Hydrogeology and Simulated Effects of Ground-Water Withdrawals in the Big River Area, Rhode Island
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Hydrogeology and Simulated Effects of Ground-Water Withdrawals in the Big River Area, Rhode Island By Gregory E. Granato, Paul M. Barlow, and David C. Dickerman ABSTRACT hypothetical ground-water withdrawal scenarios with total ground-water withdrawal rates in the The Rhode Island Water Resources Board is area that range from 2 to 11 million gallons per day. considering expanded use of ground-water resources Streamflow depletion caused by these hypothetical from the Big River area because increasing water ground-water withdrawals is calculated by demands in Rhode Island may exceed the capacity of comparison with simulated flows for the current sources. This report describes the hydrology predevelopment conditions, which are identical to of the area and numerical simulation models that simulated conditions during the 1964–98 period but were used to examine effects of ground-water without withdrawals at public-supply wells and withdrawals during 1964–98 and to describe wastewater recharge. Interpretation of numerical potential effects of different withdrawal scenarios simulation results indicates that the three basins in in the area. the study area are in fact a single ground-water The Big River study area covers 35.7 square resource. For example, the Carr River Basin above miles (mi2) and includes three primary surface-water Capwell Mill Pond is naturally losing water to the drainage basins—the Mishnock River Basin above Mishnock River Basin. Withdrawals in the Carr Route 3, the Big River Basin, and the Carr River River Basin can deplete streamflows in the Mishnock Basin, which is a tributary to the Big River. The River Basin. Withdrawals in the Mishnock River principal aquifer (referred to as the surficial aquifer) Basin deplete streamflows in the Big River Basin in the study area, which is defined as the area of and can intercept water flowing to the Flat River stratified deposits with a saturated thickness Reservoir North of Hill Farm Road in Coventry, estimated to be 10 feet or greater, covers an area of Rhode Island. Withdrawals in the Big River Basin 10.9 mi2. On average, an estimated 75 cubic feet per can deplete streamflows in the western unnamed second (ft3/s) of water flows through the study area tributary to the Carr River, but do not deplete and about 70 ft3/s flows out of the area as streamflow streamflows in the Mishnock River Basin or in the in either the Big River (about 63 ft3/s) or the Carr River upstream of Capwell Mill Pond. Because Mishnock River (about 7 ft3/s). withdrawals deplete streamflows in the study area, Numerical simulation models are used to the total amount of ground water that may be describe the hydrology of the area under simulated withdrawn for public supply depends on the predevelopment conditions, conditions during minimum allowable streamflow criterion that is 1964–98, and conditions that might occur in 14 applied for each basin. Abstract 1 INTRODUCTION Harbaugh, 1988; Harbaugh and McDonald, 1996), commonly referred to as MODFLOW, was used for The Rhode Island Water Resources Board numerical simulations of ground-water flow and ground- (RIWRB) is responsible for developing and protecting water/surface-water interactions. Reports by Craft (2001) the State’s major water resources. Water demand in and Stone and Dickerman (2002) provided much of the Rhode Island is increasing, and the RIWRB is concerned hydrogeologic data for this study on which the numerical that this increasing demand may exceed the capacity of models were developed and calibrated. The models are current sources. In the early 1960s, the State proposed representative of average hydrologic conditions for the 35- construction of a surface-water reservoir in the Big River year simulation period 1964–98. This simulation period Basin in central Rhode Island to meet these growing was selected because it includes the full period of ground- demands. At that time, the Big River Management water-supply withdrawals from the surficial aquifer for Area (fig. 1), which covers an area of about 13.4 mi2, was public supply and a large part of the most substantial established under the responsibility of the Water recorded drought in Rhode Island history (Walker and Resources Coordinating Board, forerunner of the Lautzenheiser, 1991). RIWRB. To date (2003), the U.S. Environmental Protection Agency has not given approval for construction of this reservoir. In the meantime, the RIWRB would like Location and Physiography to develop the largely untapped ground-water resources of The Big River study area covers 35.7 mi2 in the the basin as a temporary alternative to a surface-water towns of Coventry, West Greenwich, Exeter, and a small