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Streamflow, Base Flow, and Ground-Water Recharge in the Housatonic River
Basin, Western Massachusetts and Parts of Eastern New York and Northwestern Connecticut
Water Resources Investigations Report 98-4232
By Gardner C. Bent
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ABSTRACT
Streamflows for selected flow durations from 1 to 99 percent and the August median streamflows were
estimated for 11 long-term streamflow-gaging stations in and near the study area. Estimates of
streamflow and associated standard errors were determined for selected flow durations from 50 to 99
percent and the August median streamflows for 21 low-flow partial-record stations and for selected
flow durations from 1 to 99 percent and the August median streamflows for two partial-record
stations and seven short-term discontinued streamflow-gaging stations. Median streamflows per square
mile for the 10-, 50-, and 90-percent flow durations and the August median streamflows were 3.90,
1.01, 0.185, and 0.248 cubic feet per second per square mile. Streamflows per square mile at
selected flow-duration discharges between 1 and 99 percent at the 41 stations were related to basin
characteristics to explain differences in streamflow characteristics. Basin characteristics included
basin elevations, extent of stratified-drift deposits, land use, aspect, and underlying bedrock
geology types. Most streamflow differences were positively correlated to basin elevation
differences, most likely because precipitation increases with elevation, and to stratified-drift
deposits, which allow more precipitation to recharge the ground water and to discharge later than do
till and bedrock deposits.
Mean base flow was computed from continuous records of daily mean discharge at 11 long-term
streamflow-gaging stations in and near the study area. Mean annual base flow ranged from 13.4 to
24.5 inches per year. Minimum annual base flow ranged from 45 to 72 percent of mean annual rates at
the 11 long-term stations, and the ratio of base flow to streamflow (base-flow index) ranged from
0.55 to 0.80. Base-flow durations between 1 and 99 percent were calculated from streamflow records
at the 11 long-term streamflow-gaging stations. Base flow accounted for 45.5 to 85.0 percent of
total annual streamflow at the 1- and 99-percent flow durations.
Ground-water-recharge rates were computed from continuous records of daily mean discharge at 11
long-term streamflow-gaging stations in and near the study area. Mean annual ground-water-recharge
rates ranged from 17.5 to 22.4 inches per year at 10 of the 11 long-term stations. Mean annual
ground-water-recharge rates ranged from 2 to 7 inches per year higher than base flow. Minimum annual
ground-water-recharge rates ranged from 48 to 72 percent of mean annual ground-water-recharge rates.
Mean annual potential ground-water recharge was estimated from monthly climatological data collected
at six climatological stations in and near the study area. Mean potential ground-water recharge
ranged from about 17.9 to 28.9 inches per year, with a median value of 22.6 inches per year. This
median value compares well to that calculated by use of streamflow records at the 11
streamflow-gaging stations (20.0 inches per year).
Streamflows per square mile for the 10-, 50-, and 90-percent flow durations at stations in and near
the study area were similar to those computed for other unregulated long-term continuous
streamflow-gaging stations in central and eastern Massachusetts. Base-flow and ground-water-recharge
rates in the study area compared closely to results from other studies in southeastern Massachusetts
and Rhode Island, which were based on the same computational methods.
