Advanced Identification of Wetlands
in the City of Boulder Comprehensive Planning Area
/ '1 '. f 1 ]UJ
/ /i'v'r
Prepared by:
David J. Cooper, Ph.D. Ecologist
Thorne Ecological Institute
May, 1988
Prepared for.
United States Environmental Protection Agency, Region VIII
and the City of Boulder, Colorado

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A
ddd£
ADVANCED IDENTIFICATION OF WETLANDS IN THE
CITY OF BOULDER COMPREHENSIVE PLANNING AREA
Prepared for:
United States Environmental Protection Agency, Region VIII
and
City of Boulder, Colorado
' 'J.$z
SOC-L h^on 8 u^
)9g m Si q ¦
tender 00 "p® 0 s°0
Prepared by:
David J. Cooper, Ph.D. Ecologist
Thorne Ecological Institute
May 198 8

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FOREWORD
This report is being published by the City of Boulder
Planning Department as a means of disseminating the results of
the advanced identification of wetlands in the City of Boulder
Comprehensive Planning area. This project has been jointly
funded by the City of Boulder and the U.S. Environmental
Protection Agency. The aerial photographs and field data sheets
referenced in the report are on file at the City of Boulder
Planning Department in room 305 of the Park Central Building,
1739 Broadway, Boulder, Colorado. The Planning Department can be
reached by phone at 441-3270. A summary map showing the general
location of the wetlands discussed in this report is attached at
the end of the report.

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TABLE OF CONTENTS
page
A.	INTRODUCTION AND PURPOSE	1
Introduction	1
Purpose	4
B.	METHODS	5
C.	RESULTS AND DISCUSSION	12
Evaluation of Boulder Wetlands	12
Evaluation of Functions Performed by Boulder Wetlands	21
Suggestions for Priority Wetlands	24
Suggestions for Management of Boulder Wetlands	2 6
D.	LITERATURE CITED	3 0
E.	APPENDICES	31
1.	Description of Wetland Functions	31
2.	Wetland Communities of the Boulder Valley	4 0
3.	Wetland Plant Species Occurring In Boulder Wetlands	50
4.	Field data sheets	52
F.	LIST OF TABLES
1.	Aerial Photos for Boulder Wetlands	7
2.	Origin of Boulder Wetlands	13
3.	Water Sources for Boulder Wetlands	13
4.	Acreage, Origin and Water Sources of
Boulder Wetlands	14
5.	Boulder Wetlands Acreage Summary	15
6.	Number and Percentage of Boulder Wetlands
Mapped by NWI	2 0
7.	Summary Table Showing the Number and Percentage
of Boulder Wetlands Performing Each Function to
a High Degree	22
8.	Boulder Wetlands Performing Functions to a High
Degree	2 3

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9.	Boulder Wetlands Performing Three of More Functions
to a High Degree	2 4
10.	Boulder Wetlands Not Performing Any Functions to a
High Degree	24
E. MAPS
1.	1:24,000 map (1 map)
2.	1" = 400' aerials (13 aerials)
3.	1" = 100' aerials (59 aerials)

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ADVANCED IDENTIFICATION OF WETLANDS IN THE
CITY OF BOULDER COMPREHENSIVE PLANNING AREA
A. INTRODUCTION AND PURPOSE
Introduction
In the semiarid portions of the American West, water is a
critical limiting factor for most ecosystems. Total average
annual precipitation in most areas below 9,000 feet elevation is
lower than total potential evapotranspiration and soils typically
have a moisture deficit for a significant portion of the summer.
Dominant vegetation types over vast areas are grassland,
shrubland, pygmy forest and savannah. More lush vegetation
occurs only in areas where the water balance is more favorable.
This may occur on north-facing slopes in the foothills, along
water courses or other sites where water is abundant near the
ground surface. Sites receiving more water (through runoff,
groundwater discharge etc.) than can percolate into soils, run
off or be lost to evaporation will have saturated soils at some
time during the year. If soil saturation occurs during the
growing season, it becomes a leading factor structuring the
ecosystem and controlling the types of plants that can occupy the
site as well as the types of soils that will develop. These
sites, having seasonally or permanently wet soils, support
distinct types of ecosystems that occur only in these wetland
sites.
The abundant water may allow the primary production to be
significantly higher in wetlands than in surrounding uplands.
Wetlands typically support trees, shrubs and coarse herbaceous
1

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species that do not occur in the uplands. Two of the most common
wetland types are (1) riparian ecosystems adjacent to streams
where overbank flow during flood events are common, and (2) areas
where the water table is close to the ground surface. Any
activity which introduces pollution to these sites would directly
or indirectly introduce pollution into surface and ground waters
because leaching or erosion of pollutants into streams or into
groundwater flow systems would occur.
The Federal Water Pollution Control Act, as amended by the
Clean Water Act, provides the mandate for the U.S. Environmental
Protection Agency (EPA) to improve the conditions of streams and
other "waters of the United States" (Hughes et al. 1986) . The
objective of both Acts "is to restore and maintain the chemical,
physical and biological integrity of the Nation's waters". The
Acts are aimed at restoring water quality and maintaining water
in a condition that does not limit its attainable uses. The
concept of attainable uses focuses upon uses that are possible if
streams and water sources were in an undisturbed or natural
condition. This includes water chemistry, the physical structure
of aquatic habitats and the potential of the habitat-water system
to support biota.
The term "waters of the United States", as defined by the
Clean Water Act, is a very broad concept and is defined as:
a.	"all waters which are currently used, or were used in the
past, or may be susceptible to use in interstate or foreign
commerce, including all waters which are subject to the ebb and
flow of the tide;
b.	all interstate waters including interstate wetlands?
2

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c.	all other waters such as intrastate lakes, rivers,
streams (including intermittent streams), mudflats, sandflats,
wetlands, sloughs, prairie potholes, wet meadows, playa lakes, or
natural ponds, the use degradation or destruction of which could
affect interstate or foreign commerce...;
d.	all impoundments of waters otherwise defined as waters of
the United States under the definition;
e.	tributaries of waters identified" (elsewhere in the
regulations);
f.	"wetlands adjacent to waters (other than waters that are
themselves wetlands) identified in paragraphs" (a-f) "of this
section" (33 C.F.R. S328.3(a): 40 C.F.R. S230.3(s) 1986).
For purposes of this report, wetlands are defined as:
"those areas that are inundated or saturated by surface
or ground water at a frequency and duration sufficient
to support, and that under normal circumstances do
support, a prevalence of vegetation typically adapted
for life in saturated soil conditions. Wetlands
generally include swamps, marshes, bogs and similar
areas" (33 C.F.R. Part 328.3(b); C.F.R. S230.3(t) 1986).
Section 404 of the Clean Water Act regulates the discharge of
dredged or fill material into waters of the United States. The
goal of these regulations is to reduce the introduction of
pollutants into our nation's waters and to preserve and restore
the integrity of our nations waters.
Not only do wetlands play a key role in protecting the
nation's waters, but recent syntheses of scientific data have
improved our understanding of the broad range of wetland
functions (Adamus and Stockwell 1983, Sather and Stuber 1984).
Wetlands are now known to be critical in the function of:
3

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(a)	ground water recharge; (b) ground water discharge; (c) flood
water retention/detention/storage; (d) shore-line anchoring;
(e) sediment trapping; (f) nutrient retention; (g) food chain
support; (h) fish and wildlife habitat; (i) active and passive
human recreation. Not all wetlands provide all of these
functions, and most provide only a few to a very high degree.
All of these functions are valuable to human society and thus
wetlands providing any of these functions to a high degree are
very valuable to society.
Purpose
The purpose of this project was to identify, map, describe
and evaluate the functions being performed by wetlands occurring
within areas 1 and 2 of the City of Boulder Comprehensive Growth
Planning Area. The data will be used by the U.S. Environmental
Protection Agency in evaluating the applicability of the advanced
identification process which has as its purpose the designation
of wetlands which federal regulators feel are suitable or
unsuitable for disposal of dredged and fill material. Advanced
identification of key wetlands will help protect the water
quality and other wetland functions of the region and provide
local regulators and the regulated public with information to
allow appropriate advanced planning and decision making. The
advanced identification process is described in the Section 404
(b)(1)	Guidelines or 40 C.F.R. Part 230.80. Evaluation of all
wetlands in the study area will allow an objective evaluation and
make it possible to identify wetlands with the highest functional
values and also the most sensitive wetlands in the area.
4

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B. METHODS
The study area includes all land within areas 1, 2a, and 2b
of the City of Boulder Comprehensive Planning Growth Areas, as
delineated on the map by the same name and dated January, 1986.
Area 3 was not included within this study because these areas are
protected as parks and open space or are not developable in the
near future because they will not receive city utilities within a
15 year planning period. As areas change from area 3 to 2, an
evaluation of wetlands in such areas will be required by the
Planning Department.
A complete set of 1"=400/ aerial photographs for this region
were used as a preliminary guide for locating wetlands, as were
the wetland maps for this region which are available from the
U.S. Fish and Wildlife Service's National Wetlands Inventory. It
quickly became apparent during this study that many wetlands do
not appear on the National Wetlands Inventory (NWI) maps, nor are
they apparent on the 1"=400/ blueline aerials available through
the City of Boulder and Boulder County. Wetlands having a high
water table but which rarely have surface water were, for the
most part, not identified by the National Wetlands Inventory and
were not identifiable on the blueline aerials. This made it
necessary to visit all open land within the study area. Even in
the field many wetlands were not visible by casual observation
from a single location, such as a road. Thus, each parcel had to
be walked. This was especially true for flat sites and for
wetland sites that were not dominated by cattails, willows or
other rank plants. Wetlands dominated by sedges, rushes, three-
square and forbs are not always easily identified at a distance
5

