7812

• UCREFRP Catalog Number: 7812
• Author: Many
• Title: Rivers, Studies in the Science, Environmental Policy, and Law of Instream Flow
• USFW Year: 1990
• USFW - Doc Type: Rivers
• Copyright Material: YES

TABLE 3
Summary statistics for eight New England hydrologic regions

Region Median
cfsm
Mean cfsm (range)
SD 95% C.I.
lower 95% C.I.
upper Sample
size
Mountain-Windward 0.63 0.62 (0.50-0.78) 0.07 0.58 0.67 11
Mountain-Leeward 0.29 0.31 (0.21-0.56) 0.09 0.26 0.36 15
Interior-West 0.34 0.33 (0.25-0.39) 0.07 0.25 0.41 3
Interior-Central 0.17 0.21 (0.16-0.33) 0.08 0.08 0.34 4
Interior-East 0.27 0.28 (0.21-0.43) 0.07 0.22 0.33 8
Gulf of Maine 0.38 0.38 (0.37-0.38) 0.01 0.31 0.44 2
L. 1. Sound 0.36 0.40 (0.22-0.62) 0.12 -0.11 0.90 3
St. Lawrence 0.42 0.43 (0.38-0.49) 0.06 0.29 0.57 3
All regions 0.34 0.38 (0.16-0.78) 0.16 0.21 0.63 49
gland, westerly winds convey storm sys-
tems through the region during summer
months (NOAA 1977a, 1977b, 1977c). To
determine if this hypothesis was true, high
elevation gages (greater than 1,200 feet)
were sorted, using USGS topographic maps,
on the basis of whether each drainage was
predominantly on the windward (west) or
the leeward (east) side of mountain ranges.
The difference in the mean cfsm values of
these two groups was tested and found to
be significant (P < 0.05).
Streams with mean basin elevations less
than 1,200 feet were termed interior, and
were initially subdivided into western,
central, and eastern interior, dictated by
location relative to dominant mountain
ranges (as defined in Table 2). The general
position of these gaged drainages in rela-
tion to mountains was chosen as a basis for
the subdivisions, due to the importance of
topography in inducing localized climatic
and rainfall patterns (Chow 1964). Coastal
drainages are also known to have localized
climatic precipitation patterns (NOAA
1977a) and also generally low mean basin
elevation and stream slope; all or most of
these drainages were within 30 miles of
the coastline. Because of observed differ-
ences in rainfall between coastal southern
New England and the Gulf of Maine
(NOAH 1979), the coastal region was sub-
divided into Long Island Sound and Gulf
of Maine subregions. An eighth region (St.
Lawrence) included all basins located to
the north of the Appalachian Mountains,
at elevations below 1,200 feet, in an area
influenced by St. Lawrence River valley
climate (NOAA 1977b, 1977c).
The next step after eight possible hy-
drologic regions were identified, based on
physiographic basin characteristics (Table
3), was to test the statistical validity of each
region's cfsm value and to test the hypoth-
esis that significant statistical differences
exist among the regions. The mean and
median (as measures of central tendency)
were used as indices to verify that the clas-
sification of cfsm values into the hydro-
logic regions was reasonable.
Although most regions have small sam-
ple sizes, there is still good conformance
between mean and median values for all
regions. Therefore, mean regional values
could be safely used as a parametric statis-
tic for the additional analysis presented be-
low.
Sample sizes of various regions ranged
from 2 (Gulf of Maine) to 15 (mountain
leeward). The mean, median, standard de-
viation, and 95 percent confidence interval
(C.I.) for each region are presented in Table
3. Mean cfsm values ranged from 0.21 cfsm
(central interior) to 0.62 cfsm (mountain
windward). The mean and 95 percent C.I.
for each region are plotted in Figure 5.
The mountain windward region has ex-
cellent agreement among median and mean
values, as well as low standard deviation
and a small C.I. Good general conformance
is also evident for mountain leeward and
interior east regions, each of which con-
tained relatively large sample sizes.
Of the other regions, small sample size
and wide C.I.'s make statistical differentia-
tion of discharge data among those groups
difficult. For example, in the case of the
Long Island Sound gages, both the small
I Z 18 Rivers • Volume 1, Number 1 January 1990