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USGS · 70038245

Water resources inventory of Connecticut Part 5: lower Housatonic River basin

William E. Wilson·Edward L. Burke·Chester E. Thomas
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Abstract

The 557 square miles of the lower Housatonic River basin in western Connecticut include the basins of two major tributaries, the Pomperaug and Naugatuck Rivers. Nearly all water is derived from precipitation, which averaged 47 inches per year during 1931-60, In this period an additional 570 billion gallons of water per year entered the basin in the main stem of the Housatonic River at Lake Lillinonah, and some water was imported by water-supply systems from outside the basin. Almost half the precipitation--21.6 inches--was lost from the basin by evapotranspiration. Except for small amounts exported, the remainder discharged as runoff and underflow into Long Island Sound. Variations in streamflow at 6 long-term continuous-record gaging stations are summarized in standardized graphs and tables that can be used to estimate streamflow characteristics at other sites. For example, mean flow and two low-flow characteristics, the 7-day annual minimum flow for 2-year and 10-year recurrence intervals, have been determined for many partial-record stations throughout the basin. Of the 37 principal lakes, ponds, and reservoirs in the basin, 6 have usable storage of more than 1 billion gallons. The “maximum safe draft rate” (described in: “Storage of Water in Lakes and Reservoirs”) of the largest of these, Thomaston Reservoir near Thomaston, is 75.6 million gallons per day for the 10-year and 20-year recurrence intervals of annual lowest mean flow. Floods have occurred during every month, at one time or another. The two greatest floods on the Naugatuck River in historical time occurred 2 months apart in 1955. The larger, in August, had a peak of 106,000 cfs (cubic feet per second) at Beacon Falls. Since then, the likelihood of major floods has been considerably reduced by a program of flood control in the basin. Water can be obtained from three aquifers under-lying the basin-stratified drift, till, and bedrock. Stratified drift covers about 16 percent of the basin, mostly in valleys and lowlands, and its saturated part generally ranges in thickness from 10 feet in small valleys to 200 feet in the Housatonic River valley. Its transmissivity ranges from 0 to 47,000 ft 2 /day (feet shared per day). Till, deposited directly by glacial ice, forms a widespread but discontinuous mantle over bedrock in most upland areas and extends beneath stratified drift in lowlands; it ranges in thickness from 0 to 200 feet. The median value of 31 published determinations of hydraulic conductivity of till in southern New England is 0.67 ft/day and ranges from 0.013 to 29 ft/day. Crystalline bedrock underlies most of the basin and is composed principally of granite, gneiss, and schist. Sedimentary volcanic bedrock underlies only the Pomperaug River basin. Regardless of rock type, water is obtained mostly from fractures. Streambed deposits are significant features of the hydrogeologic system because they affect the amount of water from streams and lakes that can be induced to infiltrate aquifers. Based on field tests, characteristic values of vertical hydraulic conductivity of streambed deposits are 0.40 ft/day for fine-grained deposits and 14 ft/day for gravelly deposits. Ground-water supplies generally range in yield from several millions of gallons per day from large well fields to 1 gpm (gallons per minute) from single wells. Large supplies, with yields of 100 gpm or more from individual wells, are most commonly obtained from stratified drift. Yields to be expected from screened wells tapping this aquifer can be calculated by use of a series of graphs in conjunction with estimates of transmissivity and aquifer thickness. The yields of 14 principal ground-water reservoirs are estimated from aquifer characteristics and also from the amount of water that can be obtained from aquifer storage, from interception or runoff, and from infiltration of streamflow at low-flow conditions, using a hypothetical well-field arrangement for each reservoir. It is assumed that induced infiltration is restricted to an amount equal to the 7-day annual minimum stream-flow for a 2-year recurrence interval. Yields range from 1.4 to 15 mgd (million gallons per day) during periods of no recharge, and from 2.0 to 17 mgd during recharge periods. Small to moderate water supplies can be obtained from any of the aquifers under suitable conditions. For example, data from 294 wells in the basin indicate that yields of a few gallons per minute can be obtained from bedrock at most sites. The likelihood of obtaining an adequate domestic supply is slightly greater in granite than in schist and also is greater where the overburden is stratified drift rather than till. Chemical analyses of precipitation samples collected monthly from five stations in the basin during a 9-month period in 1966 show that rainfall is acidic and that sulfate is the dominant anion, probably because of industrial fumes and smoke within and near the basin. Where unaffected by man’s activities, water in the basin is generally low in dissolved-solids concentration, is of the calcium magnesium bicarbonate type, and is soft to moderately hard. In general, streamflow is less mineralized than ground water, particularly when it consists largely of direct runoff. However, streamflow becomes more highly mineralized during low-flow conditions, when most of it consists of more highly mineralized water discharged from aquifers. The median value of dissolved-solids concentration of water at 22 stream sites was 51 mg/1 (milligrams per liter) during high flow, and 68 mg/1 during low flow within the study period. Iron and manganese occur naturally in objectionable concentrations in parts of the basin, particularly in streams draining swamps and in water from bedrock containing iron and manganese-bearing minerals. Man’s activities have degraded the quality of water in streams in much of the basin, except in the Pomperaug subbasin. In the Naugatuck River basin, the degradation in quality is shown by wide and erratic changes in dissolved-solids concentration, excessive amounts of certain trace elements, a low dissolved oxygen content, and abnormally high temperatures. Ground water is degraded principally by induced infiltration of stream water containing chemical wastes, by wastes stored on the ground and by effluents from septic tanks. Below its confluence with the Naugatuck River, much of the Housatonic River and adjoining marshes, wetlands, and aquifers contain salt water. Measurements of specific conductance during low-flow conditions in 1969 indicate that the dissolved-solids concentration of water in the estuary ranged from 210 mg/1 near Twomile Island to 20,000 mg/1 near Long Island Sound. The quantity and quality of water in the basin are satisfactory for a wide variety of uses, and, with suitable treatment, the water may be used for most purposes. In 1967, the total amount of water used in the basin was about 194 billion gallons. About 90 percent of this was used for industrial purposes, and 95 percent of the industrial water was obtained from surface-water sources. In the same year, 17 municipal and private water-supply systems supplied water of satisfactory quality to about three-fourths of the population.