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on the ground.
Each wetland was numbered and that number appears on the
field data sheet for that wetland (Appendix 3). Wetlands are
identified by this same number on every aerial photo and map used
in the study. The locations of all wetlands are identified on a
single large scale (1:24,000) topographic map (map pocket). Each
wetland is also located on both l'^OO' and 1"=100' aerial
bluelines (Table 1).
In using this map system the following procedure is
suggested. Locate the area of interest on the 1:24,000 scale
map. If a wetland occurs in the area, use the wetland number
shown on the map and Table 1 to determine the 1"=400/ and l'^lOO'
aerials on which the wetland of interest is located and plotted.
It will then be routine to find the area of interest in relation
to the mapped wetlands. Note that many wetlands occur on more
than one aerial at each scale. Table 1 lists all aerials on
which each wetland occurs. Field data sheets for each wetland
are in numerical order in Appendix 4 and provide a description of
each wetland. A total of 73 maps and aerials are used in this
work. One, 1:24,000 scale base map is used, thirteen 1"=400'
scale aerial photographs, and fifty nine 1"=100' scale aerial
photographs.
The purpose of this mapping was not to plot the exact
wetland-upland boundary for regulatory purposes but to identify
in a single field visit where wetlands exist. For regulatory
purposes each wetland will have to be delineated more precisely.
Other information collected at each wetland site were a general
6

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1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
TABLE 1. AERIAL PHOTOS FOR BOULDER WETLANDS
1"=400 '
1"=400 ' 1" = 100
1"=100' 1"=100
2076-
2076-
2076-
2076-
2064-
2064-
2064-
2064-
2064-
2076-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2064-
2076-
2076-
2076-
2076-
2076-
2076-
2076-
2076-
2076-
2076-
2076-
2064-
2064-
2052-
2064-
2064-
2076-
2076-
232
¦240
•240
¦240
¦240
-240
-240
¦240
¦240
¦232
-248
¦248
¦248
-248
¦248
•248
•232
-232
-232
¦232
•248
¦248
¦256
-256
-224
-224
-256
-256
-256
¦256
-264
-272
-272
¦264
•240
¦264
¦264
-264
-264
¦264
¦264
¦248
-256
-256
•256
¦256
¦256
¦256
2076-232
2076-232
2064-232
2064-248
2064-232
2076-249
2064-224
2064-224
2076-272
2076-238
2079-24?
2076-242
2076-264
2079-
2070-
2070-
2070-
2070-
2070-
2079-
2073-
2073-
2070-
2067-
2067-
2070-
2073-
2073-
2073-
2073-
2070-
2073-
2067-
2070-
2073-
2073-
2070-
2067-
2070
2070
2082
2082
2082
2082
2082
2076
2082
2082
2082
2082
2079
2085
2073
2067
2061
2064
2064
2082
2085
246
242
246
248
248
244
240
248
248
248
252
252
252
236
236
232
232
248
256
258
260
230
228
262
260
260
254
270
272
272
-266
-264
-244
-264
-268
-268
-270
-266
-264
-254
-260
-262
-258
-260
-262
-262
2076-238
2076-240
2082-246
2070-240
2070-244
2070-246
2073-248
2070-246
2079-238
2073-248
2070-254
2073-234
2073-234
2073-234
2073-254
2070-258
2073-230
2067-262
2070-256
2082-270
2082-268
2082-266
2070-260
2058-262
2064-260
2067-260
2079-262
2082-262
2076-240
2079-240
2070-242
2076-234
2064-258
2085-264 2082-272
2085-272
2082-264
2067-258
2079-264

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49
50
51
52
53
54
55
56
57
58
59
60
1 (continued). AERIAL PHOTOS FOR BOULDER WETLANDS
1" = 4 00 '
1"=4 00 '
1" = 100 '
1"=100'
1" = 100 '
2076-256

2085-262


2076-248

2079-250
2079-248
2076-252


2079-252


2076-248

2079-248


2076-248

2076-252
2076-250
2076-248
2076-248

2079-250
2079-248

2076-240
2076-248
2079-246
2079-242
2079-248


2079-244




2073-258
2070-258



2070-260
2073-260

2064-256

2067-256


2064-256

2067-256




2073-248




2076-244
2076-242
2079-244


2079-242



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site description, notes on the soil substrate, hydroperiod
(duration of flooding or soil saturation), notes on water level
fluctuations, percentage of the area that is vegetated and
unvegetated, notes on the source of water, wetland history (if
known), current disturbance regime, and known outside threats.
The major community types occurring in each wetland area
were described as well as the approximate percentage area of the
wetland that each community occupied. Notes on the depth to
water table and hydric characteristics of the soil were listed
for each community. Soil colors, where listed, are for matrix
chroma just below the A horizon and mottle colors where they
occurred. Standard soil colors are provided from Munsell Soil
Color Charts (Munsell Color, Baltimore, MD). A species list was
made for each wetland, and the percent coverage for each species
within each community was estimated.
A wetland plant species list (flora) for the study area was
developed and is presented in Appendix 3. This list also
presents the most current (August, 1987) indicator status of each
plant species according to the National Wetlands Inventory. This
indicator status is the best scientific judgement of a panel of
experts on what percentage of the total number of individuals of
each species in the central Great Plains region occur in
wetlands. An indicator status for the Boulder Valley based on
the results of this study is also given for each species. This
information will be submitted to the National Wetlands Inventory
of the U.S. Fish and Wildlife Service for consideration in future
revisions of the National Wetlands Plant List.
The following functions were evaluated for each wetland:
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ground water recharge, ground water discharge, flood storage,
shoreline anchoring, sediment trapping, nutrient retention and
removal (long and short term), food chain support (downstream and
within basin), habitat (fish and wildlife), active recreation and
passive recreation-heritage. Each of these functions was ranked
on two different scales. The first scale ranks the intensity
with which that function was or could be performed by that
wetland in its current condition on a scale of 1-5. The
different wetland communities within each wetland were not
separately evaluated, but the entire wetland was given a single
rating. A rating of 1 indicates that that function was not being
performed and could not be performed by that particular wetland.
For example, a Juncus (rush) dominated community that never has
standing water would not and could not provide fish habitat. A
ranking of 2 indicated that the function was performed to a low
degree. A ranking of 3 indicated that the function was performed
to a medium or average degree. A ranking of 4 indicated that the
function was performed to a high degree. A ranking of 5 was
given when a function was performed to an extremely high degree.
For example, a pond built to detain flood waters on an
intermittent stream located within an urban area would likely
have a 5 ranking, if it was large enough to provide this
function, for the flood storage function and probably also for
sediment trapping.
The second ranking system is used to indicate the confidence
\
in the ranking given with the i-5 scale. This ranking system is
based on a three letter scale "a", "b", "c". A rank of "c" was
10

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given if there was great uncertainty of the degree to which the
function was being performed. A rating of "b" was given if the
rating was relatively certain, and "a" was given if the rating
was very certain. For example, in ranking the fish habitat
function, if fish were observed than an "a" was given for this
function. This rating does not indicate the quality of the fish
habitat. The quality of the habitat for fish is ranked on the 1-
5 scale. So if during this investigation a common species of
minnow was found in an intermittent stream the rating for fish
habitat function might be 2a. The 2 would denote a low
functional value for fish habitat, and the "a" denotes certainty
that the habitat does exist. If, however, the same intermittent
stream did not have observable fish populations, the rank for the
fish habitat function would be 2c.
Some functions are in conflict with each other. For
example, trapping of fine seminent is often incompatible with
ground water recharge and ground water discharge because the
sediment makes the soil surface less permeable. Sediment
trapping may also be incompatible with the flood storage and
desynchronization function because sediment accumulation reduces
the capacity of flood storage basins. Sediment trapping,
however, is a virtual prerequisite for the nutrient retention and
removal function, because nutrients many times are a component of
sediments. Thus, each wetland must be evaluated for each
function separately, and no single general rating for each
wetland is attempted. However, some wetlands clearly perform
more functions than others, and some wetlands clearly perform
certain functions to a higher degree than other wetlands. This
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will be obvious on the data sheets for each wetland provided in
Appendix 4 and in the discussion presented later in this report.
For a complete description of each wetland function evaluated in
this study see Appendix 1.
C. RESULTS
Sixty wetlands were identified in the study area. Each is
identified on the three different scales of maps and aerial
photographs provided, and each is described and its functions
evaluated.
Evaluation of Boulder Wetlands
The 60 wetlands were evaluated as to whether or not they
were existing in the landscape in presertlement times, and if
not, what was their origin. The wetlands are divided into three
categories: natural, created by agricultural practices (along
ditches, irrigated fields) or gravel mining, and created by urban
runoff. The acreage of wetlands that owe their origins to two
factors, such as naturally occurring wetlands that are enlarged
due to agricultural irrigation, have been divided and 1/2 entered
into each appropriate category. Table 2 shows the results of
this analysis.
These wetlands were further broken down into categories
which describe their primary water source. These categories are:
streams, ditches, reservoirs, high ground water or springs,
natural ponds, and urban and industrial runoff. Seven wetlands
appear to have two main sources of water. These wetlands are
listed under both categories, and 1/2 of the wetland acreage is
12

