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ON THE COVER 

Niobrara National Scenic River 

Photograph courtesy of the National Park Service
Niobrara National Scenic River Condition Assessment 

Natural Resource Report NPS/NRPC/NRR—2010/172

Sunil Narumalani 

Gary D. Willson 

Christine K. Lockert 

Paul B. T. Merani 

Great Plains Cooperative Ecosystem Studies Unit 

515 Hardin Hall 

University of Nebraska-Lincoln 

Lincoln, NE 68583-0985 

This report was prepared under Task Agreement J6067070012 of the Great Plains Cooperative 

Ecosystem Studies Unit (Cooperative Agreement between the National Park Service and the 

University of Nebraska-Lincoln CAH6000060100). 

January 2010 

U.S. Department of the Interior 

National Park Service 

Natural Resource Program Center 

Fort Collins, Colorado 
ii 

The National Park Service, Natural Resource Program Center publishes a range of reports that 

address natural resource topics of interest and applicability to a broad audience in the National 

Park Service and others in natural resource management, including scientists, conservation and 

environmental constituencies, and the public. 

The Natural Resource Report Series is used to disseminate high-priority, current natural resource 

management information with managerial application. The series targets a general, diverse 

audience, and may contain NPS policy considerations or address sensitive issues of management 

applicability. 

All manuscripts in the series receive the appropriate level of peer review to ensure that the 

information is scientifically credible, technically accurate, appropriately written for the intended 

audience, and designed and published in a professional manner. This report received formal peer 

review by subject-matter experts who were not directly involved in the collection, analysis, or 

reporting of the data, and whose background and expertise put them on par technically and 

scientifically with the authors of the information. 

Views, statements, findings, conclusions, recommendations, and data in this report are those of 

the author(s) and do not necessarily reflect views and policies of the National Park Service, U.S. 

Department of the Interior. Mention of trade names or commercial products does not constitute 

endorsement or recommendation for use by the National Park Service. 

This report is available from the Great Plains Cooperative Ecosystem Studies Unit website 

(http:snr.unl.edu/gpcesu) and the Natural Resource Publications Management website 

(http://www.nature.nps.gov/publications/NRPM). 

Please cite this publication as: 

Narumalani, S., G. D. Willson, C. K. Lockert, and P. B. T. Merani. 2010. Niobrara National 

Scenic River condition assessment. Natural Resource Report NPS/NRPC/NRR—2010/172. 

National Park Service, Fort Collins, Colorado. 

NPS 656/100866, January 2010 
iii

 
iv

Contents 

Page 

Figures ........................................................................................................................................ vii 

Tables .......................................................................................................................................... xi 

Executive Summary .................................................................................................................. xiii 

Acknowledgements .................................................................................................................. xvii 

Introduction .................................................................................................................................. 1 

Ecological Context ....................................................................................................................... 3 

Physical Setting ................................................................................................................. 3 

History, Location, and Management Direction ......................................................... 3

Climate and Microclimate ......................................................................................... 5

Air Quality ................................................................................................................. 6

Topography and Geology .......................................................................................... 7

Soils ............................................................................................................................ 7

Watershed and Hydrology ......................................................................................... 8 

Water Quality ........................................................................................................... 10

 Biological Setting ............................................................................................................ 10 

Vegetation ................................................................................................................ 10

Mammals .................................................................................................................. 11 

Birds ......................................................................................................................... 12 

Reptiles and Amphibians ......................................................................................... 14

Fishes ....................................................................................................................... 15 

Invertebrates ............................................................................................................ 18

Listed Species .......................................................................................................... 18
v

Contents 

 Land and Visitor Use ....................................................................................................... 18 

 Important Natural Resources ......................................................................................... 19 

Niobrara River Water Quantity and Quality ........................................................... 19

Tributary Springs and Waterfalls ............................................................................ 19

Diverse Plant and Animal Communities including Pleistocene Relicts .................. 20

Sandy Shorelines, Sandbars, and Wetlands ............................................................. 22

Natural Resource Condition ....................................................................................................... 23 

Condition Assessment Approach for Niobrara National Scenic River ............................ 23 

Indicator Assessment ....................................................................................................... 29 

Habitat: Niobrara River and Tributaries ................................................................. 29 

Aquatic Macroinvertebrates ................................................................................ 29

River Otter ........................................................................................................... 33

Cool-water Fishes ............................................................................................... 34 

Fish Community .................................................................................................. 36

Spiny Softshell Turtle ........................................................................................... 37

Stream Flow ......................................................................................................... 38

 Habitat: Upland Forest and Savanna ........................................................................ 41 

Elk ........................................................................................................................ 41

Ponderosa Pine ................................................................................................... 43

 Land Cover .......................................................................................................... 46 

 Fire ...................................................................................................................... 48

 
vi

Contents 

 Habitat: Spring Branch Canyon and Riparian Forest ............................................. 48 

 Paper Birch ......................................................................................................... 48

Hybrid Aspen ....................................................................................................... 50

Bailey’s Eastern Woodrat ................................................................................... 52 

 

 Bird Hybridization ............................................................................................... 53

 Habitat: Grassland ................................................................................................... 54 

Grassland Birds ................................................................................................... 54

Sand Hills Prairie ................................................................................................ 56 

 Land Cover .......................................................................................................... 57 

 Fire ...................................................................................................................... 57

 Habitat: Sandy Shorelines, Sandbars, and Wetlands .............................................. 58 

Interior Least Tern and Piping Plover ................................................................ 58 

Purple Loosestrife ............................................................................................... 62 

Whooping Crane .................................................................................................. 66 

Sediment Transport ............................................................................................. 68

Stressors and Management Strategies ........................................................................................ 69

 Conclusion .................................................................................................................................. 81 

 Literature Cited ........................................................................................................................... 85 

 Appendix A 

 Appendix B 

viii 

Figures 

page 

Figure 1. The location of Niobrara National Scenic River in Nebraska ..................................... 3 

Figure 2. Existing conditions ...................................................................................................... 4 

Figure 3. NOAA-PDSI calculated for the instrumented past, representing the spatially 

averaged conditions in the panhandle and north-central climatic regions of Nebraska .............. 6 

Figure 4. Precipitation trends from 1900 to present ..................................................................... 6 

Figure 5. Cross-section view of the middle Niobrara River Valley ............................................ 8 

Figure 6. Niobrara River watershed ............................................................................................. 9 

Figure 7. Dams on the Niobrara River and tributaries ................................................................ 9 

Figure 8. Fish observation sites in the Niobrara River and tributaries ..................................... 16 

Figure 9. Number of floaters per year, 1993–2008, Niobrara National Scenic River .............. 19 

Figure 10. Tributary waterfall in the Niobrara National Scenic River ..................................... 20 

Figure 11. Aquatic macroinvertebrate sampling sites in Niobrara National Scenic 

River ........................................................................................................................................... 30 

Figure 12. National park units of the Northern Great Plains Network sampled for 

aquatic macroinvertebrates ........................................................................................................ 30 

Figure 13. Median EPT richness and HBI value for medium and large rivers of the 

Northern Great Plains Network ................................................................................................. 31 

Figure 14. Median EPT richness and HBI value for small streams of the Northern 

Great Plains Network ................................................................................................................. 32 

Figure 15. River otter distribution in Nebraska ........................................................................ 34 

Figure 16. Location of cool-water fish collection sites in tributary streams of the 

Niobrara River ........................................................................................................................... 35 

Figure 17. Location of nine stream flow gauges in or near the Niobrara National 

Scenic River ............................................................................................................................... 39 

Figure 18. Annual model run without water diversions from the Niobrara River .................... 40 
ix

Figures 

Figure 19. The mean and standard deviation of daily stream flow at Sparks, Nebraska .......... 41 

Figure 20. Elk distribution in Nebraska .................................................................................... 42 

Figure 21. Free-ranging chronic wasting disease (CWD) positives in Nebraska ...................... 42 

Figure 22. Ponderosa pine distribution in Nebraska ................................................................. 43 

Figure 23. Change in woodland vegetation along the Niobrara River, 1939–2003, 

Keya Paha and Rock Counties, Nebraska .................................................................................. 44 

Figure 24. Change in woodland vegetation along the Niobrara River, 1939–2003, 

Keya Paha and Brown Counties, Nebraska ............................................................................... 45 

Figure 25. Niobrara National Scenic River and surrounding land cover change, 

1992–2001 .................................................................................................................................. 47 

Figure 26. Sampling locations of paper birch along the Niobrara River .................................. 49 

Figure 27. Observation points of hybrid aspen in the Niobrara National 

Scenic River ............................................................................................................................... 51 

Figure 28. Average number of Bailey’s eastern woodrat captured in 2004 and 2005 

in four habitat types in the Niobrara Valley Preserve ................................................................ 53 

Figure 29. Mean density (no./ha) and 95 percent confidence interval during 2004 and 

2005 for two songbird species in four habitat types in the Niobrara Valley Preserve ............... 55 

Figure 30. Interior least tern and piping plover distribution by county in Nebraska ................ 58 

Figure 31. Interior least tern and piping plover observation points within Niobrara National 

Scenic River ............................................................................................................................... 59 

Figure 32. Interior least tern and piping plover adults counted on the Niobrara River ............ 60 

Figure 33. Interior least tern and piping plover adults and nests counted in the Niobrara 

National Scenic River ................................................................................................................ 60 

Figure 34. Purple loosestrife infested areas interpreted from hyperspectral imageries, 

Niobrara National Scenic River, 2008 ....................................................................................... 63 

Figure 35. Delineated purple loosestrife infested areas, Niobrara National Scenic 

River, 2002 .................................................................................................................................. 64 
x

Figures 

Figure 36. Effectiveness of biological control, Niobrara National Scenic River, 2008 ........... 65 

Figure 37. Breeding and wintering areas and primary migration pathway of the 

whooping crane .......................................................................................................................... 66 

Figure 38. Whooping crane migration pathway in Nebraska ................................................... 67 

Figure 39. Niobrara National Scenic River conceptual diagram: existing and possible 

relationship of stressors to biodiversity and process indicators ................................................. 69 

Figure 40. Center-pivots located within 16 km (10 miles) of the Niobrara 

National Scenic River in 1975 (a) and 2005 (b) ........................................................................ 70 

Figure 41. Purple loosestrife distribution in Nebraska ............................................................. 73 

Figure 42. Palmer Drought Severity Index ............................................................................... 74 

Figure 43. Mean aquatic macroinvertebrate EPT richness and abundance in disturbed 

and undisturbed tributaries within Niobrara National Scenic River .......................................... 76 

Figure 44. Leafy spurge distribution in Nebraska ..................................................................... 77 

Figure 45. Common reed distribution in Nebraska ................................................................... 77 

Figure 46. Emerald ash borer locations in the United States and Canada ................................ 79 

Figure 47. Percent of ash trees to total tree resources ............................................................... 79 

xii 

Tables 

Page 

Table 1. Average increase in near surface maximum temperature (°C) in associated 

habitats compared to paper birch stands in spring branch canyons in the summer of 

1986 .............................................................................................................................................. 5 

Table 2. Air quality condition interpolation values, 2003–2007, Niobrara National 

Scenic River ................................................................................................................................. 7 

Table 3. Ecological associations of mammals in the central Niobrara River Valley ................ 11 

Table 4. Ecological associations of typical breeding birds of the central Niobrara 

River Valley ............................................................................................................................... 13 

Table 5. Expected, encountered, and previously documented reptile and amphibian 

species in the Niobrara National Scenic River .......................................................................... 14 

Table 6. Fish species collected using electroshocking and seining techniques at selected 

sites in the Niobrara River and tributaries ................................................................................. 17 

Table 7. Bird species of east-west biogeographic significance in the Niobrara River 

Valley ......................................................................................................................................... 20 

Table 8. Mammals, reptiles, and amphibians of east-west biogeographic 

significance in the Niobrara River Valley ................................................................................. 21

Table 9. Habitat indicators and stressors ................................................................................... 23 

Table 10. Indicators, corresponding vital signs, and primary information sources used 

in this condition assessment ....................................................................................................... 24 

Table 11. Niobrara National Scenic River natural resources summary .................................... 26 

Table 12. Presence of blacknose shiner (b), finescale dace (f), northern redbelly dace (n), 

and pearl dace (p) in tributary streams of the Niobrara River ................................................... 36 

Table 13. Catch per unit effort (CPUE) of fish species from the Niobrara River in 

1978 and 1991 ............................................................................................................................ 37 

Table 14. Annual mean stream flow trend results in the Niobrara River using 

Mann-Kendall test ...................................................................................................................... 38 

Table 15. Number of patches, percent land cover, and changes, 1992–2001, for 

Niobrara National Scenic River and the surrounding area ........................................................ 48 
xiii

Tables 

Table 16. Summary of paper birch stand conditions along the Niobrara River ........................ 50 

Table 17. Health and management of select hybrid aspen stands along the 

Niobrara River ........................................................................................................................... 52 

Table 18. Hybrid index of two inter-breeding species pairs along the Niobrara River ............ 54 

Table 19. Population trends of endemic and secondary grassland birds and their 

status in the Niobrara River Valley ............................................................................................ 55 

Table 20. Age and density of ponderosa pines by site .............................................................. 57 

Table 21. Comparison of piping plover and interior least tern average clutch size and nest, 

hatching, and fledgling success between the Niobrara and Missouri Rivers in 1996 

and 1997 ..................................................................................................................................... 61 

Table 22. Habitat conditions and trends .................................................................................... 83 

 
xiv

Executive Summary 

Niobrara National Scenic River spans a 122-km (76-mile) long reach of the Niobrara River in 

rural, north-central Nebraska. The scenic river encompasses 9,338 ha (23,074 acres) of land and 

water, all of which is in private ownership, except for about 320 ha (790 acres). Because the 

scenic river does not own land, it achieves management goals by coordinating and collaborating 

with federal, state, and local jurisdictions and private landowners. 

The central Niobrara River Valley is often referred to as a “biological crossroads” with plant and 

animal species representative of northern boreal forest, eastern deciduous forest, rocky mountain 

coniferous forest, tallgrass prairie, Sand Hills prairie, and mixed-grass prairie. Important natural 

resources include the Niobrara River; tributary springs and waterfalls; diverse plant and animal 

communities including Pleistocene relicts; and sandy shorelines, sandbars, and wetlands. 

 

This condition assessment was undertaken to provide NPS managers, interpreters, and planners 

with a concise synthesis, and “scorecard”, of the most current information on the natural 

resources in and around the scenic river. The assessment is divided into four sections: (1) 

Ecological Context provides an overview of the natural resources of the scenic river and region; 

(2) Natural Resource Condition identifies habitat indicators and associated measures, assigning 

a condition and trend score to each indicator; (3) Stressors and Management Strategies

discusses stressors and proposes management strategies; and (4) Conclusion determines an 

overall condition and trend score for major habitats. 

The major habitats in the scenic river—as identified by natural resource studies—are Niobrara

River and tributaries; upland forest and savanna; spring branch canyon and riparian 

forest; grassland; and sandy shorelines, sandbars, and wetlands. These habitats provide the 

ecological framework for this assessment, and their condition and trend are assessed by a suite of 

biodiversity and process indicators. Indicator condition was characterized as poor (red box) or 

good (green box) and trend was characterized as deteriorating (down arrow), stable (horizontal 

arrow), improving (upward arrow), or no trend or insufficient data (no arrow). These 

characterizations were based on a comparison of reference and existing values for the measures 

of each indicator. The scored indicators and their condition and trend are: 

aquatic macroinvertebrates good and no trend 

cool-water fishes good and no trend 

fish community good and stable 

stream flow poor and deteriorating 

elk good and improving 

ponderosa pine poor and deteriorating 

land cover (upland forest and savanna) good and improving 

fire (upland forest and savanna) poor and deteriorating

paper birch poor and deteriorating 

hybrid aspen poor and deteriorating 

Bailey’s eastern woodrat good and no trend 

grassland birds good and deteriorating 

Sand Hills prairie good and deteriorating 
xv

land cover (grassland) good and improving 

fire (grassland) poor and deteriorating 

interior least tern and piping plover good and improving 

purple loosestrife poor and improving 

In addition, five indicators, river otter, spiny softshell turtle, bird hybridization, whooping 

crane, and sediment transport were included but not scored due to lack of site-specific 

information. They were discussed to highlight rare or unique resources and important 

information needs. 

 

The scenic river’s long, narrow corridor and limited conservation ownership in the watershed 

makes it highly susceptible to stressors originating from adjacent lands. The major stressors 

emerging from this condition assessment are: 

water diversion and withdrawal: water diversions from the Niobrara River and tributaries have 

significantly altered its runoff hydrology and may impact ecological processes and biota. 

water quality degradation: fecal coliform and phosphorus are elevated in some tributaries 

possibly due to visitors hiking in streambeds. 

visitor river floating: floater days in the scenic river increased substantially between 2005 and 

2008 and recreational noise may impact waterbirds and other wildlife. 

purple loosestrife infestation: herbicides and biocontrol appear to be successful in reducing 

infestations but the plant continues to invade new areas. 

woodland expansion (fire suppression): fire suppression and changes in the grazing regime 

have allowed ponderosa pine and other woody plants to spread into grassland and to increase in 

woodland understory. 

drought: with reduced stream flow due to water diversions, drought impacts on river ecological 

processes and biota may be more severe. 

microclimate in birch stands: a key factor contributing to birch dieback may be increased 

frequency of thaw-freeze events. 

spring branch hiking: visitors walking in the streambed of spring branch tributaries results in a 

variety of physical and biological impacts. 

Other existing or potential stressors are leafy spurge infestation, common reed infestation, 

mountain pine beetle infestation, and emerald ash borer infestation. 

Based on a subjective evaluation of the indicators of the major habitats, their condition and trend 

are: 

Niobrara River and tributaries good and no trend 

upland forest and savanna poor and deteriorating 

spring branch canyon and riparian forest poor and deteriorating 

grassland good and deteriorating 

sandy shorelines, sandbars, and wetlands good and stable 

Priority management strategies to address stressors include pursuing instream flow rights to the 

Niobrara River to protect recreational and fish and wildlife resources, continuing herbicide 
xvi

applications and biocontrol to reduce purple loosestrife infestations, supporting the use of 

prescribed fire and the monitoring of fire effects by cooperating private and public land owners, 

and stimulating birch seedling establishment via mechanical removal of surface litter and 

overstory canopy. Future stressors may include the mountain pine beetle and the emerald ash 

borer. Both species have the ability to substantially alter plant communities and their resident 

wildlife. In addition to the vital-signs monitoring that will be initiated in the near future by the 

Northern Great Plains Inventory and Monitoring Network, monitoring in cooperation with the 

Nebraska Game and Parks Commission should be considered for river otter, cool-water fishes,

fish community, spiny softshell turtle, elk, and Bailey’s eastern woodrat. Important research 

needs include recreation impacts on spiny soft-shell turtles, reduced stream flow impacts on river 

morphology and biota, changes in bird hybridization rates and locations, and impacts of existing 

and potential invasive plants and insects. 

xviii 

Acknowledgements 

The authors thank the following internal (NPS) reviewers: Pamela Sprenkle, Stuart Schneider, 

and Dan Foster, Niobrara National Scenic River; Stephen Wilson, Missouri National 

Recreational River; Kara Paintner and staff, Northern Great Plains Inventory and Monitoring 

Network; Cody Wienk, Midwest Regional Office; and Bill Hanson and Rick Inglis, Water 

Resources Division. We also thank the following external reviewers: Amy Symstad, Northern 

Prairie Wildlife Research Center, U.S. Geological Survey; Ronald Zelt, Nebraska Water Science 

Center, U.S. Geological Survey; Esther Stroh, Columbia Environmental Research Center, U.S. 

Geological Survey; Mary Bomberger Brown, Tern and Plover Partnership, University of 

Nebraska; Rich Schneider, Steve Schainost, Mike Fritz, and Gerry Steinauer, Nebraska Game 

and Parks Commission; and Jim Luchsinger, Niobrara Valley Preserve, The Nature 

Conservancy. 

