Watershed Conservation Plan - Destination Erie

Lake section (see Figure 2.4). Notable exceptions to this pattern are the Sevenmile Creek subwatershed
(ranked third in the far right column of Table 5.2) and the Twentymile Creek subwatershed (whose rank is
considered anomalous, as the vast majority of that subwatershed lies outside of the study area).
5.7 Wetlands
An extensive body of information regarding wetlands, including technical definitions and classification,
the history of their abuse in the United States, and their importance for water supply, water quality, and
wildlife habitat is readily available through an on-line publication of the U.S. Geological Survey (USGS
1999), and will not be reiterated here. Their close association with floodplains is described above (see 5.6
floodplains), and their roles in supporting aquatic plants and animals are described in detail in 6.1 Animal Life
and 6.2 Aquatic Plant Life.
Wetlands are critically important and widespread features within the study area, and are vigorously
protected by state and federal regulations. Complete details regarding regulations affecting activities in
wetlands and the joint state/federal wetland permitting process are available on-line (PADEP 2007a).
Unfortunately, these regulations allow natural wetlands to sometimes be destroyed during development, under
joint permits issued by the state and U.S. Army Corps of Engineers, with the condition that wetlands of equal
or greater size are constructed elsewhere through "mitigation." This process may result in a net loss of
wetland functions in a particular area. For example, a large area of wetlands was destroyed (by in the
Walnut Creek watershed during construction of the Millcreek Mall, and this likely contributed to some of the
water quality problems now experienced in that system (PADEP 2007b).
5.8 Hydrology
Stream discharge is a measurement of the volume of water moving past a specific cross section in a
stream channel per unit time. The discharge will vary seasonally, and may fluctuate dramatically during and
following precipitation events. The persistence of a stream