

Andrew S. Reeve

Abstract

The declining population of Atlantic salmon in eastern Maine has brought the wild blueberry industry's irrigation practice of pumping water directly from ponds and streams under scrutiny. Restrictions on pumping from streams has prompted the industry to seek new water resources. One resource with potential to assist the industry to meet its irrigation needs is groundwater. However, preliminary research has shown that groundwater is not capable of completely satisfying irrigation needs. To evaluate the potential that artificially recharging the groundwater during spring run-off to retain the water for later use as irrigation, the groundwater software Visual MODFLOW was applied. Inputs necessary to describe the hydrogeologic properties of the Pineo Ridge delta in Washington County, Maine were made. Once calibration was achieved, the model was used to simulate the effects that the artificial recharge of groundwater (ARG) had on the hydrodynamics of the system. Water was recharged into the aquifer during April and May (225 Lls (4050 gpm) for 45 days) when spring flows generally make water available in nearby ponds, streams, and rivers. Then, in July and August when water is limited and needed for irrigation, the water was removed from the aquifer by pumping. The study site shows potential in that it was capable of supporting 7 pumping wells for 80 days at 8 L/s (125 gpm) each. Once the potential of the Pineo Ridge recharge site had been evaluated, three of the hydrogeologic parameters; hydraulic conductivity, storativity, and distance to a surface-water body, of the aquifer were adjusted to determine the impact that each had on the groundwater system. The goal of this evaluation was to determine the extent that each controlled the overall success or failure of an ARG site. Finally, the values for the parameters that yielded the most favorable results were applied to one simulation. Again, recharge was applied at 225 L/s (4050 gpm) for 45 days during April and May. The resulting simulation characterized an aquifer system capable of supporting 10 wells each yielding 12.8 L/s (200 gpm) for 80 days without reducing the groundwater table in the aquifer by more than 30 cm (1 ft) from observed elevations. From this study some general guidelines with which to evaluate potential ARG sites were determined. Aquifers with hydraulic conductivity values between le-4 m/s (30 ft/day) and 1.8e-4 m/s (50 ft/day) have the greatest potential for this application. Recovery of water through pumping is difficult in aquifers with specific yield values less than 0.2. Finally, the extent that the distance between the recharge site and a nearby surface-water body might assist or hinder the blueberry producers ability to recover the recharged water needs to be evaluated on a case-bycase basis.

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