US EPA

What is an ecological risk assessment?

An ecological risk assessment evaluates the potential adverse effects of human activities on the plants and animals that make up ecosystems. The risk assessment process provides a way to develop, organize and present scientific information so it is relevant to environmental decisions. When conducted for a particular place such as a watershed, the ecological risk assessment process can be used to identify vulnerable and valued resources, prioritize data collection 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 various management options.

Forthcoming picture: Backwater area. Side channels and backwaters provide breeding habitat and refuge for fish and amphibians and contribute to the biodiversity of the floodplain. These 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.

Forthcoming picture: Sandhill Crane. Caption: 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 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 Platte River special?

The 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 (such as the whooping crane) use the water, woodlands and remaining native grasslands and wet meadows in the middle Platte River valley. Surface and groundwater flows from this segment of the Platte River system are also important to the economic stability of central Nebraska by irrigating about two million acres of land, mostly for corn production.

The volume and variability of water flows to the middle segment of the Platte River have been reduced from dams in Colorado, Wyoming and Nebraska along with irrigation and other water withdrawals. Cultivated agriculture has replaced most of the native prairie and river-dependent vegetation that once occupied the middle Platte River watershed. Reductions in quality and quantity of water and habitat have prompted concern for the welfare of the sandhill crane, other migratory bird populations, and threatened and endangered fish and bird species. American Rivers, a national river conservation organization, has designated the Platte River as one of the ten most endangered rivers in America.

Forthcoming map: Middle Platte River watershed. Caption: The middle segment of the Platte River flows approximately 266 km (165 miles) from the confluence of the North and South Platte Rivers, in western Nebraska, to its confluence with the Loup River.

How can this valuable resource be protected?

Interested organization collectively developed a management goal and a scientific study approach to evaluate the environment of the middle Platte River. An ecological risk assessment will analyze the stressors and resulting ecological effects in the middle Platte River watershed. The assessment promotes community awareness of ecological problems in the watershed and will provide information to resource managers, including government officials, organizations and the public. These actions promote environmentally beneficial results.

Forthcoming picture: River with islands. Caption: 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 sandbars (as depicted in the photograph), forming islands surrounded by deep water, thus decreasing critical habitat for these birds.

How is the ecological risk assessment being done?

The landscape in the middle Platte River watershed is a mosaic of interdependent habitats that support biological communities. The ecological risk assessment brought together numerous organizations 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.

Forthcoming text Box: Key stressors being evaluated in the ecological risk assessment are:

• changes in the magnitude, timing and frequency of middle Platte River flows
• loss or disturbance of critical wildlife habitat
• changes in stream channel characteristics
• degraded water quality due to agriculture-related activities

How will the results be used?

The 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.

• Central Nebraska Public Power and Irrigation District Nebraska Public Power District
• Nebraska Department of Environmental Quality
• Nebraska Natural Resources Commission
• Central Platte Natural Resources Districts
• Nebraska Game and Parks Commission
• Tri-Basin Natural Resources Districts
• 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