CONTENTS
Abstract
Introduction
Purpose and Scope
Previous Investigations
Acknowledgments
Description of Study Area
Geology
Climate
Hydrology
Water Use
Land Use
Streamflow
Flow Durations and Estimates of August Median Streamflow
Long-Term Stations
Short-Term Stations
Factors Affecting Streamflow
Surficial Geology
Bedrock Geology
Climate
Other Physical Features
Base Flow
Long-Term Stations
Short-Term Stations
Ground-Water Recharge
Streamflow Hydrograph Analysis
Climatological Data Analysis
Summary and Conclusions
References Cited
FIGURES
1-3. Maps showing:
- Location of study area in the Housatonic River Basin, western Massachusetts
and parts of eastern New York and northwestern Connecticut
- Distribution of underlying bedrock types and stratified-drift and till deposits
- Location of long-term continuous and discontinued streamflow-gaging stations,
ground-water observation wells, and climatological stations in and near the
study area
- Hydrographs showing water-level fluctuations for selected observation wells
in the Housatonic River Basin, western Massachusetts, 1951–96
5, 6. Maps showing:
- Location of surface-water and ground-water sources used for public-water
supplies
- Location of low-flow partial-record stations, partial-record stations, and
short-term discontinued streamflow-gaging stations used in flow-duration analysis
TABLES
- Site descriptions and water levels measured in U.S. Geological Survey observation
wells completed in stratified-drift deposits in the Housatonic River Basin,
western Massachusetts, 1994–96
- Water use by municipalities within the Massachusetts part of the Housatonic
River Basin, 1994–95
- Description of long-term continuous and discontinued streamflow-gaging stations
used in streamflow, base-flow, and ground-water-recharge analyses in and near
the Housatonic River Basin, western Massachusetts and parts of eastern New
York and northwestern Connecticut
- Streamflows for selected flow durations and August median streamflows at
long-term continuous and discontinued streamflow-gaging stations
- Streamflows per square mile for selected flow durations and August median
streamflows per square mile at long-term continuous and discontinued streamflowgaging
stations
- Description of low-flow partial-record stations, partial-record stations,
and short-term discontinued streamflow-gaging stations, for which streamflow
estimates are provided
- Summary of flow-duration analysis at low-flow partial-record stations, partial-record
stations, and short-term discontinued streamflow-gaging stations
- Estimated streamflows for selected flow durations and estimated August median
streamflows at low-flow partial-record stations, partial-record stations,
and short-term discontinued streamflow-gaging stations
- Standard errors of estimated streamflows for selected flow durations and
estimated August median streamflows at low-flow partial-record stations, partial-record
stations, and short-term discontinued streamflow-gaging stations
- Estimated streamflows per square mile for selected flow durations and estimated
August median streamflows at low-flow partial-record stations, partial-record
stations, and short-term discontinued streamflow-gaging stations
- Correlation coefficients for the relations between streamflow and basin
characteristics at low-flow partial-record stations, partial-record stations,
short-term discontinued streamflow-gaging stations, and long-term continuous
and discontinued streamflow-gaging stations
- Correlation coefficients for the relations between streamflow and basin
characteristics at partial-record stations, short-term discontinued streamflow-gaging
stations, and long-term continuous and discontinued streamflow-gaging stations
- Correlation coefficients for the relations between streamflow and basin
characteristics at long-term continuous and discontinued streamflow-gaging
stations
- Estimates of minimum, maximum, and mean annual streamflow and base flow,
and base-flow indexes derived from the computer programs HYSEP and PART at
long-term continuous and discontinued streamflow-gaging stations
- Correlation coefficients for the relation of base-flow and ground-water-recharge
characteristics to basin characteristics at long-term continuous and discontinued
streamflow-gaging stations
- Streamflow, base flow, and ratio of base flow to streamflow for selected
flow durations derived from the computer program HYSEP at long-term continuous
and discontinued streamflow-gaging stations
- Estimates of minimum, maximum, and mean annual ground-water recharge and
recharge indexes derived from the computer program RORA at long-term continuous
and discontinued streamflow-gaging stations
- Estimates of mean annual potential evapotranspiration and ground-water recharge
derived from the Thornthwaite and Mather (1957) method at climatological stations
- Water budget for the Green River subbasin, western Massachusetts and part
of eastern New York, water years 1952–71 and 1995
- Basin characteristics determined by using a geographic information system
at low-flow partial-record stations, partial-record stations, short-term discontinued
streamflow-gaging stations, and long-term continuous and discontinued streamflow-gaging
stations
- Streamflow measurements made and used in analyses at low-flow partial-record
stations, partial-record stations, and short-and long-term discontinued streamflowgaging
stations, water years 1963–96
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