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MONITORING THE EFFECTIVENESS OF URBAN BEST MANAGEMENT PRACTICES IN IMPROVING
WATER QUALITY OF ENGLESBY BROOK, BURLINGTON, VERMONT
In cooperation with the Vermont Department of Environmental
Conservation, and
The City of Burlington, Vermont
Increased peak (flood) flows and decreased base (dry weather) flows, erosion,
and elevated concentrations of bacteria, nutrients, sediment, and other
pollutants in the Englesby Brook watershed are water-related problems characteristic
of urbanizing and urbanized areas. Substances carried by Englesby Brook
are flushed into Lake Champlain (fig. 1), an important resource shared by
Vermont, New York, and Quebec.
Figure 1. Blanchard Beach, at the Englesby
Brook outlet to Lake Champlain, has been closed for swimming since 1991
because of high counts of bacteria.
Some of the water-quality problems are caused or exacerbated
by the effects of large areas of impervious surfaces in the watershed,
which cause runoff from rainfall and snowmelt, along with any water-borne
substances, to be channeled directly to the Brook rather than recharging
the ground-water system. This results in rapid rises in streamflow that
contribute to streambank erosion and channel instability. During dry periods,
base flows are low because of the loss of ground-water storage, and streams
may even go dry. Urban Best Management Practices (BMPs) are actions or
procedures that are designed to minimize these problems and may include
structural measures (stormwater retrofits and stream channel rehabilitation),
source-reduction practices (street sweeping and litter clean-up days),
regulatory measures (anti-littering laws), legal measures (enforcement
of existing laws), and education. In 1999, the U.S. Geological Survey (USGS),
in cooperation with the State of Vermont and the City of Burlington, with
additional support from the Lake Champlain Basin Program, initiated a study
of the effectiveness of urban BMPs in the Englesby Brook watershed.
The objective of the USGS project is to assess the effectiveness of BMPs
in improving the water quality of Englesby Brook. The USGS is monitoring streamflow,
phosphorus, suspended solids, nitrogen, specific conductance, temperature,
pH, dissolved oxygen, and turbidity. In addition, the City of Burlington is
monitoring E. coli bacteria. The study is scheduled to continue for
approximately 7 years to evaluate stream-water quality before, during, and
after BMP implementation in the watershed. BMP implementation is planned to
begin in 2001.
The concentrations of phosphorus in Lake Champlain is a primary consideration
of the Lake Champlain Basin Program and the State of Vermont in monitoring
the effectiveness of BMPs in the Englesby Brook watershed. Excessive amounts
of phosphorus in lakes can lead to an increase in growth of algae and other
aquatic plants, which can, in turn, adversely affect the aesthetic, biological,
and recreational quality of the Lake. More than 80 percent of the phosphorus
entering Lake Champlain comes from nonpoint sources (Lake Champlain Management
Conference, 1996). An estimated 55 percent of the nonpoint-source load originates
from agricultural activities, 37 percent from urban areas, and 8 percent from
forestland (Hegman and others, 1999). The States of Vermont and New York,
the province of Quebec, the U.S. Environmental Protection Agency, and the
Lake Champlain Basin Program (Lake Champlain Management Conference, 1996)
have set reducing phosphorous loading to the Lake as a high priority. Reductions
in the amount of phosphorus reaching the Lake from nonpoint sources are being
pursued through implementation of BMPs. The Lake Champlain Basin Program (2000)
estimates that the targeted reductions in nonpoint-source phosphorus loading
to the Lake will cost tens of millions of dollars; therefore, it is important
to evaluate the effectiveness of BMPs.
Englesby Brook was selected for this study because of
on-going efforts to improve the ecological health of the Brook. In 1999,
the Englesby Brook Watershed Restoration Project team (sidebar) received
funds to implement BMPs in the Englesby Brook watershed. The USGS, the
Vermont Department of Environmental Conservation (VTDEC), and the City
of Burlington recognized this opportunity to document anticipated improvements
in water quality and to collect information that could be used to refine
future estimates of phosphorus reductions in Lake Champlain.
Evolution of the Englesby Brook Watershed Restoration Project
Clean-up efforts related to the Pine Street Barge
Canal superfund site in Burlington lead to planned implementation of improvements
in the Englesby Brook watershed, which is a heavily urbanized basin near
the Canal site. The Restoration Project team (Vermont Agency of Natural
Resources, City of Burlington, Lake Champlain Committee and U.S. Natural
Resources Conservation Service) will plan, design, and oversee implementation
of Urban Best Management Practices over the next 5 years in the Englesby
Brook watershed.
Description of Study Area
The Englesby Brook drainage is a small (0.94 mi2) urban
watershed that drains directly to Lake Champlain (fig. 2). Eighty-four
percent of the land area is in Burlington and 16 percent is in South Burlington.