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Connecticut Water Resources BulletinReport
90° N90° S · 180° W ← longitude → 180° E
Source-reported bounding extent: 41.125° to 42° latitude; -73.333333° to -72.9° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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William E. Wilson, Edward L. Burke, Chester E. Thomas. 1974. Water resources inventory of Connecticut Part 5: lower Housatonic River basin. https://pubs.usgs.gov/publication/70038245

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USGS1986

Water resources inventory of Connecticut Part 9: Farmington River basin

The Farmington River basin covers 435 square miles in north-central Connecticut upstream from Tariffville and downstream of the Massachusetts state line. Most water in the basin is derived from precipitation, which averages 48 inches (366 billion gallons) per year. An additional 67 billion gallons of water per year enters the basin from Massachusetts in the West Branch of the Farmington River, Hubbard River, Valley Brook and some smaller streams. Of the total 433 billion gallons, 174 billion gallons returns to the atmosphere through evaporation and transpiration. 239 billion gallons flows out of the study area in the Farmington River at Tariffville, and 20 billion gallons is diverted for Hartford water supply. Variations in streamflow at 23 continuous-record gaging stations are summarized in standardized graphs and tables that can be used to estimate streamflow characteristics at other sites. For example, mean flow and low-flow characteristics such as the 7-day annual minimum flow for 2-year and 10-year recurrence intervals, have been determined for many partial-record stations from the data for the 23 continuous-record stations. Of the 31 principal lakes, ponds, and reservoirs in the basin, eight have usable storage capacities of more than 1 billion gallons. Two of the largest, Colebrook River Lake and Barkhamsted Reservoir, have more than 30 billion gallons usable storage. Floods have occurred in the area in every month of the year. The greatest known flood on the Farmington River was in August 1955, which had a peak flow of 140,000 cubic feet per second at Collinsville. Since then, three major floodcontrol reservoirs have been constructed to reduce the hazards of high streamflow. The major aquifers underlying the basin are composed of unconsolidated materials (stratified drift and till) and bedrock (sedimentary, igneous, and metamorphic). Stratified drift overlies till and bedrock in valleys and lowlands; it averages about 90 feet in thickness, and is capable of large sustained yields of water to individual wells. Based on hydrologic characteristics and available recharge, sixteen stratified-drift areas are selected as the most favorable for large-scale development. Potential yields can be estimated by several methods. Small water supplies can be obtained from all aquifers. Wells in bedrock yield at least one to two gallons per minute at most sites. The probability of adequate yields for domestic supply is greater from sedimentary than from crystalline bedrock and is also greater from stratified-drift overburden than from till. The quality of water from all sources in the basin is good except where adversely affected by swamp drainage, aquifer composition or human activities. The water is generally low in dissolved-solids concentration and is soft to moderately hard. Surface water is less mineralized than ground water, especially during high-flow conditions when it is primarily direct runoff. Samples of water collected from 20 streams during high flow had 34 mg/L median dissolved-solids concentration and 16 mg/L median hardness. Samples collected from the same sites at low flow had 52 mg/L median dissolved solids and 28 mg/L median hardness. In contrast, water from wells had 112 mg/L median dissolved-solids concentration and 60 mg/L median hardness. Iron and manganese occur in objectionable concentrations ~n a few parts of the basin where streams drain swamps and aquifers are rich in iron- and manganese-bearing minerals. Five percent of streams at high flow, 21 percent at low flow, and 7 percent of ground-water samples contained iron in sufficient concentration to cause stains on plumbing fixtures and laundry. Human activities have modified the quality of water in parts of the basin. The high bacterial content of the Pequabuck River. and the high nitrate and chloride concentrations in some ground-water samples, are evidence of man’s influence. The quantity and quality of water in the basin’s streams and aquifers are satisfactory for a wide variety of uses. and, with suitable treatment, may be used for most purposes. The total amount of water used by 21 principal public supplies within the basin was 29 billion gallons in 1970. About 70 percent of this was used for domestic and commercial purposes, and nearly 30 percent was used by industry. Analyses of water from these systems show good quality.

