Hydrography The greatest amount of total streamflow is carried by the large rivers (fig. 8, table 1). Mean The NAWQA Program evaluates the quality of annual streamflow for the Kennebec River near surface and ground waters and the aquatic biological Waterville, Maine is 7,628 ft3/s. Mean annual flows of communities found in rivers and streams. An the other large rivers are: 6,140 ft3/s in the understanding of the physical aspects of surface- and Androscoggin River near Auburn, Maine; 7,632 ft3/s ground-water systems (the hydrography) is needed in the Merrimack River near Lowell, Mass.; and before these evaluations can be made. The following 934 ft3/s in the Saco River near Conway, Maine. The sections describe in detail the hydrography of the New largest river in the southern coastal Basins, the England Coastal Basins study area. Blackstone River, carries a mean annual flow of 774 ft3/s at Woonsocket, R.I. Surface Water The highest flows in all rivers are in April as the result of spring runoff and snowmelt. Fall rains The study are encompasses four large drainage produce a secondary peak in many rivers and streams basins and many smaller coastal drainages (fig. 7). in the northern part of the study area, as shown by the Most of the rivers that enter the Atlantic Ocean monthly boxplots of streamflow for the Royal River at directly are tide-affected for some distance upstream Yarmouth, Maine; the Saco River near Conway; N.H., from the mouth. The large rivers are the Kennebec the Merrimack River near Manchester, N.H.; and the 2 2 (5,893 mi ), the Merrimack (5,010 mi ), the Androscoggin River near Auburn, Maine (fig. 9). Low 2 2 Androscoggin (3,524 mi ), and the Saco (1,700 mi ) flows for the year are in July, August, and September, (Fontaine, 1979, 1980; New England River Basins when high evapotranspiration rates limit the amount of Commission, 1978, 1980a). Small northern coastal precipitation that becomes available for runoff. In rivers drain 2,500 mi2 and include the Royal northern streams, winter precipitation falls as snow (143 mi2), the Presumpscot (641 mi2), and the and is not converted to streamflow until the spring Mousam (118 mi2) Rivers in Maine (Cowing and thaw, resulting in more pronounced spring stream- McNelly, 1978), and the Piscataqua River (1,020 mi2) flows as shown on the boxplots for the Royal River, in New Hampshire (New England River Basins the Saco River, and the Androscoggin River (fig. 9). Commission, 1980b); collectively these rivers form Flow in rivers in the southern part of the study area, the northern coastal Basins and are grouped with the such as the Ipswich River near Ipswich, Mass., the Saco River Basin in this report (fig. 7). The southern Charles River at Waltham, Mass.; and the Blackstone coastal rivers drain 4,243 mi2 and include the Taunton River near Woonsocket, R.I. is more evenly distributed (530 mi2), the Charles (321 mi2), and the Ipswich throughout the colder months because winter precipi- (155 mi2) Rivers in Massachusetts, the Blackstone tation in the southern areas includes more rainfall River (480 mi2) in Massachusetts and Rhode Island, PFPF (fig. 9). Seasonal variation of streamflow can be and the Pawcatuck River (303 mi2) in Rhode Island, as reduced by extreme regulation of streamflow, as well as many smaller coastal river basins; collectively, shown in the boxplot for the Presumpscot River near these rivers form the southern coastal Basins (fig. 7). Westbrook, Maine (fig. 9). Runoff averages 40 in/yr in the mountainous Streamflow Characteristics areas of New Hampshire and averages 20 to 30 in/yr in the rest of the study area (Krug and others, 1990) Variations in streamflow were determined on the (fig. 8). Most runoff in the study area is during the basis of data collected at USGS streamflow-gaging spring and early summer. Half of the 24.6 in. of stations. The USGS currently (1998) operates 90 annual runoff in the East Meadow River, a tributary to streamflow-gaging stations in the study area. The the Merrimack River in Massachusetts, occurs from gaged sites represent a mix of large and small rivers March to May; the average annual runoff from August and their tributaries. Thirty-one of the active stations through October is less than 0.5 in/mo (Gay and are in Massachusetts, 23 are in New Hampshire, 20 are Delaney, 1980). in Maine, and 16 are in Rhode Island. Thirty-one Human activity has affected streamflow since representative streamflow-gaging stations are shown the colonists settled New England. Some human in figure 8. activities, such as diverting water for municipal

14 Water-Quality Assessment of the New England Coastal Basins in Maine, Massachusetts, New Hampshire, and Rhode Island: Environmental Settings and Implications for Water Quality and Aquatic Biota Figure 7. Generalized hydrography of the New England Coastal Basins study area.

ENVIRONMENTAL SETTING 15 Figure 8. Mean annual discharge, mean annual runoff, and location of selected streamflow-gaging stations in the New England Coastal Basins study area.

