Literature review: Hydrology -ecology relationships in Montana Prairie
wetlands and intermittent/ephemeral streams

Prepared by:

Linda Vance

Sara Owen

Jane Horton

Prepared for:

The Cadmus Group, Inc.
U.S. EPA Contract Number EP-C-08-002

May, 2013

Literature review: Hydrology -ecology relationships in Montana Prairie
wetlands and intermittent/ephemeral streams

Prepared by:

Linda Vance

Sara Owen

Jane Horton

Prepared for:

The Cadmus Group, Inc.
U.S. EPA Contract Number EP-C-08-002

MONTANA

Natural Heritage
Program

ft N T A N A

State
jflb

Library

vUNIVERSITYOF

MONTANA

P.O. Box 201800- 1515 East 6th Avenue • Helena, Montana 59602-1800 • (406) 444-5354

This document should be cited as follows:

Vance, L, S. Owen and J. Horton. 2013. Literature review: Hydrology-ecology relationships in
Montana Prairie wetlands and intermittent/ephemeral streams. Report to the Cadmus Group and
the U.S. Environmental Protection Agency. Montana Natural Heritage Program, Helena, MT. 49 pp.
plus appendices.

Executive Summary

Numerous published and unpublished studies have examined the relationship between wetland
hydrology, wetland processes and functions, and wetland-dependent biota. The goal of the
present project was to review existing studies, models, and local expert knowledge to describe
hydrology-ecology relations under natural conditions and to generate a systematic
characterization of the relationships between hydrologic regimes and biological dependencies
of prairie wetlands in Montana. This report describes the scope of the project, provides some of
the background information used to frame the literature review, summarizes the methods, and
presents and discusses the findings of the review.

The project's broad geographic scope was defined as the Prairie Pothole Region (PPR) of North
America, which extends across approximately 715,000 km 2 of five US states (Iowa, Minnesota,
North Dakota, South Dakota and Montana) and three Canadian provinces (Manitoba,
Saskatchewan and Alberta). Within that area, it focuses on the 95,907 km 2 Northwestern
Glaciated Plains ecoregion of Montana. The topical scope of the project is the pothole
wetlands of the PPR, and the intermittent and ephemeral streams present in the region.
Because the wetlands of the PPR are so important to North American waterfowl and other
migratory birds, the area has attracted substantial research interest. Scientific investigations
have been far-ranging, from basin-specific short term studies of specific species and wetland
components to long-range, landscape-level analyses and models. Over the years, this has
resulted in a more complete, and more nuanced, understanding of ecosystem processes and
functions and a better characterization of the inherent variability of the region.

In this report, we begin by describing the Prairie Pothole Region (PPR) and the wetlands and
streams that characterize it. We then discuss the methods we used to search for, summarize,
and interpret research reports, agency documents, expert knowledge and models. The extreme
variability of wetland and stream habitats in the PPR accounts for much of its diversity. In our
Results section, we examine how differences between natural and human hydrologic change
affect the functions, processes and biota that depend on wetlands and streams, and how this
affects regional diversity. This is followed by a summary of the impact of anthropogenic change
on a common suite of wetland and stream, notably 1) flood mitigation; 2) water storage and
streamflow maintenance; 3) groundwater recharge; 4) sediment retention; 5) nutrient and
chemical cycling; 6) plant community maintenance; and 7)maintenance of faunal habitat and
biodiversity. In sum, we review over 150 published sources. We conclude that ecological
responses to natural changes in wetland hydrology are variable, depending on the direction of
change and the species, guild or function affected. For example, droughts generally lead to

decreases in avian, macroinvertebrate and fish abundance, depending on the extent and
duration of the drought. Flood cycles, in contrast, promote both greater abundance and
changes in community structure. However, ecological responses to anthropogenic alteration
are almost entirely negative. This difference reflects the duration of natural vs. anthropogenic
change. Natural hydroperiods of wetlands and prairie streams vary spatially and temporally,
with flood and drought cycles altering. In contrast, human manipulations of flood frequency,
duration or extent tend to be permanent, as are the changes in wetland function that they
induce. The Discussion section sets forth some of the implications of these conclusions, and
lays out directions for future research. The Bibliography and Appendices provide more detail
about our sources and approach.

Acknowledgements

This project was funded through a contract from the United States Environmental Protection
Agency to the Cadmus Group, LLC, which subcontracted to the Montana Natural Heritage
Program (MTNHP) to carry out the literature review. Thanks are due to Laura Gabanski of EPA
Headquarters, Laura Blake of Cadmus, and Lynda Saul of the Montana Department of
Environmental Quality for pulling the project together. We were aided by a Technical Advisory
Group consisting of Eloise Kendy and Philip Gerla of The Nature Conservancy, Sean Fields of the
United States Fish and Wildlife Service, and Lynda Saul, who reviewed drafts of this report and
made helpful suggestions, as did Andrew Somor of Cadmus. Peter Ismert of EPA Region 8 also
sat in on meetings between the Technical Advisory Group and report authors. In Montana,
Beth Dodds of the Montana State Library provided helpful guidance on constructing Boolean
search strings. Randy Apfel beck of the Montana Department of Environmental Quality offered
assistance with uncovering unpublished studies. Jamul Hahn of MTNHP designed the map
template, and made several of the maps. All photos used in this report come from MTNHP staff.
Thanks, too, to the numerous hydrologists, biologists, land managers and others who
responded to our requests for information.

Despite the assistance of these and other people, errors may remain; if so, these are entirely
the responsibility of the authors.

mi

Contents

Introduction 2

Scope 3

Background: Prairie Pothole Wetlands and Intermittent/Ephemeral Streams 5

Methods 16

Results 20

Hydrology-ecology relationships: Natural vs. human disturbance 21

Flood mitigation 25

Water storage 25

Groundwater recharge 26

Sediment retention 27

Nutrient and chemical cycling 27

Plant community maintenance 28

Faunal habitat and biodiversity 30

Discussion 35

References 37

Appendix A. Approximate crosswalk between classification schemes 51

Appendix B. Keywords and search strings used in database searches 52

Appendix C: Faunal species associated with PPR wetland and streams 54

Appendix D. Number of sources describing ecological change in wetland function following
hydrologic alterations 59

Introduction

The Ecological Limits of Hydrologic Alteration (ELOHA) framework (Poff et al. 2010) is a flexible
approach to identifying appropriate environmental flows at a regional scale, based on existing
hydrological and biological knowledge of river types, their associated flow-ecology
relationships, and regulatory or voluntary condition goals (Kendy et al. 2012). ELOHA
development takes a holistic approach to building a knowledge base about flow-dependent
ecological processes andtaxonomic groups, drawing on quantitative data, qualitative literature
and expert knowledge to build consensus about the ecological limits of hydrologic alteration
(DePhilip & Moberg 2010; McManamay et al. 2011)

Although the ELOHA approach has been adopted throughout the United States to assess and
manage environmental flows for rivers (see, e.g., the case studies in the ELOHA toolbox ), it has
not been used to explore the limits of hydrologic alteration for wetlands, even though it is
widely agreed that "hydrology is probably the single most important determinant of the
establishment and maintenance of specific types of wetlands and wetland processes"(Mitsch &
Gosselink2000). In part this is due to the lack of detailed hydrologic data for all but a handful
of wetlands. While regional streamflow models can be constructed from data records for a
suite of representative sites, no such hydrologic foundation is in place for most wetland areas,
and indeed, temporal, spatial, and typological variation in the timing, duration and extent of
wetland inundation would make such an effort challenging even if more hydrologic data were
available. Nonetheless, numerous published and unpublished studies have examined the
relationship between wetland hydrology, wetland processes and functions, and wetland-
dependent biota. The goal of the present project is to review existing studies, models, and local
expert knowledge to describe hydrology-ecology relations under natural conditions and to
hypothesize ecological responses to hydrologic change.

The United States Environmental Protection Agency (EPA) contracted with The Cadmus Group,
Inc. and the Montana Natural Heritage Program to generate a systematic characterization of
the relationships between hydrologic regimes and biological dependencies of prairie wetlands
in Montana. For the first phase of the project, Montana Natural Heritage Program compiled and
reviewed ecological and hydrologic literature, existing reports, relevant studies, and available
data and summarized the existing knowledge about wetland-dependent biota and ecological
processes in eastern Montana. The purpose of this report is to describe the scope of the
project, provide some of the background information used to frame the literature review,
summarize the methods, and present and discuss the findings of the review.

Scope

The project's broad geographic scope was defined as the Prairie Pothole Region (PPR) of North
America (Figure 1), which extends across approximately 715,000 km 2 of five US states (Iowa,
Minnesota, North Dakota, South Dakota and Montana) and three Canadian provinces
(Manitoba, Saskatchewan and Alberta). As glaciers retreated some 12,000 years ago, they left
behind a landscape characterized by rolling hills and as many as 25,000,000 small wetland
basins, generally known as potholes (Winter 1989).

I I Prairie Pothole Region

Prairie Pothole Region, Montana

Figure 1. The Prairie Pothole Region

The project focuses on the 95,907 km Northwestern Glaciated Plains ecoregion of Montana.
Based on historic NWI mapping from the 1980s, which is the most comprehensive mapping
available for the entire PPR in Montana, there are 218,000 mapped wetlands, lakes, and river
features. Nearly 70% of the wetlands are temporary or seasonal. Approximately 15% of the
mapped wetlands occur as impounded reservoirs (either temporarily, seasonally, or semi-
permanently flooded) along intermittent and ephemeral streams. This number has

undoubtedly increased since the 1980s, as there are numerous small and moderate sized
reservoirs visible in recent aerial imagery that were not included in the historic mapping. Over
half (56%) of the mapped wetlands in the PPR are less than one half acre. Nearly three-
quarters (72%) of the mapped wetlands are less than 1 acre.

In Montana, glaciation reached its southern extent near the current location of the Missouri
River toward the end of the last Ice Age. Consequently, the Montana portion of the PPR has a
lighter glacial imprint than some other areas of the PPR, although retreating glaciers still left a
layer of till and debris, and carved a the rolling, hilly landscape, dotted with wetlands, similarto
that of the larger PPR (US Fish and Wildlife Service 2012a). In the western part of Montana's
PPR, along the Rocky Mountain Front, the sedimentary Two Medicine Formation of clay,
limestone and sandstone transitions to the shale and siltstone of the Colorado Shale Formation
(Figure 2). Here, coarse-textured Pleistocene-era glacial deposits have left areas of hummocky

Figure 2. Geology of Montana's Prairie Pothole Region.

pothole wetlands, similar in size to prairie pothole wetlands, but often with more hydrologic
permanence. To the east, where the landscape flattens into prairie grasslands, underlying

bedrock consists of the Cretaceous-era Claggett Formation, Judith River Formation, and
Bearpaw Shale, all consisting of almost impervious marine shales, intercalcated with sandstone
beds (US Fish and Wildlife Service 2011). Although wetlands are numerous in this area, they
tend to be less permanent than those to the west and east. In the east, the Cenozoic era Fort
Union Formation, variously made up of claystone, calcareous siltstone, and sandstone, is
overlain in parts by glacial Flaxville gravels. Two large outwash channels form the Big Muddy
and Dagmar valleys, running north to south. The most complex area of Montana's PPR is the
Missouri Coteau in the extreme northeast portion of the state, a collapsed moraine with a high
density and diversion of potholes and other wetlands (Heidel et al. 2000) that are more similar
in terms of vegetation to those in the PPR of North Dakota than to those in the Montana PPR to
the west (Hargiss etal. 2008). This is also the western edge of the Williston Basin oil fields (US
Fish and Wildlife Service 2007).

