Geohydrology and water quality of stratified-drift aquifers in the lower Connecticut River basin, southwestern New Hampshire

Water-Resources Investigations Report 92-4013

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Stratified-drift aquifers discontinuously underlie 116 square miles of the Lower Connecticut River basin in southwestern New Hampshire, which has a total drainage area of 1,163 square miles. Saturated thicknesses of stratified drift within the study area are locally greater than 400 feet but generally are less. Transmissivities 1ocally exceeds 4,000 feet squared per day but are generally much less. The 20.8 square mile, or 1.8 percent, of the study area identified as having transmissivity greater than 1,000 feet squared per day represents a valuable resource. The geohydrology of stratified- drift aquifers was investigated by focusing on basic aquifer properties, including aquifer boundaries; recharge, discharge, and direction of ground-water flow; saturated thickness and storage; and transmissivity. Surficial geologic mapping assisted in the determination of aquifer boundaries. Data from more than 2,300 wells, test borings, and springs were used to produce maps of water-table altitude, saturated thickness, and transmissivity of-stratified drift. Seismic-refraction profiles were completed at 29 locations in the study area. These profiles aided in the construction of the water-table and saturated-thickness maps. Seismic- reflection data were also collected along 60 miles of the Connecticut River. A stratified-drift aquifer in southern Croydon and northern Newport was analyzed for aquifer yield using transient simulations and a two-dimensional, finite-difference ground-water-flow model. The objective was to estimate the yield after a 180-day period of pumping. Two hypothetical wells were pumped at 1.0 Mgal/d and 0.5 Mgal/d for 180 days respectively. The amount of water available for infiltration was the limiting factor. Results of analysis of water samples from 22 wells and 8 spring show that, with some exceptions, water in the stratified-drift aquifer generally meets the U.S. Environmental Protection Agency's primary and secondary drinking-water regulations.

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USGS Numbered Series
Geohydrology and water quality of stratified-drift aquifers in the lower Connecticut River basin, southwestern New Hampshire
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Water-Resources Investigations Report
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U.S. Dept. of the Interior, U.S. Geological Survey ; USGS Earth Science Information Center, Open-File Reports Section [distributor],
1 v. (various paging) :ill., maps (some col.) ;28 cm. [PGS - 325 p.]