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TABLE 2. ORIGIN OF BOULDER WETLANDS
Origin
Total
Number
Wetland Numbers
% of Total
Acreage Acreage
Natural
21
4,
5, 6
, 7,
8,
9, 11, 13,
196.1
36


19,
21,
23,
24,
26, 44, 45,




46,
50,
54,
55,
56, 60


Agricultural
29
If
2, 3
, 10
, 17
, 18, 20, 22,
306.9
56
and Mining

25,
27,
28,
29,
30, 31, 32,




34,
35,
38,
39,
41, 42, 43,




47,
48,
49,
51;
53, 57, 58


Urban
10
12,
14,
15,
16,
33, 36, 37,
44.4
8


40,
52,
59




added to each category. The results are shown in Table 3 and the
acreage calculations for each wetland are summarized in Table 4.
Table 5 summarizes the number of wetlands of different size
occurring in the study area.
TABLE 3. PRINCIPAL WATER SOURCES FOR BOULDER WETLANDS
Water
Source
Number of
Wetlands
Wetland Numbers
Acreage
% of Total
Acreage
Streams
16
Natural Pond 1
Urban/Indust- 6
rial Runoff
5, 6, 7, 8, 9, 11, 13,
14, 15, 16, 23, 44, 46,.


50,
54,
55



Ditches
19
l, :
2, 3,
, 17,
r 24,
, 28,
, 30


32,
38,
39,
42,
45,
47,


48,
49,
52,
.53,
56,
60
Reservoirs
11
10,
20,
22,
27,
29,
31,


34,
41,
51,
57,
58

High Ground
14
2, :
3, 9,
r 11,
, 18,
- 19,
r 21
Water or

24,
25,
26,
31,
35,
43,
Springs

56,
60




12, 33, 36, 37, 40, 59
93.7
138.5
163.9
118.5
20.9
12.1
17.1
25. 3
29.9
21.7
3.8
2.2
13

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TABLE 4. ACREAGE, ORIGIN AND WATER SOURCES OF BOULDER WETLANDS
WETLAND
NUMBER
ACREAGE
ORIGIN
SOURCE
1
2.3
A/M
D
2
46.2
A/M+N
D+G
3
4.2
A/M+N
D+G
4
20.9
N
P
5
3.1
N
S
6
1.4
N
S
7
0.7
N
S
8
3.4
N
S
9
11.5
N
S
10
73.3
A/M
R
11
16.1
N
G+S
12
0.8
U
U
13
0.5
N
s
14
0.1
U
s
15
0.1
U
s
16
1.9
U
s
17
8.6
A/M
D
18
4.9
A/M
G
19
1.8
N
G
20
17.1
A/M
R
21
0.4
N
G
22
2.5
A/M
R
23
10.2
N
s
24
8.5
N
G+D
25
1.8
A/M
G
26
15.9
N
G
27
6.9
A/M
R
28
4.8
A/M
D
29
6.5
A/M
R
30
1.2
A/M
D
31
5.2
A/M
G+R
32
6.3
A/M
D
33
2.1
U
U
34
19.9
A/M
R
35
4.2
A/M
G
36
2.2
U
U
37
4.9
U
U
38
4.1
A/M
D
39
4.8
A/M
D
40
1.7
U
U
41
30.2
A/M
R
42
2.2
A/M
D
43
12.8
A/M
G
44
3.2
N
s
45
4.5
N
D
46
5.5
N
S
47
4.9
A/M
D
48
3.1
A/M
D
49
4.8
A/M
D
50
34.6
U+N
S
51
1.2
A/M
R
14

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TABLE 4. CONTINUED

52
12.9
U
D

53
7.9
A/M
D

54
4.5
N
S

55
4.9
N
S

56
26.5
A/M+N
D+G

57
1.9
A/M
R

58
1.8
A/M
R

59
0.4
U
U

60
46.5
A/M+N
D+G


Abbreviations
used in Table 4.
A/M
= Agriculture
or Mining ;
N = Naturally Occurring ; .
U =
Urban Runoff
; S = Stream
; D = Ditch
; R = Reservoir
G =
Ground Water
; P = Natural
Pond ; U =
Urban/Industrial
TABLE 5. BOULDER WETLANDS ACREAGE SUMMARY TABLE
Less than one acre
One to ten acres
Greater than ten acres
7 WETLANDS
39 WETLANDS
14 WETLANDS
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This data describes the types of wetlands occurring in the
Boulder valley very well. Most natural wetlands occur along
natural stream systems in oxbows, along shores and in overflow
areas. Many of these streams once had wide floodplains and
meandered extensively. Abandoned or seldom used channels were
vegetated, held water and usually did support wetlands. However,
most of these backwater areas, particularly along Boulder Creek,
have been filled and the wetlands lost. Only one natural pond
(Sombrero Marsh, wetland number 4) occurs in the study area. The
natural wetlands appear to support a number of plant species that
are not found in the more recently created wetlands. For
example, Lobelia siphilitica and Agalinis tenuifolia both of
which are rare in the Boulder Valley were found in the remaining
fragments of sloughs in the Boulder Creek, Bear Creek and South
Boulder Creek system. In addition, species of Bidens spp.,
Leersia oryzoides and other plant species are most common in the
sandy channels of these drainages. Most of the area occupied by
these species has been lost to urbanization. Spiranthes
diluvialis which is found in some wetlands in City of Boulder
Open Space in the South Boulder Creek drainage near U.S. 36, is
extremely rare in the Rocky Mountain region. This species was
found in wetland 21 in the study area (which did not include the
Open Space lands designated as Area 3 of the Comprehensive Plan).
Most of the mature cottonwood-willow stands in the Boulder Valley
occur along the major natural drainages in the region, and these
are prized wildlife habitat.
Almost two thirds of the wetlands in the study area
apparently are totally or partially a result of man's activities,

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particularly agriculture and gravel mining. Twenty nine wetlands
are associated with ditches, leaks from ditches, flood irrigated
fields, reservoir margins and backwaters, and leaks from
reservoirs (Table 2). Wetlands located along reservoir margins,
ditch banks and natural streams support woody vegetation, while
wetlands in other sites tend to have saturated soils for longer
periods of time during the growing season and support herbaceous
wetland communities. Some of the wetlands created by leaking
reservoirs and ditches are among the largest and most
biologically diverse; wetlands in the study area. For example
wetland number 34, located north and east of Twin Lakes in the
Gunbarrel area appears to be supported primarily by leakage from
the lakes and wetland number 49 supported by leaks from a large
ditch, are both large and biologically diverse wetlands.
It may seem that because more than one half of the study
area's wetlands have been produced by man's activities that more
wetlands occur in the Boulder Valley now than prior to
settlement, but this probably is not true. Presettlement
wetlands were probably found along streams and rivers and in
landscape depressions. All streams and rivers in the study area
have been partially or totally channelized and their flows are
now regulated. Agricultural and urban development has clustered
along Boulder Creek throughout the Boulder Valley and most
natural wetlands have been destroyed. Spring runoff water that
once inundated floodplains at the mountain front and on the Great
Plains is retained in mountain reservoirs for municipal use or
diverted into ditches and canals for agricultural uses. Seeps

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from ditches and reservoirs, and extensive flood irrigation have
created high water tables and wetlands in many parts of the
Boulder Valley that in presettlement condition were dry uplands.
Municipal water ends up in sewer lines and is transported to
water treatment plants, and as street runoff. Urban wetlands are
the result of the redistribution of street runoff, much of which
has been diverted from streams.
Man's activities to divert water for municipal and
agricultural uses has created completely different patterns of
water distribution, resulting in wetlands in different locations,
and of different type than occurred naturally in the Boulder
Valley. Most likely the area of wetlands supported now is
similar to that in pre-settlement conditions, however the types
and functions of wetlands are probably very different. For
example, presently many wetlands occur away from floodplains, and
few occur along floodplains, whereas in presettlement condition,
most likely the majority of wetlands occurred along floodplains.
Important wetland functions that have been largely lost due to
these changes include flood storage and desynchronization, native
fish and wildlife habitat, water quality control (sediment and
nutrient cycling), food chain support and shoreline anchoring.
The types of functions that have increased due to these changes
include increased habitat for waterfowl (created by open water
reservoirs) and active recreation.
In attempting to understand the cumulative impacts of human
development upon water and wetlands in the Boulder Valley, the
redistribution of water for municipal and agricultural uses is
important to understand. In addition, the profound effect of
18

