Ecology of Red Maple Swamps in the Glaciated Northeast: A ...

inflow^
Outflows
OF
SWQ
SWI
Fig. 25. Inflow-outflow components and
water budget equation for a red maple
swamp (based on Novitzki 1982).
GWI
R
Water Budget Equation:
whore*
P + OF + SWI + GWI a ET + SWO + R
P = praclp~tatron fall~ng on the wetland
OF - overland flow Into tho wettand
SWI - streamflow Into the wetland
GWI = groundwater flow Into the wetland
ET - svapotransp~rat~on out of the wetland
SWO - stroeinflow out of tho wettand
R ror:hargo from wotlnnci to groundwater
slope wetlands). Other pertinent information on
the two wetlands is given in Table 2.2.
Total surface-water discharge from each wetimd
mounted to approximately 48% of precipitation.
The spring n~onths (March-May) accounted
for 70-75% of tl~e total annual discharge at both
sibs. By analyzing well and stream hydrographs,
UBrien determined that nearly 93% of the total
discharge from both wetlands originated as
~mdwater irdlow. The discharge of groundwater
was relatively rapid, however, and OBrien swrnieed
that there was insufficient storage to mainbin
perennial streandlow, While both red maple
swamps were primarily zones of groundwater discharge,
the Conant had wetland recharged the
~undwater system for 6 weeks in the late surnmer
and early fall. During this dry period of the
year, the volume of groundwater recharge from the
wetland was several orders of magnitude greater
than surface-water discharge.
Low vertical permeability in the well-decompcrsed
organic ssil at the Route 2 wetland caused
artesian conditions to exist at that site for most of
the year; groundwater was prevented from discharging
at the surface of the wetlmd by the
organic soils. High horizontal permeability in
these soils allowed groundwater to discharge lat-
erally along the edges of stream channels. Where
the channels had cut through the entire organic
deposit, exposing the underlying sands, groundwater
discharge was considerable. The artesian pressure
beneath the organic material was relieved by
discharge of groundwater into the stream channels
instead of to the wetland surface; consequently, the
surface was relatively dry during much of the
growing season.
Woo and Vdverde (1981) reported similar fmdings
from a study of a perched red maple swamp
in southern Ontario. During 1 year of detailed
hydrologic measurements, they found that water
Table 2.2. Gerzeral characteristics of red maple
forested wetlands studied by O'Brien (1977).
Route 2 Conant Road
Feature
-
wetland
-
wetland
-
Surficial geology Glaciofluvial Till
Wetland size @la) 85 72
Watershed size (ha) 319 290
Soila 1 m sapric 3 m hernic-fibric
a Sapric refers to well-decompcpsed organic soil, while hemic and
fibrir refer to moderately well decomposed and poorly
decomposed organic soils, respectively.