The topical scope of the project is the pothole wetlands of the PPR, and the intermittent and
ephemeral streams present in the region. Although intermittent and ephemeral streams may
connect pothole wetlands during high water periods, they are included here as an independent
subject of interest. Like shallow, temporary prairie potholes, they may be overlooked as a
landscape feature simply because they are both small and impermanent (Armstrong et al.
2012), but in fact, they perform multiple ecosystem functions in this semi-arid environment.
The larger lakes that occur in parts of the area, and the perennial rivers and streams, were not
included. These are sufficiently different from pothole wetlands and impermanent streams in
their distribution, extent and function that they would be better addressed separately.

Background: Prairie Pothole Wetlands and Intermittent/Ephemeral Streams

Although multiple wetland classification schemes can be applied to PPR wetlands 1 , the Stewart
and Kantrud system, developed specificallyforthe PPR (Stewart & Kantrud 1971), was used for
this project. Unlike the Cowardin system (Cowardin etal. 1979) used in the National Wetlands
Inventory, which allows for multiple and contiguous wetland types with a single depression
(e.g., a Palustrine Aquatic Bed wetland with a Palustrine Emergent fringe), the Stewart and
Kantrud scheme classifies the entire depression, or basin, and the class is determined by the
presence or absence of water in the basin center, with wetlands classified as permanent, semi-

See Appendix A for an approximate crosswalk between classification schemes in broad use in the United States.

permanent, seasonal, temporary, or ephemeral (Figure 2) 2 This classification is widely used in
the literature, and employs commonly understood terminology. Most importantly, the Stewart
and Kantrud schema best supports the description of flow-ecology relationships. The
permanence of water in a wetland, as well as its source and fate also drives the chemical
characteristics of the water, particularly salinity, and consequently, vegetation structure and
composition and associated food webs. Because hydroperiods can shift over time at site, basin,
and regional scales, both from natural and human causes, describing flow-ecology relationships
for all wetland types is critical.

Although there is a complex and dynamic relationship between PPR wetlands and local and
regional groundwater tables (Labaugh et al. 1998) most pothole wetlands receive the majority
of their water from spring snowmelt, with occasional reflooding from summer thunderstorms.
However, water permanence is highly variable, both spatially and temporally. In the Stewart
and Kantrud system, permanent wetlands have surface water during all years. In semi-
permanent wet\ar\ds, the center of the wetland basin contains surface water during most of the
season in most years. The center of a Seasonal wetland basin contains surface water through
mid-summer during most years. Temporary wetlands hold water for as little as two weeks
during most years, although heavy precipitation during mid-summer can fill the wetland for a
brief time. Ephemeral wetlands are small depressions that hold water for less than two weeks
only in the wettest years (Figures 2 to 5).

n

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Figure 2. Hypothetical hydrograph of a temporary wetland during an average water year; the same
pattern would be seen in an ephemeral wetland in a wet year.

Stewart and Kantrud (1971) a I so include a I kali ponds or lakes, and fens in their classification. Because these are
rarely described in the literature on the PPR, we did not consider them as part of this review.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Figure 3. Hypothetical hydrograph of a seasonal wetland during an average water year.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Figure 4. Hypothetical hydrograph of a semi-permanent wetland duringan average water year;
groundwater supplies a baseflow, and snowmelt runoff and precipitation raise water levels during
spring, and autumn rains provide another influx.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Figure 5. Hypothetical hydrograph of a permanent wetland during an average water year;
groundwater supplies a baseflow, and snowmelt runoff and precipitation raise water levels during
spring, and autumn rains provide another influx. The balance between precipitation and groundwater
influences will depend on wetland size and weather patterns (Roth and Capel 2012)

Each wetland type has characteristic vegetation patterns, arrayed in generally concentric zones
(Figure 6). In permanent wetlands or ponds, a low prairie zone at the outer margin transitions

Low prairie

Wet meadow

Low prairie

Wet meadow
Shallow marsh

Deep marsh

KJ-

Low prairie
Wet meadow

Shallow marsh

Deep marsh
Open water

Low prairie

Wet meadow
Shallowmarsh

Figure 6: Stewart and Kantrud wetland classes. Top to bottom: temporary wetland; seasonal
wetland; semi-permanent wetland; permanentwetland.

to wet meadow, then to shallow marsh, then to deep marsh, and finally to open water atthe
center (Figure 7). Temporary wetlands have only an outer low prairie zone and an inner wet
meadow zone (Figure 8).

Figure 7. Deep marsh zones adjacent to open water in a permanently flooded wetland

Figure 8. Temporary wetland with wet meadow zonation

Wetlands of the PPR may be groundwater recharge sites, groundwater discharge sites, or flow-
through systems (Winter 1989; but see also van der Kamp & Hayashi 1998). However, most are

recharge sites, losing some intercepted snowmelt and rain to groundwater, and the remainder
to the atmosphere through evapotranspiration (van der Kamp & Hayashi 1998).

PPR wetlands typically run a water deficit, with seepage and evaporative loss exceeding inputs.
This effect becomes more pronounced along an east-west gradient, with wetlands in the
western portion of the region (e.g., Montana, Alberta) being less likely to have season-long
water than wetlands in the eastern portion (e.g., Iowa). In most of the Montana PPR, for
example, less than 5% of wetlands have semi -permanent or permanent water in typical water
years (Figure 9), with the highest concentration along the Rocky Mountain Front and the Little
Rockies, and in the Missouri Coteau. Although water regimes are largely driven by substrate
and geologic setting, this distribution also reflects the precipitation patterns across the state.

SASKATCHEWAN

37.5

75

150
H Miles

-A.

Legend

B Semipermanent and Permanent Wetlands
I I HUC 4 Boundary

Figure 9. Distribution of semi-permanent and permanent wetlands in Montana, based on 1980s NWI
(individual wetland size enhanced for purposes of illustration)

The Missouri Coteau to the east receives the most annual rain, while snow levels are highest in
the central and western part of the state (Figure 10). However, these graphs do not capture

10

9 -
8 -
7 -
6 -
5 -
4 -
3 -
2 -
1 -

■

i

■

■ . . . ■

/

Medicine Lake, Montana

9 -
8

7 -
6 -

5 -

4 -
3
2
1 -

1 1

1 ■ II

-----

/

Havre, Montana

9 -
8

7 -
6 -
5 -

4 -
3 -
2

1 -

■

|

| 1

1 I .1

... 1

/

Cut Bank, Montana

Figure 10. Average precipitation and snowfall across Montana PPR from east (Medicine Lake) to
center (Havre) to west (Cut Bank), in inches. Source: Western Climate Science Center

the significant hydrologic inputs to westernmost PPR wetlands from snowmelt originating in the
steep catchments along the Rocky Mountain Front. In general, semi-permanent and
permanent wetlands are more likely to have a groundwater connection than seasonal or
temporary wetlands. However, in extremely wet periods, wetlands that are typically

11

precipitation-fed may also have some groundwater flow. Conversely, during drought years,
precipitation-fed wetlands may "disappear," and be dominated by low prairie vegetation, while
wetlands that are semi-permanent in wet years may lose groundwater connection, and be
seasonally flooded only, if at all (Shjieflo 1968; van der Valk2005; Kahara etal.2009).

The most detailed study of hydrologic variability in PPR wetlands was carried out by Niemuth et
al. (2011) from 1988 to 2007 in~40,000 wetland basins in North and South Dakota and eastern
Montana. Using fixed-wing aircraft, the researchers collected aerial photographs of all
wetlands in 10.4 km 2 sampling blocks (n=263to 380) during May of each project year. The
circa 1980 National Wetland Inventory was used as a baseline for wetland extent under
"optimum" water conditions, and wet area for each wetland site within the sampling block was
calculated as a percentage of the corresponding NWI polygon. The percentage of wetland
basins with water varied from year to year for all wetlands in the study area. In drought years
(1988-1992 and 2002 -2005), less than 20% of temporary wetlands had water during May, while
in deluge years (1993-2001), as many as 50% of temporary wetlands were wet. This variability
was also seen on a spatial scale; from year to year, the wet area percentage of basins varied
across the study area, with no observed east-west gradient. Although climate variability
explained some of the observed patterns, there was enough variability across space and among
water regimes to suggest other factors were at play. Other studies have documented the
influence of land use (Voldseth et al. 2007), soil types (Gleason and Euliss 1998), catchment size
and wetland density (Kahara et al. 2009) on wetland water levels.

Like wetlands, streams in the Prairie Pothole Region are characterized by relatively frequent
and random flooding and drying events, which are reflected in temporally variable turbidity and
water chemistry (Mullen et al. 2011). Intermittent streams typically have both surface water
and groundwater sources, even though they do not flow continuously year round. These low-
gradient, sinuous channels will often lose flow in shallow riffle areas by midsummer, appearing
as a series of small pools connected by subsurface flows (Figure 11). Ephemeral streams have
no groundwater source, and flow only during snowmelt or in response to precipitation events
(Figure 12). In some drainage basins, ephemeral channels feed intermittent streams, but in
others, flows dissipate before reaching any more permanent water bodies. In both kinds of
prairie streams, water exchanges between groundwater and surface waters are common.
Ephemeral streams typically have thin alluvial deposits, and maintain water tables below their
channels only when precipitation is frequent and heavy. Flows

12

Figure 11. Intermittent Little Sandy Creek, Choteau County, Montana, appearing as a series of pools.

Figure 12. Ephemeral stream, Valley County, Montana.

diminish rapidly along the downstream gradient, with large transmission losses producing
shallowgroundwater recharge (Shaw & Cooper 2008). In areas where silts and clays effectively
seal surfaces, however, streambeds may remain moist just below the surface for several days.
Intermittent streams are often fed by shallowgroundwater spreading laterallyfrom wetlands,
ponds and lakes due to the impermeable nature of clays and silts in the glacial till (Preston

13

2011). Some vertical migration occurs, but it is much more restricted compared to the lateral
migration.

Both ephemeral and intermittent streams occur throughout the PPR, often in the broad coulees
that drain alluvial flats, and sometimes connect potholes in isolated basins. Nevertheless, the
number of stream miles in each category cannot be ascertained easily. The United States
Geological Survey has produced a digital NHD from topographical maps, but ephemeral streams
are lumped together with intermittent streams. Moreover, the gentle, rolling topography of
the area is not easily captured on 10m digital elevation models (the best commonly available),
so drainage paths a re difficult to predict. However, Vance (2009) developed a GIS model that
provided estimates of each class for Montana, based on channels that have been digitized from
1:24,000 topographic maps for the National Hydrography Dataset.That model categorized 28%
of stream reaches in the Northwest Glaciated Plains ecoregion as intermittent, while some 64%
of reaches were either ephemeral or had such low flows that they were not even represented
in 1:100,000 topographical maps. Across all 4 th code Hydrologic Units (HUC 4) in the Montana
PPR, only 7.26% of National Hydrography Dataset (NHD) stream reaches were classified as
permanent. As is true with permanent and semi-permanent wetlands, most were along the
Rocky Mountain Front or Little Rockies, or in the Missouri Coteau. Figures 13, 14 and 15, based
on Vance (2009), show the distribution of ephemeral, intermittent and perennial streams,
respectively.