16 Water-Quality Assessment of the New England Coastal Basins in Maine, Massachusetts, New Hampshire, and Rhode Island: Environmental Settings and Implications for Water Quality and Aquatic Biota 9.1 8.4 ------1 1 11.5 11.5 11.1 15.2 12.8 13.3 14.6 14.4 12.2 20.6 14.9 12.1 20.2 13.9 15.3 13.2 13.3 14.4 16.4 15.8 17.4 1941 1 1 1 1 1 1 8.8 9.9 6.7 9.0 7.6 9.1 ------1 1 1 11.6 11.0 11.3 11.0 13.5 14.4 13.6 14.1 14.2 15.0 15.3 12.7 17.2 13.4 10.1 16.0 13.8 12.9 16.6 12.2 1965 1 1 1 1 1 Drought years Drought 9.5 8.8 8.4 8.8 9.7 -- -- 1 1 1 1 11.9 15.7 17.1 10.4 29.2 16.1 18.4 14.0 13.8 21.3 16.7 10.5 20.6 13.5 13.5 10.6 10.6 13.4 15.8 15.4 17.2 12.7 1985 1 1 1 1 New Hampshire, and and Hampshire, New

-- -- 28.5 36.1 35.6 32.5 50.9 34.5 39.2 40.4 37.2 51.6 39.0 31.5 43.0 32.5 34.4 26.6 34.7 29.1 29.2 20.3 27.2 37.3 33.5 38.4 36.3 40.1 40.4 1973 1 1 1 1 1 1 1 1 -- 29.3 39.7 36.6 31.7 44.1 35.1 37.8 34.3 37.8 31.6 42.2 34.9 26.1 37.5 27.7 29.6 22.8 29.7 24.9 32.9 23.1 30.5 33.9 36.0 37.5 34.6 36.8 34.8 1978 1 1 1 1 1 1 1 1 Annual runoff in inches, by water year by inches, in runoff Annual Flood years Flood -- -- 31.6 42.8 36.8 50.5 36.8 37.9 38.7 46.2 40.9 47.0 42.8 32.7 42.1 35.4 36.9 29.6 36.6 38.1 36.8 30.2 41.6 39.8 38.7 38.8 37.9 39.8 35.0 1984 1 1 1 1 1 1 1 1 -- 22.2 27.7 25.6 22.8 35.5 25.5 28.0 25.5 26.4 22.2 32.9 26.4 20.9 29.7 20.3 23.1 18.0 22.4 20.3 22.6 16.6 21.6 27.6 23.0 26.1 25.3 26.6 23.7 Mean 1 1 1 1 1 1 1 1 inches annual annual runoff, in in runoff, /s 3 55.1 61.6 73.3 721 971 960 182 200 138 274 925 934 879 282 706 576 187 305 306 175 774 579 349 flow, flow, Mean 4,445 7,628 6,137 1,360 5,273 7,632 in ft annual annual stream- 1930-96 1925-96 1928-79 1987-96 1928-96 1994-96 1964-96 1988-96 1929-96 1913-24 1931-96 1949-96 1975-95 1929-96 1916-96 1934-96 1903-96 1937-96 1936-96 1935-96 1923-96 1930-96 1937-96 1903-09 1931-96 1939-96 1966-96 1925-96 1912-13 1940-96 1929-96 1940-96 1939-96 record in in record Period of of Period water years 2 69.6 96.9 73.5 34.7 30.3 43.3 91.2 353 516 572 141 577 385 452 183 622 471 435 125 183 251 416 295 200 area, in mi in 2,715 5,179 3,263 3,092 4,635 Drainage Drainage station station Gaging Gaging number 01111500 01112500 01118500 01116500 01064118 01100000 01102000 01103500 01104500 01105000 01105730 01109000 01046500 01047000 01048000 01049000 01049205 01054200 01059000 01055000 01057000 01060000 01064500 01065500 01073500 01076500 01081000 01092000 01096500 /s, cubic feet per second; --, no data available;Locations shown on figure 8.] 3 Gaging station name station Gaging Streamflow characteristics for selected gaging stations in the New England Coastal Basins study area, in Maine, Massachusetts, Maine, in area, study Basins Coastal England New the in stations gaging selected for characteristics Streamflow Runoff values significantly affected by water-useactivities andarenot representative of natural conditions. 1 , square miles; ft miles; square , 2 N.H. Manchester, Kennebec River at Bingham, Maine at Bingham, Kennebec River Maine North Anson, River at Carrabassett Maine Mercer, near River Sandy Maine Pittsfield, near River Sebasticook Maine Waterville, near River Kennebec Maine Gilead, at River Wild Androscoggin River nearAuburn, Maine Maine Swift River Roxbury, near Maine Paris, South River near Androscoggin Little Maine Yarmouth, at River Royal Presumpscot Maine River near Westbrook, Saco N.H. River near Conway, Maine Ossippee at Cornish, River LampreyNewmarket, near N.H. River N.H. Plymouth, at River Pemigewassett N.H. at River Tilton, Winnepesaukee Merrimack below River nearFalls Goffs NashuaPepperell, Mass. River at East Mass. at Lowell, Merrimack River nearIpswichRiver Ipswich, Mass. Mass. at Dover, Charles River Mass. at Waltham, Charles River Neponset River at Norwood,Mass. Indian Head River at Hanover, Mass. Mass. Norton, near River Wading R.I. Forestdale, River at Branch R.I. near Woonsocket, River Blackstone R.I. at Westerly, Pawcatuck River R.I. at Cranston, Pawtuxet River Table 1. Table Rhode Island [mi

ENVIRONMENTAL SETTING 17 Figure 9. Distribution of monthly streamflows for selected gaging stations, for water years 1973-93 unless otherwise noted, in the New England Coastal Basins study area. Locations of stations shown on figure 8. Eight-digit number in upper corners of plot area are gaging-station numbers.

