Office of the Regional Executive for Biology - Central Region
 |
| About USGS / Science Topics / Maps, Products & Publications / Partnerships / Education / Newsroom / Jobs |
Bureau of Reclamation Research Needs
TITLE:
Riparian Ecology of Western
Rivers Affected by Reclamation Operations
SUBMITTING BUREAU: Bureau of Reclamation
Originating Office: Technical Service Center (TSC)
DATE SUBMITTED: April 29, 1998
BIN NUMBER: BOR03CR99
BRD REGION: Central and Western
DESCRIPTION OF NEED: The Bureau of Reclamation has developed structures throughout the western United States for water storage, diversion to agricultural users, and power production. The operation of these facilities modifies river flow, and effects downstream environments that extend beyond the river channel and associated aquatic habitats and resources.
All of the riparian zone adjacent to the river channel, regardless of whether it is actually inundated, is affected by river condition each year. Vegetation within the riparian zone is dynamic, and the pattern and pace of its change is a response to the frequency, duration, and timing of flooding, as well as to the dynamics and chemistry of ground water. These influences are both direct and indirect. For example, floods can influence the abundance of herbivores that in turn influence the abundance of particular plant species. The river hydrograph and sediment load influence soil development processes, litter decomposition rates, and nutrient availability and cycling, which in turn influence plant vigor.
The nature of the riparian vegetation influences the kinds and abundances of animals that will be present. The animals using the riparian zone can in turn influence the vegetation through herbivory, burrowing, or other activities. Beaver, many insects, and some fish transfer matter and energy between the river and riparian zone by spending part of their life cycles in each. Individual riparian species, whether animals or plants, may have their distribution and abundance tightly or only loosely coupled to the nature of the river on which they reside. Declines in the quality and quantity of western riparian habitat has led to some tightly coupled species being declared federally Threatened or Endangered (e.g., Southwestern Willow Flycatcher). Especially in desert environments, a healthy riparian zone promotes high local and regional biodiversity.
Water resource managers should understand how operations and the consequent quality and quantity of the river flow will affect riparian vegetation and animal communities. The decline of cottonwood trees downstream of Flaming Gorge and other western dams, for example, has been attributed to reservoir release patterns made without knowledge or consideration of requirements for cottonwood regeneration. Although there is now a good understanding of cottonwood biology, cause-and-effect relationships between dam operations and the dynamics of most other riparian plant and animal populations are poorly understood. BRD studies within the Green River system below Flaming Gorge Dam have contributed significantly to understanding how dam operations have affected the riparian environment, and provide insight as to how operations there and elsewhere might be constrained to avoid habitat degradation. Studies building upon and expanding this knowledge base can be used to suggest flow management alternatives that maintain, to the extent desired, the ecological/functional attributes of the riparian zone.
Objective/Questions: The objective is to enhance ecological knowledge concerning how river condition (hydrology and water quality) influences riparian community structure and dynamics in arid and semi-arid landscapes. Specific inter-related questions include:
(1) What are the direct and indirect effects of river regulation on populations and communities of riparian animals, especially herbivores?
(2) Do modified flows reduce the vigor and survivorship of trees in remnant riparian woodlands? To what extent?
(3) How are floodplain nutrient dynamics, including floodplain-river exchanges, influenced by flow regulation?
(4) What factors contribute to the successful invasion of non-native plant species?
(5) How does river regulation influence the composition of non-woody riparian plant communities and the animals dependent upon them, especially butterflies?
(6) How should the Bureau of Reclamation operate facilities in order to promote riparian habitat quality, species health, and biological diversity?
MANAGEMENT PROBLEM WITH NEED: The Bureau of Reclamation's Strategic Plan includes the goal to manage "water and related reources in a manner that is ecologically sound and that promotes habitat quality, species health and biological diversity of the West." The Bureau of Reclamation needs specific, scientifically sound ecological information on downstream effects of river regulation on riparian species and habitats in order to meet this goal. Gathering this information requires an interdisciplinary approach, with scientists working closely with resource managers along both modified and unmodified river systems, and in both short-term and long-term study environments. BRD is uniquely positioned to address this research need.
BUREAU CONTACT: S. Mark Nelson, D-8220, Denver Federal Center, Bldg. 56, P.O. Box 25007, Denver CO 80225, tel: 303-445-2225, fax: 303-445-6328, msnelson@do.usbr.gov
BRD PRIMARY CENTER: Fort Collins Science Center (MESC)
BRD CENTER CONTACT: Douglas C. Andersen
RESULTS OF USGS-INITIATED COMMUNICATION: Douglas C. Andersen contacted Christine Karas of Reclamation's Upper Colorado Regional Office by telephone in October. He also discussed ongoin research activities and needs related to Reclamation operations of Flaming Gorge on the upper Green River with two members of her staff (Karen Blakney and Karen Bennett) following his invited presentation on wildife use of constructed wetlands at the Bureau of Reclamation Wetlands Workshop in Las Vegas, Nevada, November 3 through 4, 1998. Andersen communicates on a regular basis with Reclamation biologist Mark Nelson (Reclamation Technical Service Center, Denver) who is a collaborator on cooperative research, and is communicating with Lower Colorado Regional Office personnel (John Swett, Barbara Ralston) regarding their joint research activities along the lower Colorado River.
DATE SUBMITTED TO REGIONAL OFFICE: November 30, 1998
PREPARED BY: Douglas C. Andersen
U.S. Department of the Interior | U.S. Geological Survey
URL: http://biology.usgs.gov/cro/99bor-3.htm
Page Contact Information:
tlwilliams@usgs.gov
Page Last Modified:
