General Facts of this Project
Prepared by the U.S. Geological
Survey
in Cooperation with New Hampshire
Department of Environmental Services
and U.S. Environmental Protection
Agency
By Thor E. Smith
Current Schedule
for River Assessments
As of October 11, 2000, time-of-travel
assessments are scheduled for the following rivers during the months of
October and November 2000. The scheduled dye injection and sampling
dates are subject to change due to streamflow and weather conditions, and
the schedule shown here will be updated accordingly. The methods
of the study and a list of the river reaches to be studied are detailed
in subsequent sections of this document.
River
Study dates
Contoocook
Oct. 16 - 27
Androscoggin
Nov. 6 - 17
What are
time-of-travel assessments?
Time-of-travel is a term used
to identify assessments of transport rates for water flowing underground
or at the surface. One objective of time-of-travel involves measuring the
time it takes a dissolved (miscible) substance to flow through the earth
or in a river from the point of injection to a location at a known distance
away where water is withdrawn (e.g. a well or intake, respectively) for
use. In addition, data collected in these assessments can be used to estimate
the time it takes for a substance to spread or disperse over the width
of a river and estimate the rate a substance is dispersed with distance
from the point of injection.
-
Table 1. River reaches for time-of-travel
analyses in New Hampshire.
[ft3/s - cubic feet per
second where one cubic foot is about 7.5 gallons]
River
|
River Length in Miles
|
Assessment Reach
|
USGS
Gage No.
|
Median discharge
in ft3/s |
Discharge exceeded
90-percent of the time
in ft3/s |
Ammonoosuc
|
10
|
Dam at Lisbon
to
Woodsville intake |
01137500
|
110.
|
46.
|
Androscoggin
|
14
|
Dam at Dummer
to
Berlin intake |
01154000
|
2000.
|
1600.
|
Connecticut
|
15
|
Dam at Bellows
Falls to
Westmoreland intake |
01154500
|
6200.
|
2000.
|
Contoocook
|
10
|
Dam at West Hopkinton
to Riverhill intake
|
01085500
|
420.
|
100.
|
East Branch Pemigewasset
|
6
|
Confluence of
Franconia Brook to Lincoln Intake
|
01074520
|
180.
|
80.
|
Exeter
|
12
|
Dam near Brentwood
/ Fremont town line to Exeter intake
|
--
|
--
|
--
|
Lamprey
|
10
|
Wadley falls to
Durham / UNH intake to Newmarket intake
|
01073500
|
170.
|
4.
|
Mascoma
|
5
|
Mascoma Lake outlet
to
Lebanon intake |
01150500
|
130.
|
50.
|
Merrimack
|
14
|
Amoskeag Dam outlet
to Pennichuck intake
|
01092000
|
3400.
|
1200.
|
Oyster
|
5
|
Old Mill Road
bridge to
Durham/UNH intake |
01083000
|
10.
|
1.
|
Piscassic
|
10
|
State route 101
crossing to Newmarket intake
|
--
|
--
|
--
|
Salmon Falls
|
12
|
Northeast Rochester
to
Somersworth intake |
01072100
|
130.
|
40.
|
Sugar
|
7
|
Claremont / Newport
townline to Claremont intake
|
01152500
|
210.
|
70.
|
Rhodamine WT is
a flourescent red-pink liquid dye. The dye is intended to simulate a chemical
spilled into the river as an experiment to observe how quickly a substance
would spread-out and occupy the width of the river and how quickly a substance
would travel from the location along the river where it was introduced
to the location where water is withdrawn. In the assessment, dye is
injected into the river
water as an instantaneous mass or slug. The dye will quickly mix with
the river water vertically, and will more slowly mix horizontally as the
dye cloud flows downstream.
Once the dye
is injected, personnel will move to a location at a known distance downstream
of the injection point and prepare to begin sampling. At this first location,
samples will be taken at three or more stations across the channel at regular
intervals. The interval for sampling will vary depending on the slope or
grade of the river, but may be on the order of once every 15 minutes to
once every hour, until the dye cloud has passed. After the dye cloud passes,
personnel will set-up an automatic sampling instrument at the location
of the intake where water is withdrawn from the river.
Set-up of the
automatic sampling instrument may occur the same day or a couple days after
the dye injection depending on the slope of the river. Automatic sampling
instruments will syphon up to 1 liter (about a quart) of river water on
a regular interval (again anywhere from once every 15 minutes to once every
hour may be applied) and are limited to a total of 24 samples. Personnel
will visit the samplers daily. Samples will be removed and transported
to our office laboratory for dye concentration measurements.
Our
Mission, This Project, and You
As the nation's
largest water, earth and biological science, and civilian mapping agency,
the USGS works in cooperation with more than 2,000 organizations across
the country to provide reliable, impartial, scientific information to resource
managers, planners, and other customers. This scientific information is
gathered in every state by USGS scientists to minimize the loss of life
and property from natural disasters, contribute to the sound conservation,
economic and physical development of the nation's natural resources, and
enhance the quality of life by monitoring water, biological, energy, and
mineral resources.
The mission of the USGS with
respect to these time-of-travel assessments is to provide scientific
information to U.S. Environmental Protection Agency (USEPA), NHDES,
and local officials, which would assist towns to protect drinking water
from contamination should such a hazard from a spill ever occur. Such
time-of-travel assessments are programs called Source Water Assessment
and Protection (SWAP) programs administered by the states. The SWAP
programs are required for each state as set forth in amendments made
by congress to the Safe Drinking Water Act in 1996. Review, approval,
and funding for each program is managed through the U.S. Environmental
Protection Agency. For more general information on State of New Hampshire
SWAP programs check out the the following web sites:
State of New Hampshire,
Department of Environmental Services, Drinking Water Source Assessment
Program
USEPA
Office of Ground Water and Drinking Water
More Information
For technical
questions regarding this project, contact:
Thor Smith,
Hydrologist
New Hampshire
- Vermont District
U.S. Geological
Survey, Water Resources Division
361 Commerce
Way
Pembroke, NH
03275-3718
Phone: (603)
226-7814 Email: tesmith@usgs.gov
For general questions or comments,
contact:
Ken Toppin:
Supervisory Hydrologist
New Hampshire
/ Vermont District office
U.S. Geological
Survey, Water Resources Division
361 Commerce
Way
Pembroke, NH
03275-3718
Phone: (603)
226-7808 Email: ktoppin@usgs.gov
Related links:
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-- Water -- Geography
6/13/00 |