18 Water-Quality Assessment of the New England Coastal Basins in Maine, Massachusetts, New Hampshire, and Rhode Island: Environmental Settings and Implications for Water Quality and Aquatic Biota drinking-water supplies, result in reducing the amount coastal Basins had the largest number of dams (697) of water flowing in a stream. Use of streamflow for (table 2). Almost 36 percent of all dams were used for hydroelectric power generation can regulate the timing recreation, 18.8 percent for water supply, 17.5 percent and magnitude of yearly low and high flows without for hydroelectric power generation, and 7.8 percent for affecting the total flow, and often creates artificial high irrigation. The rest of the dams were used for flood and low flows on a daily basis. Flood-control control (7.3 percent), as fire ponds (1.2 percent), or reservoirs diminish the magnitude of yearly high other uses (10.3 percent) (table 2). Location of dams flows. Many rivers and streams in the study area are from the top three categories are shown in figure 10. affected by more than one of these activities. In general, most of the hydroelectric power dams are Currently, most of the unregulated rivers are in the in the northern part of the study area, and recreational White Mountains physiographic section (fig. 2), but a and water-supply dams are primarily in the southern few small streams in the rest of the study area remain and central parts (fig. 10). unregulated. The largest unregulated rivers include the The effects of reservoirs, impoundments, and Sandy River (Kennebec River Basin) and the Swift lakes on streamflows can be seen in data collected River (Androscoggin River Basin) (table 1; fig. 7). during April 1987, when widespread flooding caused The timing and magnitude of yearly low flows record or near-record flows, including those in the (base-flow regulation) and high flows (peak-flow Saco River near Conway, N.H. and the Pemigewassett regulation) are regulated in most of the medium-sized River at Plymouth, N.H. (fig. 11). While streamflow rivers and all of the large rivers. Peak and baseflow is in these and other unregulated basins increased and regulated by storage reservoirs and hydropower dams. decreased swiftly during this flood, flows in nearby There has been a shift in water-management practices rivers of similar sizes that had significant storage (the in the large, northern river basins in the study area. Ossipee River at Cornish, Maine and the Winnipe- From the mid 1800s to mid 1960s, storage was used to saukee River at Tilton, N.H.) were relatively increase flows for driving logs downstream, but since unaffected by the flood (fig. 11). the 1960-70’s storage is used for flood control and for Large and small hydroelectric power dams also providing consistent flows for power generation for produce large shifts in streamflows on a daily basis as industrial users and commercial electricity providers. water is released to provide power during peak Thus, large peaks in flow are reduced, as water is held electricity-use hours and held back later in the day back in the spring, and normal summer to fall low during low electricity use (fig. 12). The degree of flows are increased as this stored water is released daily-streamflow regulation at a location depends on throughout the year. its proximity to upstream hydropower dams and There were more than 1,600 dams throughout whether those dams are managed in such a way as to the study area in 1996 (U.S. Army Corps of Engineers, cause large shifts in flow throughout the day. Daily- 1996). The Androscoggin River Basin had the streamflow regulation generally has a negative impact smallest number of dams (91), whereas the southern on aquatic habitats.

Table 2. Summary of dams, by major river basin, in the New England Coastal Basins study area, in 1995-96 [Data from U.S. Army Corps of Engineers

Number of dams by major category or purpose

River basin Water Fish and Flood Hydro- Fire Recreation Irrigation Other Total supply wildlife control electric pond Kennebec 3 5 5 54 12 9 0 9 97 Androscoggin 9 3 7 53 11 1 0 7 91 Saco and northern coastal 18 7 7 73 71 6 0 23 205 Merrimack 100 1 53 93 232 1 5 52 537 Southern coastal 176 6 48 12 255 2 122 76 697 Study area total 306 22 120 285 581 19 127 167 1,627

ENVIRONMENTAL SETTING 19 Figure 10. Location of dams used for recreation, water supply, and hydroelectric power generation in the study area. Data from the U.S. Army Corps of Engineers.

20 Water-Quality Assessment of the New England Coastal Basins in Maine, Massachusetts, New Hampshire, and Rhode Island: Environmental Settings and Implications for Water Quality and Aquatic Biota Figure 11. Selected storm hydrographs from unregulated and regulated streams and lakes for a large runoff event (March-April 1987) in the New England Coastal Basins study area in Maine, Massachusetts, Rhode Island, and New Hampshire, 1987.

Figure 12. Daily streamflow regulation on the Kennebec River at Bingham, Maine, June 18-21, 1995.