1

Introduction 

In response to increasing threats to the biological integrity of national parks, the U.S. Congress 

passed legislation in 2003 (Fiscal Year 2003 Appropriations Act) that instructed the National 

Park Service to assess environmental conditions in watersheds where park units are located. In 

response to this legislation, the Water Resources Division of the National Park Service initiated a 

multi-year program to fund natural resource condition assessments for each of the 270 park units 

with significant natural resources. These condition assessments synthesize existing research and 

inventory and monitoring data into a knowledge base for use in park resource planning, decision 

making, accountability reporting, and partnership and education efforts. Condition assessments 

answer this important question: what does the best available science say about overall condition 

of important park natural resources? 

Each condition assessment results in a written report and maps that 

• Characterize park natural resources within a larger ecosystem context; 

• Convey resource condition status for a set of individual indicators as well as overall 

conditions by watershed, habitat types, or park management zones; 

• Highlight data and knowledge gaps, and resource condition threats; 

• Describe resources considered most at-risk; 

• Recommend effective resource management strategies. 

Condition assessments are likely to contribute to 

• Strategies and priorities for a park’s resource management program; 

• Watershed or landscape scale partnership/education efforts; 

• Mid to long-term park planning efforts including a General Management Plan and 

Resource Stewardship Strategy; 

• Department of Interior “land health” goals and Office of the Management and Budget 

“natural resource condition” scorecards. 

The condition of natural resources at Niobrara National Scenic River (referred to as “scenic 

river”) is assessed based on a synthesis of preexisting data (i.e., data available before December 

2009) identified in a review of the natural resource literature about the scenic river, the Niobrara 

Valley Preserve, Fort Niobrara National Wildlife Refuge, Nebraska state parks, and to a lesser 

extent, other national park units in the northern Great Plains. Interviews with scientists, 

inventory and monitoring specialists, and resource managers provided information not recorded 

in the literature. No new field data were collected for this condition assessment. This 

assessment uses a scorecard approach to present the condition of major habitats in the scenic 

river that is similar in approach and format to the State of the Parks reports for Canadian 

National Parks (Dobbie et al. 2006). Scorecards are a status assessment tool that reflect where a 

site or project is at a particular point in time and provide easy to understand feedback for 

management decisions (Stem et al. 2005). 

This condition assessment includes five major sections: 
2

Ecological Context: This section includes a brief administrative history and management goals 

for the scenic river and provides an overview of its natural resources in the context of the central 

Niobrara River Valley. 

Natural Resource Condition: This section describes the scorecard approach used to assess the 

condition of the major habitats in the scenic river. It identifies habitat indicators and associated 

measures and establishes reference and existing values for those measures. It provides a 

synthesis of existing information for each indicator and, when data are adequate, assigns a 

condition score and trend that is based on a comparison of the values of reference and existing 

measures. 

Stressors and Management Strategies: This section identifies the stressors emerging from the 

condition assessment and proposes management strategies to deal with these stressors. 

Conclusion: This section determines an overall condition and trend score for each habitat and 

discusses the rational for assigning that score. 

Appendices A and B: Appendix A includes a summary of sampling method and data analysis for 

each indicator and Appendix B describes GIS file structure and products. 
3

Ecological Context 

Physical Setting 

History, Location, and Management Direction 

In 1991, Public Law 102-50, the Niobrara National Scenic River Designation Act, amended 

section 3(a) of the Wild and Scenic Rivers Act of 1968 to designate portions of the Niobrara 

River in Nebraska as a unit of the national Wild and Scenic Rivers System. The purpose of the 

Wild and Scenic Rivers Act is to protect selected American rivers and their adjacent terrestrial 

environments for the benefit and enjoyment of the American people. The segment of the scenic 

river located within the Fort Niobrara National Wildlife Refuge is managed by the U.S. Fish and 

Wildlife Service; the remainder is managed by the National Park Service as a unit of the National 

Park System. 

The 122-km (76-mile) long scenic river is located in rural, north-central Nebraska and 

encompasses 9,338 ha (23,074 acres) (Fig.1). It is bounded on the north by plains and dissected 

plains and on the south by the Nebraska Sand Hills (Sand Hills is presented as two words as used 

in An Atlas of the Sand Hills, Ann Bleed and Charles Flowerday, editors, 1990). Valentine, 

Nebraska (population 2,820), is the largest town in the region. Access to the scenic river is by 

Nebraska State Highway 12 and U.S. Highway 20 which generally parallel the Niobrara River to 

the north and south, respectively, and by Nebraska State Highways 183, 7, and 137 and other 

unpaved roads which generally lie perpendicular to the Niobrara River. Fourteen bridges cross 

the Niobrara River within the scenic river boundaries (Fig. 2). 

Figure 1. The location of Niobrara National Scenic River in Nebraska. 
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5

Climate and Microclimate 

The central Niobrara River Valley, the region encompassing the scenic river, has an 

intercontinental climate typical of the Great Plains (Rosenberg 1986). Average annual 

precipitation is about 51 cm (20 in) with 75 percent falling as rain during the growing season 

from April to September. Winter precipitation is usually snow with an average annual 

accumulation of 94 cm (37 in). Average monthly temperature ranges from -5°C (23°F) in 

January to 24°C (75°F) in July. Winds ranging from 8–24 kmph (5–15 mph) are common 

throughout the year and are generally out of the north in the winter and out of the south in the 

summer. 

On north-facing slopes along the scenic river, water underlying the Sand Hills migrates along the 

relatively impervious Rosebud Formation to emerge in side canyons and valleys known as 

“spring branch canyons.” The microclimate in the spring branches is significantly cooler than 

the surrounding landscape (Steuter and Steinauer 1993) (Table 1). 

The Palmer Drought Severity Index for the Sand Hills shows the high variability of moisture 

conditions in the region including the long-term drought episodes in the 1930s and mid-1950s 

(Istanbulluoglu 2008) (Fig. 3). Long-term weather data for Nebraska indicates an increase in 

precipitation up to 10 percent has occurred for most of the state except the far west (U.S. 

Environmental Protection Agency 1998) (Fig. 4). By 2100, precipitation in eastern and central 

Nebraska could increase by an additional 10 percent (with a range of 5–20 percent) in spring, 

summer, and fall, and 15 percent in winter (with a range of 5–20 percent). Temperatures could 

increase by 1.6°C (3°F) in spring and summer and 2.2°C (4°F) in fall and winter (U.S. 

Environmental Protection Agency 1998). 

Table 1. Average increase in near surface maximum temperature (°C) in associated habitats compared to 

paper birch stands in spring branch canyons in the summer of 1986 (Source: Steuter and Steinauer 

1993). 

Date Associated habitats

Prairie Pine/Oak Deciduous forest 

6/27 5.0* 4.8* 1.2 

7/4 8.0* 5.8* 2.0 

7/7 5.4* 4.4* 2.4 

7/10 8.6* 2.8* 1.4 

7/17 11.4* 6.0* 1.2 

7/22 9.0* 3.6* 1.4 

8/4 9.2* 8.8* 3.2 

8/13 8.0* 4.6* 2.8*

8/15 9.6* 6.4* 3.0*

8/28 8.0* 8.0* 3.4*

*

indicates a significant (P≤0.05) difference compared to birch stands (ANOVA, Tukey’s test) 
6

Figure 3. NOAA-PDSI calculated for the instrumented past, representing the spatially averaged 

conditions in the panhandle and north-central climatic regions of Nebraska (Source: Istanbulluoglu 2008). 

Figure 4. Precipitation trends from 1900 to present (Source: U. S. Environmental Protection Agency 

1998). 

Air Quality 

The scenic river is a class II air quality area under the Clean Air Act. Air quality is not 

monitored in the scenic river or in the central Niobrara River Valley region but has been 

estimated for several parameters based on regional air quality monitoring data 

(http://www.nature.nps.gov/air/Maps/Air/atlas/IM_materials.cfm). Air quality is generally good 

but with significant concern over nitrogen deposition (Table 2). 

 
7

Table 2. Air quality condition interpolation values, 2003–2007, Niobrara National Scenic River (Source: 

National Park Service 2007). 

 

Ozone Atmospheric 

Deposition 

Atmospheric 

Deposition Visibility Condition 

(ppb) 

4th Highest 

8-Hour 

(kg/ha/yr) 

Total-N Wet 

Deposition 

(kg/ha/yr) 

Total-S Wet 

Deposition 

(DV) 

Visibility Group 50 

Minus Natural 

Conditions 

66.34 4.22 1.51 7.83 

Moderate Concern Significant Concern Moderate Concern Moderate Concern 

Topography and Geology 

The topography of the scenic river is varied and ranges from 549 to 792 m (1,801 to 2,598 ft) 

above sea level (Mason 2005, U.S. Department of Interior 2006). East of Valentine, the 

Niobrara River is entrenched from 46 to 107 m (151 to 351 ft) below the uplands to the north and 

south. High terraces lie at different levels above the river channel and below the general level of 

the uplands. Steep valley sides or breaks occur on both sides of the river and along the lower 

course of its tributaries. The valley floor widens considerably as the river flows east of County 

Line Bridge and widens more east of Meadville. 

The geologic framework of the upper scenic river (i.e., middle Niobrara River Valley) consists of 

four formations (Diffendal and Voorhies 1994) (Fig. 5). The Rosebud Formation is the bedrock 

of the Niobrara River channel, lower valley walls, and lower courses of its major tributaries. On 

the north side of the river, the Valentine Formation of sandy stream deposits overlies the 

Rosebud and forms gentle slopes. The Ash Hollow formation is hard, sandy deposits with layers 

of volcanic ash which forms a caprock on the north rim of the valley. On the south side of the 

valley, Eolian Sands rest on the Rosebud Formation and are the stabilized dunes of Pleistocene 

and Holocene ages. The lower scenic river is characterized by a broad valley, with the river 

flowing over a thick layer of Pierre Shale (Diffendal and Voorhies 1994). 

Soils 

Within the Niobrara River Valley, Sarpy (loamy fine sand) soils occur on bottomland along the 

river and its tributaries while Tripp (fine sandy loam) soils are generally found on the terraces. 

Little soil development exists on rough broken land and steep bluffs (Layton 1956). 
8

Figure 5. Cross-section view of the middle Niobrara River Valley (Source: Johnsgard 2007). 

Watershed and Hydrology 

The Niobrara River begins near Lusk, Wyoming, and flows some 861 kilometers (535 miles) 

across north-central Nebraska to its confluence with the Missouri River at the town of Niobrara 

(Istanbulluoglu 2008) (Fig. 6). Major tributaries include the Snake River, Minnechaduza Creek, 

Keya Paha River, and Long Pine Creek. The Niobrara River is primarily a groundwater-fed 

stream that drains approximately 19,312 km2 (7,456 mi2) of basin area (Istanbulluoglu 2008). 

The Nebraska Sand Hills play a dominant role in the hydrology of the Niobrara and Snake Rivers 

as the primary groundwater source (Bentall and Shaffer 1979). The word “Niobrara” means 

“running water” in the Dakota language and is descriptive of the river’s constant year-around 

flow averaging about 236 m3

 (8,334 ft3) per second. Four structures, Mirage Flats Project, 

Merrit Dam and Reservoir, Cornell Dam, and Spencer Dam either dam and/or divert water from 

the Niobrara River (Fig. 7). One of these, Cornell Dam, is located within the Fort Niobrara 

National Wildlife Refuge. 

In the western portion of the scenic river, the Niobrara is confined to a single channel with few 

islands (Johnsgard 2007). East of County Line Bridge, the valley widens and the river spreads 

into multiple meandering channels with numerous sandbars. Primarily in the entrenched portion 

of the scenic river numerous waterfalls occur on the tributary creeks that drain groundwater from 

the Sand Hills (Mason 2005). The highest is Smith Falls, which drops 19 m (63 feet) into the 

river valley. The Niobrara is unique as a prairie river because for most of its middle section, its 

channel flows directly over bedrock, producing areas of riffles and rapids (Johnsgard 2007). 
9

Figure 6. Niobrara River watershed. 

Figure 7. Dams on the Niobrara River and tributaries (Note: Cornell Dam is not shown. The reservoir 

behind the dam is completely filled with silt and provides no water storage) (Source: Istanbulluoglu 2008). 
10

Water Quality 

Water quality in the region is generally good, with some impacts from human activities such as 

recreation and agriculture (National Park Service 1995). During the years 1947 to 1994, 50 

water quality monitoring stations in and around the scenic river provided baseline information 

for 281 different water quality parameters (National Park Service 1995). Ten stations are in the 

boundaries of the scenic river, five of which provide long-term records. A review of these 

historical records identified several water quality concerns. A small number (1.2 percent) of pH 

readings were found to be outside pH screening criteria for aquatic life uses. In addition, 5.5 

percent of turbidity values, 32 percent of fecal coliform values, 20 percent of E. coli values, 0.3 

percent of dissolved fluoride values, 4.5 percent of beryllium values, 8.5 percent of copper 

values, and 8.3 percent of lead values exceeded water quality screening criteria utilized by the 

Water Resources Division, NPS (Troelstrup 2006). In 2001, the scenic river started collecting 

water samples at major bridge crossings on the Niobrara River and from tributaries. Those 

samples have also suggested good water quality (National Park Service, P. Sprenkle, natural 

resource specialist, personal communication, 22 June 2009). 

Biological Setting 

Vegetation 

Five hundred and eighty-one species of vascular plants are known from the central Niobrara 

River region, about one-third of the Nebraska flora (Churchill et al. 1988). South of the river 

valley, dune sands support Nebraska Sand Hills prairie with dominant grasses such as sand 

bluestem (Andropogon hallii) and prairie sandreed (Calamovilfa longifolia) (Pool 1914) (Fig. 5). 

Along the south slopes of the valley permanently flowing springs and seeps produce a moist 

forest habitat dominated by eastern deciduous trees including green ash (Fraxinus 

pennsylvanica), basswood (Tilia americana), and ironwood (Ostrya virginiana) (Tolstead 1942). 

In some sheltered spring branch canyons around tributary streams, paper birch (Betula 

papyrifera), hybrid aspen (Populus tremuloides x P. grandidentata) and associated ferns and 

club mosses are relicts of the Pleistocene ice age (Johnsgard 2007). Small patches of tallgrass 

prairie are found on the river bottoms. Characteristic tall grasses include big bluestem 

(Andropogon gerardii), switchgrass (Panicum virgatum), and indiangrass (Sorghastrum nutans). 

On the north side of the valley, mixed-grass prairie, dominated by little bluestem (Schizachyrium 

scoparium) and western wheatgrass (Pascopyrum smithii), covers the river terraces and the 

rolling uplands. Ponderosa pine (Pinus ponderosa) occurs primarily on the canyon slopes. 

Ponderosa pine is also found south of the river on steep slopes and cliffs and has invaded sandy 

upland sites. The central Niobrara River Valley is the eastern-most extent of the ponderosa pine 

community in the Great Plains (Johnsgard 2007). 

Several highly aggressive, exotic plants are known from the region including purple loosestrife 

(Lythrum salicaria), leafy spurge (Euphorbia esula), Canada thistle (Cirsium arvense), spotted 

knapweed (Centaurea maculosa), and non-native common reed (Phragmites australis australis). 

These species tend to partially or completely replace native plant communities. In addition, salt 

cedar (Tamarix ramosissima and T. parvifora), a shrub or small tree that has clogged and 

dewatered streams in western Nebraska, may pose the potential for similar ecological damage in 

the Niobrara River Valley (Johnsgard 2007). 
11

Mammals 

The diverse habitats of the central Niobrara River Valley support over forty species of mammals 

(Bogan 1997). The largest number of species are found in upland prairie followed by riparian 

forest (Johnsgard 2007) (Table 3). Bison (Bison bison) and elk (Cervus elaphus), extirpated in 

Nebraska in the late 1800s, were reintroduced (bison) or extended their range (elk) into the area 

by the mid-1900s. Both white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) 

occur in the region, but in recent years, white-tailed deer have moved farther west replacing the 

more open-habitat, smaller, and less adaptable mule deer (Johnsgard 2007). Most predators were 

extirpated by the early 1900s but coyotes (Canis latrans) persist and are widespread. The 

mountain lion (Felix concolor) was extirpated from Nebraska by 1900 but several confirmed 

sightings in the Niobrara River Valley suggest a resident population may exist in the area 

(Nebraska Game and Parks Commission 2009a). The most biogeographically significant 

mammals are the eastern woodrat (Neotoma floridana baileyi), which occurs in the scenic river 

as a subspecies disjunct by 190 km (118 miles) from other subspecies, and the bog lemming 

(Synaptomys sp.), a Pleistocene relict now mostly found farther to the north and east (Johnsgard 

2007). 

Table 3. Ecological associations of mammals in the central Niobrara River Valley (Source: Johnsgard 

2007). 

Species Upland 

prairie 

Rock 

outcrop

Pine 

woods

Scrub 

thicket

Riparian 

forest

Dry 

meadow

Wet 

meadow

Swamp Riparian 

edge

Masked shrew x x 

Hayden’s shrew x 

Northern shorttailed shrewx x x x 

Eastern mole x x x 

Eastern 

cottontail

x x x x 

Black-tailed 

jackrabbit 

x 

White-tailed 

jackrabbit 

x x x 

Black-tailed 

prairie dog 

x 

Thirteen-lined 

ground squirrel 

x 

Spotted ground 

squirrel 

x x 

Fox squirrel x x 

Plains pocket 

gopher 

x 

Olive-backed 

pocket mouse 

x 

Silky pocket 

mouse 

x 

Hispid pocket 

mouse 

x x x 

Ord’s kangaroo 

rat 

x 

Beaver x 

Plains harvest 

mouse 

x 
12

Table 3. Ecological associations of mammals in the central Niobrara River Valley (continued) (Source: 

Johnsgard 2007). 

Species Upland 

prairie 

Rock 

outcrop 

Pine 

woods 

Scrub 

thicket 

Riparian 

forest 

Dry 

meadow 

Wet 

meadow 

Swamp Riparian 

edge 

White-footed 

mouse 

x x x 

Deer mouse x x x x x x 

Grasshopper 

mouse 

x 

Prairie vole x x 

Meadow vole x x x 

Muskrat x 

Meadow 

jumping 

mouse 

x x 

Porcupine x 

Coyote x x x x x 

Raccoon x x x x 

Long-tailed 

weasel 

x x x x x x 

Least weasel x x x 

Mink x x x 

Striped skunk x x x 

Spotted skunk x x x 

Badger x 

Bobcat x x x x x 

Elk x x x x x 

Mule deer x x x 

White-tailed 

deer 

x x x 

Pronghorn x 

Bison x x 

Birds 

A total of 185 species of birds are known or believed to breed in the central Niobrara River 

Valley, which represents about 90 percent of the Nebraska breeding avifauna (Ducey 1989, 

Johnsgard 2007). These species occupy wetlands (23 percent), forests (22 percent), open woods 

or woody edges (20 percent), grasslands and old fields (19 percent), shrublands (five percent), 

urban (four percent), bank or cliff (four percent), and river shorelines or sandbars (three percent) 

(Johnsgard 2007) (Table 4). Birds found in the riparian floodplain forest are predominantly 

eastern or northeastern species including whip-poor-will (Caprimulgus vociferus), eastern 

phoebe (Sayornis phoebe), eastern wood-pewee (Contopus virens), eastern bluebird (Sialia 

sialis), wood thrush (Hylocichla mustelina), yellow-throated vireo (Vireo flavifrons), ovenbird 

(Seiurus aurocapilla), black-and-white warbler (Mniotilta varia), and scarlet tanager (Piranga 

olivacea). In the ponderosa pine stands on the north side of the river valley, western birds such 

as the black-billed magpie (Pica hudsonia) associate with more northern species such as the redbreasted nuthatch (Sitta canadensis) and red crossbill (Loxia curvirostra). Upland prairie species 

whose breeding ranges center on the Great Plains and that commonly breed in the central 

Niobrara River Valley include Swainson’s hawk (Buteo swainsoni) and lark bunting 

(Calamospiza melanocorys). In the central Niobrara River Valley, the range of the western and 

northern-oriented sharp-tailed grouse (Tympanuchus phasianellus) overlaps with the easternoriented greater prairie-chicken (Tympanuchus cupido) (Johnsgard 2007). 
13

Table 4. Ecological associations of typical breeding birds of the central Niobrara River Valley (Source: 

Johnsgard 2007, Nebraska Game and Parks Commission, J. Jorgensen, non-game program manager, 

personal communication, 3 November, 2009). 

