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At present (1999) there are eight project elements.
These eight elements are as follows:
Element 1. -- Database Development
Element 2. -- Factors Influencing Sandhill Crane Health and Distribution
Element 3. -- Surficial Geology and Geochronology
Element 4. -- Channel Characteristics and Morphology
Element 5. -- Sediment Transport Modeling
Element 6. -- Wet Meadow Hydrology, Biotic Resources, and Environmental Factors
Element 7. -- Habitat Use and Requirements of Spring-Staging Migrant Waterfowl
Element 8. -- Evaluation of Anthropogenic Manipulations of Hydrology, Channel, and
Habitat for Ecosystem Improvements
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Element 1. -- Database Development
Development of a database containing integrated information on the geology, hydrology,
ecology, geography, and socioeconomic factors of the project area is a continuing
effort of this study element. The intent is to make integrated spatial
database products available to the Department of the Interior and other clients who are concerned
with natural resource management of the central Platte River.
The database will use a logical design based on the spatial, temporal,
and thematic characteristics of the data. There will be a continued focus on identifying
and cataloging specific data sets for inclusion in the project database. It is important
to provide access to the database through the Internet to satisfy cooperator
needs. This element also involves continuing to catalog and display of aerial
photographs and videographs that have been obtained at least yearly by the U.S. Fish and
Wildlife Service and the Bureau of Reclamation over the last several decades. Project-specific
data collection within the other study elements will need to be incorporated into the data base,
which will incorporate study data for surficial geology, channel morphology, groundwater,
river stages, soils, plant community composition, and migratory bird populations.
Element 2. -- Factors Influencing Sandhill Crane Health and Distribution
The Platte River Valley of Nebraska is the principal spring staging area for sandhill cranes in
North America and has the largest gathering of cranes in the world. Information collected in
recent years suggests a marked decline in the capacity of both adult and juvenile sandhill cranes to acquire
nutrient reserves needed for migration and reproduction.
The area of the river used by cranes has also declined over time. These changespotentially have major implications regarding the status of the midcontinent population and the
whooping crane, which occupies similar habitats. Included in this element are studying the magnitude of change in
the rate and total amount of nutrient storage among juvenile and adult sandhill cranes, investigating
proximate factors responsible for the change in condition, and determining whether condition the status
is correlated with status of local wet meadows, cropland, or channel. This element will document
the current distribution of sandhill cranes in the Platte Valley, identify changes in distribution
over the past two decades, and, with the aid of GIS techniques and in concert with Element 1, assess
how the distribution of sandhill cranes currently relates to channel morphology, the distribution and
condition of wet meadows, and the characteristics of cropland. Work evaluating how changes in wet
meadows and the channel affect crane condition and distribution will be linked with the work being
conducted in Elements 3, 4, and 6 to help identify streamflows necessary to maintain wet meadow and
channel habitats in a status suitable for crane needs.
Element 3. -- Surficial Geology and Geochronology
The goal in this element is to characterize the geologic setting of the Platte River.
Specific scale studies will examine the geomorphology
of the river channel and the stratigraphy of floodplain deposits to determine past river
positions, interchannel terraces, and wet meadows and will place these depositional features in a temporal
context. The Platte River from Lexington, Nebr., to Chapman, Nebr.,
is being examined at an intermediate or subregional scale, to characterize the fluvial architecture of the Pliocene and Pleistocene
sediments in the valley floor. Also, valley stratigraphy
is being determined at this scale from test wells. At the regional scale, the whole Platte River is being considered in order to place the shorter
reaches into context. Such factors as regional tectonics, local structure, and climate change are important
aspects of the evolution of the Platte River.
Element 4. -- Channel Characteristics and Morphology
Investigations in channel morphology help to define and group characteristic reaches, provide
a framework for examining the interaction of flowhydraulics and vegetation on banks and island bars, and
identify critical reaches for more intensive study. This study element focuses on grouping reaches on the
basis of flow and sediment characteristics, stability of the bed and banks of the channel, and biotic
considerations. The physical characteristics of these reaches are identified by examining
river profile, observing planform changes, and cross-section changes, analyzing stage-trends, and comparing hydraulic
and sediment characteristics along the reach. This investigation relies on previously collected data.
The interaction of vegetation and geomorphology near the channel banks is an important aspect of
understanding the stability of the channel form. The resistance to erosion from vegetation is difficult
to quantify, and measures to alter this resistance are complicated by interactions with streamflow magnitude
and duration, local hydraulic conditions, and biotic factors. This interaction is examined by comparing
detailed streamflow duration and hydraulic data to the vegetation communities in these sensitive areas
near the channel boundary. Surveys of a limited number of bank segments, islands, and bars will
define the role of vegetation in stabilizing these landforms. This work will be augmented
by prediction of local velocities and stress fields from the sediment-transport modeling (Element 5).