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mountain reservoirs and irrigation canals in reducing seasonal
variation in stream water volume and the elimination of regular
flood events has eliminated an essential component of streamside
wetland functioning. Sediment retention and nutrient cycling are
dependant upon the flooding, as are many food chain and habitat
characteristics. In addition, plant species such as plains
Cottonwood and peach-leaf willow depend upon flood scouring to
create sand bars which are essential seed beds for germination
and establishment of new populations. It is also essential to
understand that at present these streams are not capable of
supporting the types of wetland and riparian ecosystems that they
once did, nor can the ecosystems be recreated by a tree planting
program. What is lost is the ecosystem function, and this can
only be restored by restoring the hydrology of presettlement
Boulder Valley streams and creeks which includes some large flows
and creek bed and bank scouring and high sustained flow in the
spring and early summer as the high mountain snowpack melts.
The wetland maps created during this project were compared
with the National Wetland Inventory (NWI) Maps produced by the
U.S. Fish and Wildlife Service for eastern Colorado to see which
Boulder wetlands they had identified from aerial photographs.
The NWI wetland maps for the Boulder area were mapped from
1:80,000 black and white aerial photographs that had been flown
in 1975. Mapping of eastern Colorado was also one of the first
efforts at wetland mapping by the U.S. Fish and Wildlife Service.
Thus, an attempt was made to determine what types of wetlands
they had consistently identified, and what types they had
19

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consistently missed and these results are presented in Table 6.
This data indicates that the wetlands most accurately mapped
by NWI were those with standing water (ponds and reservoirs,
streams and ditches). Wetlands that can be detected only by
TABLE 6. BOULDER WETLANDS MAPPED IN THIS STUDY AND BY NWI
Number mapped	Number mapped
Type of Wetland	this study	bv NWI
Stream sections	16	9
Ditches	19	7
Reservoirs and Ponds	12	11
High Water Table	14	6
Urban and Industrial	6	2
tonal changes due to differences in vegetation are not easy to
identify. In particular, as mentioned earlier, wetlands
supported by a high water table that rarely have standing water
support vegetation that is similar is size and color in certain
seasons to the upland grasslands. It makes these wetlands
difficult to identify on aerial photographs. The overall
accuracy of the the current NWI maps for the study area, makes
them of limited value as a baseline evaluation of existing
wetlands. This probably also applies to other areas of the Front
Range mapped at the same time. In addition, the NWI maps
identified many wetlands which do not currently exist. Whether
this is due to misidentification by the NWI or whether recent
drainage projects have destroyed wetlands is not known.
20

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Evaluation- Of Functions Performed Bv Boulder Wetlands
Table 7 summarizes the number of wetlands performing each
function to a high degree (a ranking of 4 or 5). The results of
this analysis indicate that flood storage is the function a large
percentage of the wetlands most likely do perform. Other
functions that are performed to a high degree include sediment,
trapping, short-term nutrient retention and wildlife habitat.
This indicates that many wetlands occupy landscape depressions
and receive water from streams or uplands and that this water can
have a rather long residence time in the wetland. Many of the
wetlands also have high biological productivity and are rather
isolated from human disturbances.
Two functions do not appear to be performed by very many
Boulder wetlands. These are active recreation and fish habitat.
This is because most of the wetlands are not suitable for the
types of active recreation activities covered by this function
(canoeing, swimming etc.), most are not open to the public and
few have perennial open water and other habitat features which
can support healthy populations of native fish species.
Most other functions are performed to a high degree by less
than 1/4th of the wetlands surveyed. Table 7 lists the Boulder
wetlands that perform each function to a high degree. Table 8
)
lists the Boulder wetlands that perform three or more functions
to a high degree. Table 9 lists the Boulder wetlands that do not
perform any functions to a high degree. These tables will be
valuable for the advanced identification process and will make it
easier to determine the most valuable wetlands for each function
and for multiple functions in the study area.
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Wetlands that occur along irrigation ditches, farm ponds and
that are fed by leaks from irrigation ditches are those
performing the fewest functions to a high degree. Wetlands fed
by surface waters from streams, adjacent to streams, very
isolated from housing developments, or those surrounded by urban
and/or industrial development are the wetlands that perform
functions to the highest degree.
TABLE 7. SUMMARY TABLE SHOWING THE NUMBER AND PERCENTAGE
OF BOULDER WETLANDS PERFORMING EACH FUNCTION TO A HIGH DEGREE
FUNCTION
NUMBER
PERCENTA
Ground Water Recharge
7
11.7
Ground Water Discharge
11
18.3
Flood Storage
29
48. 3
Shoreline Anchoring
11
18.3
Sediment Trapping
19
31.7
Long Term Nutrient Retention
8
13 . 3
Short Term Nutrient Retention
19
31.7
Downstream Food Chain Support
8
13.3
Within Basin Food Chain Support
11
18.3
Fish Habitat
3
5.0
Wildlife Habitat
17
28.3
Active Recreation
2
3.3
Passive Recreation
8
13 . 3
It should be understood that the functions listed were
evaluated based on methodology developed by the Adamus technique
(Adamus and Sockwell 1983). While this technique has not been
regionalized to local conditions in the western United States the
method does provides an accurate framework for evaluating wetland
functions. The ratings for each function are not based on
quantitative data and a limited data set on these functions was
available. This study was carried out knowing the limitations of
the methodology. However, every wetland was evaluated with
22

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exactly the same methodology and perspective. In addition, the
data base used to evaluate Boulder wetlands is derived from
experience based on hundreds of wetlands studied in the Front
Range area by the principal investigator. Thus, the functional
ratings are a valid comparitive evaluation of the Boulder
wetlands, but they neither provide absolutes, nor do they compare
the Boulder wetlands to wetlands occurring in any other region.
TABLE 8. BOULDER WETLANDS PERFORMING FUNCTIONS TO A HIGH DEGREE
UNCTION	WETLAND NUMBERS
Ground Water Recharge
11, 13, 14
Ground Water Discharge
18, 19, 20
49, 54
Flood Storage
2, 3, 4, 9
21, 26, 33
48, 49, 50
Shoreline Anchoring
1, 5, 6, 7
Sediment Trapping
3, 4, 7, 9
36, 39, 41
Long Term Nutrient
Retention
10, 16, 21
Short Term Nutrient
Retention
4, 12, 14,
36, 39, 48
Downstream Food Chain
1, 5, 7, 8
Support
Within Basin Food Chain	4,	7, 8, 12, 13, 26, 39, 46, 54, 56,
Support	60
Fish Habitat	8,	39, 54
wildlife Habitat	4,	8, 10, 12, 13, 25, 26, 39, 41, 46,
49, 50, 51, 54, 56, 60
Active Recreation	8,	10
Passive Recreation	4,	8, 13, 21, 26, 31, 39, 54
23

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TABLE 9. BOULDER WETLANDS PERFORMING THREE OR MORE
FUNCTIONS TO A HIGH DEGREE
1, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 21, 26, 33, 35, 36,
39, 41, 46, 48, 49, 50, 51, 52, 54, 56, 60
TABLE 10. BOULDER WETLANDS NOT PERFORMING ANY
FUNCTIONS TO A HIGH DEGREE
22, 28, 29, 30, 32, 38, 42, 44, 55, 57, 58
To more critically evaluate any single wetland in the study
area its boundaries must be more accurately delineated and data
collected to quantify its functions. This data would be most
valuable in determining what type of mitigation, if any, could
replace the functions lost due to any filling activities.
Suggestions for Priority Wetlands
In determining which wetlands should be designated as
priority wetlands several factors must be kept in mind. First,
within the study area no pristine wetlands occur: all have been
impacted by human activities. Second, many wetlands have been
created by human activities through the redistribution of water
on the landscape. Thus, wetland functions that once were
performed may not be performed at present and functions that now
are being performed may not have been performed in the past.
Because human activities have changed so much of the physical
landscape and the ecological processes that structure the
biological characteristics of the study area, it is not
reasonable to limit priority wetlands to those which are
naturally occurring remnants of wetlands that occurred in
presettlement times.
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Based upon the functions that now are important to human
society and to the other organisms that are part of the
biological community of the study area, a number of wetlands are
identified as being most important. Each is listed and discussed
below and the order in which they are discussed is not in order
of their quality.
*	Sombrero Marsh (#4). This wetland is large, natural and
provides a number of wetland functions. It is essential that
this be a priority wetland.
*	South Boulder Creek (#54). This section of the Creek is
channelized, but supports very well-developed riparian vegetation
and provides a number of functions.
*	Four Mile Canyon Creek (#23 and #55). This section of the
Creek is heavily over-grazed (#23) but supports riparian forest
and with proper management has good potential to be a valuable
wetland.
*	IBM wetland (#33). This wetland provides an important
water quality function treating runoff from the IBM plant.
*	South Boulder Creek wetlands (#'s 25 + 26). These wetland
areas are among the most diverse and complex in the study area.
A number of habitats and communities are present and they appear
to be largely natural and performing a number of functions.
*	South Boulder Creek floodplain wetlands (#'s 2 + 3).
These large wetland areas are the last remnants in good condition
of what once were very extensive wetland complexes on this broad
floodplain area. Considerable biological diversity occurs.
*	Boulder Creek and adjacent wetlands (#'s 8 + 21). Boulder
25