ENVIRONMENTAL SETTING 21 Urbanization, which creates increased demands thunderstorms or hurricanes. The “Great Hurricane of on water resources, has resulted in base-flow depletion 1938” resulted in the worst natural disaster in New in a number of rivers in eastern Massachusetts and England (Paulsen and others, 1940). The flood was Rhode Island. Two examples of base-flow depletion caused by heavy rainfall followed by a hurricane and in eastern Massachusetts are in the Charles River an ocean storm wave. Another major flood occurred Basin and in the Ipswich River Basin. In the Charles in April 1987, primarily across the northern part of the River Basin, withdrawals and diversions for drinking study area. This flood caused the peak flow record of water have reduced the average runoff in the basin 186,000 ft3/s for the Kennebec River at Sidney, Maine above Waltham, Mass., to just 16.6 in/yr (table 1). The (Nielsen and others, 1994). Years with the highest nearby Indian Head River basin, which has fewer amounts of total runoff (1984, 1978, and 1973) had demands on the surface-water system, has an average approximately 25 to 35 percent higher runoff than the annual runoff of 27.6 in/yr at Harvard, Mass. A mean annual runoff for most basins (table 1). comparison of the monthly flows in the Charles River Droughts are more difficult to define than floods upstream (at Dover drainage area) and downstream (at because they have no distinct beginning or end. Yet Waltham drainage area) (fig. 9) shows that the flow in they can be quantified by examining the frequency of the river does not increase downstream as expected less-than-average precipitation. A major prolonged because of these diversions. drought in 1961-69 resulted in the drought of record in A combination of surface-water withdrawals New England. This drought had a serious effect on and ground-water pumping lowered baseflow in the agriculture and water supply in the region. Ground- Ipswich River Basin. Towns in the headwaters of the water storage, the primary source of streamflow basin rely on wells for drinking-water supplies. The between rainfall events (Barksdale and others, 1966), wells are completed in coarse-grained sand and gravel was also severely depleted. Ordinarily in New aquifers that are in direct hydraulic connection with England, ground-water storage is replenished during the river. During the summer of 1996, 15 to 20 mi of each non-growing season. This depletion was the river ran dry because ground-water pumping had observed over the winter of 1964-65 and resulted in induced so much water from the river into the aquifer record-low streamflows during 1965, the driest year (D. LeVangie, Massachusetts Department of Environ- ever recorded in the study area. Other periods of mental Management, Water Supply Division, oral drought were from 1939-44, 1947-50 (Hammond, commun., 1996). Farther downstream in the Ipswich 1991; Maloney and Bartlett, 1991; and Wandle, 1991), River basin, towns rely on surface water for their and from 1980-81 (Walker and Lautzenheiser, 1991). drinking water. From November to May, water is In the northern part of the study area, years with the diverted out of the river into reservoirs for drinking lowest total runoff (1985, 1965, and 1941) have 50 to water. Also, none of the wastewater generated in the 65 percent of the average annual runoff (table 1). This basin is returned to the Ipswich River. compares to only 40 to 55 percent of the average annual runoff in the southern part of the study area, Floods and Droughts where diversions of water out of the basins leaves less of the total water budget for instream flow. Although annual peak flows generally are in the spring, major flooding can occur at any time during Lakes, Reservoirs, and Wetlands the year. Typically, spring floods are caused by intense rainfall and by the melting of snow. The flood There are hundreds of lakes, ponds, reservoirs, of spring 1936 was caused by intense rains and and wetland areas of various sizes throughout the unseasonably warm weather that melted the snowpack. study area (table 3, Anderson and others, 1976). The The severity of the flood was increased by ice jam two largest natural lakes are Moosehead Lake break-ups in the rivers and a surge in runoff because (124 mi2) in Maine and Lake Winnipesaukee (78 mi2) the soil was frozen and impermeable. This flood in New Hampshire (fig. 7). The greater the number resulted in a peak discharge of 161,000 ft3/s for the and total area of lakes, reservoirs, and wetlands in a Merrimack River near Lowell, Mass. (Station basin, the greater the natural potential for storage of 01100000, fig. 8; Gadoury and others, 1994). Floods runoff during storms (Benson, 1962). Additional in the summer and fall are caused primarily by storage potential may be provided by flood-control

22 Water-Quality Assessment of the New England Coastal Basins in Maine, Massachusetts, New Hampshire, and Rhode Island: Environmental Settings and Implications for Water Quality and Aquatic Biota

Table 3. Numbers and total areas of lakes and wetlands greater than 0.1 square miles in the major river basins of the New England Coastal Basins study area in Maine, Massachusetts, New Hampshire, and Rhode Island [mi2, square miles; data from Geographic Information and Retrieval System land cover data base (Anderson and others, 1976)]