SASKATCHEWAN

37.5 75

•&

legend

□ HUC 4 Boundary
Ephemeral Streams

Figure 13. Ephemeral or very low-flow intermittent streams in Montana's PPR

14

SASKATCHEWAN

37 5 75

150

■H Miles

^

Legend

□ HUC 4 Boundary
Intermittent Streams

Figure 14. Intermittent streams in Montana's PPR

37 5 75

150

■I Miles

Legend

□ HUC 4 Boundary
Perennial Streams

Figure 15. Perennial streams in Montana's PPR.

15

Although Montana's PPR is sparsely populated, human activities have a large footprint.
Management plans for three of the four Wildlife Refuges operating in Montana's PPR note the
challenges posed by agriculture, oil, gas, and other human development activities (US Fish and
Wildlife Service 2012b; US Fish and Wildlife Service 2011; US Fish and Wildlife Service 2007),
noting their contribution to wetland loss and deterioration 3 through direct disturbance and
infrastructure development. While PPR biota have adapted to natural cycles of drought and
inundation, water use associated with the growth of extractive industries and changes in
agriculture may alterthese cycles in as-yet unanticipated ways, and long-term impacts of
climate change are uncertain.

Because the wetlands of the PPR are so important to North American waterfowl and other
migratory birds, the area has attracted substantial research interest. Scientific investigations
have been far-ranging, from basin-specific short term studies of specific species and wetland
components to long-range, landscape-level analyses and models. Over the years, this has
resulted in a more complete, and more nuanced, understanding of ecosystem processes and
functions (Gilbert et al. 2006) and a better characterization of the inherent variability of the
region. Despite the uncertainty associated with future large-scale land use change, it should be
possible to extrapolate from what is known about hydrology-ecology relations under natural
and altered conditions on smaller scales to predict what may occur on basin- and region-wide
scales, and to articulate precautionary limits of hydrologic change. That was the focus of this
literature review.

Methods

A modified causal criteria analysis method (Norris etal.2008, Greet etal. 2011) was used to
frame a systematic search of literature on hydrology-ecology relationships in wetlands and
intermittent/ephemeral streams of the PPR. Causal criteria analysis follows an 8-step
approach, beginning with identifying a broad question (Step 1) and selecting a geographic
context for the question (Step 2). The goals and scope of the project -determining how PPR
wetland processes, functions and biota respond to changes in the frequency, scope and
duration of inundation, whether natural or anthropogenic— addressed the first two steps. Step
3 in the process involves developing a conceptual cause-and-effect model, and Step 4 includes
documenting the potential causes and effects that will be explored. Drawing on a preliminary
review of the literature and our own knowledge of PPR wetlands and floodplain systems, a
conceptual model that included potential causes and effects was constructed (Figure 16 and
Table 1).

The mineral estate on the fourth Refuge, the Charles M. Russell National Wildlife Refuge, was withdrawn for 20
years in 1993, and there is a current effort to extend the withdrawal (US Fish and Wildlife Service 2012 b).

16

Overgrazing ^

Excavation T 4

Catchment-level Land
Cover Change 1 s

Draining 1 s

Ditching 1 s

Outflow from wetland
A

Surface Water
Impoundment 1 s

Water diversions

Groundwater
extraction 'T"

Inflow to wetland
A

Inundation and drying
in intermittent and
erjhemeral streams A

Inundation timing,
duration and extent

A

Vegetation

composition and

structure A

Causes

Water availability and
quality A

Functions (water storage, groundwater recharge, streamflow maintenance,

flood mitigation, sediment retention, nutrient/chemical cycling, plant

community maintenance, faunal habitat, biodiversity sj,

Invasives and upland
plant species 1 s

I

Cover and nest site
availability A

LEGEND

Increase

t

Decrease

vb

Change

A

Food availability 4,

Suitability for wetland and aquatic

species reproduction, rearing and

foraging (birds, amphibians, mammals,

macroinvertebrates, fish) 4/

17

Figure 16. Conceptual model of effects of hydrologic alteration on wetland processes, functions

Table 1. Hydrology-ecology causes and effects chosen for investigation

Hydraulic alteration

Hydrologic change

Ecological effect

Inflow divers ion or
impoundment

Decreased extent, duration or frequency of
inundation

Loss of bioticand abiotic
function

Groundwater extraction

Decreased extent, duration or frequency of
inundation

Loss of bioticand abiotic
function

Outflow impoundment

Increased extent, duration or frequency of
inundation

Loss of bioticand abiotic
function

Drainingor ditching

Decreased extent, duration or frequency of
inundation

Loss of bioticand abiotic
function

Excavation or dredging

Increased extent, duration or frequency of
inundation

Loss of bioticand abiotic
function

Loss of upland native
vegetation

Increased extent, duration or frequency of
inundation

Loss of bioticand abiotic
function

Increasein upland road
density

Changed extent, duration or frequency of
inundation

Loss of bioticand abiotic
function

The literature review (Step 5) covered both anthropogenic and natural (e.g., drought-induced)
changes to hydrology, which often differ in scope, extent, and severity. For example, drought
and deluge cycles will affect all wetlands and streams within a given basin or complex, while
human activities (depending on their nature) may only affect some. Therefore, for each piece
of information reviewed, it was noted whether the change agent was natural or anthropogenic.
A wide array of possible ecological responses was also examined, such as shifts in
physiochemical functioning within wetlands; changes in the abundance, biotic integrity and
community composition of vegetation; and differences in survival, reproductive success and
behavior in faunal species.

To find peer-reviewed published literature, literature searches were conducted using BioOne
and Environment Complete. These databases were chosen because they capture a range of
fields, including environmental policy and agriculture, as well as hydrology and ecology. The list
of keywords and search strings used is included in Appendix B. The Montana Natural Heritage
species occurrence databases were searched to develop a list of all faunal species associated
with PPR wetland and stream ecosystems. Occasional oraccidental species were excluded from
the final list (Appendix C). Each species was used as a search term.

18

Grey literature was researched in the United States Geological Survey (USGS) Publications
Warehouse ( http://pubs.er.usgs.gov/ ) and in the online Catalog of U.S. Government
Publications ( http://catalog.gpo.gov ). Google and Google Scholar were used to find other
governmental and non-governmental reports, theses and dissertations. Reports from advocacy
groups, or online papers prepared by undergraduate students were excluded from the review.

Unpublished results, studies, and models were investigated by contacting people suggested by
the project's technical advisory group 4 , and others known to be involved with research on PPR
wetland and floodplain issues. Management plans from the four USFWS wildlife refuges in
Montana's PPR (Benton Lake NWR, Bowdoin NWR, Medicine Lake NWR and Charles M. Russell
NWR) were reviewed, as were plans from the Bureau of Land Management, which has
extensive land holdings in the area.

All data sources located through the search were given a preliminary review to assess relevance
to the current study in terms of 1) geographic scope and 2) inclusion of some element of the
hypothesized cause and effect relationships. Preference was given to studies and reports from
the PPR, as well as studies and reports that reference hydrologic change as a causal factor in
the phenomenon under investigation. This led to the exclusion of some sources. For example, a
study on the role of tiger salamanders in PPR wetland food webs (Benoy 2008) was excluded
because it had no link to hydrology, as was a study reporting on the relative efficacy of avian
species survey approaches in the PPR (Niemuth et al. 2006). Studies on biocriteria
development were similarly excluded if they subsumed hydrologic modification into general
human disturbances, rather than investigating specific causes and effects (e.g., Apfelbeck 1999;
Jones 2004).

References retained for further analysis were recorded in a Microsoft Access database, with a
front-end data entry interface to ensure that every reviewer recorded the same information in
a consistent way. For each source found through a database search, the search string was
recorded, anda unique identifier was assigned to the article. A "Notes" section allowed the
reviewer to enter a synopsis of the source's findings or to highlight salient conclusions, record
the geographic location, and make other observations about the source. Defined entry fields
with drop down menus limited the response recorded. Entry fields included study design,
number of control or reference sites, number of sample or impact sites, direction of impact,
wetland class affected, lifeforms affected, vegetation response , water quality/quantity
response, soil impacts, stressors, affected functions, inflow or outflow affected; timing of
inundation, extent of inundation, and duration of inundation.

Lynda A. Saul, Montana Department of Environmental Qual ity; Phil ip J. Gerla,The Nature Conservancy; Sea n
Fields, US Fish and Wildlife Service; and EloiseKendy, The Nature Conservancy.

19

The primary goal was to summarize impacts of hydrologic alteration on wetland and stream
functions, processes and biota. In a full causal criteria analysis, each source is weighed in terms
of the support it provides for some element of the cause and effect hypothesis, with weights
allocated based on study design and analysis. For example, a before-and-after impact design
with a control (BACI) is generally given more weight than a study that only investigates
responses to an impact affecting a single site. Most of the sources reviewed for this project
reported on observations or models, rather than the results of controlled experiments. Like
rivers, wetlands and streams are challenging systems from an experimental design perspective,
because of their spatial heterogeneity, temporal variability, and network connectivity (Konrad
et al. 2011). Therefore, after consultation with project technical advisers, it was decided that
the studies reviewed would not be weighted individually at this time. Instead, general
conclusions from the literature are reported, and in the overall trend of support for different
elements of the conceptual model is evaluated in the Discussion section.

The Results section, below, describes sources, summarizes the general hydrology-ecology
relationships described in the literature review, and specifically examines ways in which
hydrologic alteration (cause) has been shown to affect function, processes and biota in
wetlands and streams (effects). The inferences that can be drawn from this review are included
in the Discussion section, along with questions requiring further examination.

Results

Our searches yielded over 200 potential sources. Of these, we found 150 unique sources
relevant to our review, including 115 peer-reviewed articles, 22 reports by federal or state
agencies, 4 master's theses, 4 management plans, 2 posters, 1 conference proceeding, and 2
books. We found 65 sources dealing with hydrologic impacts on abiotic functions in Prairie
Pothole wetlands and intermittent and ephemeral streams (43 peer-reviewed publications, 12
reports, 4 management plans, 3 theses, 2 books, and 1 proceeding). Six additional sources, all
from peer-reviewed journals, focused on potential impacts of climate change on wetland
hydrology. We also reviewed 21 sources focusing on wetland and stream vegetation (15 from
peer-reviewed journals and 6 agency reports).