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Creek is the largest waterway in the study area and is
channelized throughout its extent. It does support luxuriant,
although decadent, riparian forests and provides a number of
important wetland functions. Wetland number 21 is the last
remnant of what was once a rich and diverse lowland floodplain
ecosystem type. It supports a unique flora (for the study area),
and once provided an important flood attenuation function. This
ecosystem has all but been destroyed by human activities, and
this wetland is not a great example of an undisturbed community.
A similar, but species poor, community survives at wetland number
9, along Skunk Creek at the CU Research Park, but that wetland
will soon be destroyed.
*	Twin Lakes (#34 + 41). This pair of reservoirs and the
associated wetlands on the north and eastern side are large, have
considerable diversity and could provide some important
functions. This wetland is chosen mainly for its large size.
*	Bear Creek - Boulder Creek confluence wetland (#11).
Located along Bear and Boulder Creeks this is one of the last
remaining large wetlands in the Boulder Creek area and within the
City limits proper. It contains extensive wetlands but is
heavily impacted by cattle grazing. This wetland could provide
a very important wetland in the middle of the city.
Suggestions for Management of Boulder Wetlands
Direct and indirect human use of wetlands can control the
functions wetlands perform. For example, heavy livestock grazing
can degrade the understory of a riparian forest so badly that
instead of preventing bank erosion, the banks of the riparian

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forest are eroding. Wetlands that are heavily grazed might also
be so saturated with nutrients from livestock excrement that the
wetlands will not provide any water quality function for incoming
surface waters. The suggestions provided here will help
Boulder's wetlands perform high quality functions.
(1)	Grazing management. Livestock should not be allowed to
graze in riparian corridors and fences must be erected to exclude
the animals.
(2)	The City should consider the use of'controlled releases
from Barker and Gross Reservoirs to provide stream flows larger
than presently occur to reinitiate the geological processes that
cause sediment erosion and deposition in Boulder Creek and South
Boulder Creek. Bare sediment is the required seed bed for
cottonwood and peach-leaf willow trees. These two species form
the majority of tree canopy vegetation in our riparian zones in
the Boulder Valley and currently these species are not
reproducing because appropriate seed bed is not regularly
created. These are two most important trees for providing high
recreation value as well as fish and wildlife habitat and the
perpetuation of these species should be considered a high
priority.
Controlled releases need not be of flood size or endanger
property and lives, but they should be large enough to create
some erosion and deposition in the channel and banks. The timing
of the releases must be be when the trees are releasing their
seeds. This stream management technique will need to be tried a
few times to determine the proper flow volume to provide trie
needed seed beds. It need occur only once every few years .and

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this could be years when there is ample snow melt water for
filling reservoirs.
(3)	At least one abandoned dump is located adjacent to a
priority wetland, Sombrero Marsh. This dump is the property of
the Boulder Valley School district and currently there is no
information available describing whether or not toxic pollutants
exist in the dump. The City should encourage the School District
to identify possible toxic materials in their dumps and determine
the extent of pollution that is escaping from the dump into
Sombrero Marsh.
(4)	Many streams in the Boulder Valley have eroded their
channel so that the creek is much lower than the adjacent banks
and floodplain. These streams do not support adjacent
riparian vegetation and the value of these streamside habitats is
very small compared to banks with diverse riparian vegetation.
The City should consider some small projects to enhance stream
sides. One area to consider such a project is along South
Boulder Creek between South Boulder Road and Baseline Road.
These projects should not be expensive, and some of the goals of
these projects could be fulfilled if the controlled releases from
upstream reservoir described in number 2 above were implemented.
(5)	Develop storm water retention/detention'facilities in
new housing and commercial areas. Adequate storm water
management in areas with largely impermeable surfaces will reduce
peak flows into wetlands and help protect them from serious
erosion.
(6)	Develop wetland tertiary water treatment systems for
T O

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effluent from the municipal water treatment plant that is too
high in nitrogen compounds. Carefully designed wetlands are
widely used in many parts of the U.S. for wastewater treatment.
The removal of nitrogen compounds from wastewater would enhance
water quality downstream and increase the fish habitat function
in many portions of Boulder Creek. In addition, these wetlands
could be quite large and add significant acreage to the existing
Boulder wetlands and could provide functions such as wildlife
habitat, especially for water birds.
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D. LITERATURE CITED
Adamus, P.A., and L. Stockwell. 1983. A Method for Wetland
Functional Assessment, Vol. I, and Vol. II. U.S. Department of
Transportation. Federal Highway Administration.
Adamus, P.R., Clairain, E.J., Smith, D. R. and Young, R.E.
1987. Wetland Evaluation Technique (WET). Department of the
Army, Waterways Experiment Station, Corps of Engineers, PO BOx
631, Vicksburg, Mississippi.
Cooper, D.J. 1986. Structure and classification of Rocky
Mountain Wetlands. Pages 66-146. In: Windell, J.T., Willard,
B.E., Cooper, D.J. and others. An Ecological Characterization of
Rocky Mountain Montane and Subalpine Wetlands. U.S. Department
of the Interio. Fish and Wildlife Service. Biological Report
86(11).
Hughes, R.M., Larsen, D.P., and Omernik, J.M. 1986. Regional
Reference Sites: a Method for Assessing Stream Potentials.
Environmental Management 10: 629-635.
Sather, H. and Stuber, P. 1984. Proceedings of the National
Wetland Values Assessment Workshop. U.S. Department of the
Interior. Fish and Wildlife Service. FWS/OBS-84-12.
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APPENDIX 1 : DESCRIPTION OF WETLAND FUNCTIONS
The following is a description of each function listed
above, and a description of how each function was evaluated in
the field. Also included is a description of how the ranking
system for that function was used in the field. These functions
and the indicators of whether or not a function is currently or
could potentially be performed by a wetland are from "A Method
For Wetland Functional Analysis: Volumes I and II" by Paul Adamus
and L. Stockwell, published by the Federal Highway Administration
(Adamus and Stockwell 1983). This manual has recently been
revised and updated and is published by the U.S. Army Corps of
Engineers in draft form as the Wetland Evaluation Technique (WET)
(Adamus et al. 1987). This latter document has been utilized
only slightly because it appeared when this work was already in
progress.
Ground Water Recharge. This function involves the movement
of surface water or precipitation into the ground water flow
system. This is a very difficult function to estimate without
actual flow measurements. Physical characteristics of a wetland
that appear to be good indicators that ground water recharge is
occurring are: porous underlying strata, low sediment trapping
efficiency, a dam occurring on the waterway at the wetland
location, a densely vegetated basin, a constricted outlet,
surface water inflow is greater than surface water outflow, the
wetland occurs high in the basin and the wetland is irregularly
shaped with high wetland edge to wetland area ratio. A dam site
on alluvium would most likely perform this function and would be
given a high rating. A moving stream in alluvium would likely
31

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have a medium chance of performing this function. A fast moving
stream on clay substrate (which is relatively impermeable) would
probably not perform this function or perform it very slightly.
It would thus get a low ranking.
Ground Water Discharge. This function involves the movement
of ground water into surface water (e.g. springs). It is very
difficult to estimate whether or not this function is operating
unless it is actually seen or measured. Factors which give an
indication that this function may be performed include:
unconstricted outlet, occurs low in the watershed (low hydrologic
head), lithologically diverse (different bedrock types, some of
which may be waterbearing), a dam upstream (which would be
recharging the ground water just upstream), and the basin is not
silty. Many wetlands occur due to ground water discharge. For
example wetland number 19 is located on the side of a hill where
a large spring occurs. Other examples of wetlands occurring
where this function occurs are adjacent to a reservoir (such as
wetland number 34 east and north of Twin Lakes in Gunbarrel). An
example of a wetland where this function would probably be of low
value is wetland number 4, Sombrero Marsh, (a seasonal pond-marsh
on fine-textured substrate which is probably isolated from the
underlying ground water).
Flood Storage. Flood storage is the process by which peak
flows (from runoff, surface flow, ground water interflow and
discharge and precipitation) enter a wetland basin and are
delayed in their downslope journey. This function includes flood
desynchronization. This latter process involves the simultaneous
32

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storage of peak flows in numerous basins within a watershed and
their subsequent gradual release in a non-simultaneous, staggered
manner. Wetlands which are known to perform this function
typically have some of the following characteristics: occur in a
large watershed, are along an order 1 or 2 (very small) stream,
the size of the wetland is greatly increased in flood times, the
basin is large and deep, has a low gradient, sediments are
unsaturated (not permanently saturated), has high above-ground
and/or below-ground storage, has no outlet and has dense
vegetation. A wetland that would most likely perform this
function to a high degree would occupy a large and broad, low
gradient basin (such as wetland numbers 40 and 9) or a small
basin that has a dam on it (for example wetland numbers 52 and 50
in the South Boulder Creek drainage between Valmont Road and
Arapahoe Avenue). Wetlands that most likely would not perform
this function would be channelized stretches of streams (for
example wetland number 5, and 6 along Bear Creek) and the
numerous irrigation ditches and canals in the study area.
Shoreline Anchoring. Shoreline anchoring is the
stabilization of soil at the water's edge or in shallow water by
plant species with fibrous roots and may include long-term
accretion of sediment and/or peat. Wetlands that perform this
function occur along open water (lakes and streams). Rating this
function is done under the assumption that vegetation density and
vegetation type and wetland width are important predictors.
Wetlands dominated by woody vegetation located along streams in
which the stream bottom is largely covered by fibrous roots
surely provide this function to a high degree (for example
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wetland number 54 along South Boulder Creek where the entire
channel bottom in many areas is covered with fine and medium
sized tree roots. Wetlands that would not perform this function
are those that do not have open water.
Sediment Trapping. Sediment trapping is the process by
which inorganic particulate matter of any size is retained and
deposited within a wetland or its basin. This function may be
performed for short-term or long-term. Wetlands which perform
this function typically have the following characteristics: no
outlet, surface water input exceeds surface water output, dense
vegetation, and gently sloping wetland edges. They also have
deposits of mud or organics which indicate deposition. Wetlands
that perform this function to a high degree occur behind a dam
(such as wetland number 16), or occur in a detention pond in
urban areas (for example wetland number 14 along Goose Creek at
30th and Mapleton Street). Flood irrigated fields with dense
vegetation (such as wetland numbers 2 and 3) probably also
perform this function.
Nutrient Retention "and Removal. Nutrient retention is the
storing of nutrients within the substrate and vegetation of
wetlands. Nutrient removal is the purging of nitrogen nutrients
by conversion to gas (denitrification) while nutrient retention
may involve trapping of runoff-borne nutrients in wetlands before
they are carried downstream or to underlying aquifers. Nutrient
storage in wetlands may be for long-term (greater than 5 years)
or short-term (30 days to 5 years). The most critical nutrients
for retention in aquatic ecosystems and removal are nitrogen and
34