Land use within the watershed consists of residential (56 percent), commercial,
industrial, and educational (23 percent, including parts of the University
of Vermont campus), golf course (18 percent), forest (3 percent), and parks
and recreation (less than 1 percent). Average annual precipitation in Burlington
is 34.5 inches, with an average of 3.7 inches during each of the summer
months and 2.0 inches during each of the winter months. Average annual
temperature is 44.6 Fahrenheit (F), averaging 67.9F in the summer, and
19.2F in the winter. An estimated 24 percent of the Englesby Brook watershed
is composed of impervious surfaces (Center for Watershed Protection, written
commun., 2000).
Figure 2. Location of the stream-gaging
and water-quality-monitoring station and land-use areas in the Englesby
Brook watershed.
Data Collection/Sampling Methods
During the summer of 1999, the USGS constructed a stream-gaging
station with a concrete control and v-notched, sharp-crested weir about
1,200 feet upstream of the Brookís outlet to Lake Champlain (fig.
3). The weir enables collection of accurate, continuous stream-flow data.
Water-quality data are collected at the same site using three methods.
An automated, refrigerated sampler collects stream-water samples when streamflow
increases during storms or periods of snowmelt. These samples are analyzed
at the VTDEC Laboratory for total phosphorus, total nitrogen, and total
suspended solids. A water-quality meter collects specific conductance,
temperature, pH, dissolved oxygen, and turbidity data at 15-minute intervals.
Water samples also are manually collected from the stream during selected
storms and base-flow periods for analysis of
E. coli bacteria at
the Burlington Main Wastewater Treatment Facility (fig. 2). Precipitation
is measured at the Facility, about 1 mile away from the USGS collection
site, using a tipping bucket rain gage.
Figure 3. The USGS Englesby Brook monitoring
station and site. The v-notch weir is in the lower right of the picture,
and the stream-gaging station is on top of the high river bank to the left.
Initial Results of Water-Quality Monitoring
Provisional data on stream discharge and rainfall; concentrations
of total phosphorus, total suspended solids, and total nitrogen; specific conductance
and temperature; pH; dissolved oxygen; and turbidity for selected storms from
September 1999 through early January 2000 are shown in figure 4. Flows in Englesby
Brook are highly dependent on rainfall, as shown in figure 4a, but not all similar
storms produce the same discharge pattern.
Overall, the graphs of concentrations of phosphorus and suspended solids
(figs. 4b and c) are similar. Concentrations appear to peak during storms,
indicating that most of the phosphorus may be attached to the suspended solids;
this has been observed elsewhere (Litke, 1999). Large values of suspended
solids and phosphorus generally are detected in the stream during storms that
follow relatively long dry periods (Storms 2, 4, and 6), because these substances
accumulate in the watershed and then are ìflushed outî by storm-induced
runoff. In contrast, storms that closely follow previous storms (Storms 3
and 5) do not produce such large concentrations of suspended solids and phosphorus.
Nitrogen data (fig. 4d) follow a pattern inverse to that for phosphorus and
suspended solids. Peaks in streamflow correspond to troughs in the nitrogen
concentration, indicating that nitrogen may be diluted by high flows.
The pattern for specific conductance (fig. 4e) also is
generally inverse to that for streamflow. Specific conductance values are
high at the beginning of each storm, low during the storm peak, then high
again as the stormflow recedes. Whereas temperature (fig. 4e) and pH (fig.
4f) do not show consistent patterns related to storms, dissolved oxygen
(fig. 4g) and turbidity (fig. 4h) generally increase during storms and
decrease after storms.
Figure 4. Stream discharge, physical and chemical
characteristics of water, and rainfall at Englesby Brook for selected storms,
September 1999 - January 2000. These data are PROVISIONAL ONLY (subject
to review and revision). Each rainfall bar represents 2 hours. Data are
for individual stormsógaps in data lines represent time between
storm dates. Nitrogen data are missing for storm 2; temperature for storm
1; and turbidity for storms 2, 6 and 7.
Golf
Course
Residential
Commercial
Figure 5. Examples of land use in the Englesby
Brook watershed, Burlington, Vermont.
SUMMARY
This study is designed to provide useful water-quality
information to those involved in protecting and managing the quality of
Lake Champlain and its tributaries. A long-term monitoring program to determine
how tributary water quality changes with upstream BMP implementation will
provide critical information for understanding the effect of management
actions on streams and lakes.
REFERENCES CITED
Hegman, William, Wang, Deane, and Borer, Catherine, 1999, Estimation of Lake
Champlain basin-wide nonpoint source phosphorus export: Grand Isle, Vt., Lake
Champlain Basin Program, Technical Report no. 31, 81 p.