Eighteen of the sources on abiotic function, climate change and vegetation dynamics were
literature reviews, without new data. Fifty-five of the studies reported on data collected in field
surveys or inventories. Fourteen sources reported on models, either constructed following field
surveys carried out in support of the model, or built on existing data. Three involved analyses of
existing data with no new data collection

Faunal habitat requirements and responses to disturbance were by far the most common topic
of study encountered in our review, with waterfowl, shorebirds and other avian species the

20

fauna most frequently investigated. Thirty of the sources examined habitat requirements or
disturbance responses for particular species of waterfowl orshorebirds; eight covered
waterfowl and shorebird habitat more generally. An additional 10 sources covered multiple
faunal species associated with wetlands or streams. Fourteen sources focused on
macroinvertebrates; 10 emphasizing wetland communities and 4 examining stream
communities, although in the case of wetlands, the scope of inquiry was typically invertebrates
as a food source for birds. Three investigations involved amphibians, and three discussed
vertebrates (notably bird nest predators). Seven sources reported on fish, all in the context of
intermittent streams.

Of the sources we reviewed on hydrology-ecology relationships and their impacts on fauna or
faunal habitat, 51 were from peer-reviewed publications, 5 were agency reports, 4 were
management plans 5 , 2 were posters, 1 was a thesis and 1 was a book. Forty-two sources
reported on original field work. Nine were literature reviews, or summaries of the literature in
management plans. Eleven presented models 6 , and one was an analysis of existing data. The
growth of modeling in wetland and stream ecology is especially apparent in more recent
sources. It is also a function of several interacting opportunities: better and more available
technology, including GIS and desktop computers capable of processing large datasets; the
accessibility of large-scale data sets, such as the North American Breeding Bird Surveys, land
cover maps from the National Land Cover Dataset, ReGAP and Landfire, and climate data; an
increased awareness of the importance of landscape-level factors on PPR biota, especially birds
(Naugle et al. 2001; Johnson & Werner 2010); and the need for integrated conservation and
management efforts (Loesch et al. 2011; Niemuth et al. 2011).

Hydrology-ecology relationships: Natural vs. human disturbance

The extreme variability of wetland and stream habitats in the PPR accounts for much of its
diversity. Despite the relative stability of semi-permanently and permanently flooded
wetlands, the vacillating conditions associated with seasonal, temporary and ephemeral
wetlands may be even more conducive to the maintenance of food webs and waterfowl
populations, because they thaw and warm early, while more permanent wetlands are still ice-
covered (Kantrud et al. 1989). These wetlands may be particularly important for shorebirds as
foraging sites during migration (De Leon & Smith 2009), providing energy reserves essential to

Management plans and one book are doublecounted in the breakdowns, as they covered both abiotic features
andfaunal habitat.

Some of the sources we count as reportingoriginal field workalso presented modeled inferences; these are not
included here.

21

the continued journey (Morrison & Myers 1989; Colwell & Oring 1988). North Dakota studies
found that shorebirds select shallow, sparsely vegetated sites typically associated with
temporary and seasonal flooding (Niemuth et al. 2006). Krapu and colleagues (2006) also found
that seasonal wetlands were preferred foraging areas for mallard ducklings, especially in years
when some water was available. However, others (Stephens et al. 2005) found that wetland
density was negatively correlated with nest success, presumably because predators also tend
to occur in greater numbers in wetland-rich environments. Both foraging and rearing success
are influenced by invertebrate densities (Anteau and Afton 2008), which in turn depend on the
nutrient cycling and sediment oxidation that occurs during dry periods, and the productivity
pulse that occurs upon restoration of water levels (Anteau 2011).

Many studies of the impact of water level fluctuations on biodiversity have focused on
individual wetlands or wetland types. However, several researchers have emphasized the
importance of understanding wetland complexes (Weller et al. 1988, Winter and Rosenberry
1995, Galatowitsch &Biederman 1998, Weller et al. 1999, Murkin etal.2000, Naugleetal.
2001, Johnson et al. 2010). Wetland complexes are clusters of wetlands with differing water
regimes, often connected by surface water during fluvial periods, or by groundwater during
drier years. At the landscape scale, complexes contribute to diversity of vegetation structure
and function, and facilitate dispersal of amphibians, and small mammals, as well as foraging
birds (Semlitsch 1998, Joyal etal. 2001).

Intermittent and ephemeral streams in Montana's PPR aresimilarto semi-permanent and
seasonal/temporary wetlands in terms of hydroperiod variability. Stagliano (2005) developed
an aquatic ecological classification forstreams and rivers in the Missouri River drainage of
Montana, which includes most of the streams and rivers in Montana's PPR (a small number of
PPR streams along the Rocky Mountain Front drain north into the St. Mary's basin). After
analyzing over 100,000 fish and macroinvertebrate data records and collecting field surveys to
fill data gaps, he delineated ecosystem types based on the presence of specific biological
communities and abiotic features of the drainage. Truly ephemeral streams were not included
in his classification, as they are generally fishless, with macroinvertebrate populations that are
too spatially and temporally variable to permit robust analysis. Forthe Missouri River drainage
of the PPR, he found one consistent intermittent stream type, the Northern Glaciated
Intermittent Stream, a 1 st to 3 rd order stream with an average wetted width of 3 meters,
originating in alluvium and sedimentary geology. These are characterized by long pools, usually
vegetated, separated from each other by narrow riffle areas that typically dry by early summer,
forming isolated pools. Although they may sustain fish populations in wet years, in drought
years, they often lose their connectivity to the fish recruitment pools of downstream reaches
and become fishless. Reference-condition Northern Glaciated Intermittent Stream communities
will have fathead minnows, brook sticklebacks, lake chubs (not as common), brassy minnows

22

and northern redbelly dace; with some anthropogenic alteration, the community is co-
dominated by fathead minnows and brook sticklebacks only, and in degraded or non-vegetated
streams, only fathead minnows will be found. Because water permanence in these streams is
so tenuous, several of their associated fish species are listed as Species of Concern or Potential
Species of Concern in Montana (Table 2).

Table 2. Species of concern associated with intermittent streams in Montana's PPR

Scientific Name

Conservation rank

Brassy minnow

Hybognathus hankinsoni

Potential Species of Concern

Brook stickleback

Culaea inconstans

Potential Species of Concern

Northern redbelly
dace

Chrosomus eos

Species of Concern

Pearl dace

Margariscus margarita

Species of Concern

In general, the life-history characteristics of prairie stream organisms are highly suited to
surviving harsh, disturbance-driven habitats. Stream communities in general have high
resilience (Dodds et al. 2004), recovering rapidly from flooding and drying events.
Macroinvertebrate communities show high resilience to disturbance, with populations
generally recovering to pre-disturbance levels within 1 month, in part because of their high
reproductive potential, and in part because of the availability of colonists from nearby water
bodies (Hax&Golladay 2013). However, resilience may be more pronounced in response to
flooding than to drying, especially if there is no hyporheic zone providing a refugium (Fritz &
Dodds 2004). Fish and amphibians may also benefit from the seasonal loss of connectivity in
intermittent streams, which isolates them from potential predators (Spranza & Stanley 2000;
Meyer eta I. 2007).

PPR wetlands and their biotic communities are also well-adapted to natural disturbances other
than drought-deluge cycles (Winter and Rosenberry 1998), including fire (Higgens 1984) and
grazing by bison and other native ungulates (McNaughton 1986). However, while natural
disturbances may have positive impacts on community diversity (DeKeyseret al. 2008),
contemporary human disturbances have been negative. Across the PPR, agricultural drainage,
excavation, groundwater extraction, and conversion have directly altered individual wetlands
and wetland complexes, creating more isolated, and often more permanent wetlands (Krapu et
al., 2003, Blann etal. 2009). Agricultural practices in surrounding uplands alter land cover,
surface roughness, and soil moisture regimes, thus affecting the hydroperiod of wetlands (van

23

der Valk2005, Voldseth et al. 2007, Voldseth et al. 2009). PPR wetlands are also vulnerable to
climate change (Poiani and Johnson 1993, Ojima et al. 1999, Johnson et al. 2005). If, as some
models indicate, conditions become warmer during winter, or drier, PPR wetlands can be
expected to experience shorter hydroperiods with lower water levels, effectively eliminating all
but the wettest wetlands (Clairand Ehrman 1998, Mortsch 1998, Johnson et al. 2005).

Agriculture and urbanization have also led to pollution, hydrologic disturbance and physical
modification of streams. These changes can exaggerate effects of flooding and drying, creating
conditions outside the range of adaptation for many stream organisms, by disrupting river
connectivity, increasing or decreasing sediment loads, decreasing connection to riparian zones,
and altering food webs (Dodds et al. 2004). When water extractions lead to lower water levels
in intermittent streams, water temperatures may rise to levels that are lethal for some biota,
while oxygen levels may drop below what is necessary to sustain fish (Lake 2003). Small dams,
water diversions and stock ponds have had the most significant negative impacts on fish
communities in intermittent streams (Winston et al. 1991). Anywhere dams occur, even small
stock pond earthen dams, reductions inflow alter downstream water temperatures, cause
unnatural water level fluctuations, and change sediment and nutrient transport. The spring
flows stored behind stock pond dams would otherwise fill pools, and provide brief connectivity
between pools to allow recolonization by downstream fish populations (Franssen et al. 2006).

The following pages describe the impact of anthropogenic change on a common suite of
wetland functions. Since the mid-1990s, one approach to wetland assessment has emphasized
the function of a wetland, rather than its structural features (Smith et al. 1995). While not all
wetlands perform all functions at the same level, most wetlands share a common suite of
functions, notably 1) flood mitigation; 2) water storage and streamflow maintenance; 3)
groundwater recharge; 4) sediment retention; 5) nutrient and chemical cycling; 6) plant
community maintenance; 7)maintenance of faunal habitat and biodiversity. Intermittent and
ephemeral streams provide many of the same functions as wetlands, acting as islands of
moisture in dry uplands, creating habitat for plant and animal species, trapping sediments,
sequestering and cycling nutrients, and contributing to the maintenance of perennial streams,
rivers and lakes. In addition, these small waterways often provide critical corridors between
otherwise isolated ecosystem components. Even when ephemeral streams are dry, their
channels can hold enough moisture to support vegetation that is lush in comparison to the
surroundings by mid-summer, providing food, shelter and shade. In northern Montana, where
intermittent and ephemeral reaches are often interspersed along a channel, small groundwater
pools may also provide water for wildlife, rearing areas for waterfowl, and breeding sites for
amphibians (Vance 2009).

24

Here, impacts on wetland and stream function are summarized in narrative terms. Appendix D
lists the numbers of sources describing impacts of individual anthropogenic changes on each
wetland function.

Flood mitigation

In the 1990s, economically catastrophic flooding in the PPR spurred considerable interest in the
potential of flood attenuation through wetland restoration. Wetlands store both surface water
and overland runoff from precipitation so that they do not enter streams and rivers during a
flood event (Kantrud et al. 1989; Murkin 1998; Winter & Rosenberry 1998; Winter 1989).
Several studies reported that drainage of temporary and seasonal wetlands has contributed to
increased runoff in the PPR, thus increasing flood frequencies (Cemohous 1979; Moore &
Larson 1979). However, some models indicate that the ability of wetlands to mitigate the
impacts of low-frequency, high magnitude events is minimal (Simonovic &Juliano 2001;
Bengtson & Padmanabhan 1999). Technical investigation on this subject is ongoing, particularly
in the Red River Basin of Minnesota, North Dakota, and Manitoba (Philip Gerla, personal
communication, March 15, 2013).