reservoir. part of East Greenwich, Rhode Island (fig. 1). The area In 1995, the U.S. Geological Survey (USGS) and includes the entire Big River Drainage Basin (30.9 mi2) RIWRB began a cooperative study of the hydrogeologic and that part of the Mishnock River Drainage Basin setting and water resources of the Big River area and the (3.3 mi2) that is upstream from a USGS partial-record effects of ground-water withdrawals from water-supply streamflow measurement site at State Route 3 (station wells on the hydrology of the area (fig. 1). Unconsolidated 01115970). The study area is part of the Seaboard stratified sand-and-gravel deposits are capable of Lowland section of the New England physiographic producing high yields (greater than 300 gal/min) from province (Fenneman, 1938, pl. 1). Landforms are individual wells in the area. These coarse-grained deposits characterized by a series of north- to northwest-trending form the principal aquifer in the Big River Area, which is hills and valleys. The highest point in the basin is on the defined as the surficial aquifer. The aquifer is unconfined southwestern boundary of the study area at an altitude of and is in hydraulic connection with rivers, brooks, lakes, 600 ft on Raccoon Hill (pl. 1). Valley bottoms have ponds, and wetlands. altitudes that generally are below 300 ft; the lowest This report is the third in a series of reports altitude in the study area is 240 ft along the Mishnock produced from the cooperative study. Craft (2001) River where it leaves the study area near Route 3. presented hydrogeologic data collected from July 1996 The Big River drains to the north and is through October 1998; Stone and Dickerman (2002) tributary to the east-flowing Flat River and South characterized the glacial geology and hydraulic properties Branch of the Pawtuxet River (fig. 2). The primary of the stratified deposits underlying the area. tributaries to the Big River are the Congdon, Nooseneck, and Carr Rivers and Bear Brook (fig. 1). The Big River Purpose and Scope flows into the Flat River Reservoir, which is controlled by a dam that maintains the reservoir’s water This report describes the hydrogeology of level at an altitude of about 248 ft. The reservoir, the Big River study area, the development and calibration which is connected to Maple Root Pond, generally of steady-state and transient numerical ground-water-flow is less than 12 ft in depth (Guthrie and Stolgitis, models of the surficial aquifer of the study area, and an 1977) and floods the northern end of the Big River evaluation of the effects of 14 ground-water-withdrawal Basin. The reservoir is the largest surface-water body in scenarios on the hydrologic system. The USGS finite- the study area and is used for recreational purposes only. difference ground-water flow model (McDonald and 2 Hydrogeology and Simulated Effects of Ground-Water Withdrawals in the Big River Area, Rhode Island Flat River 71O40' Reservoir O H 71 35' i ll F a r m R o a Harkney d Brook River Hil l State Route 3 oad O Bear Brook R 41 40' E A S T Hickory G R E E N W I C H Maple Root Pond KC02 C O V E N T R Y Mishnock KC01 W E S T G R E E N W I C H Phelps Reynolds Lake Pond Pond Old Mishnock 95 Capwell Mill npike Pond Tur Mud Bottom Br Carr New London Nooseneck River Carr River Pond ook Big Tarbox Pond Sweet O 41 37'30" River Pond Brook River EXPLANATION Raccoon STRATIFIED DEPOSITS 95 State Route 3 TILL AND BEDROCK W E S T G R E E N W I C H E X E T E R STUDY-AREA BOUNDARY o 7171 45'45' Congdon MASSACHUSETTS BIG RIVER MANAGEMENT 42o 00' RHODE ISLAND AREA BOUNDARY MASSACHUSETTS Millbrook Tur npike KC01 Pond WATER-SUPPLY WELL Providence AND IDENTIFIER 71o 15' 41O35' New London 0 1 MILE CONNECTICUT 0 1 KILOMETER 0 10 MILES 41o 30' STUDY Base from U.S. Geological Survey AREA 0 10 KILOMETERS Coventry Center, RI, 1:24000, photorevision as of 1970, Hope Valley, RI, 1:24000, photorevision as of 1970, GANSETT BAY NARRA Crompton, RI, 1:24000, photorevision as of 1970, Slocum, RI, 1:24000, photorevision as of 1970, SOUND Big River Management Area, Rhode Island Water Resources Board BLOCK ISLAND Polyconic projection, NAD 1927 Figure 1. Location of the Big River study area, distribution of stratified sand-and-gravel deposits, and the boundary of the Big River Management Area, Rhode Island. Introduction 3 71O45' MASSACHUSETTS O 42 00' N i p m B u er Riv l 01111300 c a R c . k h s nc t a o r n B e R iv e RHODE r ISLAND CONNECTICUT Providence Scituate Reservoir 71O15' ver Ri t e STUDY x u Fl t at Rive w r a et P x AREA u S. Branch wt . a P R k c y o a n COW 411 h s B i r e M v i R 01115770 01117000 g i MASSACHUSETTS B r e v i R 01115630 t n t u t H e s n a g 01117800 a EXW 6 r r a N r e iv R 41O30' SNW 6 od o W Kingston 01117500 14266 er iv R ound nd S k Isla uc e at od Pawc Rh EXPLANATION Sound land k Is 01117500 U.S.