Lake Champlain Basin Program, 2000, Preliminary evaluation of progress toward
Lake Champlain Basin Program phosphorus reduction goals: Grand Isle, Vt.,
Internal report prepared for the Lake Champlain Steering Committee, 42 p.
Lake Champlain Management Conference, 1996, Opportunities for Actionóan
evolving plan for the future of the Lake Champlain Basin: Lake Champlain Basin
Program, 92 p.
Litke, D.W., 1999, Review of phosphorus control measures in the United States
and their effects on water quality, U.S. Geological Survey Water-Resources
Investigations Report 99-4007, 38 p.
Data Availability
Provisional (subject to review and revision) real-time
continuous streamflow data can be found at the USGS Englesby Brook web
site:
http://vt.water.usgs.gov/CurrentProjects/Englesby/Englesby.htm.
The site also provides a description of the study. Real-time hourly water-quality
data will be available at that site in the year 2000.
DEFINITIONS
Base flow--Streamflow coming from ground-water
seepage into a stream.
Dissolved oxygen--A measure of the amount
of oxygen that is dissolved in water. Dissolved oxygen is needed by fish
and zooplankton to survive. Rapidly moving water, such as that found in
a mountain stream, usually contains much more dissolved oxygen than stagnant
water.
E. coli bacteria (Eschericia coli)--A bacterial
species that inhabits the intestinal tract of man and other warm-blooded
animals. Although the coliform bacteria are not themselves directly harmful,
their presence in excessive numbers suggests the possible presence of other
species that are harmful to human health.
Impervious--A term used to describe certain
types of solid material, such as rock, clay, asphalt, or concrete, which
prevent water seepage into the ground.
Lake Champlain Basin Program--A federally-funded
initiative working in partnership with agencies, organizations, and individuals
to develop and implement concepts put forth in the comprehensive planning
document, Opportunities for Action: An Evolving Plan for the Future of
the Lake Champlain Basin (Lake Champlain Management Conference, 1996).
The Basin Program is guided by the Lake Champlain Steering Committee, which
represents a broad spectrum of Lake-Basin interests and organizations from
New York, Vermont, and Quebec, including local government and citizen representatives,
scientists, state government, and federal agencies.
Lake Champlain Management Conference--A
31-member board representing various interests in the Basin, which led
the Lake Champlain Basin Program during the development of Opportunities
for Action (Lake Champlain Management Conference, 1996).
Load--The material that is moved or carried
by a natural transporting agent, such as a stream, a glacier, or the wind.
Nitrogen--Nitrogen, in the forms of nitrate,
nitrite, or ammonium is a nutrient needed for plant growth. Excessive amounts
in water can lead to over-productive aquatic growth. Nitrogen is naturally
abundant in the environment and also is introduced through sewage and fertilizers.
Nonpoint-source pollution--Sources of pollution
such as atmospheric deposition, agricultural runoff, or seepage from septic
systems that contribute pollutants to rivers and lakes at numerous and
widespread locations rather than at a single discharge point.
pH--pH is a measure of how acidic or basic
water is and ranges from 0-14. A pH of 7 is neutral, less than 7 is acidic,
and greater than 7 is basic. pH is a measure of the relative amount of
free hydrogen and hydroxyl ions in the water and is an important indicator
of chemical changes in water.
Phosphorus--Phosphorus is an essential
element for plant life, but when there is too much of it in water, it speeds
up the aging process of lakes. Phosphorus enters streams from point sources,
primarily wastewater-treatment facilities, and from nonpoint sources, such
as applications of lawn fertilizers and disposal of animal wastes.
Runoff--That
part of precipitation, snow melt, or irrigation water that enters streams, rivers,
drains, or sewers without first infiltrating the ground.
Specific
conductance--A measure of the ability of water to conduct an electrical
current. Specific conductance is related to the type and concentration of ions
in solution and can be used for approximating the total dissolved solids (such
as salt) content of water by testing its capacity to carry an electrical current.
Suspended
solids--Solids that are not in solution and can be removed by filtration.
Turbidity--Turbidity
is a measure of the cloudiness of water. Water cloudiness is caused by material,
such as dirt and residue from leaves, that is suspended in the water. Clear
water has low turbidity. Brown, silt-laden water, such as a river during a storm,
has high turbidity.
Watershed--The
land area that contributes water to a particular stream, river, or lake. It
is a land feature that can be identified by tracing a line along the highest
elevations that enclose a land area on a map around the designated point on
the stream, river, or lake (usually the outlet or mouth).
By Laura Medalie
Layout and Design: Debra H. Foster, Ann Marie Squillacci
Graphics: Anita Cotton
For more information, please contact:
District Chief
U.S. Geological Survey
361 Commerce Way
Pembroke, NH 03275
(603) 226-7807 Phone
(603) 226-7894 FAX
or E-mail: dc_nh@usgs.gov
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