Lakes Wetlands (and reservoirs) River basin Number of lakes Total area of lakes, Percent of basin Total area of wet- Percent of basin 2 2 greater than 0.1 mi2 in mi area in lakes lands, in mi area in wetlands Kennebec 221 335 5.6 241 4.1 Androscoggin 97 133 3.8 68 1.9 Saco and northern coastal 156 137 3.3 109 2.6 Merrimack 251 174 3.5 55 1.1 Southern coastal 269 95 2.3 151 3.6 Study area total 994 874 3.8 624 2.7 reservoirs and other reservoirs that increase the natural Aquifers potential by drawing water down below the There are three main types of aquifers in the uncontrolled outlet. Based on the area of lakes, study area—stratified drift, till, and bedrock. The reservoirs, and wetlands, the Kennebec River Basin highly permeable, relatively shallow (less than 100 ft), has almost twice the amount of natural storage discontinuous stratified-drift aquifers that occupy most potential as the other basins. The Southern coastal river valleys in New England are the principal source Basins have the smallest area of lakes and, therefore, of drinking water for many communities that use ground water. Glacial-till aquifers are characterized the smallest amount of natural potential for storage of by low permeability but can supply sufficient water to surface-water runoff during storms (table 3). shallow wells for households and farm use. Fractured- Lakes support extensive recreational activities. bedrock aquifers are the primary source of drinking Lake Winnipesaukee in New Hampshire (fig. 7) and water to rural households and are an important source Sebago Lake in Maine (fig. 7) have evolved over the of water to a few public-supplied, commercial and past century into popular recreational centers that industrial users. support a large seasonal population and contain A digital compilation of the sand and gravel extensive shoreline residential developments. resources for the States of Maine, New Hampshire, Massachusetts, and Rhode Island (Marvinney and Moosehead Lake (fig. 7), and other large, remote lakes Walters, 1993; Koteff, 1993; and Stone and Beinikis, in Maine and New Hampshire are still relatively 1993; Cain and Hamidzada, 1993) was used to undeveloped. Recently, the U.S. Fish and Wildlife determine the extent of stratified-drift deposits Service (1991) established the Lake Umbagog (fig. 5b). Stratified-drift deposits cover 21 percent of National Wildlife Refuge in the headwater region of the study area and range from 3.7 percent of the the Androscoggin River Basin in Coos County, N.H. Kennebec River Basin to 53 percent of the southern and Oxford County, Maine. The Refuge was coastal Basins (fig. 5b). established primarily to protect the pristine lake from Stratified-drift aquifers consist mainly of sand and gravel deposited in layers by meltwater streams future shoreline development and to protect flowing from the retreating glacial ice. The areal endangered wildlife and plant species and their distribution, thickness, and hydraulic properties of habitats. stratified-drift aquifers are directly related to their mode of deposition. Most stratified-drift aquifers in Ground Water the study area formed in a glacial-lake environment in inland and upland areas, in a marine environment near Ground water is an important source of water coastal areas north of Boston, Mass., and as large for streams and lakes and is used for domestic, public, outwash plains in the Cape Cod region. Stratified-drift commercial, and industrial water supplies. It is aquifers that contain significant amounts of saturated, available in highly variable quantities in all the coarse-grained ice-contact and outwash deposits can geologic units of the study area (table 4). yield high quantities of water (table 4).

ENVIRONMENTAL SETTING 23 Wells Wells 4 /d. 2 in Maine, Massachusetts, Massachusetts, Maine, in /d, with a median of only 200 ft 200 only of median a with /d, 2 moraine deposit that a wellscreened is in. Transmis- morainal differing in screened wells 114 from sivity 15 - from ranged Island, R.I., on Block units 17,5000 ft water to wells, but can contain lenses of sand and and sand of lenses contain can but wells, to water be could yield moderate of wells which from gravel developed. Glacial-lake deposits, wherefound, act as buried deposits permeable more to unit confining a them. overlying or beneath Marine clays are notasignificant slowly. aquifer and can act as a confining unit to more permeabledeposits buried beneathor overlyingthem. are commonly used to supplydomestic drinking water. drilled, or driven wells and to springs. Largest yields yields Largest springs. to and wells driven or drilled, thickness saturated the where areas in wells from are large, thedepositsis are coarse grained, and in hydraulic contact with a nearby surface-water body as a source of induced recharge. plies of ground water in the study area,especially in areas where the saturatedthickness thelarge, is deposits are coarse grained, well sorted,and in hydraulic contact with a nearby surface-water body as a source of induced recharge. Under the mostfavor- gal/min 1,500 to more than from 500 conditions, able of water can be obtained from individual, gravel- packedwells screened in these deposits. Yields depend greatly on the lithologic unit within the the within unit lithologic the on greatly depend Yields These depositsare too finegrained to yield significant Yields small to moderateYields amounts of water to dug, 4 ft/d in ft/d -7 Specific yield is approxi- is yield Specific 1 Specific yieldis negligible. Poros- 2 Hydraulic propertiesHydraulic characteristics water-bearing General 1,000 ft/d for outwash and ice-contact deposits. A Newin aquifers study stratified-drift of detailed Hampshire showed that the calculatedhydraulic sand fine to very-fine well sorted, for conductivity is sand 12 medium sorted ft/d; about about is well sand ft/d; 51 is well coarse to very-coarse sorted about 970 ft/d;andgranules (or gravel) can ft/d. 1,000 exceed clays. marine ity of fine sand ranges from 24 to 36 percent. In In percent. 36 to 24 from ranges sand fine of ity conduc- hydraulic and increases porosity general, tivity decreases with decreasing particlesize for glacial sediments. reported hydraulic conductivity values ranging ranging values conductivity hydraulic reported from 3 - 2,100 ft/d, withamedian of 27ft/d. mately 0.2. Porositycoarse of gravel rangesfrom 24 to 36 percent. 4 ft/d. is about sand fine very ft/d; 1 than less ally Hydraulic conductivity is as low as 2.3x10 as low is as conductivity Hydraulic 0 - 2000 - rangesfrom (k) 35 conductivity Hydraulic - 1000 water release and low permeability have clays Marine 0 - 0 - 150- 2800 gener- are clay and silt of conductivities Hydraulic sup- large of source potential best the are deposits These in feet 0 - 1,000study A of morainal aquifers on Block Island,R.I., Range in Range in thickness, /d, feetsquared per day] 2 --Deposits --Composed com- of --Dark-blue to gray silt, silt, gray to --Dark-blue --Well to poorly sorted, sorted, poorly to --Well --Stratified deposits of sand sand of deposits --Stratified These deposits are in the southern- the in are deposits These 3 Geologic units, hydraulic properties, and general water-bearing characteristics in the New England Coastal Basins study area, study Basins Coastal England New the in characteristics water-bearing general and properties, hydraulic units, Geologic Geologic and occurrence unit Geologic clay and fine sand; tan where weathered. Containlayers of sand and gravel. Under- in out crop may and deposits outwash lie stream valleysto upabout 400 feet above locations). sea 5afig. general (see for level and gravel in outwash plains and valley valley and plains outwash in gravel and Maine in altitude feet 400 Below trains. andHampshire,New outwash can overlie marine orlacustrine deposits. plex, glacially deformedsediments of which till and clay, silt, gravel, sand, locally overlie sand and gravel deposits at the heads of promorainal large outwash plains. most part of thestudy area (see fig. 5a). stratified deposits of sand, gravel, and cob- Land boulders. silt some and bles, with forms include eskers, kames, kame deltas, extensive an Not terraces. kame and deposit in the study area. fine and silt, clay, of blue-gray consist sand;may contain lenses of mediumsand. in composition similar are deposits These general 5a for (see fig. deposits marine to locations). Outwash deposits Outwash deposits clays Marine deposits moraine End Ice-contact deposits deposits (lacustrine) Glacial-lake NewHampshire, and Rhode Island 4. Table [ft/d, foot per day; gal/min, gallons per minute; ft