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phosphorus compounds, although other nutrients may also be
important.
Wetlands that perform the nutrient retention or removal
function for long-term typically have the following
characteristics; high sediment trapping function, organic matter
accumulation, no outlet, flooded permanently or semi-permanently
(this creates reducing soil conditions which support active
populations of denitrification bacteria and also minimizes the
oxidation of organics which facilitates peat accumulation). An
example of a wetland with long-term nutrient retention functions
would be one with highly productive vegetation and highly organic
soils that are permanently saturated (for example wetland number
2 which is flood irrigated and grazed pasture land. Other
examples would be where sediment retention is high, because many
nutrients are received adsorbed to sediments, for example wetland
number 16. Many wetlands located in'urban and industrial areas
would perform this function.
Wetlands that perform this function for short-term typically
have the following characteristics: high net biological
productivity, sediment retention, non-acid soils, and/or occur in
watersheds that are highly developed including urban, industrial,
and/or agricultural land uses with eroding soils and/or where
fertilizer is applied. An example of a wetland that performs
this function for the short-term is one with extremely productive
vegetation and permanently saturated soils. Most densely
vegetated cattail (Typha) stands would meet this criterion (for
example, wetland number 33 located at IBM's facilities). A
wetland that would not perform this function would have a very
35

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sparse vegetation, little sediment retention, and a steep slope
which would keep sediment moving (for example wetland number 6
along Bear Creek which is channelized and has little edge
vegetation, or wetland number 37 in Gunbarrel which is largely an
alkali flat with little plant production).
Food Chain Support. Food chain support is the direct or
indirect use of nutrients, in any form, by animals inhabiting
aquatic environments. Food chain support may occur within that
wetland basin or downstream. Wetlands that perform downstream
food chain support typically have the following characteristics;
an outlet, non-acidic waters, not sandy substrate, not
permanently flooded, a dense and diverse vegetation with high
sustained productivity, not stagnant or with severe scouring, not
hypersaline, good flushing flows, and vegetation overhanging the
water. An example of a wetland that would provide high quality
downstream food chain support would' be number 54, South Boulder
Creek. Wetlands that perform within-bas'in food chain support
typically have the following characteristics; not stagnant water,
highly productive vegetation, irregularly shaped wetland with no
outlet, without being entirely shallow and warm water in the
summer, and has good mixing of the water. An example of a
wetland that would have high within- basin food chain support
value would have high diversity of plants and animals.
Habitat. Habitat includes those physical and chemical
factors which affect the metabolism, attachment, and predator
avoidance of the adult or larval forms of fish, and the food and
cover needs of wildlife in the place where they reside. These
36

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factors determine the suitability of a given site for an animal
species. For this study, habitat was evaluated for fish and for
wildlife (birds and mammals) separately. Wetland physical and
chemical characteristics that are good for one species is not
necessarily good for another species, thus there are few
indicators of good habitat for animals in general.
Wetlands that provide good fish habitat typically have the
following characteristics; some open water which is not shallow,
not acidic, not turbid, no barriers to migration, no oxygen
stagnation, no artificial fluctuations, not oligotrophic, not
flashy, cool water temperatures with some shade. An example of a
wetland that provides these characteristics is wetland number 38
which has cool flowing water, shade, and is not turbid or flashy.
Wetlands which do not have open water are all examples of
wetlands that do not provide the fish habitat function.
Wetlands that provide good wildlife habitat typically have
some of the following characteristics; good edge ratio, islands,
high plant diversity, some (but not excessive) alkalinity,
sinuous and irregular basin, the basin and wetland are not small,
gentle gradient, no artificial water level fluctuations, not moss
dominated, pH exceedes 6.0, some open water, not urban or deep
water, not channelized or farmed, undisturbed by man, and has
good food sources. An example of a wetland that would probably
provide high quality wildlife habitat would support a diverse and
productive vegetation, have some open water, be fairly
undisturbed and provide some isolation from man's activities
(such as wetland number 4, Sombrero Marsh).
Active Recreation. Active recreation refers to recreational
37

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activities which are water-dependant and can occur either in an
incidental or obligatory manner in wetlands. This includes the
following activities: swimming, boating, canoeing, kayaking and
sailing. Hunting is not water-dependant and is not considered
here. Wetlands that provide this function typically have the
following characteristics; direct evidence of actual use for a
certain activity, convenient public access, mostly unvegetated,
some sand, little debris, slow standing water, channels and boat
launch facilities, permanently flooded basin, no algal blooms and
not weedy. A wetland that would provide these characteristics in
the study area would typically be a reservoir (such as Twin Lakes
in Gunbarrel, wetland number 41), although certain streams large
enough to support boating also would support this function. Most
wetlands in the study area however, do not support this function
to a high degree because there is limited public access, little
or no open water and many large water bodies, such as Boulder
Reservoir, are already in public ownership as Parks land and
management focuses on active recreation.
Passive Recreation and Heritage Value. This function
includes use of wetlands for aesthetic enjoyment, nature study,
picnicking, education, scientific research, open space,
preservation of rare species, maintenance of the gene pool,
protection of archaeologically or geologically unique features,
maintenance of historic sites and numerous other activities.
Wetlands that perform this function typically have the following
characteristics; rare plants, landscape diversity, unity of
landscape elements, are a natural area, scarcity of this type of
38

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wetland, freedom from eyesores. Some of the remaining fragments
of the Boulder Creek oxbow complex near Foothills Highway
(wetland number 21) support rare plants, but do not provide any
of the other characteristics of this function. Some of the
larger wetland complexes such as Sombrero Marsh (wetland number
4) support many of the features that are characteristic of this
function. Many wetlands in the study area do not provide this
function to a high degree at present.
39

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APPENDIX 2 : WETLAND COMMUNITIES OF THE BOULDER VALLEY
A perplexing variety of combinations of plant species
presents itself to anyone investigating wetlands in the Boulder
Valley. Species sort out along gentle and almost imperceptible
gradients of depth to water table and drainage, alkalinity, water
aeration, disturbance regime (including grazing and artificial
water level manipulations) and other environmental factors and
typically occupy distinct, and well-defined portions of these
gradients. At first glance the vegetation complex at each
wetland is difficult to subdivide into communities or ecosystem
types. However, with experience it can be seen that a large
number of distinct communities occur again and again across the
landscape, repeatedly in similar ecological situations.
The primary objective of this study was to map and describe
the functions of wetlands in the Boulder Valley. However, a
sidelight was to begin to develop a framework for describing the
types of wetland communities that occur along the Colorado Front
Range. This includes the regions from Pueblo to Fort Collins.
From my work on wetlands in this region over the past several
years I feel that it is possible and practical to develop a
classification of wetland types for this region. However, it
should be recognized that this region presents a fantastic array
of species and a tremendous variety of different habitats and so
the number of different and repeated community types that will be
found here will be quite large. It should also be recognized
that an understanding of vegetation science is necessary to
develop and employ such a classification of ecosystems or
40

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communities. Communities are abstract units that are a synthesis
of many different stands which have similar floristic composition
and occur in sites with similar environmental characteristics.
It should not be expected that each stand (example) of a certain
community will be identical to other stands. It should also be
remembered that many stands will be fragments of a particular
community due to disturbance eliminating certain species. Also,
mixtures of communities can and do occur where the environmental
gradients are gentle.
The following discussion presents a preliminary
classification of the wetland vegetation of the Boulder Valley.
The 27 communities described here all occur in the study area,
however the discussion is based not only on data from Boulder but
from hundreds of other wetland communities I have investigated in
the region. It will take several more years before a more
complete characterization of Front Range wetlands can be
produced. Three general types of wetlands occur in the Boulder
Valley, using the terminology I have discussed more completely
elsewhere (Cooper 1986): communities in permanent shallow water;
communities with seasonal or permanent high water tables but
without permanent standing water; and communities adjacent to
running water. Within each of these categories there are several
subcategories based on dominant vegetation form, eg. forested,
)
shrub etc. The system further subdivides communities based on
substrate (water, mineral or organic soils) and water chemistry
(minerotropic vs. ombotrophic for organic substrates, and fresh
vs. saline for mineral substrates). This classification leads to
a number of rather distinct ecosystem types, for example, marshes
41

