Contents V 18. Total groundwater withdrawals during July, August, and September calculated with the conjunctive-management model for current rates of streamflow depletion specified for the Hunt River and increased rates of streamflow depletion specified for the Annaquatucket and

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Stratified g lacial drift consisting largely of sand and gravel constitutes the only aquifer capable of supporting continuous yields of 100 gpm (6.3 1/s) or more to individual we lls.The aquifer covers about a third of the 79 mi 2 (205 km 2 ) study area, occurring main ly in stream valleys that are less than a mi le wide. Its saturated thickness is commonly 40 to 60ft (12 to 18 m); its transmissivity is commonly 5,000 to 8,000 ft 2 /day (460 to 740m 2 /day).The aquifer is hydraulically connected to streams that cross it and much of the water from heavily pumped wells wi ll consist of infiltration induced from them. Potential sus tained yield from most parts of the aquifer is 1 imited chiefly by the rate at which infiltration can be induced from streams or low streamflow, whichever is smaller .Ground-water withdrawa ls deplete streamflow; and if large-scale development of ground wate r is not carefully planned and managed , periods of no streamflow may result during dry weather.Potential sustained yield varies with the scheme of well development, and is evaluated for selected areas by mathematically simulating pumping from assu med schemes of we! Is in models of the stream-aquifer system. Results indicate that sustained yields of 5.5, 3.4, 1.6, and 1.3 mgd (0.24, 0.15, 0.07, and 0.06 m 3 /s) can be obtained from the stratified-drift aquifer near Slatersville, Oakland, Harrisville, and Chepachet, respectively. Pumping at these rates wil 1 not cause streams to go dry, if the water is returned to streams near points of withdrawal.A larger ground-water yield can be obtained, if periods of no streamflow along reaches of principal streams are acceptable.Inorganic chemical quality of water in the stream-aquifer system is suitable for most purposes; the water is soft, slightly acidic, and generally contains less than 100 mi lligrams per litre of dissolved sol ids. Continued good quality ground water depends on maintenance of good quality of water in streams, because much of the water pumped from we! Is wil 1 be infiltrated from streams.

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