24 Water-Quality Assessment of the New England Coastal Basins in Maine, Massachusetts, New Hampshire, and Rhode Island: Environmental Settings and Implications for Water Quality and Aquatc Biota The . Yields of wells that that wells of Yields . High-yielding wells in frac- in wells High-yielding 6 in Maine, Massachusetts, Massachusetts, Maine, in In Massachusetts, sedimentary- Massachusetts, In 9 10 and have low porosity. Theycontainand have recoverable low porosity. water in secondary openingssuchasjoints, fractures, and bedding or cleavage planes. The water in frac- tured bedrock aquifers is generally confined. in Yields bedrock wellsdepend on size, the number, and degree fractures of water-bearing interconnection of tured bedrock are relatively rare; only 2 percent have have percent 2 only rare; relatively are bedrock tured yieldsgreater than 100 gal/min tap bedrock aquifers in Rhode Island commonly range from 1 to 20 gal/min. water slowly and theyield of dug wells is small once Dug out. in the casing well pumped water is stored of little periods dry to go during likely are in till wells typically till in wells of Yields precipitation. no or gal/min. 5 to 1 from range (over wells drilled inventoried of yield average 13,700)is 14.3 gal/min. rock aquifers have higher median yields (12 gal/min) gal/min) (12 yields median higher have aquifers rock com- and gal/min) (6 aquifers crystalline-rock than of yields median have wells industrial or mercial gal/min. 30 Bedrock formations are dense, relatively impermeable, impermeable, relatively dense, are formations Bedrock Till can be a source of water to dug wells. Till transmits transmits Till wells. dug to water of source a be can Till The The 5 Manycrys- 8 Numeric 7 2 5 to 0.01percent. Hydraulic propertiesHydraulic characteristics water-bearing General -5 to 2.8 ft/d. Cross-sectional models over a a over models Cross-sectional ft/d. to 2.8 -4 porosities and specific yields of these tills ranged ranged tills these of yields specific and porosities from 22.1 to 40.6 percent and from 3.9to 31.2 percent, respectively. scale of several miles in fractured crystalline bed- White the in relief high to of moderate rock physio- England New the of section Mountain graphic province indicate that the hydraulic con- ft/d. 0.086 than is less ductivity that the horizontal hydraulic conductivity of tills of conductivity hydraulic horizontal the that metamorphic igneous (crystal- and from derived 65 ft/d. 0.004 - from rocks line) ranged ers (1993) indicated that the hydraulic conductiv- from range bedrock crystalline in fractured ity 2.8x10 Mirror near flow ground-water of modelling conductivi- hydraulic that indicates N.H., Lake, ties are about 0.09 ft/d for bedrock aquifers hilltops. and hillsides upper beneath talline rocks have a high number of fractures but areconnected.few Therefore, poros- the effective inter- of percentage the as is defined which ity, connected pore space, is generally much less than ranges and rocks crystalline of porosity total the from 5.0x10 Single-hole hydraulictesting doneby Hsieh and oth- 6 0 - 325 showed New A England of till in southern study in feet drilled is wells drilled with feet, 309 greater than wells of percent 75 feet 400 than less in depth. Range in Range in thickness, Average depth of of depth Average /d, feetsquared per day] 2 —Continued Veeger and Johnston, 1996. Veeger in --Bedrock formations --Till, the most extensive glacial glacial extensive most the --Till, Geologic units, hydraulic properties, and general water-bearing characteristics in the New England Coastal Basins study area, study Basins Coastal England New the in characteristics water-bearing general and properties, hydraulic units, Geologic Geologic and occurrence unit Geologic Moore and others, 1994. Domenico and Schwartz, 1990. StoneSirkin, and and Johnston, 1996. Veeger Melvinand others, 1992. Data from the Site Inventory U.S. Geological Ground-Water data Survey’s base. Harte, 1992. Tiedeman and others, 1997. Johnston,1985, p. 374. HansenSimcox, and1994. 1 2 3 4 5 6 7 8 9 10 consist of a variety of igneous and meta- and igneous of variety a of consist morphic rocks. Igneous rocks include granite, pegmatite, and granodioritewith or intru- volcanic basic of amounts smaller sive rocks. Metamorphic rocks consist largely of metamorphosed sedimentary phyllite, gneiss, schist, include and rocks quartzite, and slate. Bedrock formations valley steep and ridges, hills, on outcrop walls. deposit in the study area, is an unsorted, sand, silt, clay, of mixture unstratified gravel, angularcobbles, and boulders. whereparticularly few feet, Below first the very and clay-rich commonly is till thick, upland in bedrock the covers Till dense. com- and thicknesses varying in areas monly underlies stratified-drift deposits in areas. lowland other and valleys Crystalline Bedrock Crystalline Till deposits Till NewHampshire, and Rhode Island Table 4. Table [ft/d, foot per day; gal/min, gallons per minute; ft