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and fens. Both of these ecosystem types have a high water table,
do not have permanent standing water and are dominated by
herbaceous plants. Fens have organic (peaty) soils while marshes
have mineral soils. Several different marsh and fen community
types, dominated by different plant species occur due to
different conditions created by elevation, temperature, water
quality etc.
I. Communities in Permanent Shallow Standing Water
A.	Dominated by Floating Plants.
1.	Chara sp. community. This community was found in
Sombrero Marsh, in alkaline standing water water. It occupies
semi-pennanently flooded areas. This appears to be the only
species occupying this site.
B.	Dominated by Rooted Submergent Plants.
2.	Persicaria amphibia community. This community
occupies water from 1-3 feet in depth, and typically occurs along
the fringes of reservoirs. It was found at both Baseline
Reservoir and Hayden Lake. The water regime of these water
bodies is artificially controlled and in late summer these sites
may be dry.
3.	Mvriophvllum exalbescens community. This community
was found only in standing water of wetland number 51 in eastern
Boulder. It is most likely found in nutrient rich water.
4.	Potamoqeton pectinatus - P. foliosus - Elodea
canadensis community. This community is composed of one or more
species of thin leaved submergent plants and occurs in sites that
are permanently flooded and may have slow moving water. The
42

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plants probably can not stand aessication and hence are not
emergent. This community occurs in slowly moving deep water
(wetland number 25, 13) of streams, large canals, and in some
places can be rather weedy, filling canals with plants.
C. Dominated by Rooted Emergent Plants.
5.	Typha latifolia ^ Lemna minor. This community is
common in potholes with shallow standing water (less than 12
inches). Lemna is a floating aquatic plant that proliferates in
high nutrient, slightly alkaline to neutral pH waters. The Typha
typically forms an overstory.
6.	Potamogeton gramineus - Sagittaria cuneata ^ S.
latifolia - Alisma plantago-aquatica ^ Ceratophy1lum demersum
community. This community occupies shallow water (6-24 inches)
of ponds and reservoirs and is very common. The community rarely
has more than two species present and it seems to be
interchangable which species occur.
II. Communities with High Water Table, but Without Permanent
Standing Water
A. Herbaceous wetlands with organic soils and mineral rich
water supplies (fens).
7.	Carex nebraskensis community. This community is
very characteristic of open, flats with very shallow (1-6 inches)
standing water in the early summer and a water table at or very
near the soil surface during the entire growing season. The
community is dominated by this one species of sedge, although
Carex lanuginosa, C. hystricina, Juncus balticus and other
species may also occur. This community may accumulate true peat,
like high altitude or northern fens. For the most part the peat

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is thin (less than 10 inches) but does indicate long-term
nutrient storage.
8.	Tvpha latifolia - T. anoustifolia - Scirpus
lacustris - S. acutus community. This community is typically
dominated by one or two of the species listed above. It forms
dense and productive stands, where healthy, and usually leads to
the formation of soils rich in organics. This is probably the
most common community in the Front Range. Species diversity is
usually low due to shading and possibly allelopathic effects (the
inhibition of one organism by another via the release of
chemicals into the environment). This community may provide many
water quality functions that are important in urban, agricultural
and industrial areas, including sediment retention, nutrient
retention, ground water recharge and flood attenuation.
B. Herbaceous wetlands with mineral soils and fresh water.
9.	Scirpus americanus community. This community is
very common on loamy to clayey soils with neutral to high pH. It
rarely occurs on soils with pH greater than 7.7. This community
is common as a fringe around the Tvpha-Scirpus community (#8
listed above) that occupies wetter sites. The water table is
rarely above the soil surface, but always is close to the
surface. This community may occupy large areas (wetland numbers
11, 24, 34) where ground water discharge occurs. This community
is not easily distinguished and identified as wetland from a
distance or from aerial photographs. However, Scirpus americanus
is a true and abundant obligate wetland plant species in our
region and it occurs only in wetlands.
44

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10.	Juncus balticus community. This species dominates
communities that occupy seasonally wet meadows. These areas
typically have a long grazing history, and this species
reportedly is an "increaser", being unpalatable to cattle. The
stands may have a variety of associated species.
11.	Eleocharis macrostachva - Juncus spp. community.
Communities dominated by Eleocharis are found where there is
usually some standing water early in the growing season, but they
are drier later in the summer. A number of Juncus species may
occur, including J. balticus. J. interior. J. dudlevi and J.
lonaistvlis. These stands are usually small and are found in
complexes with stands dominated by Tvpha. Scirpus and other
wetland plant species.
12.	Agrostis aicrantea community. Redtop dominates
communities found in irrigated hay meadows. It usually is the
dominant plant species but occurs with Phleum pratense. Dactvlis
glomerata. Festuca pratensis and other tall grasses which are all
native to Eurasia and have been widely introduced into pastures
in our area. A number of forbs including Trifolium spp. are
typically found as well.
13.	Poa pratensis - Trifolium pratense community. This
community occurs in irrigated or naturally wet pastures that are
either intensively grazed or mowed. These areas are usually
marginally wetlands because the soils are usually transitional
between hydric and non-hydric, the plant community is typically
dominated by species that are ranked as facultative or
facultative upland by the National Wetlands Inventory. However,
the soils are usually saturated long enough during the growing
45

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season to call them wetlands.
14.	Spartina pectinata community. Spartina typically
thoroughly dominates this community, although it is common to
find a number of other common species as well. Prairie cordgrass
is typically found at springs, on the margins of sloughs and in
some areas may form an organic soil. The stands are usually very
productive. This community probably was very common along river
floodplains, on the edges of ox-bows and sloughs and in
floodplain margins in presettlement times. This community now,
however is very restricted in its occurrence.
15.	Phalaris arundinacea - Circium arvense community.
This community typically occurs in disturbed wetland sites where
the water table has been artificially lowered by diverting a
stream, streams downcutting into their floodplain or other
reasons. These species are weedy in nature and are very rapid
and powerful colonizers of damp, highly organic substrates.
16.	Persicaria lapathifolia - Persicaria maculata -
grass community. This community occurs in wet spots in irrigated
hay meadows dominated by the Aarostis aiaantea. or other grass-
dominated community. It is very easily identified due to the
broad leaf nature of the smartweeds (Persicaria).
C. Herbaceous wetlands with mineral soils and alkaline water source.
17.	Scirpus paludosus community. This is an alkaline
marsh community that occurs in shallow seasonally standing water,
or where a high water table, near the soil surface occurs. Soils
always are alkaline and there is usually very low species
diveristy. It is also a very uncommon community, and in the
46

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Boulder Valley the only large stand is at Sombrero Marsh.
18.	Puccinellia distans - Spercmlaria media community.
This community is characteristic of extremely alkaline wetlands
that have a seasonally or permanently high water table. It
usually occurs as an ecotone between Scirpus americanus or
Scirpus paludosus and upland communities. The capillary rise of
alkaline water through heavy soils results in a net accumulation
of solutes at the soil surface. Few species can germinate and
become established in this environment. This is most likely the
most salt tolerant wetland community occurring in our area.
19.	Distichlis spicata - Iva axillaris community. This
community occurs in slightly drier sites than those occupied by
the Puccinellia distans - Spercmlaria media community. Some
stands are not regulatory wetlands. They are characterized by
Distichlis and may not have other species present, except Hordeum
iubatum which is ubiquitous.
20.	Juncus compressus communities. This species
dominates communities that are not as alkaline as the latter two
communities, but that are none-the-less alkaline. They typically
fringe wetland communities dominated by Scirous americanus. but
are rather uncommon in the area.
21.	Atriplex spp. communities. A community found on
seasonally wet sites on the edges of reservoirs where there is a
distinct summer drawdown is typically characterized by species of
Atriplex. The species present are usually annuals, weedy and
tolerate of highly alkaline soils and water.
47

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III. Communities Adjacent to Running Water
A. Herbaceous wetlands.
22.	Glvceria maxima - Anemone canadensis community.
This community occurs along ditches, small streams and slough
where there is usually some moving water during portions of the
growing season. The communities may be quite species rich and
lush. Anemone may form a complete ground cover as it does in
parts of wetlands number 1, 42, and 6 in this study. A taller
overstory with grasses and other species usually also occurs.
23.	Leersia orvzoides - Bidens cemua community. This
community occupies ditches and sloughs along the major drainage
systems in the area. It is lush and species rich and supports
many species that are rare in the Boulder valley, including:
Lobelia siphilitica and Agalinus tenuiflora. It probably
represents a community type and flora that was abundant along the
sloughs of Boulder Creek in presettlement condition. This type
is nearly lost from the Valley.
24.	Impatiens capensis - Stellaria araminea community.
This distinctive community is found along irrigation ditches of
the South Boulder Creek system. It is distinctive because it
lines the ditches with lush and flowery plants. Both of these
species are not native.
25.	Nasturtium officionale - Bacopa rotundifolia -
Berula erecta community. This community is limited to springs
and rapidly moving water that is well-oxygenated. This community
is very distinctive aijd indicative of these conditions. These
species usually choke the channel with lush foliage and probably
have enormous nutrient absorption capacity, thus providing a
48

