The Meeting of Two Rivers
Quick Description TheFarmington River
travels in a southeasterly direction through the town of Farmington
until it reaches the “flats” (see figure one).
Here the river turns north and enters a section known as the
“bathtub,” referring to slower moving, warmer,
sediment-laden waters where it meanders through floodplains in
Farmington, Avon and Simsbury.
It is also at this point where the Pequabuck
River drains into the Farmington. This meeting of two rivers
is called a confluence. In geography, confluence describes
the meeting of two or more bodies of water. It usually refers
to the point where a tributary joins a more major river, called the
mainstem, when that major river is also the highest order stream in
the drainage basin. This confluence is where “The Meeting of
Two Rivers” EarthCache takes place.
Location: Farmington,
CT Boat Launch Parking Area: N
41o43.033’ W 072o50.454’
Listed by: CTGEOSURVEY
Purpose: This EarthCache is published
by the Connecticut Geological and Natural History Survey of the
Department of Environmental Protection. It is one in a series
of EarthCache sites designed to promote an understanding of the
geological and biological wealth of the State of Connecticut.
Supplies: Bring this write up,
something to measure with and a camera.
Directions: From RT 4 in
Farmington turn onto RT 10 heading south. At the second
traffic light turn right onto Meadow Rd. The parking area is
on the right immediately after passing the brown stone bridge.
Long Description:Stretching across two states, 33 towns and 609
square miles, the Farmington River Watershed is an essential
resource for life in Connecticut and Massachusetts. The watershed
supports abundant recreational opportunities, unique fish, wildlife
and plant habitats as well as hydropower generation. The
Watershed’s reservoirs and aquifers provide clean water to
about 1 million people (33% of Connecticut’s entire
population.) The Farmington River is the main river that runs
through this watershed and was the first river in the state of
Connecticut to have a section federally designated as “Wild
& Scenic”.
It is also the only river in the Northern
Hemisphere to flow in all four compass directions. Its length
is 81 miles via its longest branch and it is a sub-basin of New
England’s largest river system, the Connecticut River
Watershed. The total elevation change of 2,170 feet reflects a
fairly dramatic drop in topography from the source waters in
southern Massachusetts to the lowlands where the Farmington drains
into the Connecticut River.
Geological Time: Five to twenty thousand years ago
during the end of the last Ice Age, thick glacial ice began melting
and the ice front progressively melted northward. The land
beneath the glacial mass was depressed because of the weight of the
ice. When the ice melted the ground slowly rose back to its
former elevation. Thus the land area directly south of the
melting ice front had a lower elevation relative to the land
farther to the south that had already
“rebounded”. Meltwater tended to collect in these
low areas forming lakes and ponds.
In addition, glacial debris left in the low areas between New
Britain and Bristol helped create the dam barrier that backed up a
temporary lake, called Glacial Lake Farmington, against the
retreating ice front. Meltwater streams entering these
temporary lakes deposited deltas and terraces composed of sand and
gravel in places against the edge of the melting ice. Glacial
Lake Farmington formed in the Farmington River Valley at the same
time as a similar lake, called Glacial Lake Hitchcock, formed in
the Connecticut River Valley.
When the ice front melted north of Tariffville, Glacial Lake
Farmington drained eastward into Glacial Lake Hitchcock and in the
process deepened the gorge at Tariffville sufficiently that the
modern Farmington River continues to drain through the gorge.
The draining of Glacial Lake Farmington left the lake basin at the
modern confluence of the Farmington and Pequabuck as a
“bath-tub”-like lowland. Thus the modern
Farmington River flows northward because of the erosional deepening
of the Tariffville gorge during the draining of Glacial Lake
Farmington.