Species Upland 

prairie

Rock 

outcrop

Pine 

woods

Scrub 

thicket

Riparian 

forest

Dry 

meadow

Wet 

meadow

Swamp Riparian 

edge

Total reported 

species

18 6 11 28 37 14 8 7 14 

Characteristic species

Long-billed 

curlew

B J 

Lark bunting B 

Western 

meadowlark

J J 

Eastern 

meadowlark

J 

Chestnutcollared 

longspur

B J 

Rock wren B 

Red-tailed 

hawk

J J B J 

Prairie falcon J J B 

Say’s phoebe J 

Black-headed 

grosbeak

B J 

Rose-breasted 

grosbeak

 J 

Indigo bunting J 

Lazuli bunting J 

Bell’s vireo J 

Red-breasted 

nuthatch

 J 

White-breasted 

nuthatch 

J 

Loggerhead 

shrike 

 B 

Spotted 

towhee 

B 

Eastern woodpewee  J 

Red-headed 

woodpecker 

B 

Hairy 

woodpecker 

 B 

Downy 

woodpecker 

B 

Eastern 

kingbird 

 B 

American crow J B 

Black-capped 

chickadee 

B 

House wren B 

Black-andwhite warbler B 

Yellow warbler B 
14

Table 4. Ecological associations of typical breeding birds of the central Niobrara River Valley (continued) 

(Source: Johnsgard 2007, Nebraska Game and Parks Commission, J. Jorgensen, non-game program 

manager, personal communication, 3 November, 2009). 

Species Upland 

prairie

Rock 

outcrop

Pine 

woods

Scrub 

thicket

Riparian 

forest

Dry 

meadow

Wet 

meadow

Swamp Riparian 

edge

Common 

yellowthroat 

B 

Orchard oriole B 

Baltimore oriole B 

Common grackle J B 

Upland sandpiper B 

Black-crowned 

night heron 

J B 

Mallard J B 

Blue-winged teal J B 

Wood duck B B 

Spotted sandpiper B 

Least tern J 

Piping plover J 

Belted kingfisher B 

Note: Characteristic species shown with the letter B are those that Beed (1936) regarded as unique to 

that single community type. The ruddy duck, northern shoveler, American coot, least tern, and black tern 

have been excluded as not typical of most Niobrara riparian habitat. Where the letter J appears it refers 

to additional species or additional typical habitats as judged by Johnsgard (2007) and by Ducey (1989). 

Reptiles and Amphibians 

During 2003 and 2004, 22 species of reptiles and amphibians were found near bridges in the 

lower portion of the scenic river (Fogell and Cunningham 2005) (Table 5) and an additional 

seven species were previously collected in or near the scenic river (Lynch 1985). Species 

recorded in the central Niobrara River Valley and associated wetlands include Blanchard’s 

cricket frog (Acris crepitans blanchardi), western chorus frog (Pseudacris triseriata), bull frog 

(Rana catesbeiana), northern leopard frog (Rana pipiens), common snapping turtle (Chelydra 

serpentina), and painted turtle (Chrysemys picta) (Johnsgard 2007). Species found in association 

with drier habitats include plains spadefoot toad (Spea bombifrons), ornate box turtle (Terrapene 

ornata), pale milk snake (Lampropeltis triangulum), prairie rattlesnake (Crotalus viridis), and 

six-lined racerunner (Cnemidophorus sexlineatus viridis). 

Table 5. Expected, encountered, and previously documented reptile and amphibian species in the 

Niobrara National Scenic River (Source: Fogell and Cunningham 2005). 

Common name Scientific name Expected Found Previously 

documented

Blanding’s turtle Emydoidea blandingii Y N Y 

Bullfrog Rana catesbeiana Y Y Y 

Common garter 

snake

Thamnophis sirtalis Y Y Y 

Common snapping 

turtle

Chelydra serpentina Y Y Y 

Eastern fence lizard Sceloporus consobrinus Y Y Y 
15

Table 5. Expected, encountered, and previously documented reptile and amphibian species in the 

Niobrara National Scenic River (continued) (Source: Fogell and Cunningham 2005). 

Common name Scientific name Expected Found Previously 

documented

Eastern hognose 

snake

Heterodon platyrhihos Y N Y 

Great Plains toad Bufo cognatus Y Y Y 

Lesser earless lizard Holbrookia maculata Y Y Y 

Many-lined skink Eumeces multivirgatus Y N Y 

Milk snake Lampropeltis triangulum Y Y Y 

Northern cricket frog Acris crepitans Y Y Y 

Northern leopard 

frog

Rana pipiens Y Y Y 

Northern water 

snake

Nerodia sipedon Y N Y 

Ornate box turtle Terrapene ornata Y Y Y 

Painted turtle Chrysemys picta Y Y Y 

Plains garter snake Thamnophis radix Y Y Y 

Plains leopard frog Rana blairi Y Y N 

Plains spadefoot 

toad 

Spea bombifrons Y Y Y 

Prairie rattlesnake Crotalus viridis Y Y Y 

Racer Coluber constrictor Y Y Y 

Ringneck snake Diadophis punctatus Y Y N 

Six-lined racerunner Cnemidophorus 

sexlineatus 

Y Y Y 

Smooth green 

snake 

Liochlorophis vernalis Y N Y 

Smooth softshell 

turtle 

Apalone mutica Y N N 

Spiny softshell turtle Apalone spinifera Y N Y 

Tiger salamander Ambystoma tigrinum Y N Y 

Western chorus frog Pseudacris triseriata Y Y Y 

Western fox snake Elaphe vulpina Y N N 

Western hognose 

snake 

Heterodon nasicus Y Y Y 

Woodhouse’s toad Bufo woodhousii Y Y Y 

Total 

found/expected 

 = 22/31 (71%) 

Fishes 

More than 68 fish species are found in the Niobrara River drainage (Schainost 2008) including 

30 species that have been reported in the central Niobrara River Valley which encompasses the 

scenic portion of the river. A recent (2003–2005) study of fish composition in the scenic portion 

of the river and its tributaries found 27 species of fish at 18 sites (Dietsch 2008) (Table 6, Fig. 8). 

The greatest number of unique species (17) was found at a site on the Niobrara River upstream 

from Smith Falls; however, the overall species richness was greater at sites downstream from 
16

Norden Bridge (Dietsch 2008). The distribution and occurrence of these species varied along 

the river. Species such as the red shiner (Cyprinella lutrensis), sand shiner (Notropis 

stramineus), and bigmouth shiner (Notropis dorsalis) were numerous and widespread throughout 

the river. Long-nose dace were present at most sites, but generally found in higher numbers at 

sites upstream from Norden Bridge, and carpsuckers were confined to sites downstream of the 

bridge. Some native (brook stickleback [Culaea inconstans], plains topminnow [Fundulus 

sciadicus], western silvery minnow [Hybognathus argyritis]) and non-native species (brown 

trout [Salmo trutta], rainbow trout [Oncorhynchus mykiss]) were limited to just a few sites. 

Game fish such as largemouth bass (Micropterus salmoides), green sunfish (Lepomis Cyanellus), 

bluegill (Lepomis macrochirus), and channel catfish (Ictalurus punctatus) were found throughout 

the river, but were more commonly found downstream from Norden Bridge. 

Figure 8. Fish observation sites in the Niobrara River and tributaries (Source: Dietsch 2008). 
17

Table 6. Fish species collected using electroshocking and seining techniques at selected sites in 

the Niobrara River and tributaries (Source: Dietsch 2008). 

Site Description Species Identified 

Niobrara R below Borman Bridge near 

Valentine, NE 

BMS, BKT, CCF, CCA, GP, LND, NP, 

RSH, SSH, SRH, STC, WSK 

 Tributary below Borman Bridge BKS, PTM 

Niobrara Mainstem above Cornell Dam BMS, BKT, FHM, GP, LND, NP, RSH, 

SSH, SRH, WSK 

 Minnechaduza Creek CCH, LMB, LND, SRH, STC, WSK 

Tributary downstream from Refuge BridgeTributary 2 None 

 Niobrara Mainstem just upstream from Fort 

Falls 

BMS, CCA, CCH, GSF, LND, RSH, 

SSH, SRH, STC, WSK 

Big Beaver Creek BM, CCH, FHM, LND 

 Crooked Creek CCH, LND 

Kewanee Creek None 

 Niobrara Mainstem 1 1⁄2 miles upstream from 

Smith Falls 

BMS, BM, CCA, CCH, FHM, GP, LMB, 

LND, MC, NP, RSH, SRH, STC, WSV, 

WSK, YWP 

Smith Falls RBT 

 Unnamed Tributary 3 None 

Long Pine Creek BMS, BM, BKT, CCH, FHM, LMB, LND, 

RSH, SSH, SRH, STC, WSK, FHC, BLG, 

RCS, QCS 

 Laughing Water Creek BKT, LND, RSH 

Niobrara Mainstem below Meadville Bridge BMS, BM, CCF, CCH, FHM, LMB, LND, 

PTM, RSH, SSH, SRH, STC, WSK, FHC, 

BLG, RCS, QCS 

 Plum Creek BMS, BM, CCH, FHM, GSF, LMB, LND, 

PTM, RSH, SSH, SRH, WSK, BLG, RCS 

Niobrara River upstream from Carns Bridge BMS, BM, CCF, CCA, CCH, FHM, LMB, 

RSH, SSH, SRH, STC, WSK, FHC, RCS, 

QCS 

 Niobrara River downstream of Eglehoff rapids BMS, CCH, FHM, GSF, LMB, LND, RSH, 

SSH, SRH, STC, WSK 

Note: BLG, bluegill; BMS, bigmouth shiner; BM, brassy minnow; BKS, brook stickleback; BKT, brown 

trout; CCF, channel catfish; CCA, common carp; CCH, creek chub; FHC, flathead chub; FHM, fathead 

minnow; GP, grass pickerel; GSF, green sunfish; LMB, largemouth bass; LND, longnose dace; MC, mirror 

carp; NP, northern pike; PTM, plains top minnow; QCS, quillback carpsucker, RBT, rainbow trout; RCS, 

river carpsucker; RSH, red shiner; SSH, sand shiner; SRH, shorthead redhorse; STC, stone cat; WSV, 

western silvery minnow; WSK, white sucker; YWP, yellow perch 
18

Invertebrates

Invertebrate species are largely unknown in the central Niobrara River Valley except for the 

dragonflies and damselflies, butterflies and skippers, and mollusks (Johnsgard 2007). Forty-five 

species of dragonflies and damselflies have been reported in or near the Niobrara River Valley 

and are nearly equally divided between eastern and western geographic affinities (Johnsgard 

2007). The butterflies and skippers of the Niobrara Valley Preserve include 148 species, more 

than 70 percent of the species of butterflies reported for the state of Nebraska and more than 90 

percent of the 177 total species known from South Dakota (Dankert and Nagel 1988, Marrone 

2002). A high proportion of these species are of widespread distribution (Johnsgard 2007). 

During a 1992 to 1996 inventory of molluscs at 20 sites on the Niobrara River or tributary 

streams, only two species of clams (Anodonta grandis grandis and Stophitus undulates) were 

collected at two sites (Freeman and Perkins 1997). 

Listed Species 

No federally-listed endangered or threatened plants are known from the scenic river (U.S. 

Department of Interior 2006). The small white lady’s-slipper orchid (Cypripedium candidum ), a 

State of Nebraska At-risk species, occurs in the central Niobrara River Valley (Schneider et al. 

2005). Its status in the scenic river is not known. 

 

In terms of animals, the federally-listed interior populations of the least tern (Sternula antillarum

athalassos) and piping plover (Charadrius melodus) nest in the lower reaches of the Niobrara 

River including a portion of the scenic river (Adolf et al. 1998). Whooping cranes (Grus 

americana) rest and feed along the central Niobrara River Valley for short periods during their 

spring and fall migrations (Johnsgard 2007). The river otter (Lontra canadensis), a state 

threatened species, has expanded its range in Nebraska following reintroductions in the 1980s 

and is now occasionally seen in the scenic river (Johnsgard 2007, Nebraska Game and Parks 

Commission 2009). Three cool-water fishes that inhabit tributaries of the middle Niobrara River 

are state-listed as either state endangered (blacknose shiner [Notropis heterolepsis]) or state 

threatened (finescale dace [Phoxinus neogaeus] and northern redbelly dace [P. eos]). Two 

skippers (Iowa [Atrytone arogos iowa] and Ottoe [Hesperia ottoe]) and the regal fritillary 

butterfly (Speyeria idalia), At-risk species in Nebraska, are known from the middle Niobrara 

River Valley and may occur in the scenic river (Johnsgard 2007). 

Land and Visitor Use 

Cattle ranching is the dominant land use in the more arid western portion of the Niobrara River 

watershed, whereas row-crop agriculture dominates in the eastern portion. The town of 

Valentine is located at the western end of the scenic river and has an active tourism industry 

which is focused on river use. The upper reach of the Niobrara River is noted as one of the 

country's outstanding rivers for floating and is enjoyed by thousands of canoeists and tubers 

annually (Shultz 2009) (Fig. 9). A portion of the river flows through a federally designated 

wilderness in the Fort Niobrara National Wildlife Refuge (U.S. Department of Interior 2006). 

Hunting, fishing, and trapping also occur within the scenic river boundary although access is 

often limited by private landowners (U.S. Department of Interior 2006). 
19

Figure 9. Number of floaters per year, 1993–2008, Niobrara National Scenic River (Source: Shultz 2009). 

Important Natural Resources 

Important natural resources of the scenic river were identified from the discussions of 

Outstanding Remarkable Values in the final General Management Plan (U.S. Department of 

Interior 2006). They follow: 

Niobrara River water quantity and quality 

The Niobrara River is primarily a groundwater-fed stream and has fairly stable flow throughout 

the year (Istanbulluoglu 2008). Dams constructed to generate power and to hold and divert water 

for irrigation may impact stream flow, especially in groundwater driven streams such as the 

Niobrara (Istanbulluoglu 2008). Although water use from the Niobrara River began in the 

1940s, a very significant increase in annual diversion began in 1965. This has resulted in a 

decline in annual runoff and a decline in mean daily flows in all months except January 

(Istanbulluoglu 2008). The State of Nebraska has designated the Niobrara River as a Class A 

State Resource Water. Water quality degradation which would adversely affect existing use is 

not allowed (Nebraska Department of Environmental Quality 2009). This designation also 

extends to the tributaries of the river. 

Tributary springs and waterfalls 

Over 230 waterfalls exist on the southern spring branch tributaries of the Niobrara River along a 

48-km (30-mile) section of the scenic river (Mason 2005). The spring branch tributaries are 

groundwater fed from the adjacent Sand Hills and form waterfalls as they erode to the resistant 

Rosebud Formation. Many of these waterfalls are convex and buttressed, a morphology highly 

unusual in North America (Mason 2005) (Fig. 10). 

25,000

30,000

35,000

40,000

45,000

50,000

1993 2001 2002 2003 2004 2005 2006 2007 2008

Year

# of Floaters per Year
20

Figure 10. Tributary waterfall in the Niobrara National Scenic River (photo by National Park Service). 

Diverse plant and animal communities including Pleistocene relicts 

The central Niobrara River Valley has unusually diverse plant and animal communities including 

species representative of northern boreal forest, eastern deciduous forest, Rocky Mountain 

coniferous forest, tallgrass prairie, Sand Hills prairie, and mixed-grass prairie (Johnsgard 2007) 

(Tables 7 and 8). This high diversity is primarily due to the river valley providing an unbroken 

east/west riparian corridor connecting the dryer shortgrass and mixed-grass prairies in the west 

with the more humid tallgrass prairie and eastern deciduous forest to the east (Kaul et al. 1988). 

Plants and animals have migrated along this corridor and intermingle in a transition zone 

centered on the scenic river. Several of the overlapping eastern and western species pairs of 

birds produce hybrids with new plumage patterns, songs, mate-selection behavior, and breeding 

adaptations (Johnsgard 2007) (Table 7). Also, as climate changed over geologic time, plants and 

animals typical of past colder conditions survived due to the cool and wet microclimate of the 

spring branch canyons (Kaul et al 1988) (Table 8). Paper birch and hybrid aspen, both boreal 

disjuncts, have declined in recent years possibly due to regional climate variations and the lack 

of disturbance, such as fire, that provides sites for seed germination (Steuter and Steinauer 1993, 

Stroh and Miller 2009). 

Table 7. Bird species of east-west biogeographic significance in the Niobrara River Valley (Source: 

Johnsgard 2007, Nebraska Game and Parks Commission, J. Jorgensen, non-game program manager, 

personal communication, 3 November, 2009). 

Eastern species Western species 

Northern bobwhite 

American woodcock 

Barred owl (eastern population) 

Whip-poor-will 

Chimney swift 

Red-bellied woodpecker 

Blue jay 

Great crested flycatcher 

Western grebe 

Clark’s grebe 

Eared grebe 

Cinnamon teal 

Ferruginous hawk* 

Prairie falcon* 

Golden eagle 

Merlin 
21

Table 7. Bird species of east-west biogeographic significance in the Niobrara River Valley (continued) 

(Source: Johnsgard 2007, Nebraska Game and Parks Commission, J. Jorgensen, non-game program 

manager, personal communication, 3 November, 2009). 

Eastern species Western species 

Red eyed vireo 

Purple martin 

Blue-gray gnatcatcher 

Wood thrush 

Brown thrasher 

Black-and-white warbler 

American redstart 

Ovenbird 

Northern cardinal (eastern population) 

Orchard oriole 

Red-headed woodpecker 

Greater prairie chicken 

Eastern wood pewee 

Eastern phoebe 

Scarlet tanager 

Eastern towhee 

Rose-breasted grosbeak 

Indigo bunting 

Eastern meadowlark 

Baltimore oriole 

Long-billed curlew* 

Willet 

Wilson’s phalarope 

Common poorwill 

Black-billed magpie 

Violet-green swallow 

Pygmy nuthatch 

Rock wren 

Townsend’s solitaire 

Yellow-rumped warbler 

Cassin’s sparrow* 

Brewer’s blackbird 

Sharp-tailed grouse 

Western wood pewee 

Say’s phoebe 

Western tanager 

Spotted towhee 

Black-beaded grosbeak 

Lazuli bunting 

Western meadowlark 

Bullock’s oriole 

Note: Closely related (congeneric) species pairs are shown by italics; species with strong Great Plains 

affinities are indicated by asterisks. 

Table 8. Mammals, reptiles, and amphibians of the east-west biogeographic significance in the Niobrara 

River Valley (Source: Johnsgard 2007). 

Eastern species Western species 

Mammals 

Northern short-tailed shrew 

Least shrew 

Eastern mole 

Evening bat 

Southern bog lemming 

Woodchuck 

Franklin’s ground squirrel 

White-footed mouse 

Meadow jumping mouse 

 Gray fox 

Northern myotis 

Eastern cottontail 

 White-tailed deer 

Merriam’s shrew 

Little brown myotis 

Townsend’s big-eared bat 

Bushy-tailed wood rat 

Least chipmunk 

Black-tailed prairie dog* 

Northern pocket gopher 

Plains pocket mouse* 

Olive-backed pocket mouse* 

Silky pocket mouse 

Swift fox (very rare)* 

Pronghorn (reestablished) 

Elk (reestablished) 

Bighorn sheep (reintroduced) 

Western small-footed myotis 

Desert cottontail 

Mule deer 
22

Table 8. Mammals, reptiles, and amphibians of the east-west biogeographic significance in the Niobrara 

River Valley (continued) (Source: Johnsgard 2007). 

Eastern species Western species 

Reptiles 

Blanding’s turtle 

Ornate box turtle 

Yellow mud turtle 

Ringneck snake 

Common (northern) watersna

Fox snake 

Smooth green snake 

Six-lined racerunner 

Eastern hognose snake 

Amphibians 

 Northern cricket frog 

 Plains leopard frog 

 Great Plains toad 

Wandering garter snake 

Prairie rattlesnake* 

Short-horned lizard 

Western hognose snake* 

Note: Closely related (congeneric) species pairs are shown by italics; species with ranges centered on 

the Great Plains are indicated by asterisks. 