Element 5. -- Sediment-Transport Modeling
The use of multidimensional flow and sediment-transport models will assist in the understanding
of potential channel changes that result from streamflow and manipulation of vegetation on islands and banks.
Surveys of topography and grain-size distributions will be done to predict local sediment rating curves and
critical flows for initiation of motion for grain sizes in both main and secondary flow channels. These
surveys resolve topographic variability in the channel itself at 10-cm vertical resolution or better,
and horizontal variability is characterized with meter-scale accuracy. At the same location, detailed
grain-size surveys will be carried out to characterize spatial and vertical (at-a-point)
variability in sediment grain sizes. For a variety of real and hypothetical flow-discharge scenarios,
model results will be used to make preliminary assessments of the role of hydrographs in maintaining
or modifying channel and bank morphology. In addition, velocity and bottom stress maps of the critical
reach will be compared to vegetation patterns to assess the roles of
various flows in promoting or discouraging certain types of riparian vegetation.
Element 6. -- Wet Meadow Hydrology, Biotic Resources, and Environmental Factors
A series of interrelated scientific tasks seek to answer ecological questions about habitat changes that put
important biological communities at risk. This element is designed to develop a better understanding
of wet meadow ecology, including the relationship between geomorphology, hydrology, vegetation, and
aquatic invertebrates. This understanding will help formulate models on which to base maintenance
and rehabilitation strategies for the habitat. The decreased size of wet meadow landscape by corn monoculture
has significantly decreased the availability of nutrients for migrating water birds. Increased pumpage
for irrigation and public water supply has potentially altered river flows have changed the water
table in wet meadow areas. Native wet meadows rely on shallow ground water for survival. Data collection
in the established study sites of wet meadow habitats focuses on surficial geology, elevation, connection
with the river channel, basic vegetation and ground water configurations, and invertebrate sampling.
A monitoring program must include methods that do not disturb whooping cranes and other species of
interest so that sampling can proceed efficiently through the entire staging season for birds
and the whole growing season for vegetation.
Element 7. -- Habitat Use and Requirements of Spring-Staging Migrant Waterfowl
The Platte River Valley of Nebraska is a vitally important staging area for midcontinent waterfowl
during spring migration. Wetland and cropland resources in this region are important to waterfowl
for obtaining sufficient energy to complete migration and for storing nutrient reserves (primarily
fat and protein) for reproduction. Water conditions in the basin and in the Rainwater Basin to the
south influence waterfowl habitat-use patterns and movements between the two regions, but our
understanding of these dynamics, and how they affect the acquisition of nutrient reserves and outbreaks of disease
is very poor. This element evaluates the movements of snow geese and northern pintails
and the significance of various habitats to these and other migrant species, relative to water
conditions. This study element will monitor female northern pintails and snow geese using radiotelemetry
to determine habitat use, movement patterns, and survival rates. Additional data on turnover rates
(migrational movements out of the region) and habitat-use patterns will be collected. These tasks use
GIS-related data (Element 1) for analyses of habitat-use patterns and provide georeferenced data
to the database. Study Proposal
Element 8. -- Evaluation of Anthropogenic Manipulations of Hydrology, Channel, and
Habitat for Ecosystem Improvements
Water will never again flow naturally in the Platte River because water used for irrigation and power
generation support the important socioeconomic aspects of agricultural production. However, under
current or renegotiated river management, some ecosystem rehabilitation efforts can and are being
used to improve habitat quality and quantity for the thousands of water birds that
migrate through or nest in the Platte Valley Habitat, and wildlife managers in the basin, including
the U.S. Fish and Wildlife Service, the Whooping Crane Maintenance Trust, and others, are currently
implementing interventions that are aimed at improving ecosystem functions. Anthropogenic manipulations
of the water and habitats of the Platte River floodplain need to be evaluated to determine their
effects on the ecosystem and to determine their success. This element is scheduled to begin in
1999 and will become one of the most important elements of the program. Two areas
will be investigated: (1) managed rehabilitation of wet meadows, which includes ground water/
surface water interactions and ground water pumpage, and (2) modifications to the channel by
removing woody vegetation and altering channel banks. Investigations include physical
and biological assessment before alteration, monitoring of the system during alteration, and
assessment after alteration, which includes the cumulative effects from a series of anthropogenic
manipulations.
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