As flow-through systems, intermittent and ephemeral streams are not generally considered to
have flood mitigation functions. However, alteration of these systems can increase flooding
downstream. Agricultural drainage systems often involve channelization of these low-order
streams, typically involving dredging and deposition of dredged material in berms. This
channelization reduces sinuosity, limits floodplain connectivity, and over time, leads to channel
incision, all of which can increase flows to downstream receiving waters (Lenhart et al. 2012).

Water storage

The PPR has historically cycled between drought and deluge (Donovan & Grimm 2007). Under
natural conditions, wetlands "fill and spill" during years of normal to above-normal spring
precipitation, creating surface water connections between basins, with wetlands in the lower
basin filling as topographically higher wetlands reach storage capacity. Spring flows, either
from snow and ice melt on frozen ground or from rain-on-snow events, are the main source of
wetland water. Summer rain infiltrates directly into upland soil where it does little to increase
wetland water levels (Woo & Rowsell 1993). In general, wetland class reflects waterstorage
capacity, with ephemeral wetlands storing the least amount of water, and permanent wetlands
storing the most (Gala etal. 2012). However, the sheer number of ephemeral and temporary
wetlands means that collectively, their storage capacity is significant (Hayashi etal. 2003). In
one South Dakota study, researchers measured the amount of water in small, seasonal,
temporary wetlands and semi-permanent wetlands in a 1600-acre study area just after the

25

vernal thaw in April, and found them to hold 158.7 acre feet of water, even though they were
not full at the time of the study. Extrapolated to the larger Altamont Moraine (249 square
miles), this would have meant 15,800 acre feet was being stored in similar wetlands (Hubbard
& Linder 1986). However, water storage functions can be affected by local land use, when roads
and culverts in the contributing watershed block runoff (Shaw et al. 2012). Agricultural impacts
on water storage vary. For example, increased sedimentation from agriculture can fill shallow
basins and reduce storage capacity (Detenbeck et al. 2002; Martin 1985). Conversion of native
grasslands to agriculture can also result in higher runoff rates during spring rains because of less
surface water interception by native grasses (Voldseth et al. 2009), unless stubble management
practices are implemented (Granger et al. 1984; Conly & van der Kamp 2001). Direct draining
and ditching of wetlands is probably the most significant impact to wetland water storage
functions (Brunet 2011; Hubbard & Linder 1986; Bengtson & Padmanabhan 1999; Moore &
Larson 1979; Winter 1989; van der Kamp & Hayashi 1998).

Groundwater recharge

Snow accumulation is highly uneven on upland slopes, creating spatial variation in infiltration
and overland flow, and summer rainfall infiltrates only the top layers of soil. Consequently,
uplands play a limited role in groundwater recharge. In the PPR, most groundwater recharge
occurs under wetland inundation zones (Woo & Rowsell 1993), and indeed, wetlands are the
main source of recharge to prairie aquifers (van der Kamp & Hayashi 1998). In deluge periods,
when high water levels push vegetation to wetland margins, groundwater recharge is greater
than in drought periods, when evapotrans pi ration rates are higher (Winter & Rosenberry 1998).
In general, more water is lost to the atmosphere from plants rather than through open water
evaporation (Labaugh et al. 1998). Consequently, decreases in surface or groundwater inflow to
more permanent wetlands, to the extent they promote vegetation establishment, will reduce
groundwater recharge functions. However, even small seasonal wetlands contribute to
maintenance of groundwater early in the season. Hubbard and Linder (1986) estimated that
12% of the water in small wetlands in their 1600-acre study area generated groundwater that
flowed beyond the wetland. That amount, they concluded, would be sufficient to spread 1.4
inches of irrigation water across 160 acres of crops, or water 1,700 cattle for a year.

Locally, draining and ditching can affect yields in shallow wells, while regional aquifers will still
be replenished if the diverted water is captured in reservoirs and ponds (van der Kamp &
Hayashi 1998). Factors that impact water storage will also affect groundwater recharge. For
example, planting permanent grass for nesting cover increases infiltration in uplands through
macropores, while trapping snow and surface water that would otherwise collect in wetland
basins; this reduces the water available for groundwater recharge (van der Kamp et al. 2003).
Upland grazing can be managed to reduce upland plant leaf area and ground cover, and thus

26

increase water levels and hydroperiod, if it can be managed to minimize soil compaction
impacts and surface litter loss (Voldseth et al. 2007).

Intermittent streams are more commonly groundwater discharge sites than recharge sites.
However, one study found that damming of intermittent streams in headwater reaches can
have positive effects on riparian vegetation downstream of the dam, by expanding hyporheic
connectivity in the riparian zone; groundwater recharge was also noted below the dam (Duke
et al. 2007). Although this was a Texas study, these patterns are visible across Montana's PPR,
where stock ponds and other impoundments may have lush riparian zones in the immediate
downstream area. However, the effect disappears a short distance downstream, and pre-dam
aquatic and riparian habitat is overtaken by encroaching upland vegetation, and often, invasive
plant species.

Sediment retention

Sediment retention is generally considered to be a water quality function of wetlands,
capturing soil-bound nutrients and pesticides, and trapping soil particles that would otherwise
enter streams and rivers. In the highly cultivated parts of the PPR, wetlands typically receive
excessive sediment. Consequently, most of the sources we reviewed focused on the negative
aspects of sediment retention, e.g., limited water storage capacity (Guntenspergen etal.2002),
impacts on seed emergence (Jurik et al. 1994), and invertebrate egg banks (Gleason & Euliss
1998; Euliss & Mushet 1999). In deeper wetlands with longer hydroperiods, sedimentation may
also increase turbidity, thus limiting light penetration into the water column, which affects
macrophyte production (Zimmer etal. 2003) and alters food webs(McCabe & O'Brien 2013).
Both soil tillage and heavy grazing are causes of sedimentation (Dieter 1990) although practices
such as conservation tillage can reduce some of the impacts (Freeland & Richardson 1997).

In their natural state, neither intermittent nor ephemeral streams are a major source of
sediment for downstream waters. However, when these streams are excavated, widened, or
used for drainage, sediment transport increases, especially if the alterations are accompanied
by crop tillage or other soil-disturbing activities in the upstream drainage area (Lenhart et al.
2012; Schilling et al. 2011) or by heavy grazing near the stream (van der Kamp et al. 2013; Rosso
& Fernandez Cirelli 2013).

Nutrient and chemical cycling

Nutrient and chemical cycling is also a wetland water quality function when considered in terms
of protecting streams, lakes and rivers. However, wetlands themselves can become nutrient
impaired (Silver & Vamosi 2012; North 2000). The biogeochemistry of wetlands is complex.
Hydroperiod determines the duration of oxicand anoxic soil conditions, which drive nutrient

27

and chemical transformation, while surrounding land uses and chemical composition of
contributing flows determine the amount of influx (Brunet 2011; Guntenspergen et al. 2002).
In the case of nitrogen, hydroperiod will determine both organic matter decomposition and
microbial nitrogen mineralization, which regulates the release of ammonium to soils, and its
potential for plant uptake. The alternating wet/dry cycles characteristic of most seasonal and
temporary wetlands promote nitrification and denitrification. If hydroperiod in a wetland is
shortened through consolidation drainage, denitrification may slow. Similarly, when flow-
through wetlands are modified into closed systems, nutrients and salts are often concentrated.

Changes to nutrient cycling within a wetland may manifest in different ways. For example,
when land use or hydrologic alteration cause excess nitrogen inputs, plant biomass may
increase. In turn, this can produce higher litter loads that depress germination of some seeds,
impede survival of seedlings (Neill 1995), and create anoxic conditions (Golds borough &
Crumpton 1998; Zeng et al. 2011). In cultivated watersheds, where the flux of inorganic
sediments into wetlands can be twice as high as in native grassland watersheds, phosphorus
levels will also increase (Martin & Hartman 1987). High nitrogen and phosphorus levels in
wetlands often promote the growth of cattails (Neelyetal. 1989), which lower dissolved
oxygen in wetland waters while increasing oxygen flow to soils (Rose & Crumpton 1996). This
altered plant community composition increases sediment capture, ultimately causing filling of
the wetland, and a loss of functions dependent on water storage capacity.

In the past decade, there has been considerable interest in carbon sequestration potential in
PPR wetlands. In one study, researchers concluded that restoring all farmed wetlands in the
region could sequester as much as 378 million metric tons of organic carbon over a 10-year
period, offsetting 2.4% of the fossil emissions reported for North America in 2002 (Euliss etal.
2006). This study noted that carbon storage was highest in semi-permanent wetlands,
suggesting that hydrologic alterations which reduce inundation periods or areal extent of a
wetland would have negative impacts on carbon storage.

Streams in the glaciated prairie typically lack woody debris, which is an important component in
nutrient cycling insofaras ittraps organic matter during flow events (Quist&Guy 2001).
However, even grassy streambeds will trap and cycle nutrients. When intermittent and
ephemeral stream channels are dredged to provide drainage, replacement of grassy
streambeds by bare soil results in a loss of nutrient cycling capacity (Brunet & Westbrook 2012;
Dodds &Oakes2006).

Plant community maintenance

Native plant communities in the PPR are uniquely adapted to the varying hydroperiods caused
by climatic oscillations. Hydrology affects biochemistry, and hydrology and biochemistry

28

together determine plant community dynamics. Depending on the source and residence time of
water, wetland salinity will vary (Labaugh etal. 1998). Recharge wetlands, driven by
precipitation, are the least saline, while wetlands with significant groundwater discharge can be
highly saline (Kantrud et al. 1989). Plant communities vary with hydroperiod fluctuations under
normal conditions. For example, in a semi-permanent wetland with a ring of emergent
vegetation under "normal" water conditions, drought will result in more vegetation moving into
the center of the wetland, while under deluge conditions, all vegetation may be drowned out,
with the wetland becoming an open water lake (Winter & Rosenberry 1998). However, when
seasonal or semi-permanent wetlands are excavated to increase residence time of water,
emergent vegetation and the macroinvertebrate communities that depend on it may be lost
permanently (Euliss & Mushet 2004). Changes in vegetation create feedback loops, affecting
physiochemical properties of wetlands. Wetlands with emergent macrophytes will have lower
light levels, higher nutrient levels, higherdissolved methane levels, higher particulate organic
matter, lower temperatures with less diurnal variation, and lower oxygen levels than open
water(Rose &Crumpton 1996)

Plant communities in wetlands also change when upland land uses alter hydroperiod (Voldseth
et al. 2007), sediment input (Jurik et al. 1994; Dieter 1990) and nutrient loads (Neely et al.
1989). Wetlands surrounded by cropland exhibit less diversity and species richness than those
surrounded by native grasses, and have a greater number of invasive species (Guntenspergen
et al. 2002). Just as plant communities shift with hydrologic change, hydrology can change
when land use alters plant communities. For example, researchers in Saskatchewan examined
a 30-year record of water levels in wetland with a 950 acre basin. For 12 years, all the land
surrounding the wetlands was in dryland cultivation. Over a three year period, a third of the
land was converted to a permanent cover of smooth brome and alfalfa to provide habitat for
nesting ducks. Within four years of the conversion, the wetlands surrounded by permanent
grass dried out, while water levels remained normal in the wetlands surrounded by dryland
crops (van der Kamp et al. 1999).