Sandy shorelines, sandbars, and wetlands 

The lower portion of the scenic river is characterized by a broad flood plain with multiple 

meandering channels of the river. Sandy shorelines, unvegetated sandbars, and wetlands are 

common. Endangered whooping cranes are occasionally seen feeding and roosting along this 

reach of the river during both fall and spring migrations (Austin and Richert 2001). These 

sightings have become more common in recent years perhaps as the population of migrating 

birds has increased (Johnsgard 2007) or to heightened awareness of the species by the public. 

The endangered interior least tern and threatened piping plover feed and nest on unvegetated 

sandbars and sandy islands from the lower portion of the scenic river downstream to the 

confluence of the Niobrara and Missouri Rivers (Adolf et al. 1998). Both species nest in 

exposed habitats often losing their nests to floods, predation, or human disturbance. Exotic 

plants, especially purple loosestrife, have infested river shorelines and wetlands along the lower 

scenic river (Narumalani and Swain 2009).

 
23

Natural Resource Condition 

Condition Assessment Approach for Niobrara National Scenic River 

The major habitats in the scenic river, as adapted from Johnsgard (1995) and Ducey (1989), are 

Niobrara River and tributaries; upland forest and savanna; spring branch canyon and riparian 

forest; grassland; and sandy shorelines, sandbars, and wetlands. These habitat types provide the 

ecological framework for the assessment, and their condition and trend are assessed by a suite of 

biodiversity and process indicators (Table 9). Stressors affecting the condition and trend of these 

habitats are presented in Table 9, but they are discussed more fully in the section titled “Stressors 

and Management Strategies.” 

Table 9. Habitat indicators and stressors. 

Habitat Biodiversity indicator Process indicator Stressor

Niobrara River and 

tributaries

(36%)

• Aquatic 

macroinvertebrates 

• River otter 

• Cool-water fish 

• Fish community 

• Spiny softshell turtle 

• Stream flow • Water diversion and 

withdrawal 

• Water quality degradation 

• Visitor river floating 

• Purple loosestrife 

infestation 

Upland forest and 

savanna

(35%)

• Elk 

• Ponderosa pine 

• Land cover 

• Fire 

• Mountain pine beetle 

infestation (possible) 

• Woodland expansion (fire 

suppression) 

• Drought 

Spring branch 

canyon and 

riparian forest 

(10%)

• Paper birch 

• Hybrid aspen 

• Bailey’s eastern 

woodrat 

• Bird hybridization • Microclimate in birch 

stands 

• Spring branch hiking 

• Emerald ash borer 

infestation (possible) 

• Woodland expansion (fire 

suppression) 

• Drought 

Grassland

(8%)

• Grassland birds 

• Sand Hills prairie 

• Land cover 

• Fire 

• Woodland expansion (fire 

suppression) 

• Drought 

• Leafy spurge infestation 

Sandy shorelines, 

sandbars, and 

wetlands

(10%)

• Interior least tern 

and piping plover 

• Purple loosestrife 

• Whooping crane 

• Sediment 

transport 

• Purple loosestrife 

infestation 

• Common reed infestation 

Note: Habitat percentages are based on land cover interpretations. 
24

Vital signs (i.e., a subset of physical, chemical, and biological elements and processes of park 

ecosystems that represent the overall health or condition of park resources, see 

http://science.nature.nps/gov/im/monitor/glossary) of the scenic river that were identified in the 

Northern Great Plains Inventory and Monitoring Plan (Gitzen et al. 2009) are the basis for 13 of 

20 indicators used in this condition assessment (Table 10). The other seven indicators are 

included based on recommendations in natural resource inventories of the scenic river, recent 

research reports, proposed research, and policy or legal mandates (i.e., listed species) (Table 10). 

Indicators are organized by habitat and their condition assessed in the next section. 

For most indicators, one or more measures are identified and the existing values of these 

measures (i.e., existing conditions) are compared to reference conditions suggested by historical 

data, monitoring data from the scenic river or an environmentally similar area, or expert opinion 

(Table 11). Ideally, reference conditions should be based on the range of variation in natural 

ecosystems; but for the Niobrara River watershed, quantitative baselines that predate significant 

human disturbance do not exist except for pre-settlement fire histories. For five indicators, no 

condition assessment is possible due to inadequate, site-specific information. They are included 

to highlight rare or unique resources and important information needs. 

An indicator is considered in good condition when 50% or more of its measures have values that 

correspond with or fall within a range of reference values (see Dobbie et al. 2006). Conversely, 

an indicator is considered in poor condition when less than 50% of its measures have values that 

correspond with or fall within a range of reference values (see Dobbie et al. 2006). Trend is 

noted for an indicator that has a measure or measures with multiple year data that are similar 

(stable) or different (deteriorating or improving). Indicator condition is summarized by a red box 

(indicating poor), a green box (indicating good), or an open box (no assessment). Trend is 

indicated by a downward arrow (deteriorating), a horizontal arrow (stable), an upward arrow 

(improving), or no arrow (no trend or insufficient data). Details of each indicator assessed, 

including a summary of sampling method and data analysis, are available in Appendix A. A 

summary of GIS (Geographic Information Systems) products derived from indicator sources are 

available in Appendix B. 

Table 10. Indicators, corresponding vital signs, and primary information sources used in this condition 

assessment. 

Indicator Vital signa Information sourceb

Aquatic macroinvertebrates Aquatic macroinvertebrates Research 

River otter None Monitoring 

Cool-water fish None Monitoring 

Fish community None Monitoring 

Spiny softshell turtle None Proposed research 

Stream flow Surface water dynamics Gauge record 

Elk None Research 

Ponderosa pine Upland plant communities Research 

Land cover Land cover and use Satellite data 
25

Table 10. Indicators, corresponding vital signs, and primary information sources used in this condition 

assessment (continued). 

 

Indicator Vital signa Information sourceb

Fire Extreme disturbance Research 

Paper birch Riparian/floodplain plant 

communities 

Research 

Hybrid aspen Riparian/floodplain plant 

communities 

Assessments of stand health 

Bailey’s eastern woodrat None Research 

Bird hybridization Land birds Research 

Grassland birds Land birds Research 

Sand Hills prairie Upland plant communities Research 

Interior least tern and piping 

plover 

Interior least tern and piping 

plover 

Monitoring 

Purple loosestrife Treatment of exotic infestations Monitoring 

Whooping crane Land birds Monitoring 

Sediment transport None Research 

a Vital signs not included as indicators are Stream/River Channel Characteristics, Surface Water 

Chemistry, Aquatic Contaminants, Exotic Plant Early Detection, Visitor Use, and Soundscape. The 

vital signs not included and in bold are discussed as stressors. 

b Primary source of information used to assess the condition of indicators; see Table 11 for references for 

information sources. 
26

Table 11. Niobrara National Scenic River natural resources summary. 

Habitat Indicator Measure Reference 

condition 

Existing 

condition 

Source 

Niobrara 

River and 

tributaries 

(36%) 

Aquatic 

macroinvertebrates 

(Niobrara River) 

Aquatic 

macroinvertebrates 

(tributaries) 

EPT richness 

HBI (0–10 index) 

EPT richness 

HBI (0–10 index) 

0–7 

4.41–7.55 

2–8 

3.5–7.5 

7 

4.72 

3 Berry Falls 

4 Fort Falls 

5 Smith Falls 

5.13 Berry Falls 

4.57 Fort Falls 

3.53 Smith Falls 

Troelstrup 

2006, Rust 

2006 

River otter None 

Cool-water fish Presence (no. of 

tributaries) 

1 (blacknose 

shiner) 

2 (finescale 

dace) 

3 (northern 

redbelly dace) 

2 (pearl dace) 

1 (blacknose 

shiner) 

4 (finescale 

dace) 

4 (northern 

redbelly dace) 

3 (pearl dace) 

Schainost 

2008 

Fish community Richness 

CPUE (fish/ft.) 

24/30 

0.467–3.035 

27/30 

0.612 

Kantck and 

Churchill 

1993, 

Gutzmer et al. 

2002, Dietsch 

2008 

Spiny softshell turtle None 

Stream flow 

(Niobrara River) 

Mean annual flow 

(acre ft.) 

Mean daily 

discharge (cfs) 

434,448–

659,742 

~750 (July) 

~700 (Aug.) 

~720 (Sept.) 

491,086 

~570 (July) 

~520 (Aug.) 

~550 (Sept.) 

Wen and 

Chen 2006, 

Istanbulluoglu 

2008 

Upland 

forest and 

savanna 

(35%) 

Elk Calf:cow ratio 

Cow survival (%) 

Ave. rate of 

increase 

0.30–0.35 

89–91% 

0.20–0.31 

0.31–0.57 

92% 

0.21 

Stillings 1999, 

Frickle et al. 

2008, Rapid 

City Journal 

2009 

Ponderosa pine Mean fire interval 

(yrs.) 

 

Density (trees/ha) 

Fire type 

Extent (ha/study 

site) 

8.6 

 

 

380 

 

Surface 

83–123 (1939) 

36.0 

 

 

2,250 

 

Crown 

235–219 (2003) 

Tolstead 

1947, 

Steinaur and 

Bragg 1987, 

Guyette 

2005, 

Narumalani 

2009a 

 
27

Table 11. Niobrara National Scenic River natural resources summary (continued). 

Habitat Indicator Measure Reference 

condition 

Existing 

condition 

Source 

Upland forest 

and savanna 

(35%) 

(continued)

Land cover Contagion index 

ShDI index 

68.68 

0.8551

70.58 

0.8255 

Narumalani 

2009b 

Fire Mean fire 

interval (yrs.) 

Fire type 

8.6 

Surface 

36.0 

Crown 

Guyette 2005 

Spring branch 

canyon and 

riparian forest

(10%) 

Paper birch Saplings (no./ha) 

Seedlings 

(no./ha) 

Dead trees 

(no./ha) 

Live trees 

(no./ha) 

Basal area 

(m2/ha) 

19,760 

30,000 

? 

? 

1,235-1,482 

0.64 

0 

19.5 

17.6 

6.0 

Uchyll 1991, 

Steuter and 

Steinauer 1993, 

Stroh and Miller 

2009 

Hybrid aspen Mature trees 

(no.) 

Root suckers 

(no.) 

Many? 

Many? 

Few 

Few or none 

Schlarbaum 

2008, Shepperd 

2008 

Bailey’s eastern 

woodrat 

Density (no./ha) 0.5–2.2 0.72 Rainey 1956, 

Barbour and 

Humphry 1982, 

Frost 2007 

Bird 

hybridization 

 None 

Grassland 

(8%) 

Grassland birds Density (no./ha) 1.25–2.68 1.08–1.16 Frost 2007 

Sand Hills prairie Mean fire 

interval (yrs.) 

Woodland extent 

(ha/study site) 

8.6 

83–123 (1939) 

36.0 

235–219 (2003) 

Guyette 2005, 

Narumalani 

2009a 

Land cover Contagion index 

ShDI index 

68.68 

0.8551

70.58 

0.8255 

Narumalani 

2009b 

Fire Mean fire 

interval (yrs.) 

Fire type 

8.6 

Surface 

36.0 

Crown 

Guyette 2005 
28

Table 11. Niobrara National Scenic River natural resources summary (continued). 

Habitat Indicator Measure Reference 

condition 

Existing 

condition 

Source 

Sandy 

shoreline, 

sandbars, and 

wetlands 

(10%)

Interior least tern 

and piping plover 

Monitoring reach 

census (no.) 

Clutch size 

(mean no./nest) 

Nest success 

(%) 

Fledging 

success (%) 

150–321 (tern) 

79–207 (plover) 

2.3–2.6 (tern) 

3.5–3.7 (plover) 

36–69 (tern) 

25–83 (plover) 

13–88 (tern and 

plover) 

289 (tern) 

207 (plover) 

2.6 (tern) 

3.6 (plover) 

52 (tern) 

35 (plover) 

37 (tern) 

36 (plover) 

Adolf et al. 2001,

Ferland and 

Haig 2002, 

Jorgensen 2006, 

Wilson 2007 

Purple 

loosestrife 

Area (ha) 0 (presettlement) 

954 (2002) 

469 Narumalani and 

Swain 2009 

Whooping crane None 

Sediment 

transport 

None 
29

Indicator Assessment 

Habitat: Niobrara River and Tributaries

Indicator: Aquatic Macroinvertebrates (water quality) 

Source for Reference Condition: Macroinvertebrate Sampling in Similar Streams 

in Parks of the Northern Great Plains 

 

Aquatic macroinvertebrates can reveal whether a body of water is 

healthy or unhealthy based on the presence or absence of certain 

sensitive species, as well as the overall diversity of organisms. 

Different species show different sensitivity to pollution and 

changing stream conditions, with Ephemeroptera (mayfly), 

Plecoptera (stonefly), and Trichoptera (caddis fly) (referred to as 

EPT) being among the most sensitive orders and Chironomidae, 

worms and midges, being less sensitive (U.S. Environmental 

Protection Agency 1997). Macroinvertebrates have been collected 

from several sites encompassing the entire Niobrara River basin in 1998, 2000, and 2008 by the 

Nebraska Department of Environmental Quality, however, study sites within the boundaries of 

the scenic river were limited (Nebraska Department of Environmental Quality, K. Bazata, 

surface water section, personal communication, 20 November, 2009). In 2004 and 2005, Rust 

(2006) sampled macroinvertebrates in the mainstream Niobrara River and three of its tributaries 

(Berry Falls, Fort Falls, and Smith Falls) within the scenic river (Fig. 11), and in aquatic systems 

in parks of the Northern Great Plains (Fig. 12). Several metrics were compared including EPT 

richness and the modified Hilsenhoff Biotic Index (HBI). EPT richness is the number of taxa 

(genera or species) in these three pollution sensitive orders, and HBI is a measure of water 

quality based on the tolerance of specific organisms to organic pollution and associated decline 

in dissolved oxygen concentrations. High EPT values and low HBI values are indicators of 

better water quality (U.S. Environmental Protection Agency 1997). 

The Niobrara River was dominated by Ephemeroptera and non-insects, and intolerant organisms 

(22 percent) outnumbered tolerant (17 percent) in both abundance and richness. EPT richness 

was seven, and EPT was a dominant 54.4 percent (Rust 2006). Compared to other medium and 

large rivers in the Great Plains, the composition of the macroinvertebrate community of the 

Niobrara River indicates it is in excellent condition (Troelstrup 2006). Richness metrics were all 

higher than median values for other large rivers in the northern Great Plains parks. Furthermore, 

percent contribution of EPT was high and contribution of Chironomidae and average tolerance to 

organic pollution (HBI) was lower than median values for other rivers (Troelstrup 2006) (Fig. 

13). 

Berry Falls, Fort Falls, and Smith Falls tributaries were similar to the Niobrara River in that the 

macroinvertebrate communities all had greater numbers of intolerant than tolerant organisms. 

Smith Falls had the highest EPT richness (5) and lowest HBI (3.53), suggesting it had the best 

water quality to support sensitive macroinvertebrate species. Berry Falls had the lowest EPT 

richness (3) and highest HBI (5.13), indicating signs of impairment (or not able to support 

designated uses) compared to the other tributaries studied. Fort Falls had an EPT richness of 4, 

and a HBI of 4.57. Comparing median values of the tributaries to other small streams in the 

Macroinvertebrate sampling in a 

tributary of the Niobrara River 
30

Northern Great Plains, Berry Falls is somewhat impaired, Fort Falls is slightly impaired, and 

Smith Falls is in moderately good condition (Troelstrup 2006) (Fig. 14). 

This indicator is in good condition and the trend is unknown. 

Figure 11. Aquatic macroinvertebrate sampling sites in Niobrara National Scenic River (Source: Rust 

2006). 

Figure 12. National park units of the Northern Great Plains Network sampled for aquatic 

macroinvertebrates (Source: Rust 2006). 
31

 

 

Figure 13. Median EPT richness and HBI value for medium and large rivers of the Northern Great Plains 

Network. Note: The median EPT Richness for KNRI-Missouri River equals zero. DETO=Devil’s Tower 

National Monument; FOLA=Fort Larned National Historic Site; FOUN=Fort Union Trading Post National 

Historic Site; KNRI=Knife River Indian Villages National Historic Site; MNRR=Missouri National 

Recreation River; NIOB=Niobrara National Scenic River, SCBL=Scotts Bluff National Monument; 

THRO=Theodore Roosevelt National Park (Source: Rust 2006, Troelstrup 2006). 

0

1

2

3

4

5

6

7

8

EPT Richness

0

1

2

3

4

5

6

7

8

9

10

HBI Value

fairly poor 

good 

very poor 

excellent 

very good 

fair 

 poor 
32

Figure 14. Median EPT richness and HBI value for small streams of the Northern Great Plains Network. 

NOTE: the median EPT Richness for BADL equals zero. AGFO=Agate Fossil Beds National Monument; 

BADL=Badlands National Park; FOLA=Fort Larned National Historic Site; MORU=Mount Rushmore 

National Memorial; NIOB=Niobrara National Scenic River; WICA=Wind Cave National Park (Source: Rust 

2006, Troelstrup 2006). 

0

1

2

3

4

5

6

7

8

9

EPT Richness

0

1

2

3

4

5

6

7

8

9

10

HBI Value

excellent 

very good 

good 

fair 

fairly poor 

poor 

very poor 
33

Indicator: River Otter

Source for Reference Condition: Not Established 

The river otter is widely distributed across North America in a variety 

of aquatic habitats including marine coasts, lakes, marshes, 

reservoirs, and streams (Toweill and Tabor 1982, Larivere and 

Walton 1998). The primary habitat requirement for river otters is 

permanent water with abundant fish or crustacean prey and relatively 

high water quality. In addition, river otters require riparian 

vegetation as cover when they are feeding, denning, and moving on 

land. Because of their high mobility and low densities, river otters 

require relatively long reaches of streams and rivers.

In Nebraska, the river otter was historically common in all major river drainages (Jones 1962, 

1964) but they were rare by 1908 and apparently were extirpated from the state in the early 

1900s (Jones 1964). Unregulated trapping was most likely the primary cause (Nebraska Game 

and Parks Commission 2009b). Between 1986 and 1991, more than 150 river otters were 

released at seven sites across the state including a site on the Niobrara River in Sheridan County 

(upstream from the scenic river) (Nebraska Game and Parks Commission 2009b). River otters 

were listed as endangered in Nebraska in the 1980s and reclassified as state threatened in 2005. 

The State of Nebraska conducts annual monitoring for river otters by searching for otter signs at 

bridge crossings that are located near release sites. The results of these surveys and sightings of 

otter family groups suggest that viable populations have become established in portions of 

several watersheds (Nebraska Game and Parks Commission 2009b) (Fig. 15). Biologists expect 

river otters to expand their ranges from the release sites into other suitable habitats. River otters 

have been sighted in the scenic river portion of the Niobrara River (Johnsgard 2007) but these 

may be transient individuals. Although suitable habitat exists within the scenic river, river otters 

may avoid these areas because of high human use. High density recreational use along 

waterways may adversely affect river otters by altering their habitat use and daily activity 

patterns (Giere and Eastman 2000). 

The river otter population is likely increasing in the Niobrara River watershed but a resident 

population has not been found in the scenic river. This indicator is not assessed due to lack of 

information. 

 

River otter 
34

Figure 15. River otter distribution in Nebraska (Source: Nebraska Game and Parks Commission 2009). 

Indicator: Cool-water Fishes 

Source for Reference Condition: Historic Sampling in Tributary Streams to the 

Niobrara River and State Listing 

Four rare, cool-water fish species are native to the Niobrara 

River watershed in north-central Nebraska. The blacknose 

shiner is state-endangered, the finescale dace and northern 

redbelly dace are state-threatened, while the pearl dace 

(Margariscus margarita) is a Species At-risk (Tier 1) 

(Schneider et al. 2005). Populations of these species are 

glacial relicts of more typical northern species that persist 

outside of their primary geographic range following repeated glaciations (Hrabik 1990). The 

spring-fed Niobrara River and its tributaries provide cool, clear, slow-moving, and wellvegetated waters that are critical for survival of these species in Nebraska. 