ENVIRONMENTAL SETTING 25 The largest sole-source aquifer in the study area The Rhode Island Water Resources Board has is the Cape Cod glacial aquifer, which covers 440 mi2 identified 21 high-yielding stratified-drift aquifers, in southeastern Massachusetts (fig. 5b). The aquifer is termed ground-water reservoirs, with transmissivity composed of extensive outwash deposits overlying and equal to or exceeding 4,000 ft2/day and saturated interbedded with layers of lacustrine clay, silt, very thicknesses equal to or exceeding 40 ft (Trench, 1991). fine sand and till. Combined, the glacial deposits These ground-water reservoirs represent only a small range in thickness from 100 ft at the western end of the fraction of the total area underlain by stratified drift in peninsula near the Cape Cod Canal to about 1,000 ft at Rhode Island. High-yielding public-supply wells tap the northern end near the town of Truro (Leblanc and many of these ground-water reservoirs. A typical others, 1986). The water table of the aquifer is public-supply well may yield 700 gal/min in the dominated by six hydraulically independent flow cells deeply saturated, permeable areas (Johnston, 1985). or mounds. Ground water flows radially from the Fractured-bedrock aquifers primarily store and center of the flow cells towards the Atlantic Ocean or transmit water through intersecting fractures (table 4; ocean inlets. Analysis of the aquifer system shows fig. 13). These fractures were formed as a result of that approximately 270 million gallons of water flows cooling stresses in magma, tectonic activity, erosion of through the six cells on a daily basis (Olcott, 1995). In overlying rock, and the freeze-thaw activities of 1985, the aquifer provided water to 128 municipal glacial ice sheets that once covered New England wells and more than 20,000 private wells (Persky, (Hansen and Simcox, 1994). Brittle and coarser- 1986). grained rocks, such as granite and basalt, generally The USGS and the State of New Hampshire have wider and more continuous fractures than those conducted a cooperative program from 1983 to 1995 of finer-grained rocks such as schist and gneiss. Most to assess the State’s stratified-drift aquifers, which bedrock ground-water supply wells in the study area included a description of the areal extent, are less than 700 ft deep. Generalized hydraulic geohydrology, potential yield, and quality of water in properties and aquifer characteristics of fractured- these aquifers (Medalie and Moore, 1995). The largest bedrock aquifers are summarized in table 4. stratified-drift aquifer in the State is the Ossipee Lake aquifer in the upper Saco River Basin in east-central New Hampshire (Moore and Medalie, 1995) and west- Recharge, Discharge, and Ground-Water Levels central Maine (Tepper and others, 1990). This aquifer Ground water is recharged by precipitation that is an example of a valley-fill system formed in a infiltrates the land surface and percolates through the glacial-lake environment. Stratified-drift landforms in soil layer to the water table, which is the upper surface the Ossipee Lake aquifer include eskers, kames, of the saturated layer (or saturated zone). The water outwash, fine-grained lacustrine, and alluvial deposits. contained in the saturated zone moves in the direction The USGS, in cooperation with the Maine of decreasing head from recharge areas to areas of Department of Conservation, Maine Geological ground-water discharge. This usually corresponds to Survey, and the Maine Department of Environmental areas of topographic uplands to areas of topographic Protection, has been mapping Maine’s “significant” lowlands (fig. 13). The rate of ground-water flow is sand and gravel aquifers since 1981. One well-studied dependent on the hydraulic conductivity of aquifer aquifer, the Little Androscoggin aquifer in materials and the hydraulic gradient. southeastern Oxford County, Maine, is an example of Most of the recharge in New England is in late a valley-fill aquifer system that formed in a lowland autumn and early spring, when precipitation is greatest bedrock valley near the coast and was either partly or and evapotranspiration is lowest. Vegetation, soil completely inundated by the ocean during the last permeability, climatic conditions, and impervious glaciation (Morrissey, 1983). The surficial deposits urban areas can affect the rate of recharge to aquifers. consist of highly permeable sand and gravel that were Average annual recharge to stratified-drift deposited in contact with glacial ice at the northern aquifers from precipitation is approximately half of part of the valley and outwash sand deposited in front the annual precipitation. This equals about 20 to of the ice that overlies a thick layer of impermeable 24 in/yr in glaciated areas of eastern Massachusetts marine silt, clay, and fine sand at the southern part of (Knott and Olimpio, 1986; Leblanc and others, 1986; the valley. Bent, 1995; and Hansen and Lapham, 1992), in