Hydrologic alteration can also facilitate the spread of exotic and invasive species. Saltcedar
(Tamarixspp.) establishes in areas where water tables have been lowered, or along wetland
margins in areas that have been overgrazed, burned, or otherwise cleared of vegetation
(Ohrtman et al. 2011). Because it is a heavy water user, and increases evapotrans pi ration from
wet sites, saltcedar has the potential to further modify hydroperiod in temporary wetlands
(Sexton et al. 2006). Salt cedar is also becoming an increasingly common invader in Great Plains
streams where groundwater levels are being lowered by pumping, displacing riparian species
that depend on high water tables. Its deep roots, prolonged seed dispersal period, drought and
salinity tolerance allow itto thrive in intermittent and ephemeral streams, or perennial streams
that have lost permanence following water diversion (Stromberg et al. 2008). Although it is not

29

yet widely naturalized north of the Missouri River, a combination of hybridization, cold
adaptation and warming temperatures threaten to expand its range into the Montana PPR
(Lesica& Miles 2001)

Faunal habitat and biodiversity

All of the sources in the literature review supported the conceptual model's hypothesis that
changes in inflow to, or outflow from, a wetland, will alter hydroperiod, which in turn will affect
faunal habitat, either by decreasing the number and size of preferred breeding and foraging
sites, making them less suitable, or by changing interspecific relations.

There is no single "best" hydroperiod for PPR fauna; rather, individual species and guilds 7 select
for wetlands whose hydroperiod bestsuits their needs (Figure 17). For example, Murkinetal.
(1997) manipulated water levels in experimental marshes to associate bird presence with
habitat types. Over the 10-year study period, they found that different species selected
different flooding regimes: yellow-headed blackbirds preferred shallow, open water with
emergent vegetation; red-winged blackbirds selected densely-vegetated shallow margins of
semi-permanent wetlands; and coots were consistently found in deep water with interspersed
vegetation patches. Most dabbling ducks selected similar habitat (open water with interspersed
vegetation patches), while diving ducks such as ruddy ducks, canvasbacks and lesserscaup
gravitated to deeper, open water.

Overall, relationships between ducks and hydrologic alteration are complex, and hydrologic
modifications intended to expand habitat may reduce or impair it. One study reported that
artificial flooding of a wetland complex, rather than improve deepwater habitat for scaup,
resulted in an increase in fish, which in turn decreased the amphipod population preferred by
scaup as a high-energy food source (Strand et al. 2007). A case study on Benton Lake Wildlife
Refuge in Montana detailed the impacts associated with artificial flooding of seasonal wetlands
to provide recreational use. Diversion of irrigation return flows and agriculturally-impacted
waters from local creeks has led to elevated and increasing selenium contamination; decreasing
diversity in vegetation; increased invasive weeds; declining wetland and bird productivity; and
avian botulism outbreaks (Heitmeyer et al. 2009).

Both natural and anthropogenic decreases in the amount of available wetland habitat can
affect bird populations. Spring breeding surveys indicate that populations of all common duck
species (northern pintail, mallard, blue-winged teal, northern shoveler, gadwall, green-winged

Appendix C, which lists the species used in our literature search, a I so includes guild assignments for each,
courtesy of Sean Fields of the US Fish and Wildlife Service.

30

Uplands

(CRP, Cultivation

Native Prairie)

Low
Prairie

Wet
Meadow

Shallow Marsh

Deep Marsh

Permanent Open
Water

Dabbling Waterfowl (e.g. Mallud)

D Gonial Nesting
— Shorqbirdste.g American
Water

—Diving Waterfowl (e.g. Redhead)--
Birdsfe g American Bilteijn}—
\vocel)--
Mrds(e g American

Grs ssland Birdsft .g Red-winged Bla cktsird) -

-Terrestnal Mammals, Reptiles, ^mphibians(e.g. Skunk) —

-Aquatic Mammals, Reptiles,

-lnvertebrates(i

:oot)~

Amphi(pians(e .g. N Painted Turtle) —
g. Odonata Family)

Uplands

(CRP, Cultivation

Native Prairie)

Low Wet

Prairie Meadow

GravelfMud Beach Loss

(Consolidation, vegetation
encroachment)

Permanent Open Fresh/Brae dish Water
(Inflows causing reduction of alkali conditions)

-Dabbi

ng Waterfowl-

-Diving Waterfowl Increasing-

-Colonial Nc sting Birds

■ Shoreb i rds -

-Water-birds

■Grassland Birds-

■Terrestriti

Mammals, Reptiles, Amphibians

Brin e shnmp -

Figure 17. Waterfowl use of inundation zones in freshwater (top) and brackish (bottom) wetlands in
the PPR.

31

teal, American wigeon, canvasback, red head, and scaup) rise and fall in concert, and correlate
strongly to the number of observed seasonal, semi-permanent or permanent wetlands (Drever
2006). Correlations have also been noted between numbers of wetlands and pied-billed grebe,
blacktem, American bittern, sora, and American coot ( Niemuth &Solberg 2003). It has been
suggested that one of the reasons behind the correlation is that conditions favoring wetland
abundance (i.e., unusually wet conditions the previous year, or heavy winter snow and/or
spring precipitation) also shift the ratio of temporary to seasonal wetlands in that year (Forcey
et al. 2007). In extremely wet years, otherwise temporary or seasonal wetlands may be
absorbed into larger, semi-permanent basins (Kahara et al. 2009). However, while wetter
conditions may favor diving and dabbling ducks, they may disadvantage shorebirds.

Several sources reported on the importance of seasonal and temporary wetlands forshorebird
foraging and waterfowl nesting. Steen and Powell (2012) found that, at the landscape level,
only the density of small seasonal wetlands within a 2-km radius was a predictor of black tern
breeding and foraging. Walker and colleagues (2013) predicted, from field surveys, that blue-
winged teal, gadwall, mallard, northern pintail, and northern shoveler will be most abundant in
landscapes with small-to-medium size temporary or seasonal wetlands, with the highest site
occupancy occurring in areas with the most overall wetland area. Also using a model based on
results of field surveys, Reynolds and colleagues (2006) found that populations of the same five
species would decrease by as much as 37% if small seasonal wetlands in private ownership in
North and South Dakota were drained. These conclusions are supported by field survey
findings that mallard ducklings were 1.5 times more likely to die when the percentage of
seasonal basins containing water was < 18% than when the percentage was >40% (Krapu et al.
2003). Conversely, mallard duckling survival is highest when there are seasonal wetlands with
open water and a fringe of emergent vegetation within Vi kilometer of a nest (Bloom et al.
2012). Several researchers have also noted the importance of seasonal and temporary
wetlands to migrating and resident shorebirds (Skagen et al. 2008). De Leon and Smith (2013)
identified seasonal wetlands a critical foraging ground for long-billed dowitchers, stilt, semi-
palmated and least sandpipers, and American avocet. The availability of seasonal wetlands with
water also determines the frequency and length that some birds, notably mallards, will stop
during migration (Krementz et al. 2011). Niemuth and colleagues (2006) surveyed 1,181
temporary and seasonal wetlands surrounded by cropped fields in North Dakota over a 10-
week period in spring of 2001, observing a total of 4,050 shorebirds of 25 species. Data analysis
indicated that shorebirds selected temporary wetlands with shallow water, little emergent
vegetation, a large perimeter (i.e., a meandering shoreline), and other wetlands nearby.

The importance of small, temporary and seasonal wetlands to birds is due in large part to the
food sources they provide. Small, shallow wetlands warm earlier in the season than larger,
more permanent wetland, and provide an abundant source of invertebrate protein for

32

shorebirds and dabbling ducks during the early season (Swanson et al. 1974). When these
wetlands are drained to consolidate water in lower, semi-permanent or permanent wetlands,
vegetation composition and macroinvertebrate communities change (Anteau 2011), to the
detriment of foraging shorebirds. Artificial management of water levels can also affect
invertebrate species density and abundance in more permanent wetlands. Anthropogenic
manipulation of water levels that extend inundation, or increased sedimentation from
surrounding uplands, may promote the growth of aggressive macrophytes such as Typha and
Phalaris; these, in turn, can lead to increased amounts of litter, negatively affecting
macroinvertebrate abundance and causing shifts in trophic structure (Lavergne & Molofsky
2004; Werner &Zedler2002; Christensen &Crumpton 2010; Mabry & Dettman 2010).

Three sources reported some positive impacts of hydroperiod alteration. One source, reporting
on a GIS analysis, identified more upland nesting opportunities for mallards and pintails when
ephemeral wetlands were converted to cropland (Drever 2006). One after-impact study, which
contradicted many other studies, found higher brood survival for upland nesting ducks in areas
of lower wetland density (Stephens et al. 2005). A third study found that white-faced ibis, which
are not native to the PPR, have been establishing there since the 1970s; the authors surmise it
is due to increased numbers of permanent and semi-permanent ponds being created by
consolidation drainage, and the associated increase in cattail-dominated vegetation (Shaffer et
a I. 2007).

Although macroinvertebrate community composition has been investigated as a potential
bioindicator of wetland condition (Apfelbeck 1999; Hentges 2008; Tangen et al. 2003) and as a
means of identifying relict wetlands that have been subjected to cultivation (Euliss etal. 2001),
macroinvertebrates are rarely used to track specific effects of hydrologic alteration in wetlands.
However, stream ecologists have examined the relationship between flow alteration and
macroivertebrates, focusing on resistance and resiliency. Under natural conditions,
macroinvertebrates will recolonize stream habitats within a week of interrupted flows being
resumed (for example, when rains follow a drought period) or after an intense flood, either
drifting downstream from upstream pools and/or subsurface water, crawling upstream, or
hatching from eggs deposited by aerial adults (Dodds etal. 2004). By contrast, anthropogenic
alterations that do not mimic wet-dry cycles may alter communities permanently, especially if
water is diverted from springs or seeps that provide refuge during dry periods (Fritz & Dodds
2004).

Amphibian use of PPR wetlands has received relatively little attention, even though three of the
four species associated with PPR wetlands in Montana are listed as species of concern
(northern leopard frog, Great Plains toad, and Plains spadefoot), primarily as a result of habitat
loss and fragmentation. In an Iowa study of eight amphibian species, researchers found that all

33

species were least likely to be found in seasonal wetlands in farmed areas, and most likely to be
found in seasonal wetlands embedded in native grasslands (Balas et al. 2012). They theorized
that this was a function of wetlands in native grasslands having longer and more stable
hydroperiods than farmed wetlands, where sedimentation often fills wetlands, and where
crops extract water from soils. This theory is supported by a study of amphibian populations in
Theodore Roosevelt National Park in North Dakota, outside the PPR, where there has been no
grassland conversion, and where populations of boreal chorus frog, Woodhouse's toad,
northern leopard frog, plains spadefoot and Great Plains toad have remained stable since the
1920s (Hossack & Stephen 2002). Direct alterations of hydroperiod have also been found to
affect amphibian presence and condition. For example, Euliss & Mushet (2004) carried out a
control-vs-impact study of excavated, semi-permanent wetlands compared to seasonal
wetlands, reporting deeper and more permanent water favored tiger salamanders over boreal
chorus frogs and northern leopard frogs, which did not reproduce in the salamanders'
presence. Benoy (2008) also found that tigersalamander presence increased when water
permanence increased in wetlands, mimicking the effects of planktivorous fish in changes to
the wetland food web.