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major water quality function.
B.	Shrub wetlands.
26.	Salix exicrua community. The sandbar willow
community is distinctive and the primary shrub-dominated
community found along river wetland systems in the study area.
The stems of this willow are reddish-purple and very flexible.
Their flexibility allows them to colonize stream channels and
floodplains and bend flat onto the soil surface during flooding.
Thus they are not eroded, do not accumulate much debris, yet
stabilize the channel and floodplains. This community provides
vital shoreline anchoring and sediment trapping functions. It
also provides food chain support and habitat functions because of
its use by insects, birds, deer and other animals.
C.	Forested Wetlands.
27.	PopuIus sarqentii - Salix anvadaloides - Bromoosis
inermis community. This community is dominant along the major
streams and irrigation canals in the study area. It is the only
forested wetland community in the study area. It may have not
only plains cottonwood and peach leaf willow, but also supports
Fraxinus pennsvlvanica. Acer necrundo. Alnus tenuifolia. Gleditsia
tricanthos. Ulmus americana and other trees and large shrubs. It
this provides major wildlife habitat, food chain, shoreline
anchoring, nutrient retention and removal functions. It also
provides shade in streams that creates good fish habitat. These
forested waterways also are among the most important passive
recreation sites in the area and many are preserved for that function.
49

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APPENDIX 3. PLANT SPECIES OCCURRING IN BOULDER WETLANDS AND
THEIR STATUS ACCORDING TO THE NATIONAL WETLANDS INVENTORY
AND THEIR STATUS IN THE STUDY AREA
Scientific Name
Cannon Name
NWI Rank
Boulder
Acer negundo
box elder
fac
facu
Agalinus tenuifolia
agalinus
facw
facwf/obl
Agropyron repens
quack grass
fac
fac
Agropyron sndthii
western wheatgrass
facu
facu-
Agrostis gigantea
redtop
facw
facw
Alisma plantago-aquatica
plantain
obi
obi
Alnus tenuifolia
narrow-leaf alder
no
facw
Alopecurus aequalis
foxtail
obi
obi
Ambrosia artanisiifolia
ragweed
facu
facu
Anemone canadensis
anemone
facw
facw
Apocynum sibiricum
dogbank
fac
facu
Arctium minus
burdock
upl
facu
Asclepias incarnata
marsh milkweed
obi
obi
Aster ericoides
aster
facu
facu-
Aster falcatus
aster
fac
facu- -
Aster hesperius
aster
obi
facw+/obl
Aster laevis
aster
upl
facu
Bacopa rotundifolia
water-hyssop
obi
obi
Berula erecta
berula
obi
obi
Bidens cernua
nrrHing hnr-marignlH
obi
obi
Bidens frondosa
beggars tick
facw
obi
Brcsnopsis inermis
smooth brome
upl
upl
Calamagrostis canadensis
canada reed grass
obi
obi
Carex brevior
sedge
fac
fac
Carex hystricina
sedge
obi
obi
Carex lanuginosa
sedge
obi
obi
Carex nebraskensis
sedge
obi
obi
Carex praegracilis
sedge
facw
facw
CeratophyHum danersum
hornwort
obi
obi
Cicnorium intybus
chicory
upl
upl
Cirsium arvense
canada thistle
facu
fac
Cyperus inflexus
galingale
obi
obi
Dactylis glcroerata
orchard grass
facu
facu
Dipsacus sylvestris
teasle

fac
Distichlis spicata
saltgrass
facw
fac
Echinochloa crus-galli
barnyard grass
facw
fac
Eleagnus angustifolia
russian olive
fac
fac-
Eleocharis coloradoensis
spike rush
obi
obl
Eleocharis macrostachya
spike rush
obi
obi
Elodea canadensis
elodea
obi
obi
Elymus canadensis
canada wildrye
facu
facu
Epilobium adenocaulon
willow-herb
obi
obi
Epilobium leptophyllum
willow-herb
facw+
facw/obl
Pestuca pratensis
meadow fescue
fac
fac
Fraxinus pensylvanicus
green ash
facw
fac
Gleditsia tricanthos
honey locust
fac
facu
Glyceria maxima
manna grass
obi
obi
Helenium autumnale
helenium
facw
facw

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Helianthus nuttalli
nuttals sunflower
fac
fac-
Hordeum jubatum
foxtail barley
facw
facw-
Impatiens capensis
impatiens
facw
facw
Iris missouriensis
iris
obi
facwf
Iva axillaris ?
marsh elder
fac
fac
Juncus alpinus
rush
obi
obi
Juncus arcticus
rush
obi
facw
Juncus articulatus
rush
obi
obi
Juncus bufonis
rush
obi
obi
Juncus canpressus
rush
no
obi
Juncus dudleyi
rush
fac
facw
Juncus gerardii
rush
no
obi
Juncus interior
rush
fac
fac/facw
Juncus longistylis
rush
facw
facw
Juncus nodosus
rush
obi
obi
Juncus saximontanus
rush
facw
facw
Juncus tracyi
rush
no
facw/obl
Juncus torreyi
rush
facw
facw/obl
Leersia oryzoides
rice cutgrass
obi
obi
Lanna minor
duckweed
obi
obi
Lobelia siphilitica
lobelia
obi
obi
Lolium perenne
ryegrass
facu
facu
Lycopus airericanus
water horehound
obi
obi
Lycopus asper
water horehound
obi
obi
Lotus tenuis
lotus
upl
facu
Medicago sativa
alfalfa
upl
facu
Melilotus officionalis
sweet clover
facu
facu
Mentha arvense
mint
facw
facw+
Monarda fistulosa
pink bergamot
facu-
facu-
Muhlenbergia asperifolia
alkali muhly
facw
facw
Myriophyllum exalbescens
water milfoil
obi
obi
Nasturtium officionale
water-cress
obi
obi
Oenothera coronopifolia
evening primrose
upl
facu-
Oligoneuron rigidum
stiff goldenrod
facu
facu-
Panicum virgatum
switchgrass
fac
fac/facu
Pastinacea sativa
parsnip
upl
upl
Persicaria amphibia
smartweed
obi
obi
Persicaria coccinea
smartweed
obi
obi
Persicaria hydropiper
smartweed
obi
obi
Persicaria lapathifolia
smartweed
obi
obi
Persicaria maculata
smartweed
obi
obi
Persicaria pensylvanica
smartweed
facw+
facwf
Phalaris arundinacea
reed canary grass
facw+
facw+/obl
Phleum pratense
timothy
facu
fac/facu
Plantago lanceolata
englisn plantain
fac
fac
Plantago major
camion plantain
fac
fac
Poa canpressa
Canada bluegrass
facu
facu
Poa pratensis
kentucky bluegrass
facu
fac
Polypogon mcnosepliensis
rabbits foot grass
obi
obi
Populus sargentii
plains cottonwood
fac
fac
Populus Xacuminata
cottonwood
fac
fac
Potemogeton foliosus
pondweed
obi
obi
Potamogeton gramineus
pondweed
obi
obi
Potamogeton pectinatus
pondweed
obi
obi
Prunus airericanus
american plum
upl
upl

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Puccinellia-airoides
alkali grass
obi
obi
Puccinellia aistans
alkali grass
obi
obi
Ranunculus cymbalaria
shore buttercup
obi
obi
Ranunculus macounii
buttercup
obi
obi
Ribes aureum
golden current
facw
facw
Rorippa palustris
cress
obi
obi
Rumex crispus
dock
facw
facw
Rumex salicifolius
willow dock
obi
facw/obl
Sagittaria cuneata
arrowroot'
obi
obi
Sagittaria latifolia
arrowroot
obi
obi
Salix amygdaloides
peach leaf willow
facw
facw
Salix exigua
sandbar willow
obi
facw/obl
Scirpus acutus
softstem bulrush
obi
obi
Scirpus arnericanus
three square
obi
obi
Scirpus lacustris
hardstem bulrush
obi
obi
Scirpus paludosus
alkali bulrush
obi
obi
Scirpus pallidus
bulrush
obi
obi
Scirpus microcarpus
bulrush
obi
obi
Sisyrinchium montanum
blue eyed grass
fac
fac
Solidago gigantea
golden rod
facw
facw
Sonchus oleraceus
ccw thistle
facu
facu
Sorgastrum avenaceum
yellcw indian grass
facu
facu
Spartina pectinata
prairie coragrass
facw
facw/obl
Spergularia media
sand spurry
no
facw
Spiranthes diluvialis
orchid
no
obi
Sporobolus airoides
alkali sacaton
fac
fac
Sporobolus asper
big dropseed
facu
facu
Stachys palustris
hedge nettle
obi
obi
Stellaria graminea
chickweed
no
facw
Thermopsis divaricarpa
golden banner
upl
upl
Thlaspi arvensis
pennycrest
upl
facu-
Trifolium pratense
red clover
facu
facu
Trifolium repens
white clover
facu
facu
Typha angustifolia
narrow leaf cattail
obi
obi
Typha latifolia
broad leaf cattail
obi
obi
Ulmus arnericanus
american elm
fac
facu
Verbena hastata
blue vervain
facw
facw/obl
Veronica anagallis-aquatica
speedwell
obi
obi
Abbreviations: upl : less than 1% of this species' occurrence is in wetlands
facu : 1-33% of this species' occurrence is in wetlands
fac : 33-66% of this species' occurrence is in wetlands
facw : 66-99% of this species' occurrence is in wetlands
obi : greater than 99% of this species' occurrence is in wetlands
no : not listed on the National Wetlands Inventory wetlands
plant list for Region 5, the Central Great Plains
+ : on the higher end of the range
- . : on the lower end of the range
? : I am unsure what ranking this species should receive
/ : this species could be either of the two ranks, but I am
unsure which rank is more accurate at present

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