 

Historically, the blacknose shiner was one of the most common fish species sampled in northcentral Nebraska (Schainost 2008). However, it is now documented at infrequent intervals and 

in very low abundance; it was last recorded in 1995 (Schainost 2008). The finescale dace and 

northern redbelly dace have been sampled more frequently and consistently, but in relatively 

small numbers. The pearl dace is quite common in localized areas (Schainost 2008), but its 

preferred habitat is limited (Cunningham 2006). None of these species have been recorded 

directly in the scenic portion of the Niobrara River. However, they have been found in multiple 

tributaries to the scenic river (Schainost 2008) (Fig.16). Several additional streams within a 10-

mile radius of the scenic river also support these species. 

Between 1893 and 2004, the Niobrara River and its tributaries were sampled for fish species 

numerous times but sample sites and methods used varied during this period of monitoring 

Blacknose shiner, photo by 

National Park Service 
35

(Schainost 2008). Therefore, it is impossible to identify statistical population trends for coolwater species based on occurrence data (Table 12). However, three of these fishes inhabit the 

same tributaries that they were found in historically (1893–1939), and they were discovered in 

other tributaries in recent years (these tributaries may not have been previously sampled). The 

blacknose shiner is found in only one of the tributaries that it occupied historically, but like the 

other species, it was discovered in additional tributaries. 

This indicator is in good condition based on the long-term persistence of these species in a few 

tributaries and the greater number of tributaries in which they now occur. Indicator trend is not 

known. However, this assessment is tenuous given that these fish species are of conservation 

concern in Nebraska due to their restricted habitat which faces a variety of threats such as 

increased turbidity, siltation, introduction of non-native fish, increased groundwater pumping, 

and climate change (Schneider et al. 2005). 

Figure 16. Location of cool-water fish collection sites in tributary streams of the Niobrara River (Source:

Schainost 2008).

 
36

Table 12. Presence of blacknose shiner (b), finescale dace (f), northern redbelly dace (n), and pearl 

dace (p) in tributary streams of the Niobrara River (Source: Schainost 2008). 

Streams 1893-1939 1963-1973 1974-1985 1986-2004

Bone Creek n fnp fnp 

Coon Creek n 

Cottonwood Creek p bfnp 

Dry Creek fnp 

Evergreen Creek fn 

Fairfield Creek n 

Gordon Creek bfnp bfp 

Long Pine Creek b p 

Minnechuduza Creek bn fn fnp 

Niobrara River b 

Sand Creek f 

South Fork Fairfield 

Creek 

n nf 

Spring Branch p 

Willow Creek bfnp 

Indicator: Fish Community 

Source for Reference Condition: Fish Species Sampling in 1982 and Fish 

Population Trends Below Spencer Dam 

The first significant study of the fishes of the Niobrara River and its 

tributaries occurred in 1973 as part of a Nebraska statewide stream 

basin survey (Mestl 1993). A total of 41 species were collected by 

seining. The second major study occurred from 1976 through 1978 

when the Niobrara River was intensively sampled (by seining, 

hoopnetting, and explosives) above and below Spencer Dam 

(located about 62 km [38 miles] downstream of the scenic river) 

(Mestl 1993). That inventory was repeated in 1991 using the same 

sampling methods used during the 1976-1978 study. Between 1978 and 1991, some species, 

mainly habitat and/or food specialist such as the sand shiner, declined (as measured by catch per 

unit of effort or CPUE) while others, mainly generalist such as the channel catfish, increased 

(Mestl 1993) (Table 13). 

In a study to determine fish population trends below Spencer Dam, sampling (seining and 

electroshocking) was conducted each fall from 1993 through 2001, except no sampling was done 

in 1993 (Gutzmer et al. 2002). Over the nine years of the study, the species most observed were 

the sand shiner, red shiner, and flathead chub (Platygobio gracilis). The CPUE for all species 

ranged from 0.467 fish/foot to 3.035 fish/foot and was not significantly different between years 

for shocking (p=0.4879), seining (p=0.4879), and total number of fish sampled (p=0.1164) 

(Gutzmer et al. 2002). 

Specific to the scenic river, fish species were sampled in a 50-km (31-mile) reach of the Niobrara 

River (Niobrara Valley Preserve) in 1982 (Kantak and Churchill 1993) and a 56-km (35-mile) 

 Channel catfish 
37

reach of the river from Borman Bridge to Carns Bridge in 2003–2005 (Dietsch 2008). Twentyfour species were collected in the earlier study and twenty-seven in the later study. Neither study 

reported fish abundance or CPUE but Dietsch (2008) noted that several fish species were 

widespread and several others were confined to reaches downstream from the Norden Dam. 

This indicator is in good condition and steady based on the high diversity of fish species in the 

scenic river (27 of 30 known species) and no significant difference among years in fish species 

richness below the Spencer Dam. 

Table 13. Catch per unit effort (CPUE) of fish species from the Niobrara River in 1978 and 1991 (Source:

Mestl 1993). 

Species 1978 1991 

Sand Shiner 37.8 1.2 

Red Shiner 15.1 10.9 

Flathead Chub 11.5 5.0 

Channel Catfish 5.4 10.8 

Green Sunfish 0.9 < 0.1 

River Carpsucker 0.8 6.0 

Bluegill 0.3 0.2 

Shorthead Redhorse 0.2 < 0.1 

Emerald Shiner 1.0 1.8 

Silvery Minnow 1.0 < 0.1 

Carp < 0.1 < 0.1 

Spotfin Shiner < 0.1 0.2 

Sauger < 0.1 0.2 

Indicator: Spiny Softshell Turtle

Source for Reference Condition: Not Established 

The spiny softshell turtle is found in both lakes and rivers, 

especially those with mud or sand bottoms, throughout Nebraska 

(Freeman 1998). The species is known to inhabit much of the 

Niobrara River Valley but information is lacking on population 

size and distribution, habitat characteristics, and response to 

disturbance (Allen 2008). 

 

The spiny softshell turtle is long-lived with a life expectancy of 50 

years or more (Freeman 1998). Individuals are active during the 

day and feed on aquatic plants, a variety of invertebrates, and some small vertebrates. The spiny 

softshell turtle is the most aquatic of turtles in Nebraska, preferring to bask on logs or banks and 

to nest on banks close to the water. The turtle is sensitive to disturbance and will quickly 

abandon basking sites when approached (Allen 2008). Additionally, turtles rest buried in sand in 

shallow water. These activity patterns make this turtle especially sensitive to disturbance from 

canoes and other recreation activities on the Niobrara River (Allen 2008). In addition, 

decreasing stream flow of the Niobrara River threatens to limit the habitat available to this 

species (Allen 2008). 

Spiny softshell turtle
38

This indicator is not assessed due to the lack of site-specific information. A study to evaluate the 

potential effects of recreational use of the Niobrara River on the species is proposed for 2009–

2011 (Allen 2008). 

Indicator: Stream Flow 

Source for Reference Condition: An Analysis of Long-Term Gauge Records of 

Stream Flow 

The Niobrara River and its tributaries are in hydraulic 

connection with the aquifers in the region and, in most years, 

groundwater seepage accounts for 90 to 95 percent of the 

river’s total discharge (Nebraska Department of Natural 

Resources 2004). Stream flow is affected by both climatic 

factors (precipitation and temperature) and groundwater 

withdrawal. Stream flow, sediment load, and other factors 

determine channel morphology which acts as a template for 

aquatic and bottomland ecological processes (Naiman et al. 

1993, Scott at al. 1996). 

In 2005, a study conducted in Nebraska and northwestern Kansas, analyzed trends in 

precipitation and temperature for 28 weather stations, and stream flow for 110 gauging stations 

in eight major river basins (Wen and Chen 2006). Analyses of precipitation and temperature 

showed no significant trends over a 50-year period. For 12 stream flow gauges in the Niobrara 

River Basin, three showed significant downtrends in stream flow, two showed significant 

uptrends, and the remaining seven showed no trends (Table 14). The analysis used in this study 

(Mann-Kendall test) was appropriate for detecting monotonic, or gradual and continuing, trends 

in stream flow over an extended period of time but not for detecting sudden changes (U.S. 

Geological Survey, R. Zelt, associate director NAWQA, personal communication, 7 October 

2009). Two of the stations with decreasing trends are located in Box Butte County in 

northwestern Nebraska, a region that has experienced a large decline in the water table likely due 

to heavy irrigation use (Wen and Chen 2006). Only one of the 12 gauges with a complete record 

is located on the Niobrara River within the scenic river boundary (station 6461500 near Sparks, 

Nebraska) (Fig. 17). That station showed no significant trend in stream flow over the 58-year 

gauge record (Table 14). 

Table 14. Annual mean stream flow trend results in the Niobrara River using Mann-Kendall test (Source: 

Wen and Chen 2006 ). 

Basin Station ID Drainage 

(mile2) 

Period Z-score P-value Trend 

Niobrara 6444000 313 1947–2003 2.361 0.018 Increasing 

6453500 505 1949–1994 -1.086 0.278 Insignificant

6453600 812 1957–2003 1.212 0.226 Insignificant

6454500 1,400 1946–2003 -2.912 0.004 Decreasing 

6455500 1,460 1946–2003 -3.428 0.001 Decreasing 

6457500 4,290 1945–1991 -2.708 0.007 Decreasing 

6459500 660 1947–2003 -1.675 0.094 Insignificant

6461000 390 1948–1994 -0.757 0.449 Insignificant

Niobrara River, photo by 

National Park Service 
39

Table 14. Annual mean stream flow trend results in the Niobrara River using Mann-Kendall test 

(continued) (Source: Wen and Chen 2006). 

Basin Station ID Draingage 

(mile2) 

Period Z-score P-value Trend 

Niobrara 6461500 7,150 1945–2003 -1.529 0.126 Insignificant

6463500 458 1948–2003 2.367 0.018 Increasing 

6465000 11,070 1940–2001 1.699 0.089 Insignificant

6465500 11,580 1938–2003 1.804 0.071 Insignificant

Figure 17. Location of nine stream flow gauges in or near the Niobrara National Scenic River. The gauge 

near Sparks is indicated by the number 6 (Source: Istanbulluoglu 2008). 

Merritt Dam on the Snake River (a tributary of the Niobrara River upstream of the Sparks gauge) 

began storing water in February 1964 for the Ainsworth irrigation project. In a recent study, 

hydrological implications of water storage and diversion on the Snake River to stream flow in 

the Niobrara River were investigated by separating the Niobrara River flow data into before 1965 

and after 1964 periods (Istanbulluoglu 2008). This study showed a significant downward step 

trend (sudden change) in annual runoff in the Niobrara River at the Sparks gauge after 1964 but 

no difference in precipitation for the same periods (i.e., before 1965 and after 1964) 

(Istanbulluoglu 2008) (Fig. 18). Also, in all months except January, mean daily flows declined 

after 1964 with the greatest declines occurring in the summer months of July (24.4 percent), 

August (25.0 percent), and September (24.7 percent) (Fig. 19). Standard deviation of the mean 

daily flows in each month were also altered following major water storage and diversion in the 

watershed (Fig. 19). 
40

A demonstration study of hydraulic microhabitats at the Sparks gauge on the Niobrara River 

found deeper hydraulic niches are only available during periods of higher stream discharge 

(Alexander et al. 2009). However, a more detailed analysis is needed before determining what 

effects future water deletions in the Niobrara River watershed might have on higher stream 

discharge and deeper microhabitats and associated aquatic organisms (Alexander et al. 2009). 

This indicator is in poor condition and declining based on a sudden and ongoing decrease in 

annual and daily flows at the Sparks gauge and uncertainty over the effects of these decreases on 

aquatic habitats and organisms. This assessment is supported by American Rivers 2008 

designation of the Niobrara River as one of America’s most endangered rivers based on 

irrigation diversions and lack of an in-stream flow water right for the scenic river (American 

Rivers 2008). 

Figure 18. Annual model run without water diversions from the Niobrara River. Observed is annual runoff 

as measured by the gauge at Sparks. Calculated is modeled annual runoff without water diversions in 

the Niobrara River Basin (Source: Istanbulluoglu 2008). 
41

Figure 19. The mean and standard deviation of daily stream flow at Sparks, Nebraska (Source: 

Istanbulluoglu 2008).

Habitat: Upland Forest and Savanna 

Indicator: Elk 

Source for Reference Condition: Demographic Measures of Elk in Re-established 

Herds 

Elk are native to Nebraska but were extirpated from the state in the 

early 1880s as a result of unregulated market and subsistence hunting 

(Frickle et al. 2008). Elk began to migrate into western Nebraska in 

the 1950s and 1960s from reestablished herds in Wyoming, and by 

the early 1970s, a herd had become established in the Pine Ridge of 

Northwestern Nebraska. In addition to the Pine Ridge, elk recolonized four other areas in northern and central Nebraska after the 

late 1980s. Elk herds are now found along the length of the North 

Platte River from the Wyoming border to Lake McConaughy, in 

Lincoln County in central Nebraska, in Boyd County in northeast 

Nebraska, and along the Niobrara River in Cherry and Sheridan counties (Frickle et al. 2008) 

(Fig. 20). Individuals from the herds in northern Nebraska are occasionally observed within the 

boundary of the scenic river (U.S. Department of Interior 2006). 

Elk 
42

Figure 20. Elk distribution in Nebraska (Source: Nebraska Game and Parks Commission 2008). 

The distribution and number of elk in Nebraska will likely increase due to the availability of 

suitable habitat, highly regulated hunting, and increasing landowner tolerance (Frickle et al. 

2008). Demographic measures (average calf:cow ratio of 0.31:0.57, adult cow survival of 92 

percent), and average rate of increase (r) of 0.21 for herds in the Pine Ridge indicate a growing 

population (Stillings 1999). Most herds in the state are expected to double in size in the next five 

years as annual population growth of 15 percent to 20 percent is likely under the current harvest 

limits (Frickle et al. 2008). This indicator is in good condition and increasing. Future threats 

include chronic wasting disease (CWD), a fatal disease of the central nervous system of whitetailed deer, mule deer, and elk that has infected free-roaming deer and captive elk primarily in 

western and north-central counties in Nebraska (Nebraska Game and Parks Commission 2009c) 

(Figure 21). 

Figure 21. Free-ranging chronic wasting disease (CWD) positives in Nebraska (Source: Nebraska Game 

and Parks Commission 2009c). 
43

Indicator: Ponderosa Pine 

Source for Reference Condition: Historic Density of Ponderosa Pine in the Pine 

Ridge, Historic Photographs, and Fire History 

Ponderosa pine and associated shrubs, forbs, and grasses characteristic of the 

Rocky Mountains occur in continuous and isolated stands in Nebraska as far 

east as the transition zone between the mixed and tallgrass prairies (Tolstead 

1947). In the central Niobrara River Valley, ponderosa pine occurs on the 

north side of the river on steep cliffs and rocky soils on the eroded edge of 

the Crookston Table; and on the south side in scattered stands between the 

deciduous forest of the valley walls and the prairies of the Sand Hills 

(Steinauer and Bragg 1987) (Fig. 22). 

Prior to European settlement, ponderosa pine was restricted to the steep 

slopes of the Niobrara River Valley and spring branch tributaries by frequent 

prairie fires that originated primarily in the Sand Hills to the south (Steinauer and Bragg 1987, 

Ortmann et al. 1996). The recent spread of ponderosa pine into adjacent prairie and an increase 

in the density of trees in established stands is likely due to a longer fire return interval as a result 

of almost complete fire suppression (Steinauer and Bragg 1987, Guyette 2005). In 1947, mature 

stands of ponderosa pine in the Pine Ridge of Nebraska (about 100 km [62 miles] west of the 

Figure 22. Ponderosa pine distribution in Nebraska (Source: Kaul and Rolfsmeier 1993). 

Ponderosa pine
44

central Niobrara River Valley) averaged about 380 trees/ha (Tolstead 1947). At that date, the 

Pine Ridge was presumably still subject to recurrent fire. This is in contrast to the results of a 

more recent study in the Niobrara Valley Preserve that found a density of 2,250 trees/ha in a 

stand protected from fire (Steinauer and Bragg 1987).

Recent mapping of woodland cover (primarily ponderosa pine), in two, five-km (three-mile) 

study reaches along the Niobrara River within the scenic river, found a 248 ha (613 acre) 

increase in woodland cover over a 64-year period (Narumalani 2009a) (Figs. 23 and 24). The 

increase in ponderosa pine extent and stand density is likely to continue in the future. Recent 

large fires in western Nebraska have involved crown fire that killed all of the trees in dense 

stands of ponderosa pine (Nebraska Forest Service 2007). As the density of ponderosa pine 

increases in the central Niobrara River Valley, crown fires that kill stands of pine are likely to 

occur. This indicator is in poor condition and decreasing. 

Figure 23. Change in woodland vegetation along the Niobrara River, 1939–2003, Keya Paha and Rock 

Counties, Nebraska (Source: Narumalani 2009a). 
45

Figure 24. Change in woodland vegetation along the Niobrara River, 1939–2003, Keya Paha and Brown 

Counties, Nebraska (Source: Narumalani 2009a). 
46

Indicator: Land Cover 

Source for Reference Condition: Based on Analysis of 1992 and 2001 Land Use 

and Land Cover Datasets 

The National Land Cover Dataset (NLCD) 1992 was the first land cover mapping project with a 

national scope. NLCD 1992 provides 21 land cover classes that were derived from unsupervised 

classification, modeling, and ancillary data (see Vogelmann et al. 1998). The NLCD 1992 effort 

was completed in December 2000, and it is one of the most widely used land cover datasets in 

the United States with applications including environmental reporting, climate change modeling, 

Clean Water Act studies, and biodiversity and conservation assessments. The success of NLCD 

1992 initiated the process for developing NLCD 2001. This effort provided additional 

information beyond land cover, including impervious surface and canopy density. 

Because of the differences in methodologies used and the land cover categories, a direct, pixelto-pixel comparison of NLCD 1992 and 2001 is not recommended. In 2008, the NLCD 

1992/2001 Retrofit Land Cover Change Product was developed as a stopgap measure to offer a 

more accurate and useful guide to change analysis than was possible by direct comparison of the 

two land cover products. A comparison of the NLCD 1992 and 2001, using the retrofit change 

product, identified changes in the number of patches and percent land cover for seven land cover 

classes in a 3,977 km2

 (1,535 sq. mile) area that is centered on the scenic river (Narumalani 

2009b) (Table 15, Fig. 25). The entire Niobrara watershed was not chosen because the Niobrara 

River extends 861 km (535 miles) from Wyoming to northeast Nebraska. The scenic river 

comprises only 122 km (76 miles) of this extent, lying closer to the mouth of the river, and land 

use changes concentrated around the scenic river area would have a greater impact than those 

that would occur upstream. 

The retrofit product calculated the percent land cover and landscape indices, including a 

Contagion Index and Shannon Diversity Index (ShDI). Percent land cover in the grassland/shrub 

class showed the largest relative increase while percent land cover in the agriculture class 

showed the largest relative decrease. The Contagion Index refers to the tendency of patch types 

to be spatially aggregated—that is, to occur in large, contiguous distributions. Contagion Index 

values increased from 1992 to 2001, indicating that larger continuous patches of land cover were 

detected for the later date. This may be due to the increase in percent land cover of 

grassland/shrub cover types from 75.28 to 78.67. Grasslands increased during this time period 

possibly because of the implementation of the U.S. Department of Agriculture’s Conservation 

Reserve Program (CRP) whereby landowners were rewarded for seeding large tracts of 

agricultural land with native grasses (Drummond 2007). This is supported by the substantial 

decrease in percent land cover of agricultural lands from 11.08 to 5.23. The ShDI supports this 

observed decrease. ShDI is one of several indices that are often used to measure biodiversity. A 

decrease in ShDI from 0.86 in 1992 to 0.83 in 2001 is indicative of an increased dominance of a 

land cover class (i.e., grassland/shrub). 