Because the project emphasized pothole wetlands, the literature search yielded only passing
references to fish, which are typically only present in larger permanent wetlands with surface
water inflows or outflows, or as introduced species in ponds. The literature on prairie streams
also contained little mention offish. Because of the harsh and fluctuating conditions that
aquatic organisms face in intermittent streams, where hypoxia and hyperthermia are common,
only a handful of fish species are found, and intermittent prairie streams will often be fishless
(Smale &Rabeni 1995). When fish assemblages do occur, impacts of hydrologic disturbance
depend on the availability and proximity of refugia (Franssen et al. 2006) and the duration of
the disturbance (Dodds et al. 2004). Permanent water diversions will lead to loss of fish
populations (Stagliano2005). Similarly, connecting intermittent streams to more permanent
water bodies through dredging or consolidation drainage may introduce predators that
decimate the small fish characteristic of intermittent streams (Spranza & Stanley 2000).

Research reports on mammal use of PPR wetlands and intermittent/ephemeral streams are
limited, except when linked to nest predation (Brook et al. 2008; Drever et al. 2004). However,
a number of small mammals use grasslands in and around PPR wetlands, including skunks
(Lariviere & Messier 2000), meadow voles, shrews, ground squirrels, deer mice and meadow
jumping mice (Wiewel et al. 2007), and native ungulates typically bed down in the cooler, taller
grass found near stream channels on hot summer days.

34

Discussion

As has been observed in other flow-ecology studies (McManamay et al. 2011), the literature
review conducted for this project demonstrates that ecological responses to natural changes in
wetland hydrology are variable, depending on the direction of change and the species, guild or
function affected. Droughts generally lead to decreases in avian, macroinvertebrate and fish
abundance, although depending on the extent and duration of the drought, consequences may
be expressed more as changes in community structure. Flood cycles, in contrast, promote both
greater abundance and changes in community structure, in part because flooding increases
available habitat by increasing the areal extent of wetland and stream habitats.

However, ecological responses to anthropogenic alteration are almost entirely negative. This
difference reflects the duration of natural vs. anthropogenic change. Natural hydroperiods of
wetlands and prairie streams vary spatially and temporally, with flood and drought cycles
altering. In contrast, human manipulations of flood frequency, duration or extent tend to be
permanent, as are the changes in wetland function that they induce. For example, drained
wetlands are effectively trapped in a permanent drought condition; similarly, shallow flow-
through wetlands that are excavated and impounded will be flooded indefinitely.

Most of the studies that discuss the source of anthropogenic change focus on agriculture
(Appendix D), primarily because that has been the most widespread human land use activity in
the PPR. However, agriculture perse, while implicated in the change of surface runoff patterns
and increases in sedimentation, is not the principal cause of all hydrologic change. Instead, it is
the manipulations of hydrological conditions that often accompany agriculture: water pumping
and diversion; tilling of shallow wetlands; excavation of wetlands to provide more permanent
water storage; various forms of draining; dredging and channelization of intermittent and
ephemeral streams; and impoundments of seasonal stream flows by dams or culverts. Any
kind of development that alters surface permeability or changes flow patterns are likely to have
similar impacts on functions, processes and biota, including construction of infrastructure for
energy extraction and development, groundwater pumping for residential or industrial use, and
impoundments for recreational use. However, these effects have not yet been extensively
studied; this is an area requiring further research.

Region-wide surveys of wetlands (e.g., Niemuth et al. 2011) and models predicting climate
change impacts (e.g., Naugle et al. 2001; Johnson et al. 2005) were the only sources in our
review that quantified changes in wetland extent, class and distribution based on hydrologic
inputs. However, precipitation was the only factor that could be quantified. Unlike rivers,
which can be instrumented to link specific flows to specific responses, wetlands have more
diffuse inputs, which vary on both spatial and temporal scales. Consequently, we do not find
good support for specific precautionary limits on hydrologic alteration, beyond those that can

35

be expressed in terms of their effects (e.g., loss of permanence, loss of hydrophytic vegetation,
changes in a real extent of a wetland, etc.).

The review raises several questions of scale. As noted earlier, while individual wetlands were
once the main focus of research, in recent years attention has shifted to wetland complexes
(Johnson & Werner 2010; Shaw et al. 2012). Individual wetlands may not be the appropriate
units for evaluating, or regulating, hydrologic alteration, except in the case where the wetland
is so large or so unique (e.g., certain alkaline lakes) that it is the only habitat feature of its kind
in an area. Instead, it may be better to emphasize specific wetland landscape profiles as a
target. In areas where human disturbance is minimal, wetland abundance, diversity of wetland
types, and characteristic wetland size are linked to such landscape-level factors as
geomorphology, basin hydrology, and regional or local climate (Johnson 2005). Consequently,
similar landscapes can be expected to have similar wetland "profiles." These profiles in turn
establish which wetland functions are associated with a particular region (e.g., subbasin,
watershed, subwatershed), and maintenance (or restoration) of that profile can be targeted.
This approach has been adopted as a wetland assessment tool in Montana (Vance et al. 2006;
Mclntyre et al. 2011; Newlon 2012) and Colorado (Lemly & Gilligan 2012). Once a "natural"
profile is established, it would be possible to set thresholds of acceptable (and unacceptable)
change, e.g., no more than 10% loss of semi -permanent wetlands. Such targets could frame
precautionary limits on hydrologic modification. Wetland landscape profiling is similarto the
"thunderstorm maps" (Loesch et al. 2011) used to identify duck habitat conservation targets,
but emphasizes wetlands rather than wetland-dependent species.

A final caveat about the results of the literature review is in order: with the exception of agency
reports and unpublished documents, very few studies and research reports examine wetlands
or intermittent and ephemeral streams in Montana. Although impacts of hydrologic alteration
on waterbirds can be extrapolated from adjacent states and provinces, more research on faunal
use of seasonal and temporary wetlands in arid areas may be warranted. Because it lies mostly
west of the Missouri Coteau, Montana's prairie wetlands differ from those in the eastern parts
of the PPR, with less wetland and stream density, fewer permanent wetlands and perennial
streams, distinct climate patterns, and a different geologic profile.

36

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49

APPENDICES

50

Appendix A. Approximate crosswalk between classification schemes

Stewart and Kantrud 1

Cowardin/USFWS

Natureserve Ecological System

Army Corps of Engineers HGM

1. Ephemeral pond

Not a wetland

Great Plains Mixed Grass Prairie

Lacking wetland hydrology, soils and vegetation

II. Temporary Pond

PEMA

Great Plains Prairie Pothole

Temporary/Seasonally Ponded Prairie Pothole Systems

Fresh

Great Plains Prairie Pothole

Brackish

Great Plains Prairie Pothole

III. Seasonal Ponds (and Lakes)

PEMC

Fresh

Great Plains Prairie Pothole

Temporary/Seasonally Ponded Prairie Pothole Systems

Slighly Brackish

Great Plains Prairie Pothole

Moderately brackish

Great Plains Prairie Pothole

IV. Semi-permanent Ponds (and Lakes)

PEMF, PEMG; PUS (C and G),

Fresh

PABF

Great Plains Open Depression Wetland

Depressional Wetlands 2

Slighly Brackish

Great Plains (Open or Closed) Depression Wetland

Moderately brackish

Great Plains Closed Depression Wetland

Brackish

Great Plains Saline Depression Wetland

Saline

Great Plains Saline Depression Wetland

IV. Permanent Ponds (and Lakes)

PEMH, PEMG, PABH

Not defined

Slighly Brackish

NA Arid West Emergent Marsh

Moderately brackish

NA Arid West Emergent Marsh

Brackish

NA Arid West Emergent Marsh

Saline

Great Plains Saline Depression Wetland

V. Alkali Ponds (and Lakes)

PEMA, PEMC, PUSA, PUSC

Great Plains Saline Depression Wetland

VI. Fen Ponds

The Stewart and Kantrud scheme was intended as a regional typology, and describes the entire wet land based on duration of flooding, whereas Cowardin was intended as a national

classification, and describes wetlands at the habitat component level to facilitate inventory and mapping. In the Cowardin system, a single wetland basin may have two or more habitat

components, usually defined by water regime. Natureserve's ecological systems classification (Comer eta I. 2003) also aggregates components into a single class.

In the HGM Regional Guidebook (Gilbert 2006), Prairie Pot holes a re specifically defined as h yd rologica I ly dominated by surface runoff; wetlands with a ground water source a re therefore

simply depressional wetlands

A shallow depression with ephemeral ponding in its center, or a swale that transports overland flow, would not be flooded for long enough to be a wetland in the Cowardin system.

51

Appendix B. Keywords and search strings used in database searches

DATABASE
BioOne

Prairie Pothole* AND Montana

Prairie Pothole* AND (wetland OR habitat OR hydrol* OR aquatic* OR water* OR
intermittent OR ephemeral OR stream OR waterfowl OR duck* OR *bird* OR
amphibian* OR reptile* or mammal* or nest* OR macroinvertebrate* OR
agriculture* OR land use OR development)

Prairie AND (wetland OR habitat OR hydrol* OR aquatic* OR water* OR
intermittent OR ephemeral OR stream OR waterfowl OR duck* OR*bird* OR
amphibian* OR reptile* or mammal* or nest* OR macroinvertebrate* OR
agriculture* OR land use OR development)

Pothole AND (wetland OR habitat OR hydrol* OR aquatic* OR water* OR
intermittent OR ephemeral OR stream OR waterfowl OR duck* OR*bird* OR
amphibian* OR reptile* or mammal* or nest* OR macroinvertebrate* OR
agriculture* OR land use OR development)

Northwestern Glaciated Plains

Prairie Pothole Region

Wetland* AND (Montana OR North Dakota OR South Dakota OR Alberta OR
Manitoba OR Saskatchewan

Intermittent OR Ephemeral AND stream*

{Species name OR Guild} 8 AND (wetland* OR pothole* OR habitat* OR ecology*)

Environment Complete

Prairie Pothole* AND Montana

Prairie Pothole* AND (wetland OR hydrol* OR aquatic* OR water* OR
intermittent OR ephemeral OR stream OR waterfowl OR duck* OR*bird* OR
amphibian* OR reptile* or mammal* or nest* OR macroinvertebrate* OR
agriculture* OR land use OR development)

Species names and guilds a re listed in Appendix C

52

Prairie AND (wetland OR hydrol* OR aquatic* OR water* OR intermittent OR
ephemeral OR stream OR waterfowl OR duck* OR *bird* OR amphibian* OR
reptile* or mammal* or nest* OR macroinvertebrate* OR agriculture* OR land
use OR development)