26 Water-Quality Assessment of the New England Coastal Basins in Maine, Massachusetts, New Hampshire, and Rhode Island: Environmental Settings and Implications for Water Quality and Aquatic Biota Idealized geohydrologic section in the glaciated Northeast (modified from Randall and others, 1988). others, and Randall from (modified Northeast glaciated the in section geohydrologic Idealized Figure 13. Figure

ENVIRONMENTAL SETTING 27 southern Maine (Morrissey, 1983), in east-central New fields in urban areas, and from domestic leach fields in Hampshire (Tepper and others, 1990), and in rural areas. Tepper and others (1990) reported that southeastern New Hampshire (Stekl and Flanagan, approximately 80 percent of the water pumped from 1992; Mack and Lawlor, 1992; Harte and Mack, municipal wells in the Saco River Valley aquifer 1992). In southern Rhode Island, the recharge rate is between Bartlett, N.H., and Fryeburg, Maine, is estimated to be 25 to 31 in/yr (Dickerman and returned to the aquifer through septic systems. Ozbilgin, 1985; Dickerman and others, 1990; Dickerman and Bell, 1993; Barlow, 1997), 14 in/yr in Ground water discharges from aquifers through south-central New Hampshire (Harte and Johnson, seepage into streams, lakes, and wetlands; evapotrans- 1995), and about 9 in/yr in areas underlain by till piration; and withdrawal from wells (fig. 13). Ground- (Trench, 1991). water discharge, primarily from stratified-drift Runoff from till uplands (fig. 13) also provides aquifers, sustains streamflow during dry periods, large amounts of recharge to adjacent stratified-drift usually during late summer or early autumn and aquifers. A study of seepage losses to surface water during droughts. The rate of discharge per square along a 4-mi reach of the Saco River near North mile of drainage area from coarse-grained stratified Conway, N.H., in a region of high topographic relief, drift is greater than that from till (Wandle and Randall, indicates that adjacent upland areas account for nearly 1994). Ground-water evapotranspiration is another 60 percent of the recharge to stratified drift in this source of discharge from aquifers and is greatest valley (Morrissey and others, 1988). during the April to October growing season (Stekl and Factors that affect recharge to crystalline bedrock aquifers in a mountainous setting are Flanagan, 1992). Ground-water evapotranspiration described by Harte and Winter (1996). Bedrock has been estimated to range from 1 to 9 in/yr in the recharge is controlled by relief of land and bedrock northeastern United States (Lyford and others, 1984). surface above ground-water sinks (such as lakes) and Ground-water-level monitoring shows that glacial-drift stratigraphy. Recharge to crystalline water-level fluctuations are usually greater in till and bedrock aquifers is estimated to be about 3 to 5 in/yr bedrock uplands than in stratified-drift deposits (Harte and Winter, 1995). because of differences in their specific yields, which Recharge to an aquifer from surface-water are a function of lithology (fig. 14). Median water bodies is induced when withdrawal wells reverse levels for six wells show recharge occurring from natural flow directions and induce flow into the approximately January through April as rainfall and aquifer (fig. 13). Induced infiltration is an important snowmelt infiltrate the ground (fig. 14). Little source of water for many high-yielding municipal wells in the study area, especially for those wells recharge occurs during the summer growing season, within a few hundred feet of lakes, rivers, and however, and ground-water levels decline from April wetlands. through October. Recharge begins again in the late fall Artificial recharge of aquifers is a minor after the growing season, continues into December, component of total recharge, but does occur in areas and ends when the ground freezes. After the ground where farmland is irrigated, from municipal leach thaws, the annual recharge cycle begins again.

28 Water-Quality Assessment of the New England Coastal Basins in Maine, Massachusetts, New Hampshire, and Rhode Island: Environmental Settings and Implications for Water Quality and Aquatic Biota Figure 14. Comparison of monthly median and ranges of water levels in selected observation wells during the 1994 water year in the New England Coastal Basins study area. Unshaded area shows the range between highest and lowest monthly water level for periods of record. (Locations of wells shown on figure 5b).

ENVIRONMENTAL SETTING 29