Figure 1.Pale green and light gray areas underlain by glacial
till; dark green area underlain by Lake Farmington
deposits; yellow= Recent river alluvium (flood plain) dark
brown areas = trap rock cliffs and talus slopes; magenta and
tan = stratified sand and gravel unrelated to Lake
Farmington (includes eskers); pale orange = river
terraces. string of triangles = esker deposits; solid
hachured lines and dashed lines = ice margin positions and inferred
ice margin positions; lines (black) with arrows = location of
glacial striations...orientation of arrow = inferred ice movement
direction. Line without arrows = drumlins; blue lines
with arrows = meltwater channels.
Glaciers dramatically affected the geologic features of the
Farmington Valley. The underlying structure of the Farmington
watershed is comprised of bedrock, till, and stratified drift
materials. The upper river valley is characterized by quickly
flowing waters due to high elevation gradients and in the lower
valley the river flattens, slows and exhibits larger alluvial
floodplains. In the Farmington River Valley, stratified drift
deposits most influence primary recharge and drinking water supply
areas due to their outstanding recharge and water bearing
ability.
This fast moving water seen in the upper section of the river
changes dramatically in the lower sections. Here it meanders
through floodplains in Farmington, Avon and Simsbury. In times of
flooding, this portion of the river becomes a natural storage area
with excess water flowing outward and over the floodplain, filling
up like a bathtub.
This EarthCache starts at the Farmington Land
Trust’s Cowley walking path pictured above, located at the
boat launch. Take this path to the listed coordinates N
41o43.180’ W
072o50.344’. You will find yourself at
the confluence of the Farmington and Pequabuck Rivers. A
confluence is described as the meeting of two or more bodies of
water at a single location. Joining together, these two
rivers have greater ability to carve through the landscape from
this point on to the confluence with the Connecticut River.
Every time a brook, stream or another river flows into each other,
it adds to the river’s flow rate and affects it’s
ability to transport nutrients, sediment, and pollutants along the
river.
Farmington River left of
log; the Pequabuck entering right of the log. At top, the
Farmington
River turns north and
continues on.
Other factors that determine the amount of
water that reaches a river and affects its flow are referred to as
catchment factors. Topography and shape of the land in the
river basin can determine the time it takes for rain to reach the
river. Watershed size, soil type and land use development are
also factors determining the velocity and volume of water to reach
the river.
Local History of the Site
For centuries, Farmington residents drove
their cows down to this location of the river and into these fields
for pasturage during the summer season. They would forge the
river a bit farther north near the gristmill to reach Indian Neck
or cross the old stone bridge over the Pequabuck to reach fields
south of the river. The brownstone bridge, a classical span dating
from 1835, was considered for demolition but spared in the
1970’s when a new span was built. Today, the ancient
bridge, the river, and the lovely Cowles parcel just to the west
form a small and charming environment for all to enjoy. The
Cowles Parcel is 3.4 acres of open space donated by Mr. and Mrs.
Sheffield Cowles to the Farmington Land Trust in 1974.
Requirements for logging the cache.
1. Send a
picture of yourself at the confluence of the Farmington and
Pequabuck Rivers with the water behind you.
2.
Calculate the flow rate in “feet per second” for
both the Farmington River and the Pequabuck River. This may
be done by measuring an equal distance along each of the rivers
banks at the confluence point, then floating an object from your
starting point to the ending point and recording the time it takes
the object to float the distance. Once the distance and time
are determined calculate the “feet per second” for each
river. Send in both rates and answer which river had a faster
flow rate and why you think that is?
References
Farmington River Watershed Association,
State of the Farmington River Watershed, August
2003
"http://www.frwa.org/publications">www.frwa.org/publications
The CT Botanical Society, The Greening of
Connecticut by Roland C. Clement, Part I: Ice Age Geology, Winter,
2000 Newsletter (Vol.27, no.4)
"www.ct-botanical-society.org/newsletter">www.ct-botanical-society.org/newsletter
Farmington Land Trust,
"http://www.farmingtonlandtrust.org/FLT_Cowles.html">www.farmingtonlandtrust.org/FLT_Cowles.html