Pothole AND (wetland OR hydrol* OR aquatic* OR water* OR intermittent OR
ephemeral OR stream OR waterfowl OR duck* OR *bird* OR amphibian* OR
reptile* or mammal* or nest* OR macroinvertebrate* OR agriculture* OR land
use OR development)

Northwestern Glaciated Plains

Prairie Pothole Region

Wetland* AND (Montana OR North Dakota OR South Dakota OR Alberta OR
Manitoba OR Saskatchewan

{Species name OR Guild} AND (wetland* OR pothole* OR habitat* OR ecology*)

53

Appendix C: Faunal species associated with PPR wetland and streams

Global/State
Rank

Common
Name

Scientific Name

Distribution
Status

Guild

G5/S3

Great Blue
Heron

Ardea herodias

Resident
Year Round

Colonial nestingwaterbirds

G4/S3B

American
Bittern

Botaurus lentiginosus

Migratory

Summer

Breeder

Colonial nestingwaterbirds

G4/S3B

Black Tern

Chlid onias niger

Migratory

Summer

Breeder

Colonial nestingwaterbirds

G5/S2B

Caspian Tern

Hydroprogne caspia

Migratory

Summer

Breeder

Colonial nestingwaterbirds

G4G5/S3B

Franklin's Gull

Leucophaeus pipixcan

Migratory

Summer

Breeder

Colonial nestingwaterbirds

G5/S5B

Double-
crested
Cormorant

Phalacrocorax auritus

Migratory

Summer

Breeder

Colonial nestingwaterbirds

G5/S3B

White-faced
Ibis

Plegadis chihi

Migratory

Summer

Breeder

Colonial nestingwaterbirds

G5/S5B

Eared Grebe

Pod ice ps nigricollis

Migratory

Summer

Breeder

Colonial nestingwaterbirds

G5/S3B

Common Tern

Sterna hirundo

Migratory

Summer

Breeder

Colonial nestingwaterbirds

G4/S1B

Least Tern

Stern u la antillarum

Migratory

Summer

Breeder

Colonial nestingwaterbirds

G5/S5B

Wood Duck

Aix sponsa

Resident
Year Round

Dabbling waterfowl

G5/S5B

Northern
Pintail

Anas acuta

Resident
Year Round

Dabbling waterfowl

G5/S5B

American
Wigeon

Anasamericana

Resident
Year Round

Dabbling waterfowl

G5/S5B

Northern
Shoveler

Anasclypeata

Migratory

Summer

Breeder

Dabbling waterfowl

G5/S5B

Green-winged
Teal

Anascrecca

Resident
Year Round

Dabbling waterfowl

G5/S5B

Blue-winged
Teal

Anas disco rs

Migratory

Summer

Breeder

Dabbling waterfowl

Global/State

Common

Scientific Name

Distribution

Guild

54

Rank

Name

Status

G5/S5

Mallard

Anas platyrhynchos

Resident
Year Round

Dabbling waterfowl

G5/S5B

Gadwall

Anas st rep era

Resident
Year Round

Dabbling waterfowl

G5/S5B

Canada Goose

Branta canadensis

Resident
Year Round

Dabblingwaterfowl

G5/S4N

Snow Goose

Chen caerulescens

Common
Migrant

Dabbling waterfowl

G5/S5B

LesserScaup

Aythya affinis

Resident
Year Round

Divingwaterfowl

G5/S5B

Redhead

Aythya americana

Migratory

Summer

Breeder

Divingwaterfowl

G5/S5B

Ring-necked
Duck

Aythya collaris

Resident
Year Round

Divingwaterfowl

G5/S5B

Canvasback

Aythya valisineria

Migratory

Summer

Breeder

Divingwaterfowl

G5/S5B

Bufflehead

Bucephala albeola

Resident
Year Round

Divingwaterfowl

G5/S5

Common
Goldeneye

Bucephala clangula

Resident
Year Round

Divingwaterfowl

G5/S4

Hooded
Merganser

Lophodytes cucullatus

Resident
Year Round

Divingwaterfowl

G5/S5B

Common
Merganser

Mergus merganser

Resident
Year Round

Divingwaterfowl

G5/S5B

Ruddy Duck

Oxyura jamaicensis

Migratory

Summer

Breeder

Divingwaterfowl

G5/S5B

Red-winged
Blackbird

Agelaius phoeniceus

Resident
Year Round

Grassland birds

G5/S3B

Nelson's
Sparrow

Ammodramus nelsoni

Migratory

Summer

Breeder

Grassland birds

G5/S5B

Marsh Wren

Cistothorus palustris

Resident
Year Round

Grassland birds

G5/S3B

Bobolink

Dolichonyx oryzivorus

Migratory

Summer

Breeder

Grassland birds

G5/S3B

Veery

Catharusfuscescens

Migratory

Summer

Breeder

Other

G5/S4B

Wi 1 1 ow
Flycatcher

Empidonax traillii

Migratory

Summer

Breeder

Other

Global/State
Rank

Common
Name

Scientific Name

Distribution
Status

Guild

55

G5/S5B,S2N

Sandhill Crane

Grus canadensis

Migratory

Summer

Breeder

Other

G5/S5B

Belted
Kingfisher

Megaceryle alcyon

Resident
Year Round

Other

G5/S3B

Red-headed
Woodpecker

Melanerpes erythrocephalus

Migratory

Summer

Breeder

Other

G5/S5B

Spotted
Sandpiper

Actitis macularius

Migratory

Summer

Breeder

Shorebirds

G5/SNA

Stilt
Sandpiper

Calidris himantopus

Common
Migrant

Shorebirds

G5/SNA

Least
Sandpiper

Calidris minutilla

Common
Migrant

Shorebirds

G5/SNA

Semipal mated
Sandpiper

Calidris pusilla

Common
Migrant

Shorebirds

G3/S2B

PipingPlover

Charadrius melodus

Migratory

Summer

Breeder

Shorebirds

G5/S3B

Black-necked
Stilt

Himantopus mexicanus

Migratory

Summer

Breeder

Shorebirds

G5/SNA

Long-billed
Dowitcher

Limnodromus scolopaceus

Passage
Migrant

Shorebirds

G5/S4B

Marbled
Godwit

Limosafedoa

Migratory

Summer

Breeder

Shorebirds

G5/S4B

Wilson's
Phalarope

Phalaropus tricolor

Migratory

Summer

Breeder

Shorebirds

G5/S4B

American
Avocet

Recurvirostra americana

Migratory

Summer

Breeder

Shorebirds

G5/S4B

Willet

Tringa semipalmata

Migratory

Summer

Breeder

Shorebirds

G5/S3B

Clark's Grebe

Aechmophorus clarkii

Migratory

Summer

Breeder

Waterbirds

G5/S4B

Western
Grebe

Aechmophorus occidentalis

Migratory

Summer

Breeder

Waterbirds

G4/S3B

Yellow Rail

Coturnicops noveboracensis

Accidental

Waterbirds

Global/State
Rank

Common
Name

Scientific Name

Distribution
Status

Guild

56

G5/S5B

American
Coot

Fulica americana

Resident
Year Round

Waterbirds

G5/S3B

Horned Grebe

Podiceps auritus

Migratory

Summer

Breeder

Waterbirds

G5/S4B

Red-necked
Grebe

Podiceps grisegena

Migratory

Summer

Breeder

Waterbirds

G5/S5B

Pied-billed
Grebe

Podilymbus podiceps

Resident
Year Round

Waterbirds

G5/S5B

Sora

Porzana Carolina

Migratory

Summer

Breeder

Waterbirds

G5/S5B

Virginia Rail

Rallus limicola

Migratory

Summer

Breeder

Waterbirds

G5/S4

Barred Tiger
Salamander

Ambystoma mavortium

Resident
Year Round

Amphibian

G5/S4

Woodhouse's
Toad

Anaxyrus woodhousii

Resident
Year Round

Amphibian

G5/S3

Plains
Spadefoot

Spea bombifrons

Resident
Year Round

Amphibian

G5/S4

Boreal Chorus
Frog

Pseudacris maculata

Resident
Year Round

Amphibian

G5/S1,S4

Northern
Leopard Frog

Lith obatesp ip iens

Resident
Year Round

Amphibian

G5/S4

Northern
Painted Turtle

Chrysemys picta

Resident
Year Round

Reptile

G5/S2

Smooth
Green Snake

Opheodrys vernalis

Resident
Year Round

Reptile

G5/S2S3

Eastern Red
Bat

Lasiurus borealis

Migratory

Summer

Breeder

Mammal

G5/S4

Least Weasel

Mustela nivalis

Resident
Year Round

Mammal

G5/S5

American
Mink

Mustela vison

Resident
Year Round

Mammal

G5/S5

Common
Muskrat

Ondatra zibethicus

Resident
Year Round

Mammal

Global/State
Rank

Common
Name

Scientific Name

Distribution
Status

Guild

57

G5/S1S3

Arctic Shrew

Sorex arcticus

Resident
Year Round

Mammal

G5/S5

Dusky Shrew

Sorex monticolus

Resident
Year Round

Mammal

G4/S2S3

Dwarf Shrew

Sorex nanus

Resident
Year Round

Mammal

G5/S2

Meadow
Jumping
Mouse

Zapushudsonius

Resident
Year Round

Mammal

G5/S4

Brassy
minnow

Hybognathus hankinsoni

Fish

G5/S4

Brook
stickleback

Culaea inconstans

Fish

G5/S3

Northern
redbellydace

Chrosomus eos

Fish

G5/S2

Pearl dace

Margariscus margarita

Fish

58

Appendix D. Number of sources describing ecological change in wetland function
following hydrologic alterations

Function

Water storage

Change vector

Agriculture

Channelization

Climate change

Dams or impoundments

Diversions

Drainingor ditching

Excavation

Groundwater extraction

Land coverchange

Overgrazing

Roads or culverts

# of sources

17
2

12
4
2
16
3
1
15
2
1

Groundwater recharge

Agriculture

Channelization

Climate change

Dams or impoundments

Diversions

Drainingorditching

Excavation

Groundwater extraction

Land coverchange

Overgrazing

Roads or culverts

10
2
6
2
7
1
1
2
9
2
1

Streamflow maintenance

Agriculture

Channelization

Climate change

Dams or impoundments

Diversions

Drainingorditching

Excavation

Land coverchange

Overgrazing

1
1
2
1
1
1
1
2
1

59

Flood mitigation

Agriculture

Dams or impoundments

Drainingor ditching

Overgrazing

2
1
8
1

Plant community maintenance

Agriculture

Channelization

Climate change

Dams or impoundments

Diversions

Draining orditching

Excavation

Groundwater extraction

Land coverchange

Overgrazing

Roads or culverts

39
5

12
4
2

13
3

Faunal habitat

Agriculture

Channelization

Climate change

Dams or impoundments

Diversions

Drainingor ditching

Excavation

Land coverchange

Overgrazing

Roads or culverts

12
1
6
2
1
5
2

12
4
2

Biodiversity

Agriculture

Channelization

Climate change

Dams or impoundments

Diversions

Drainingorditching

Excavation

Groundwater extraction

Land coverchange

Overgrazing

Roads or culverts

32
6

13
2
2

13
3

24
6
2

60

61