This indicator is in good condition and improving based on the increase in land cover in the 

grassland/shrubs class. Although this increase results in a less diverse land cover, more land 

cover is in natural or restored habitat. There is also the possibility that because two methods of 

classification were used, the results may be misleading. For example, a visual examination 
47

between the two dates indicates a definitive presence of a road network in 2001 because ancillary 

data were used (e.g., U.S. Census Bureau TIGER files) to force the inclusion of a road network. 

Inclusion of area of roads would reduce the area of the landscape classes. Other possible 

explanations for the decline in agricultural land pertains to the use of five agricultural land cover 

categories for the 1992 NLCD and only two cover categories for 2001. Similarly, for the 1992 

NLCD only two wetland classes were identified, whereas ten were delineated in 2001. 

Figure 25. Niobrara National Scenic River and surrounding land cover change, 1992–2001 (Source:

Narumalani 2009b).
48

Table 15. Number of patches, percent land cover, and changes, 1992–2001, for Niobrara National Scenic 

River and surrounding area. Contagion and Shannon Diversity Indices for 1992 and 2001 are for the 

same area (Source: Narumalani 2009b).

1992 2001 

Contagion 

68.68 

ShDI 

0.8551 

Contagion 

70.58 

ShDI 

0.8255 

 

Class # of patches % land 

cover # of patches % land cover 

Change in 

# of patches % land 

cover 

Water 2,140 1.08 434 0.86 -1,706 -0.22

Urban 197 0.14 767 2.37 570 2.23

Barren 746 0.06 78 0.02 -668 -0.04

Forest 13,113 8.55 2,152 7.42 -10,961 -1.13

Grassland/Shrub 12,221 75.28 719 78.67 -11,502 3.39

Agriculture 15,004 11.08 475 5.23 -14,529 -5.85

Wetlands 9,554 3.81 4,253 5.42 -5,301 1.61

Indicator: Fire 

Source for Reference Condition: Fire History of Ponderosa Pine Stand 

See discussion of fire frequency and effects in the Ponderosa Pine Indicator (page 43). 

Habitat: Spring Branch Canyon and Riparian Forest

Indicator: Paper Birch 

Source for Reference Condition: Stand Conditions in Northern Populations of 

Paper Birch 

Paper birch is a northern tree species that rarely occurs naturally where 

average July temperatures exceed 21°C (70°F) (Steuter and Steinauer 

1993, Stroh and Miller 2009). Over thirty stands of paper birch are 

known within the central Niobrara River Valley, a region with a warmest 

monthly average of 23°C (73°F). These stands are relicts that have 

persisted since the end of Wisconsin glaciation when the regional flora 

was dominated by boreal plants. They occur primarily along spring 

branch tributaries to the Niobrara River within and near the scenic river, 

where maximum summer temperatures are cooler than those in the 

surrounding landscape owing to a combination of north-facing slopes, 

overstory canopy, and proximity to cool spring water (Steuter and 

Steinauer 1993). 

 

Paper birch in the Niobrara 

National Scenic River, photo 

by Esther Stroh, U.S. 

Geological Survey
49

Figure 26. Sampling locations of paper birch along the Niobrara River (Source: Stroh and Miller, 2009). 

Regeneration of paper birch in the Niobrara River Valley is primarily by sprouting of mature 

trees, as stands produce a low percent of viable seeds (Steuter and Steinauer 1993). Beginning in 

the early 1980s, resource managers noted a dieback of canopy-sized trees—over 90 percent of 

trees in some stands—and the lack of resprouts and seedlings (Stroh and Miller 2009). Reasons 

for the dieback may include changes in microclimate, shading by canopy trees, pest or pathogen 

infestations, or loss of genetic diversity (Stroh and Miller 2009). In addition, some forest trees 

including paper birch exhibit unexplained cyclic population diebacks (Auclair 2005). Lack of 

seedling recruitment may be due to the lack of disturbances, such as fire, that provide suitable 

establishment sites. In 2007, an investigation of the health of the population found high tree 

mortality, very few saplings, and no seedlings (Stroh and Miller 2009) (Table 16, Fig. 26). Mean 

basal area (6.0 m2

/ha) of trees in the Niobrara River Valley is considerably lower than the range 

of basal areas found in populations within the primary range of paper birch (Uchytil 1991). 

The paper birch population will continue to decline as aged or deceased rootstocks fail to 

resprout and few microsites support conditions (e.g., mineral soil exposed by landslide or fire) 

for seedling establishment (Steuter and Steinauer 1993). This decline may accelerate in the 

future with regional temperature variations and microclimate changes. For example, early spring 

thaw-freeze conditions that can contribute to birch canopy dieback have increased in frequency 

in Niobrara River stands in recent years (Stroh and Miller 2009). The paper birch population is 

in poor condition and its future persistence uncertain due to the lack of nearby populations for 

immigration and recruitment (Stroh and Miller 2009). 
50

Table 16. Summary of paper birch stand conditions along the Niobrara River (Source: Stroh and Miller 

2009). 

Site Name Total trees (no). Dead Trees (no). Saplings Seedlings 

Borman Bridge 37 18 0 0 

Fort Falls 48 17 0 0 

Upper Coon Creek 10 7 0 0 

Coon Creek West 7 5 0 0 

Coon Creek East 10 7 0 0 

Buffalo Bridge 24 3 0 0 

Box Canyon 10 8 0 0 

Side Canyon 8 6 0 0 

Small Canyons 36 30 0 0 

Buffalo Fence 58 14 0 0 

Tyler Falls 34 17 1 0 

Wide Bend - - 0 0 

Smith Falls SP 41 19 0 0 

Brewer Bridge 94 34 0 0 

Sharp’s Camp 81 52 0 0 

Rocky Ford 57 35 6 0 

Cross country 44 32 0 0 

Dog Town 29 16 0 0 

Nature Trail 53 33 0 0 

Norden/Huddle 14 7 0 0 

Garden Creek 49 33 0 0 

Kirtpatrick 14 10 0 0 

Jeff Creek 80 30 0 0 

Hartman Island 34 23 0 0 

Lowest Site 20 14 0 0 

Total 892 468 7 0 

Indicator: Hybrid Aspen

Source for Reference Condition: Assessment of Stand Health 

 

A hybrid (Populus x smithii) of quaking aspen (Populus 

tremuloides), the most widely distributed tree in North America, 

and bigtooth aspen (Populus grandidentata), a tree native to the 

northeast and north-central United States and Canada, occurs on 

steep, north-facing slopes and benches along a half mile stretch of 

Niobrara River in and near Smith Falls State Park (Shepperd 

2008). Stands of the hybrid aspen grow in association with several 

hardwood trees and shrubs typical of the eastern deciduous forest. 

Paper birch (see Paper Birch Indicator on page 48) also grow in the 

area and both paper birch and hybrid aspen are considered relicts 

that have persisted in cool and moist sites following post-glacial warming of the climate.

 Hybrid aspen stand, 

photo by Wayne Shepperd 
51

In 2007, six hybrid aspen stands were located and mapped (Downing 2007) (Fig. 27). A recent 

assessment of the health of these stands found few mature trees but a large number of aspen logs 

among the surviving trees indicating that aspen was more prevalent in the past (Sheppard 2008). 

Some aspen saplings were present in gaps in the overstory canopy but root spouts were mostly 

missing due to shading by competing trees and shrubs (Sheppard 2008). Scale insects were 

present on the bark of many of the mature trees and may be partly responsible for the low 

number of saplings (Sheppard 2008). 

Figure 27. Observation points of hybrid aspen in the Niobrara National Scenic River (Source: Shepperd 

2008). 

Aspen is a relatively short-lived tree that regenerates primarily from root suckers following a 

disturbance, such as fire, that kills overstory stems (Uchytil 1991). Fire also kills competing 

vegetation and exposes the soil to sunlight and warmth which stimulates sucker growth. The 

suppression of fire likely resulted in the closed tree canopies at the hybrid aspen sites along the 

Niobrara River. A closed canopy appears to be the primary factor limiting successful aspen 

regeneration (Schlarbaum 2008, Shepperd 2008). 

Resource managers removed some competing canopy trees and understory shrubs at two of the 

hybrid aspen sites beginning about 10 to 15 years ago (Table 17). This has stimulated some 

suckering and seed germination. However, the suckers and seedlings/saplings that regenerate 

may be damaged or killed by deer browsing and scale insects (Shepperd 2008). This indicator is 

in poor condition and in decline although continuing treatments (i.e., competing tree and shrub 

removal) may prevent the complete loss of these stands. 
52

Table 17. Health and management of select hybrid aspen stands along the Niobrara River (Source:

Schlarbaum 2008, Shepperd 2008). 

Site Mature Trees Saplings Suckers Management Actions

1 yes yes yes clearing competing 

plants 

2 yes (a few) yes yes (a few) ? 

3 yes (a few) no no none 

4 yes no yes (a few) none 

5 yes yes ? clearing competing 

plants 

6 yes no no ? 

Indicator: Bailey’s Eastern Woodrat

Source for Reference Condition: Woodrat Densities in Other Habitats 

 

Bailey’s eastern woodrat, a subspecies of the eastern woodrat, is 

restricted to a 140-km (87-mile) section of the Niobrara River 

Valley (Jones 1964). The subspecies is believed to be a relict of 

the Pleistocene (Jones 1964) and is listed as At-risk in Nebraska 

(Schneider et al. 2005). Bailey’s eastern woodrat prefers wooded 

spring branch canyons and adjacent riparian areas with rocky 

outcrops along the Niobrara River (Jones 1964); although the 

species has expanded into the northern Sand Hills where it 

inhabits isolated groves of cedar trees (Niobrara Valley Preserve, 

J. Luchsinger, personal communication, 7 August, 2009). The 

Niobrara population of Bailey’s eastern woodrat is the only known population to make heavy use 

of needles and bark of eastern red cedar as preferred food in the summer (Genoways et al. 1997). 

 

In the scenic river, Bailey’s eastern woodrat is found in a matrix of forest and grassland habitats 

but is more abundant in wooded habitat (Frost 2007) (Fig. 28). In this habitat, woodrat density 

was estimated at 0.72/ha in both 2004 and 2005 (Frost 2007), which is within the range of 

woodrat densities found in other populations (Rainey 1956, Barbour and Humphrey 1982). 

 

The population of the subspecies has likely increased due to fire suppression and cedar 

infestation of riparian and spring branch forest habitats (The Nature Conservancy1999, Sand 

Hills Prairie Indicator this assessment). This indicator is in good condition. However, managers 

are currently restoring bottomland forest, oak and pine savanna, and grassland along the 

Niobrara River through a combination of cedar harvest and prescribed burns. Although these 

activities are necessary to restore plant community diversity and species composition, they have 

the potential to negatively impact the woodrat population (Frost 2007). 

Bailey’s eastern woodrat, photo 

by Matt Stephenson, Iowa State 

University 
53

Figure 28. Average number of Bailey’s eastern woodrat captured in 2004 and 2005 in four habitat types 

in the Niobrara Valley Preserve. Note: Mixed is a combination of cedar, cut cedar, and grassland 

(Source: Frost 2007). 

Indicator: Bird Hybridization 

Source for Reference Condition: Hybridization Indices Developed in the Late 

1950s 

In the Niobrara River Valley and adjacent uplands, hybridization 

between western and eastern members of the following pairs of 

bird taxa occurs primarily in floodplain forest and associated 

shrubby woodlands: northern (red-shafted and yellow-shafted) 

flickers (Colaptes auratus), black-headed (Pheucticus 

melanocephalus) and rose-breasted (P. ludovicianus) grosbeaks, 

lazuli (Passerina amoena) and indigo (P. cyanea) buntings, 

spotted (Pipila maculates) and eastern (P. erythrophthalmus) 

towhees, and Bullock’s (Icterus bullock) and Baltimore (I. 

galbula) orioles (Johnsgard 2007). Ancestors of these species pairs were probably 

geographically separated to the east and west of the Great Plains during the last glaciation 

(Mengel 1970; Sibley and Short 1959, 1964; Sibley and West 1959). 

 

Two of these species, the indigo bunting and Baltimore oriole, expanded their ranges rapidly 

west across the Great Plains during the early to mid 1900s possibly due to tree plantings in 

shelterbelts and fire suppression that allowed riparian forest and woodland to mature (Johnsgard 

2007). The range of the indigo bunting spread westward in Nebraska by as much as 226-km 

(140-miles) between 1955 and 1969 (Emlen et al. 1975). The Baltimore oriole was mostly 

confined to eastern Nebraska in the early 1900s, but by the 1980s, its range had expanded west to 

Sheridan County in the Niobrara River drainage (Mollhoff 2001). Based on a male plumage 

index of 0 (eastern) to 12 (western) the center of the hybrid zone for the Bullock’s-Baltimore 

orioles was near Valentine in the Niobrara River Valley (Sibley and Short 1959, 1964). A 

similar hybrid zone existed for the lazuli-indigo buntings (Sibley and Short 1959, 1964) (Table 

18). 

0

2

4

6

8

10

12

Open Mixed Cedar Hardwood

Number

Habitat type

Bullock’s-Baltimore oriole 
54

Changes in the zones of sympatry and rates of hybridization for these species pairs (see Table 23 

in Johnsgard 2007) may indicate underlying changes in riparian forest and woodland habitats 

such as the die-off of mature eastern cottonwood trees (Nebraska Forest Service 2007). The 

hybrid bird indicator is not assessed because of the absence of temporal data on trends in hybrid 

index values for inter-breeding species in the central Niobrara River Valley. A repeat of the 

studies by Sibley and Short (1959, 1964) should be conducted to provide data that would 

determine status and trend. 

Table 18. Hybrid index of two inter-breeding species pairs along the Niobrara River (Source: Sibley and 

Short 1959, 1964). 

Species 

Hybrid Index

Location

Chadron Valentine Bassett Spensor Blair 

Bullock’sBaltimore 

oriole

10.9 5.0 1.8 2.0 - 

Lazuli-indigo 

bunting1 11.9 3.4 - 1.7 - 

1

total index value – 12 western species to 0 eastern species

Habitat: Grassland 

Indicator: Grassland Birds 

Source for Reference Condition: Grassland Bird Densities in Four Habitat Types 

Grassland birds have shown steeper, more consistent, and more 

geographically widespread declines than any other group of North 

American birds (Knopf 1994). Of the 29 species of endemic grassland 

birds of the Great Plains, 23 have been observed or are known to nest 

in or near the scenic river (Ducey 1989). Of the 23 species, 13 have 

declining population trends (Knopf 1994) (Table 19). Human 

activities that have altered grassland bird habitat and depressed 

populations include cultivation of grains and pasture grasses, 

elimination of native grazers, drainage of wetlands, and planting of 

trees in shelterbelts. Also, following fire suppression in the east and 

central plains, woody plants have invaded grasslands from developing 

riparian forests. 

In the central Niobrara River Valley, eastern red cedar (Juniperus virginiana) was originally 

restricted to steep slopes, but with the suppression of fire has expanded into hardwood savannas 

and forests, ponderosa pine forest, and grassland (Ortmann et al. 1996, Johnsgard 2007). This 

species has also spread due to extensive plantings in shelterbelts and other areas. Eastern red 

cedar is characterized by rapid growth, high reproductive output, and widespread dispersal of 

seeds by birds (Briggs et al. 2002). In a recent study of the birds of the Niobrara River Valley, 

within or near the scenic river, species richness estimates were highest in open and mixed 

habitats and lowest in cedar-dominated habitat (Frost 2007). Results of the study suggest that 

cedar invasions cause decreases in overall species richness and shifts in species composition 

Western meadowlark 
55

from grassland and shrubland birds to woodland and forest birds (Fig. 29). 

With the widespread suppression of fire, eastern red cedar will continue to expand into grassland 

in the Niobrara River Valley (see Grassland Indicator). As a result, eastern woodland birds will 

replace grassland birds. This indicator is in good condition but declining based on the initial 

research in the scenic river and the general decline in grassland birds throughout the 

Great Plains. 

Figure 29. Mean density (no./ha) and 95 percent confidence interval during 2004 and 2005 for two 

songbird species in four habitat types in the Niobrara Valley Preserve (Source: Frost 2007). 

Table 19. Population trends of endemic and secondary grassland birds and their status in the Niobrara 

River Valley (Source: Ducey 1989, Knopf 1994). 

Species Population Trenda Niobrara River Valleyb

Endemics 

Ferruginous hawk +1.64** O 

Mountain plover -3.69*** - 

Long-billed curlew -1.67 B 

Sprague’s pipit -3.63*** - 

Cassin’s sparrow -2.54*** - 

Baird’s sparrow -1.75 O 

Lark bunting -2.13* - 

McCown’s longspur +7.30*** O 

Chestnut-collared longspur +0.44 O 

Secondary (more widespread) 

Mississippi kite +0.88 - 

Swainson’s hawk +1.37* B 

Northern harrier -0.36 O 

Prairie falcon +0.33 O 
56

Table 19. Population trends of endemic and secondary grassland birds and their status in the Niobrara 

River Valley (continued) (Source: Ducey 1989, Knopf 1994). 

 

Species Population Trenda Niobrara River Valleyb

Greater prairie chicken -6.85 B 

Lesser prairie chicken - - 

Sharp-tailed grouse +1.05 B 

Upland sandpiper +2.67*** B 

Burrowing owl -0.18 B 

Short-eared owl -0.57 O 

Horned lark -0.70** B 

Eastern meadowlark -2.25*** B 

Western meadowlark -0.52* B 

Dickcissel -1.63*** O 

Savannah sparrow -0.53 B 

Grasshopper sparrow -4.11*** B 

Henslow’s sparrow -4.96** - 

Vesper sparrow -0.29 B 

Lark sparrow -3.45*** B 

Clay-colored sparrow -1.20*** O 

a Annual rate (expressed as a percent) of change in population numbers; 

* = P < 0.10 ** = P < 0.05 *** = P < 0.01. 

b O = species observed or B = species nest in Niobrara River Valley 

Indicator: Sand Hills Prairie 

Source for Reference Condition: Historic and Recent Aerial Photographs and Fire 

History 

The central Niobrara River Valley is bordered on the south by Sand 

Hills prairie and to the north by mixed-grass prairie (Johnsard 2007). 

Ponderosa pine, eastern red cedar, and bur oak (Quercus 

macrocarpa) dominate the woodlands near the top of the valley 

slopes on the south and north sides of the river (Fig. 5). 

 

Invasion of trees, primarily ponderosa pine, into Sand Hills prairie 

has occurred since European settlement of the region in the mid1800s (Steinauer and Bragg 1987, Steuter et al. 1990). A study of 

ponderosa pine in the Niobrara Valley Preserve found that pine 

stands closest to the Niobrara River were older and denser than 

stands at greater distances from the river (Steinauer and Bragg 1987) (Table 20). Prior to 

settlement in the late 1800s, pine was restricted to the valley slopes due to frequent prairie fires 

that originated in the Sand Hills to the south (Pool 1914). Following settlement, fire frequency 

declined from an average of one fire every 8.6 years between 1572 and 1900 to one fire every 36 

years between 1900 and 1997 (Guyette 2005). Longer fire-free periods have permitted the 

establishment of ponderosa pine trees of sufficient size to withstand subsequent fire (Steinauer 

and Bragg 1987). 

 

Woodland invading Sand Hills 

Prairie, photo by National Park 

Service 
57

More recently, eastern red cedar, a species highly sensitive to fire, increased in the understory of 

pine woodland and invaded adjacent prairie as almost all fires in the region were suppressed after 

1900 (Guyette 2005). In addition, grazing by cattle promoted establishment of cedar and pine by 

reducing native grasses that compete with woody seedlings and saplings (Steinauer and Bragg 

1987). Cattle may also contribute to increases in cedar by dispersing seeds. Furthermore, global 

increases in atmospheric CO2 may favor the growth of C3 woody plants, such as cedar, over C4

grasses (Polley et al. 1994). 

 

Managers are attempting to re-establish and maintain Sand Hills prairie at priority sites with 

prescribed fire, herbicides, and cutting of woody vegetation (The Nature Conservancy 1999). 