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USGS1982

Water resources inventory of Connecticut Part 10: Lower Connecticut River basin

The lower Connecticut River basin study area in south-central Connecticut includes 639 square miles and is drained principally by the Connecticut River and by seven smaller streams that flow directly to Long Island Sound between the West River on the west and the Connecticut River on the east. The population in 1979 was estimated to be 210,380. Much of the industrial development and population centers are in the Mattabesset River basin in the northwestern part, and the largest water use is also in the Mattabesset River basin. Precipitation averages 47 inches per year and provides an abundant supply of water. About 20 inches returns to the atmosphere as evapotranspiration, and the remainder either flows directly to streams or percolates to the water table, eventually discharging to Long Island Sound. 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The quantity for domestic, commercial, industrial, and agricultural used was 9,000 Mgal, which was approximately 120 gallons a day per person. Public water systems providing 70 percent of these requirement and all the systems supplying water met the drinking water standards of the Connecticut General Assembly (1975). Till is widespread and generally provides only small amounts of water. Wells in till normally yield only a few hundred gallons of water daily and may be inadequate during dry periods. The thickness of of till ranges from 0 to 15 feet; a median thickness of 26 feet is estimated from information provided in drillers' logs of 467 wells penetrating underlying bedrock. The till is generally used only as an emergency or secondary source of water. Bedrock aquifers underlie the entire area and include sedimentary and crystalline (igneous and metamorphic) rock types. These aquifers supply small and usually reliable quantities of water to wells and are the chief source of water for many rural homes and farms., About 90 percent of the wells tapping bedrock yield at least 2 gal/min. The median yields from wells tapping aquifers in sedimentary, igneous, and metamorphic rocks are 11, 8, and 6.5 gal/min, respectively. The quantity of water potentially available from stratified drift was estimated on the basis of hydraulic characteristics of the aquifers, mathematical modeling of the aquifer system, and evaluation of natural and induced recharge. Long-term yields estimated or ten areas underlain by significant thickness of stratified drift range from 0.4 to 4.4 million gallons per day (Mgal/d). A change in well spacing or numbering could increase the long-term yields, but detailed modeling verification studies are needed to confirm optimal well locations. The chemical and physical (turbidity, color, taste, and sediment load) quality of water is good. The water if generally low in dissolved solids and is classified as soft to hard. Surface water is less mineralized than ground water, especially during high flow, when it is primarily derived from surface runoff rather than groundwater runoff. A median dissolved-solids concentration of 42 milligrams per liter (mg/L) and median hardness of 18 mg/L were determined from water samples collected from 26 streams during the high-flow period. During the low-flow period, median dissolved-solids concentration of 61 mg/L and median hardness of 27 mg/L were determined from sample from the same streams. The quality of water in stratified-drift and crystalline-rock aquifers is generally better than that in the sedimentary-rock aquifers. Water from 32 wells tapping stratified drift had median dissolved-solids concentrations of 116 mg/L; and 33 wells tapping stratified drift and 42 tapping crystalline rock had median hardness of 73 mg/L and 68 mg/L, respectively. 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