United States        Office of           Office of
Environmental        Besearch and      Water
Protection Agency    Development

EPA/822/F-97/003April 1997

 Backwater area. Side channels and backwaters
 provide breeding habitat and refuge for fish and
 amphibians and contribute to the biodiversity of
 the floodplain. 'fhese important ecosystems are
 formed as the river migrates across the floodplain
 during high flow periods. Lower flows caused
 by diversions primarily to support agricultural
 production facilitate conversion of these areas to
 woodlands and often to cropland.
R  A
What is an ecological risk assessment

      n ecological risk assessment evaluates the poten-
      tial adverse effects of human activities on the
     I plants and animals that make up ecosystems.
The risk assessment process provides a way to develop,
organize and present scientific information so that it is
relevant to environmental decisions. When conducted
for a particular place such as a watershed, the ecologi-
cal risk assessment process can be used to identify
vulnerable and valued resources, prioritize data collec-
tion activities, and link human activities with their
potential effects. Risk assessments provide a focal
point for cooperation among local communities and
state and federal government agencies, and a basis for
comparing different management options.
COVER PHOTO: 'Nebraska. Game & Parks Commission
COVER: The middle Platte River valley has hemispherical significance as a staging
area for migratory water birds. The region is best known for the nearly one-half million
sandhill cranes (cover photo) and several million ducks and geese that migrate annually
through the region. Approximately 50 species of mammals and 300 species.of'migratory
birds use the woodlands, grasslands and wet meadows in the Platte River valley.

Why is the middle Piaite Stiver special?
     he Platte River flows eastward across Nebraska
     providing water for irrigation, electric power,
     recreation, fish, wildlife, and community and
industrial water supplies. The middle segment of this
river has national and international environmental
importance. It is the major staging (resting)  area for
one-half million sandhill cranes and several million
ducks  and geese that migrate annually through the
             :             area. Many other species of
                          mammals, birds and fish
                          including six endangered
                          or threatened fish and
                          bird species  (such  as the
                          whooping crane) use the
                          water, woodlands,  remain-
                          ing native grasslands and
                          wet meadows in the middle
                          Platte River valley. Surface
                          and groundwater flows
                          from this segment of the
Platte Elver system .are also important to the econom-
ic stability of central Nebraska by irrigating about two
million acres of land, mostly for corn production.
The middle
segment of the
Platte River flows
266 km (165
miles) from the
confluence of
the North and
South Platte
Rivers, in western
Nebraska, to its
confluence with
the Loup River.
 Many resident and migratory birds require open sandbars and shallow
 water for nesting and roosting. Reduced river flows have changed the
 characteristics of the river, allowing shrubs and trees to colonize sand-
 bars (as depicted in the photograph), forming islands surrounded by
 deep water, thus 'decreasing critical habitat for these birds.

Key stressors beiiig
evaluated in the.
r..-..^.^r/.'S^&";'fflv<:V>-i-S" .v>?
 risk assessment brought together numerous organiza-
 tions to analyze the impact of stressors on these
 habitats and the wildlife populations in the watershed.
 A report describing the management goals for the
 Middle Platte River watershed and the analysis plan
 for the assessment will be available upon completion
 of the analysis described above.

 How will the results be used?
     ihe middle Platte River Ecological Risk
     Assessment will help resource managers predict
     how potential changes in land use and river
 flow could affect the biological communities in the
 watershed. This will enable resource managers to
 make decisions based on more information. This
 project is co-sponsored by the USEPA's Office of
 Water and Office of Research and Development as
 an effort to bring the science of risk assessment into
 the local community decision-making process.
The U. S. Environmental Protection Agency thanks the following
for their participation in this assessment effort:

   Central Nebraska Public Power and Irrigation District
   Nebraska Public Power District
   Nebraska Department of Environmental Quality
   Nebraska Natural Resources Commission
   Central Platte Natural Resources District
   Nebraska Game and Parks Commission
   Tri-Basin Natural Resources District
   Nebraska Department of Agriculture
   The Nature Conservancy
   Prairie Plains Resources Institute
   Platte River Whooping Crane Maintenance Trust
   University of Nebraska  Lincoln and Kearney
   US Fish and Wildlife Service
   US Geological Survey
   US Department of Agriculture

For more information, contact
   Robert Fenemore (WWPD)
   US EPA Region VII
   726 Minnesota Avenue
   Kansas City, KS 66101
   (913)  551-7745