Without widespread application of these management techniques, woodland will continue to 

expand into prairie (see Ponderosa Pine Indicator, this section). Considering the vast extent of 

Sand Hills prairie (5 million ha, 12.3 million acres), this indicator is in good condition but 

declining near the Niobrara River. 

Table 20. Age and density of ponderosa pines by site. Site A is closest to the Niobrara River (Source: 

Steinauer and Bragg 1987). 

Sites Age (mean yrs.) Density (no./.01 ha)

A 104 22.5 

B 89 3.7 

C 78 2.4 

D 75 1.2 

Indicator: Land Cover 

Source for Reference Condition: Based on Analysis of 1992 and 2001 Land Use 

and Land Cover Datasets 

 

See discussion of Land Cover under the Upland Forest and Savanna Habitat (page 46). 

Indicator: Fire 

Source for Reference Condition: Fire History of Ponderosa Pine Stands 

See discussion of fire frequency and effects in the Ponderosa Pine Indicator (page 43). 
58

Habitat: Sandy Shorelines, Sandbars, and Wetlands

Indicator: Interior Least Tern and Piping Plover 

Source for Reference Condition: Long-Term Monitoring of Adult Terns and 

Plovers 

The interior least tern and piping plover are federally endangered and threatened species, 

respectively. These two species commonly nest together throughout the northern Great Plains, 

primarily on bare or sparsely vegetated sandbars (Ziewitz et al. 1992). Availability of this 

essential nesting habitat has declined along most rivers in the northern Great Plains due to dam 

construction, channelization projects, altered flow regimes, and reduced sediment loads (Ziewitz 

et al. 1992). The Niobrara River is one of the least modified rivers in the northern Great Plains 

that currently supports breeding populations of both species (Adolf 1998) (Fig. 30). Most nests 

are found downstream of the scenic river where open sandbar habitat is more common. 

Figure 30. Interior least tern and piping plover distribution by county in Nebraska (Source: Nebraska 

Game and Parks Commission 2007). 

Interior least tern (left) and piping plover (right), 

photos by Nebraska Game and Parks Commission 
59

Figure 31. Interior least tern and piping plover observation points within Niobrara National Scenic River 

(Source: Blausey 2002, 2003, 2004). 

In 1975, the Nebraska Game and Parks Commission began annual monitoring of the Niobrara 

River (confluence with the Missouri River [river mile 0] to Norden Bridge [river mile 120]) for 

adult interior least terns and piping plovers (Wingfield 1978, Wingfield 1984). In 1991, 1996, 

2001, and 2006, the International Piping Plover Census (IPPC) coordinated the monitoring of 

both species on the Niobrara River and elsewhere in the Great Plains (Ferland and Haig 2002, 

Lott 2006). The IPPC monitoring includes areas within the scenic river boundary (Fig 31). 

Counts of adults of both species on the Niobrara River have varied considerably among 

monitoring years (Lott 2006, National Park Service, S. Wilson, natural resource specialist, 

personal communication, 25 September, 2007) although numbers appear to increase over time 

(Adolf et al. 2001) (Fig. 32). In 2002, the scenic river began systematic annual monitoring of 

adults and nests of interior least terns and piping plovers usually from Norden Bridge to the 

Highway 137 Bridge. As with the IPPC monitoring, counts of adults of both species in the 

scenic river boundary vary considerably from year to year whereas nests of both species appear 

to increase (Blausey 2002, 2003, 2004) (Fig. 33). 
60

1

 2005 count 

Figure 32. Interior least tern and piping plover adults counted on the Niobrara River (Source: Ferland and 

Haig 2002, Lott 2006, Jorgensen 2006). 

Figure 33. Interior least tern and piping plover adults and nests counted in the Niobrara National Scenic 

River (Source: Blausey 2002, 2003, 2004; National Park Service, S. Wilson, natural resource specialist, 

personal communication, 25 September, 2009). 

In 1996 and 1997, a study was conducted over the same Niobrara River reach as the IPPC 

monitoring to determine the reproductive success of interior least terns and piping plovers (Adolf 

et al. 2001). Average clutch size, nest success, hatching success, and fledgling success for both 

species on the Niobrara River were similar to the findings of other researchers for these species 

along the central Platte River Valley in Nebraska (Lingle 1988) and the Missouri and Cheyenne 

0

5

10

15

20

25

30

2001 2002 2003 2004 2005 2006 2007

Number of Adults

Piping plover Least tern

0

5

10

15

20

25

30

35

2002 2003 2004 2005 2006

Number of nests

Piping plover Least tern

97

291

321

150

2891

92

162

107

87

207

0

50

100

150

200

250

300

350

1981 1991 1996 2001 2006

Number

Least Tern Piping Plover
61

Rivers in South Dakota (Dirks 1990, Kruse 1993). In addition, the reproductive success of both 

species on the Niobrara River compared favorably to that of the Gavins Point reach of the 

Missouri River where piping plover nests are protected by cages and numerous nesting islands 

were roped off to restrict visitor access (Adolf et al. 2001) (Table 21). 

Most interior least tern and piping plover nests are destroyed by predators (Dirks 1990, Kruse 

1993), flooding (Lingle 1993), and humans. Predators and flooding cause some of the nest 

losses on the Niobrara River but sandbar erosion and human interference are also substantial 

factors (Adolf et al. 2001). In the summer, decreased flows and reduced sediment transport 

cause sandbars to erode which results in loss of nest sites and forage habitat for chicks (Adolf et 

al. 2001). Humans, usually not maliciously, destroy nests and chicks by stepping on them, 

dragging their canoes/tubes over them, and keeping adults away from the nests letting eggs and 

chicks chill or overheat (Tern and Plover Conservation Partnership, M. Bomberger Brown, 

coordinator, personal communication, 11 October, 2009). 

 

This indicator is in good condition and improving based on monitoring results which document 

increasing numbers of tern and plover nests in the scenic river and high reproductive success for 

both species on the Niobrara River. However, reduced stream flow (see Stream Flow Indicator), 

invasive plants (purple loosestrife), recreation (all-terrain vehicle use), and livestock pose serious 

long-term threats to both species. 

Table 21. Comparison of piping plovers and interior least terns average clutch size and nest, hatching, 

and fledgling success between the Niobrara and Missouri Rivers in 1996 and 1997 (Source: Adolf et al. 

2001). 

Piping Plover Least Tern 

1996 1997 Combined 1996 1997 Combined 

Average clutch sizea 

 Niobrara River 3.58 3.75 3.64 2.51 2.68 2.57 

 Missouri River 2.90 3.79 3.21 1.93 2.40 2.16 

 Gavins Point Reach 2.43 3.74 3.05 1.89 2.55 2.27 

Nest success (%)bc 

 Niobrara River 32.00 39.70 34.71 53.50 49.60 52.00 

 Missouri River 18.00 45.70 27.78 13.10 50.00 31.49 

 Gavins Point Reach 00.00 58.06 27.27 5.83 52.86 32.92 

Hatching success (%)d 

 Niobrara River 35.30 39.20 36.70 54.60 49.40 52.55 

 Missouri River 19.41 43.77 29.56 13.97 51.27 34.57 

 Gavins Point Reach 00.00 54.31 31.34 4.62 55.18 37.32 

Fledgling success (%)e 

 Niobrara River 23.40 55.00 35.66 32.30 44.90 37.00 

 Missouri River 51.39 43.97 46.81 61.84 45.93 48.81 

 Gavins Point Reach 0.00 31.75 31.75 22.22 50.25 53.40 

a

Gavins Point Reach is a combination of the Lewis and Clark lake and Missouri River below the dam and does not 

include captive rearing data.

b

Total number of nests hatched/total number of nests initiated. c Nest success on the Missouri River and Gavins Point Reach was the result of multiple management techniques i.e., 

caging of nests, no management was done on the Niobrara River. d

 Percent of eggs hatched per 100 eggs per species. 

e Percent of chicks fledged per 100 eggs per species. 
62

Indicator: Purple Loosestrife

Source for Reference Condition: Maps of infestations in 2002 and 2008 

 

Originally introduced from Europe in the 1800's, purple loosestrife 

has spread across many parts of North America mostly through interconnected canals and road systems, populating many of North 

America's wetlands (Stuckey 1980). The species out-competes native 

vegetation and will eventually alter a wetland's structure and 

biogeochemical processes (Thompson et al. 1987, Fickbohm and Zhu 

2006). While purple loosestrife is considered an invasive species and 

has negative impacts on wetland communities, it is also an indicator 

of sandbar and wetland conditions. Ecologists and managers must 

assess loosestrife stands to determine if underlying factors such as 

nutrient pollution and hydrological alteration have stressed native 

plants and allowed loosestrife to invade before attempting control and 

restoration (Kiviat 1999). 

In the central Niobrara River Valley, purple loosestrife occurs along portions of the scenic river, 

inhabiting sandbars and other wetland areas (Narumalani and Swain 2009). In 2008, purple 

loosestrife in the scenic river was quantified and mapped using hyperspectral airborne remote 

sensing data and geographic information technology (Fig. 34). Previously, in 2002, distribution 

of the species was mapped by ground survey crews (Fig. 35). The Middle Niobrara Weed 

Awareness Group (see http://www.mnwag.org/content/view/14/27/) administers a cooperative 

weed management effort within the scenic river corridor, and has funded biological and chemical 

control projects. Comparison of purple loosestrife stands in 2008 with those in 2002 suggest that 

biocontrol measures have been successful in reducing the area infested by purple loosestrife by 

as much as 80 percent in some areas (Narumalani and Swain 2009) (Fig. 36). 

This indicator is in poor condition but improving based on the success of weed control efforts 

since 2002. While control measures, both biological and chemical, have proven to be effective 

in reducing or even eliminating purple loosestrife, it is important to recognize that invasion of 

this species in a particular wetland may be a manifestation of underlying stressors to the 

ecosystem. If these stressors persist, the species will invade new areas and re-invade those 

where control efforts were initially successful.

Purple loosestrife 
63

Figure 34. Purple loosestrife infested areas interpreted from hyperspectral imageries, Niobrara National 

Scenic River, 2008 (Source: Narumalani and Swain 2009).
64

Figure 35. Delineated purple loosestrife infested areas, Niobrara National Scenic River, 2002 (Source:

Narumalani and Swain 2009). 
Figure 36

and Swain

6. Effectivene

n 2009). 

ss of biological control, Nio

65

brara National Scenic River, 2008 (Source: Narumalani 
66

Indicator: Whooping Crane 

Source for Reference Condition: Not Established 

 

The whooping crane is the rarest of the world’s crane species and is 

federally endangered in the United States and Canada (Canadian 

Wildlife Service and U.S. Fish and Wildlife Service 2007). The 

species was listed because of low population numbers, low 

reproductive potential, cyclic nesting and wintering habitat suitability, 

a hazardous 4,000-km (2,492 -mile) migration in the central Great 

Plains that is traversed twice annually, and many human pressures on 

the wintering grounds. Currently, the only self-sustaining, wild 

population consists of 215 individuals (2006 count) that nests in Wood 

Buffalo National Park and adjacent areas in Canada, and winters in 

coastal marches in Texas (Fig. 37). This population is threatened by 

collisions with power lines and fences, shooting, predators, disease, 

habitat destruction, severe weather, and loss of genetic diversity. 

From 60 to 80 percent of the annual mortality in the wild population 

occurs during migration, a time when cranes are exposed to manmade 

hazards such as utility lines. Whooping cranes begin migrating in late March reaching 

Figure 37. Breeding and wintering areas and primary migration pathway of the whooping crane (Source: 

Canadian Wildlife Service and U.S. Fish and Wildlife Service 2007). 

Whooping crane 
67

the nesting grounds in 2–4 weeks; the fall migration is protracted with most birds arriving on the 

wintering grounds by mid-November (Canadian Wildlife Service and U.S. Fish and Wildlife 

Service 2007). Whooping cranes are diurnal migrants that make regular stops to feed and roost. 

During migration, whooping cranes prefer to feed in freshwater marshes, wet prairies, and 

shallow portions of rivers, lakes, and reservoirs. They typically roost on unvegetated or 

submerged sandbars in wide, unobstructed channels that are isolated from human disturbance 

(Armbruster 1990). In Nebraska, whooping cranes often are recorded feeding and roosting in 

riverine habitats, especially the central Platte River bottoms (designated as critical habitat) and 

the central Niobrara River Valley (Canadian Wildlife Service and U.S. Fish and Wildlife Service 

2007) (Fig. 38). 

The number of sightings of whooping cranes on the central Niobrara River Valley has increased 

in recent years although most preferred feeding and roosting habitat (i.e., sandbars in shallow 

water) occurs downstream in the wider reaches of the river (Johnsgard 2007). In Nebraska, 

confirmed whooping crane sightings when compared with roosting habitat, suggest that 

whooping cranes select roosting sites by recognizing local and larger-scale land cover 

composition (Richert 1999). However, the availability of roosting sites with these characteristics 

in the central Niobrara River Valley, and specifically in the scenic river, is not known. As much 

as 97 percent of the suitable crane (whooping and sandhill) roosting habitat has been lost in some 

segments of the Platte River in Nebraska as a result of encroachment of the channel by woody 

vegetation following diversion and storage of water for irrigation and power generation (U.S. 

Fish and Wildlife Service 1981). Reductions in stream flow of the Niobrara River (see Stream 

Flow Indicator) may have a similar affect on the availability of roosting and feeding habitat for 

migrating whooping cranes. This indicator is not assessed due to the lack of site-specific 

information on habitat availability and use. 

Figure 38. Whooping crane migration pathway in Nebraska (Source: Platte River Whooping Crane 

Maintenance Trust, Inc. 2009).
68

Indicator: Sediment Transport

Source for Reference Condition: Not Established 

The Niobrara River downstream from Norden, Nebraska—within 

the scenic river—to its confluence with the Missouri River is 

characterized by a braided, sand-bed channel with a relatively 

steep gradient varying from about 5.3 m/km (9 ft/mile) upstream 

to about 3.4 m/km (7 ft/mile) downstream (Buchanan and 

Schumm 1990). The braided pattern and steep gradient are 

indicative of a very high sediment load. The long-term average 

annual total sediment load of the Niobrara River is 

approximately 2.9 million tons of which about 2 million tons is 

sand (Livesey 1976). 

River processes, including sediment transport, are influenced by climate, geology, and vegetation 

and land use conditions of the watershed and riparian zone (Inglis 1993). With reduced flows of 

the Niobrara River due to water diversion and withdrawal (see Stream Flow Indicator), 

aggradation features may dominate river processes leading to widening of the channel, increased 

tendency of the river to meander, and decreases in gradient resulting in reduced flow velocities 

and sediment transport (Inglis 1993). A recent hydrogeomorphic analysis of the Niobrara River 

found that flow velocity changes were the primary hydraulic adjustment to discharge changes 

(Alexander et al. 2009). This study did not address the affects of changes in discharge on 

sediment transport or, more specifically, the affects on sandbar erosion and creation. Thus, this 

indicator is not assessed. 

Niobrara River, photo by 

National Park Service 
69

Stressors and Management Strategies

The scenic river’s long, narrow corridor and limited conservation ownership in the watershed 

makes it highly susceptible to stressors originating from adjacent lands (Fig. 39). The major 

stressors and management strategies emerging from this condition assessment follow: 

Figure 39. Niobrara National Scenic River conceptual diagram: existing and possible relationship of 

stressors to biodiversity and process indicators. 
70

Water diversion and withdrawal 

With the completion of the Merritt Dam in 1965, water diversions from the Niobrara River 

increased significantly, and have altered its runoff hydrology (i.e., decreased flows) 

(Istanbulluogla 2008) and may impact ecological processes and biota (Alexander et al. 2009). In 

addition, the use of center-pivot irrigation in north-central Nebraska has increased substantially 

over the last three decades (Fig. 40). As of December 31, 2004, a total of 6,822 ground water 

wells and an additional 837 surface water appropriations were registered in the lower Niobrara 

River Basin, a surface drainage area that includes the scenic river (Nebraska Department of 

Natural Resources 2004). A majority of these wells and surface water appropriations are for 

crop irrigation. Groundwater withdrawal from center-pivot use also contributes to decreased 

flows. In response, in January 2008, the State of Nebraska determined that ground and surface 

water within the Niobrara Basin is fully appropriated and placed a moratorium on the issuance of 

new surface water permits (Alexander et al. 2009). 

 

(a) 

 

(b) 

 

Figure 40. Center-pivots located within 16 km (10 miles) of the Niobrara National Scenic River in 1975 (a) 

and 2005 (b) (Source: Remote Sensing Center 1976, Center for Advanced Land Management 

Information Technologies 2006). 
71

Management strategy should 

• Conduct research to assess the effects of groundwater diversions and withdrawals on 

Niobrara River flow, physical and ecological processes, and biota. 

• Pursue in-stream flow rights to protect recreational and fish and wildlife resources. 

• Investigate the effects of the possible removal of Cornell Dam on river hydrology and 

sediment transport.

• Monitor river flows from U.S. Geological Survey gauge data.

Water Quality Degradation 

During 2004 and 2005, reaches of the Niobrara River were sampled and no significant water 

quality concerns were identified from the assessment data (Troelstrup 2006). Similar results 

were documented in 2003–2005 when water quality data was collected from three sites on the 

Niobrara River and one site on Minnechaduza Creek (Dietsch 2008). However, forty-five of 51 

samples collected exceeded the EPA recommendation of 0.1 mg/L phosphorus for avoiding algal 

blooms. Also, E. coli was detected in all of the collected samples, however only two exceeded 

the density of 298 colonies/100 ml which is the standard for streams designated as moderately 

used recreational water. Given that these were individual sample collections rather than repeated 

samples, they do not necessarily indicate that E. coli exceeded the water quality standards for 

Nebraska (Dietsch 2008). 

Three tributaries of the Niobrara River—Berry Falls, Fort Falls, and Smith Falls—were also 

sampled during 2004 and 2005 (Troelstrup 2006). All three had low turbidity and good levels of 

dissolved oxygen. However, mean fecal coliform values for Berry Falls exceeded the standard 

(200/100 ml), while Smith Falls had individual readings exceeding the standard. Total 

phosphorus concentrations were also elevated in all three tributaries, although they did not 

violate the standard. These impacts may be the result of spring branch hiking (see Spring Branch 

Hiking, this section). 

Management strategy should 

• Monitor aquatic habitat and macroinvertebrates in the Niobrara River and its tributaries.

• Monitor physical and chemical water quality parameters of the tributaries to the Niobrara 

River.

Visitor River Floating 

Recreation occurs on the entire length of the Niobrara River but floating (i.e., canoeing, tubing, 

and kayaking) dominates use on a 48-km (30-mile) stretch of the scenic river just east of 

Valentine, Nebraska (Shultz 2009). Several factors contribute to the scenic river being a major 

recreation resource including, season-long flows with adequate water depth for floating, clear 

water, a hard rock streambed, scenic values including high landform and plant diversity, and 

easy river access with riverfront camping opportunities (Shultz 2009). In addition, the scenic 

river is a single site destination for visitors because of the absence of comparable rivers with 

similar recreation opportunities in the region (Shultz 2009). Possibly due to the promotion of 

these amenities by a mix of federal, state, and private landowners, floater days on the scenic river 

increased by 8.5 percent per year from about 36,000 in 2005 to over 46,000 in 2008 (Fig. 9). 
72

About 70 percent of these river activities occur during July and August, with the greatest use on 

Saturdays when as many as 800 canoes are on the river (Johnsgard 2007). 

In 2000, bird communities in riparian forest along the Niobrara River that were exposed to river 

recreation were compared to communities in riparian forest lacking recreation to determine if 

recreation activities altered bird community composition and spatial distribution and the flushing 

behavior of waterbirds. No apparent shift in bird species composition or spatial distribution was 

observed (at recreation use levels of 15,000 to 18,000 people) (Anderson et al. 2000). However, 

waterbirds responded by moving away from areas with recreational noise and were more than 

twice as common in areas where river use was not allowed. The interior least tern and piping 

plover are not likely affected as their nesting sites are not in a river reach that is primarily used 

for recreational floating. However, spiny softshell turtles may be vulnerable to recreational 

impacts because their peak daily activity period occurs during the daytime when recreational use 

is highest and because they utilize basking and nesting sites in areas of high human use (Allen 

2008). In addition, expansion of river otters into the scenic river may be curtailed as they avoid 

areas of high human use. 

