The lower Charles River, the water body between the Watertown Dam and the New Charles River Dam, is an important recreational resource for the Boston, Massachusetts, metropolitan area, but impaired water quality has affected its use. The goal of making this resource fishable and swimmable requires a better understanding of combined-sewer-overflow discharges, non-combined-sewer-overflow stormwater runoff, and constituent loads. This report documents the modeling effort used to calculate non-combined-sewer-overflow runoff to the lower Charles River.
During the 2000 water year, October 1, 1999–September 30, 2000, the U.S.
Geological Survey collected precipitation data at Watertown Dam and compiled
data from five other precipitation gages in or near the watershed. In addition,
surface-water discharge data were collected at eight sites—three relatively
homogenous land-use sites, four major tributary sites, and the Charles River
at Watertown Dam, which is the divide between the upper and lower watersheds.
The precipitation and discharge data were used to run and calibrate Stormwater
Management Models developed for the three land-use subbasins (single-family,
multi-family, and commercial), and the two tributary subbasins (Laundry and
Faneuil Brooks). These calibrated models were used to develop a sixth model
to simulate 54 ungaged outfalls to the lower Charles River. Models developed
by the U.S. Geological Survey at gaged sites were calibrated with up to 24 storms.
Each model was evaluated by comparing simulated discharge against measured discharge
for all storms with appreciable precipitation and reliable discharge data. The
model-fit statistics indicated that the models generally were well calibrated
to peak discharge and runoff volumes. The model fit of the commercial land-use
subbasin was not as well calibrated compared to the other models because the
measured flows appear to be affected by variable conditions not represented
in the model. A separate Stormwater Management Model of the Stony Brook Subbasin
previously developed by others was evaluated with the newly collected data from
this study; this model had a model fit comparable to the models developed by
the U.S. Geological Survey.
The total annual runoff to the lower Charles River during the 2000 water year,
not including contributions from combined-sewer-overflows except from the Stony
Brook Subbasin, was 16,500 million cubic feet; 92 percent of the inflow was
from the Charles River above Watertown Dam, 3 percent was from the Stony Brook
Subbasin, 2 percent was from the Muddy River Subbasin, and less than 1 percent
was from the combined inflows of Laundry and Faneuil Brooks. The remaining ungaged
drainage area contributed about 2 percent of the total annual inflow to the
lower Charles River. Excluding discharge from the Charles River above Watertown
Dam, total annual runoff to the lower Charles River was 1,240 million cubic
feet; 39 percent was from the Stony Brook Subbasin, 27 percent was from the
Muddy River, which includes runoff that drains to the Muddy River conduit, 7
percent was from the Laundry Brook Subbasin, and 4 percent was from the Faneuil
Brook Subbasin. Flow from the ungaged areas composed about 23 percent of the
total annual inflow to the lower Charles River, excluding discharge from the
Charles River above Watertown Dam.
Runoff to the lower Charles River was calculated for two design storms representing a 3-month and a 1-year event, 1.84 and 2.79 inches of total rainfall, respectively. These simulated discharges were provided to the Massachusetts Water Resources Authority for use in a receiving-water model of the lower Charles River. Total storm runoff to the lower Charles River was 111 and 257 million cubic feet for the 3-month and 1-year storms, respectively. Excluding discharge from the Charles River above Watertown Dam, total runoff to the lower Charles River was 30 and 53 million cubic feet for the 3-month and 1-year storms, respectively. Runoff from the various tributary areas for the design storms was about in the same proportion as that for the annual runoff.
Abstract
Introduction
Purpose and Scope
Description of the Lower Charles River and its Watershed
Climate
Land Use
Soils
Topography
Hydrology
Previous Investigations
Acknowledgments
Gaged Subbasins
Discharge
Charles River at Watertown Station—01104615
Single-Family Land-Use Station—01104630
Laundry Brook Station—01104640
Faneuil Brook Station—01104660
Multifamily Land-Use Station—01104673
Commercial Land-Use Station—01104677
Muddy River Station—01104683
Stony Brook Station—01104687
Data Management
Precipitation-Runoff Model
Functional Description of SWMM
Model Development
Data
Spatial Data
Time-Series Data
Representation of Overland Runoff
Assignment of Subcatchments to Precipitation Gages
Subcatchment Parameterization
Representation of the Drainage Network
Drainage Network Parameterization
Pond Storage
Model Calibration
Model Fit
Land-Use Subbasin Models
Single-Family Residential
Multifamily Residential
Commercial
Tributary Subbasin Models
Laundry Brook
Faneuil Brook
Stony Brook
Relative Model Fit
Design Storms
Sensitivity Analysis
Model Limitations
Runoff to the Lower Charles River
Annual and Monthly Water Budget
Single-Family Land-use Subbasin
Multifamily Land-Use Subbasin
Commercial Land-Use Subbasin
Laundry Brook Subbasin
Faneuil Brook Subbasin
Stony Brook Subbasin
Total inflows to the Lower Charles River
Design Storms
Summary
References Cited
Appendix 1A-G: Model Areas and Schematics of the StormWater Management Model (SWMM) Elements used to Represent the Model Areas
Appendix 2: Rainfall Characteristics of Storms at BWSC-CS4, Lower Charles River Watershed, 2000 water year
Appendix 3: Observed and Simulated Runoff Volume and Peak Discharge for Calibration Storms
For additional information write to:
Chief, Massachusetts-Rhode-Island District
U.S. Geological Survey
10 Bearfoot Road
Northborough, MA 01532
or visit our Web site at: http://ma.water.usgs.gov/
Copies of this report can be purchased from:
U.S. Geological Survey
Branch of Information Services
Box 25286, Federal Center
Denver, CO 80225-0286
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