Watershed Conservation Plan - Destination Erie

1.3 Watershed Plan Focus
The primary focal points of this document will honor the concerns clearly expressed by citizens in both
surveys summarized in section 1.2. The history of the watershed and its townships/ municipalities will be
summarized herein, and a review of knowledge regarding cultural and archaeological resources of the
watershed is included, but these subjects will not be principle focal points for action planning. Likewise,
recreational resources will be considered within the context of the aquatic and natural resource entities which
support recreational activities, but will not be a main subject of focus.
The main emphasis of our analysis will be natural and water resource protection, especially in relation
to streams since this is a rivers conservation plan. In particular, action planning will address water issues
central to community safety and security, and will include consideration of anticipated effects of climate
change on our natural and water resources. Since there has been no concerted regional effort to address needs
for adapting to climate change, it is hoped that this plan will be a useful "first tool" to guide the communities
within our watershed toward pre-emptive actions that will help to maintain a productive, healthy, and
biologically diverse landscape.
2 THE PHYSICAL CONTEXT OF THE PENNSYLVANIA LAKE ERIE WATERSHED
2.1 The Great Lakes Watershed
The Great Lakes watershed has played an integral role in the history and development of North America.
Home to over 10% of the United States' population and over 25% of Canada's population, the region spans
more than 1,550 km (963 mi) east-west and 1,175 km (730 mi) north-south (Figure 2.1). The Great Lakes
basin lies within the boundaries of eight American states and two Canadian provinces, and encompasses a
total area of 765,990 km 2 (295,710 mi 2 ). Of this total area, over 244,000 km 2 (94,000 mi 2 ) is water surface
and 521,830 km 2 (201,460 mi 2 ) is land area. Combined, the water volume of the Great Lakes is about 23,000
km 3 (5,500 mi 3 ), which makes it the largest surficial fresh water system on the Earth, accounting for roughly
18% of the world supply (United States Environmental Protection Agency [EPA] 2005).
The modern configuration and flow of the Great Lakes basin is thought to have been established
following the retreat of the Wisconsinan glacier and the eastward overflow of Lake Agassiz, a glacial lake
that formed on the southern margin of the Red River-Des Moines ice lobe about 11,700 years ago (Teller
1983:1). The glacial ice drained by Lake Agassiz stretched some 1,800 km (1,120 mi) from the Rocky
Mountains to north-central Ontario; at its largest extent the lake itself covered nearly 1 million km 2 (386,100
mi 2 ) and, combined with its entire watershed, encompassed over 2 million km 2 (772,200 mi 2 ) or about 2.6
times the area of the modern Great Lakes basin. Throughout its lifetime, this vast glacial lake drained either
south via the Minnesota and Mississippi Rivers to the Gulf of Mexico or east through Lake Superior and the
Great Lakes basin, depending on advance and retreat of the glacial ice and the opening/closing of available
drainage routes. Flows from the lake could be nothing short of catastrophic, sometimes exceeding 3,000 km 3
(720 mi 3 ) or about seven times the volume of present-day Lake Erie (Teller 1983:8). For most of this period,
however, outflow from Lake Agassiz was directed northeastward from the Superior, Michigan, and Huron
basins through the Ottawa and St. Lawrence Valley, effectively bypassing flow through the Erie and Ontario
basins but for a brief period sometime after 11,000 years ago (see Development of the Study Area's Drainage
System and Lake Erie, below).
The Great Lakes basin's very large size makes for considerable variations in climate, physiography, soils,
and vegetational regimes, to name just a few environmental factors. The basin's northern reaches are
dominated by the Canadian Shield—a Precambrian granitic rock formation that underlies the world’s greatest
concentration of lakes and rivers—and is characterized by a Subarctic climate, relatively shallow acidic soils,
and middle taiga to southern taiga floral communities that take the form of moist subarctic forests dominated
by conifers (e.g., spruces, firs) bounded on the north by tundra. The basin's southern reaches are characterized
by a humid continental climate; relatively deep, glacially derived soils composed of clays, silts, and sands
mixed with gravels, and boulders; and an original deciduous forest that in many areas has been superseded
by agriculture and sprawling urban development.
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