Management strategy should 

• Continue to estimate annual river recreation use.

• Determine the effects of human recreation activities on the spiny softshell turtle in terms of 

population recruitment, home range, and energy expenditures.

• Document river otter presence; if present, determine individual habitat use and movement. 

Purple Loosestrife Infestation 

Purple loosestrife is an invasive exotic plant believed to have been introduced to the northeastern 

United States by European settlers in the early 1800s (Stuckey 1980). Purple loosestrife can 

have a major negative impact on wetlands habitats resulting in reduced productivity of native 

plants and loss of biodiversity. Currently, the species is documented in 40 states including 

Nebraska with the most severe infestations occurring around the Great Lakes and in the 

northeast. The species is a prolific seed producer – each plant can produce up to two million 

seeds. Seeds are spread by wind, water, birds, and people. 

Based on a survey in 2001, about 12,000 acres of Nebraska’s wetlands are infested with purple 

loosestrife, mostly along the main rivers and waterways (Knezevic 2003) (Fig. 41). Purple 

loosestrife infests river shoreline flats and nearby wetlands along the central and lower Niobrara 

River (Fig. 41) where it has displaced native plants and impacts nesting sites for interior least 

terns and piping plovers and feeding and roosting sites for whooping cranes. Currently, The 

Nature Conservancy has initiated a biological control program on the Niobrara Valley Preserve 

by introducing Galerucella spp. beetles to control purple loosestrife. A National Park Service 

exotic plant management team has treated purple loosestrife in the scenic river with herbicides 

and biocontrol and is monitoring the effectiveness of those treatments. These efforts appear to 

be successful in reducing purple loosestrife infestations but the plant continues to invade new 

areas (Narumalani and Swain 2009). 
73

Management strategy should 

• Treat areas of purple loosestrife infestation and monitor results.

• Determine the effects of purple loosestrife encroachment on wildlife habitat and species. 

Figure 41. Purple loosestrife distribution in Nebraska (Source: Knezevic 2003). 

Woodland Expansion (Fire Suppression) 

Woodland expansion in and adjacent to the Niobrara River Valley has occurred since European 

settlement of the region (Steuter et al. 1990). This is most likely due to fire suppression resulting 

in longer fire-free intervals and a change in the grazing regime from free-ranging bison to 

confined cattle herds that reduces grass competition with pine seedling (Steuter et al. 1990). 

These changes have allowed ponderosa pine to establish patches in the grassland matrix 

(Steinauer and Bragg 1987). Eastern red cedar has also increased in woodland understory and 

spread into savanna and grassland from seeds spread by birds and cattle. As woodland increases, 

grassland and shrubland birds are replaced by woodland birds. 

Fire suppression has also impacted paper birch and hybrid aspen regeneration. Although 

historically, fire frequency in the spring branch canyons was very low, hot fires followed by 

below normal temperature likely occurred every 100–500 years which allowed abundant birch 

and aspen seed production and local seedling establishment (Steuter and Steinauer 1993). 

Management strategy should 

• Complete a comprehensive fire history of the scenic river and central Niobrara River 
74

Valley region.

• Measure woodland expansion along the entire length of the scenic river.

• Determine the status of remnant tallgrass prairie. 

• Support mechanical cedar thinning.

• Support the use of prescribed fire and the monitoring of fire effects by cooperating 

private and public land owners within the scenic river boundary.

• Determine the effects of eastern cedar removal (through prescribed fire and mechanical 

means) on Bailey’s eastern woodrat. 

Drought 

The Palmer Drought Severity Index was developed in the 1960s and uses temperature and 

precipitation in a formula to determine dryness. Index values range from 0 (normal) to -4 

(extreme drought). For the historic period (1895–1995), the scenic river was subject to severe 

drought (PDSI = -3) from 10 to 14.9 percent of the time period (Fig. 42). With reduced stream 

flow due to water diversion, drought impacts on river physical and ecological processes and 

biota may be more severe. Water diversions and drought may reduce river flows to levels not 

acceptable to river users (Shultz 2009). 

Management strategy should 

• Monitor drought occurrence in relation to river flows and sandbar development and 

persistence and possible affect on recreation use.

Figure 42. Palmer Drought Severity Index (Source: National Drought Mitigation Center 2008). 
75

Microclimate in Birch Stands

Summer maximum temperature in birch stands are within the tolerance range for the species and 

suggest that it should continue to persist at these sites. However, other climate factors besides 

summer maximum temperature can affect birch health, especially spring weather conditions 

(Stroh and Miller 2009). A key factor contributing to dieback may be increased frequency of 

thaw-freeze events over the past thirty years (Stroh and Miller 2009). 

Management strategy should 

• Stimulate birch seedling establishment via mechanical removal of surface litter and 

overstory canopy.

• Monitor birch stand condition and microclimate including the frequency of thaw-freeze 

events.

• Consider propagation and planting of birch seedlings into existing stands.

Spring Branch Hiking 

A majority of the scenic river’s visitors come to enjoy aquatic activities such as canoeing, tubing, 

kayaking, swimming, and fishing. While on the river, floaters often stop to visit several of the 

more than 230 waterfalls that occur on tributary streams. To reach the falls, visitors often must 

hike in the streambed itself. A study performed in the summer of 2006 (Laing 2008) 

investigated the effects of human disturbance (i.e. visitors walking in the streambed) on a 

number of tributaries to the Niobrara River within the scenic river boundary. The 

macroinvertebrate communities in disturbed streams showed declines in both the total number 

(abundance) and types (richness) of organisms compared to undisturbed streams (Fig. 43). 

Sensitive species were lost as the physical disturbance increased. However, in general, the 

macroinvertebrate communities in disturbed streams appear to recover after the fall, winter, and 

early spring when visitor use is low (Laing 2008). 

Management strategy should 

• Collect additional years of physical disturbance data to provide insights regarding longterm effects on invertebrates, as well as on periphyton.

• Monitor aquatic macroinvertebrates; restrict visitor use if impacts persist.
76

Figure 43. Mean aquatic macroinvertebrate EPT richness and abundance in disturbed and undisturbed 

tributaries within Niobrara National Scenic River (Source: Laing 2008). 

Other existing or potential stressors identified through this condition assessment include: 

Leafy Spurge Infestation 

Leafy spurge is an invasive plant that infests over three million acres in the northern Great 

Plains. In Nebraska, leafy spurge currently infests at least 793,184 ha (321,000 acres) mostly in 

the northeast and north central parts of the state (Masters and Kappler 2002) (Fig. 44). It is 

widespread in the scenic river region (Johnsgard 2007). Leafy spurge reproduces by both seed 

and by adventitious shoot buds. Effective seed dispersal mechanisms (animals and humans), 

high seed viability, and rapid seedling development lead to new infestations. Prolific vegetative 

reproduction maintains dense, long-lived infestations that reduce or eliminate native plant 

diversity. 

Common Reed Infestation 

The non-native common reed, which was introduced from Europe in the 1800s, is distributed 

across the United States and southern Canada. Over the past several decades, populations of the 

plant have increased in freshwater and brackish wetlands. Once established, populations can 

expand rapidly to form dense, monoculture stands that reduce plant species diversity and create 

unsuitable habitat for wildlife including migrating wading birds and waterfowl. In Nebraska, the 

most problematic infestations of the species are along the Niobrara, Platte, and Republican rivers 

(Knezevic 2008) (Fig. 45). 

0

5

10

15

20

25

EPT Richness

Disturbed Undisturbed

0

10

20

30

40

50

60

70

Abundance

Disturbed Undisturbed
77

Figure 44. Leafy spurge distribution in Nebraska (Source: Masters and Kappler 2002). 

Figure 45. Common reed distribution in Nebraska (Source: Knezevic et al. 2008). 
78

Mountain Pine Beetle Infestation 

The mountain pine beetle (Dendroclonus ponderosae) is native to the forest of western North 

America, but was not known to occur in Nebraska until the summer of 2009 when adult beetles 

were found at several locations in the panhandle of the state (Institute of Agriculture and Natural 

Resources 2009). The beetle attacks and kills all species of pine, although ponderosa pine is 

more resistant. Based on the spread and effect of the beetle in the Black Hills over the past ten 

years, dense stands of ponderosa pine in Nebraska’s Pine Ridge are at risk. In the future, the 

mountain pine beetle may spread to increasingly dense stands of ponderosa pine in the scenic 

river region. 

Emerald Ash Borer Infestation 

In 2002, the emerald ask borer (Agrilus plaipennis), an exotic beetle from Asia, was discovered 

in southeastern Michigan (Cooperative Emeral Ash Borer Project 2009). Since its discovery, the 

species has killed millions of ash trees and is now known from Illinois, Indiana, Ohio, 

Pennsylvania, Maryland, West Virginia and Ontario, Canada (Fig. 46). The emerald ash borer is 

spread primarily through the transport of infected nursery stock and firewood. 

Experts believe it is only a matter of time before the species is found throughout eastern and 

central North America. In the Great Plains, green ash dominates riparian ecosystems, native 

forests, woodlots and conservation plantings, such as windbreaks (U.S. Department of 

Agriculture 2008) (Fig. 47). In the scenic river, green ash is one of the dominant trees of the 

riparian hardwood forest which is considered an outlier of the eastern deciduous forest 

(Johnsgard 2007). This riparian forest exhibits the greatest vertebrate diversity of any of the 

habitats in the central Niobrara River Valley (Beed 1936). With the invasion of the borer and the 

subsequent die-off of ash, changes in the riparian plant community would undoubtedly affect the 

resident wildlife. 

Management Strategy should 

• Map and treat infestation of leafy spurge and common reed. 

• Track the spread of mountain pine beetle in western Nebraska. 

• Participate with the State of Nebraska and U.S. Department of Agriculture in efforts to 

detect ash borers in Nebraska. 
79

Figure 46. Emerald ash borer locations in the United States and Canada (Source: Cooperative Emerald 

Ash Borer Project 2009). 

Figure 47. Percent of ash trees to total tree resources (Source: U.S. Department of Agriculture 2008). 

81

Conclusion 

The overall condition and trend of each major habitat in the scenic river is based on a subjective 

appraisal of the condition and trend of its indicators. They follow: 

Niobrara River and Tributaries 

The Niobrara River and tributaries habitat is in good condition. Annual and daily decreases in 

stream flows have occurred following operation of the Merritt Dam in 1965, but water quality of 

the river is generally good based on the presence of pollution intolerant aquatic 

macroinvertebrates and the results of chemical water quality sampling. The fish community 

remains species diverse and stable. Furthermore, recreation use of the river continues to 

increase. This suggests that although flows have decreased, these changes have not as yet 

impacted water quality, important biota, or recreation. However, the population status of spiny 

softshell turtles, a species sensitive to stream flow variations, is not known. Concern about 

possible future impacts of reduced stream flows has lead the State of Nebraska to impose a 

moratorium on issuing new surface water permits in the Niobrara River basin. 

Water quality in Niobrara River tributaries is also good. However, visitors hiking in the 

streambed of several of the tributaries has led to the seasonal loss of some aquatic species 

although these species tend to recover during periods of low visitor use. Several of the tributary 

streams have populations of rare cool-water fishes although the status and trend of these 

populations is unclear due to inconsistent monitoring. 

Upland Forest and Savanna 

The upland forest and savanna habitat is in poor condition and deteriorating, largely due to the 

increased density of ponderosa pine and eastern red cedar; and the spread of these species from 

protected sites into savanna and open grassland. This is a result of a longer fire return interval 

that followed almost complete fire suppression beginning around 1900. Dense stands of pine 

and cedar are prone to crown fire and insect attack. A land cover change analysis that compared 

land classes between 1992 and 2001 did not detect an increase in woodland, but that may be due 

to the short time span between the dates used in the analysis. In contrast, elk are increasing in 

this habitat and in grassland due to the availability of suitable habitat and increased landowner 

tolerance. 

Spring Branch Canyon and Riparian Forest 

The Spring Branch Canyon and Riparian Forest habitat is in poor condition and deteriorating 

based on the condition and trend of its two major indicators—paper birch and hybrid aspen. 

Both of these species require sheltered microhabitats for persistence, and disturbance for 

seedling establishment and root sprouting. Long-term persistence of these species is in doubt 

considering recent changes in microclimate (increased thaw-freeze conditions) and lack of 

natural disturbance. In addition, the possible infestation of this habitat by the emerald ash borer 

would remove green ash, a dominant tree, and have secondary adverse effects on the diverse 

wildlife of the habitat. In contrast, Bailey’s eastern woodrat is in good condition and may have 

benefited from an increase in eastern red cedar, a primary food source of the woodrat. Bird 

hybridization rates and areas of sympatry may also indicate changes in this habitat, but temporal 

data are lacking. 
82

Grassland 

The Grassland habitat is in good condition in the central Niobrara River Valley region and has 

benefitted from the planting of native grasses in former crop fields. However, it is deteriorating 

in upland areas near the river. This is the result of fire suppression and the resulting invasion of 

grassland by ponderosa pine and eastern red cedar. Cedar invasion of grassland causes a 

decrease in overall bird species richness and shifts in species composition from grassland and 

shrubland to woodland and forest birds. A land cover change analysis found an increase in 

grassland/shrub from 1992 to 2001. This increase may be the result of conversion of agricultural 

fields to grassland which may have masked a small loss of native grassland to invading trees. 

Leafy spurge, an aggressive exotic, is widespread in this habitat but its site-specific impacts are 

unknown. The free-ranging elk population is increasing. 

 

Sandy Shorelines, Sandbars, and Wetlands 

The Sandy Shorelines, Sandbars, and Wetlands habitat is in good condition and stable based on 

the interior least tern and piping plover and purple loosestrife indicators. The number of adult 

terns and plovers counted on the Niobrara River has increased in recent years, however, past 

monitoring has shown population numbers to be highly variable. The nesting and foraging 

habitats of these species in the scenic river may be affected by reduced stream flow, reduced 

sediment transport, and exotic plants, especially purple loosestrife and common reed. In recent 

years, biocontrol has reduced purple loosestrife infestations by as much as 80 percent in some 

areas, but common reed may have increased in extent and density. Migrating whooping cranes 

appear to be using this habitat in greater numbers but this may be an artifact of greater public 

awareness. 

A variety of existing data sources were used to assess the condition and trend of the five major 

habitats in the scenic river. Most important were inventory and analysis of gauge records of 

stream flow, inventory and assessment of paper birch and hybrid aspen, and assessment of water 

quality based on aquatic macroinvertebrates. Also important were a number of inventories (e.g., 

birds) that were initiated in the 1970s to assess the environmental impacts of the proposed 

Norden Dam. Several of the habitat indicators were suggested by research, including studies of 

paper birch decline, elk demography, woodland expansion into grassland, and visitor impacts on 

water quality of tributary streams. Currently, resource monitoring by the scenic river is limited 

primarily to water quality, rare species (i.e., interior least terns and piping plovers), and 

recreational use. In the future, monitoring protocols being developed by the Northern Great 

Plains Inventory and Monitoring Network will include upland and riparian plant communities. 

In addition, inventories and/or monitoring in cooperation with the Nebraska Game and Parks 

Commission should be considered for river otter, cool-water fishes, fish community, spiny 

softshell turtle, elk, and Bailey’s eastern woodrat. Important research needs include recreation 

impacts on spiny softshell turtles, reduced stream flow impacts on river morphology and biota, 

changes in bird hybridization rates and locations, and impacts of existing and potential invasive 

plants and insects. 
83

Table 22. Habitat conditions and trends. 

Habitat

% of 

park 

area 

Condition and trend of habitat indicators Condition and 

trend of habitat 

Niobrara river and 

tributaries 36 

Aquatic macroinvertebrates 

River otter 

Cool-water fishes 

Fish community 

Spiny softshell turtle 

Stream flow 

Upland forest and 

savanna 

35 

Elk 

Ponderosa pine 

Land cover 

Fire 

Spring branch 

canyon and riparian 

forest 

10 

Paper birch 

Hybrid aspen 

Bailey’s eastern woodrat 

Bird hybridization 

Grassland 8 

Grassland birds 

 Sand Hills prairie 

Land cover 

Fire 
84

Table 22. Habitat conditions and trends (continued). 

Habitat % of 

park 

area 

Condition and trend of habitat indicators Condition and 

trend of habitat 

Sandy shorelines, 

sandbars, and 

wetlands 10 

Least tern and piping plover 

Purple loosestrife 

Whooping crane 

Sediment transport 

Note: Green box = good condition; Red box = poor condition; Open box = no assessment; Upward arrow 

= improving; Downward arrow = deteriorating; Horizontal arrow = stable; and No arrow = no or insufficient 

data to determine trend. 
85

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Appendix A: Sampling design and data analysis1

Habitat Indicator Source Metric Statistic/test 

Niobrara River 

and tributaries 

Aq. macroinvert. Rust 2006 EPT richness; HBI mean; std 

dev/ANOVA 

Fish community Gutzmer 2002 CPUE mean/ANOVA 

Stream flow Wen and Chen 

2006 

annual flow mean/MannKendall test 

Stream flow Istanbulluoglu 

2008 

daily discharge mean/t-test 

Upland forest and 

savanna 

Ponderosa pine Guyette 2005 fire interval mean/K-S test 

Spring branch 

canyon and 

riparian forest 

No studies 

Grassland Grassland birds Frost 2007 density mean/conf.int. 

Fire Guyette 2005 fire interval mean/K-S test 

Sandy shorelines, 

sandbars, and 

wetlands 

No studies 

1 only Indicator studies that have statistically compared data for reference and existing conditions are 

shown 

99

Appendix B: GIS data sources for Niobrara National Scenic River 

Figure Type Year Produced Producer Description 

1 Shapefile 2009 CALMIT1 Location map of scenic river 

along the Niobrara River 

6 Shapefile 2009 CALMIT Niobrara River watershed 

from US EPA 

8 Shapefile 2009 CALMIT, Adapted from 

Dietsh 2008 

Fish observations derived 

from sample points. 

11 Shapefile 2009 CALMIT, Adapted from 

Rust 2006 

Aquatic macroinvertebrate 

sampling sites. 

16 Shapefile 2009 CALMIT, Adapted from 

Schainost 2008 

Location of cool-water fish 

sampling sites in tributary 

streams. 

17 Shapefile 2009 CALMIT, Adapted from 

Istanbulluoglu 2008 

Location of nine streamflow 

gauges in or near the scenic 

river. 

23 Shapefile 2009 CALMIT Change in woodland 

vegetation interpreted from 

historic aerial photography 

24 Shapefile 2009 CALMIT Change in woodland 

vegetation interpreted from 

historic aerial photography 

25 Grid 2008 USGS Land Cover change as 

produced by the USGS using 

NLCD 1992 and 2001 Retrofit products 

26 Shapefile 2009 CALMIT, Adapted from 

Stroh and Miller 2009 

Sampling locations of paper 

birch along the Niobrara 

River. 

27 Shapefile 2009 CALMIT, Adapted from 

Shepperd 2008 

Observation points of hybrid 

aspen. 

31 Shapefile 2009 CALMIT, Adapted from 

Blausey 2002, 2003, 

2004 

Interior least tern and piping 

plover observations. 

34 ENVI2 2009 CALMIT, Narumalani 

and Swain 2009 

Areas of purple loosestrife 

infestations interpreted from 

hyperspectral imagery. 

35 ENVI 2002 NPS Areas of purple loosestrife 

infestation delineated by NPS.

36 ENVI 2002, 2008 CALMIT, NPS Effectiveness of biological 

control on a selected area of 

the scenic river. 

38 Shapefile 2009 CALMIT, Adapted from 

Platte River Whooping 

Crane Maintenance 

Trust, Inc. 2009 

Depiction of whooping crane 

migration pathways. 

42 Shapefile 2008 NDMC3 2008 Historical Palmer Drought 

Severity Index 1895-1995 

1 Center for Advanced Land Management Information Technologies 

2 Environment for Visualizing Images 3

 National Drought Mitigation Center

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