Scoping Investigation of the Causes for Significant Snow Cover Losses in Interior Watersheds of the Western United States
* What is causing the loss of snow cover or decline in snow water equivalent and how does it impact Reclamation operations in the Western United States?
In some instances at higher elevations, both warming winter season temperatures and declining precipitation are observed along with snow water equivalent declines. The causal agent for warming temperatures is better understood than for the higher elevation decline in precipitation. In other instances, lower elevation weather stations in some watersheds may show increasing precipitation. This may be consonant with several studies showing that the elevation of the rain/snow line is decreasing for many storms, and that snowmelt and runoff is occurring earlier in the season. There is relatively new evidence that anthropogenic effects (e.g., urban and industrial air pollution) are reducing orographic precipitation. Whatever the causes, continuance of this trend will have increasing and possibly detrimental impacts on water operations management in the Western United States.
Need and Benefit
In many cases, future decisions on Reclamation's project operations will be based on certain factors as they relate to the projects' basin hydrologic systems. An improved understanding of these systems and how potential or current climatic changes will affect operations is critical to Reclamation as Reclamation participates in studies, negotiations, and planning processes associated with future operations.
An example of the importance of the knowledge this study will potentially provide is the recent success of the Klamath Basin studies which were critical to the likely Endangered Species Act (ESA) re-consultation and Environmental Impact Statement (EIS) development regarding the Projects' long term operations. This effort provided an improved understanding of the Upper Klamath River Basin hydrologic system, which is needed to address the issues associated with operation of the Klamath Project. The largest component of the hydrologic system is fed by snowmelt. The water supply supporting extensive marsh lands, forested areas, developed agriculture within the basin, and hydropower, depends on this source of supply. For the Upper Klamath basin and other basins in the Western United States, knowledge of climatic impacts is critical to understanding the impact to watershed systems and the generation of electric power by Reclamation facilities within these watersheds.
Changes in snowpack that have been seen throughout the Pacific Northwest Region have also been evident in the Rocky Mountains. In addition to the Upper Klamath Basin, included in this Science and Technology (S&T) Program research project is the acquisition and examination of data for the Wind River Range, and the Upper Colorado River at Granby, Colorado. The interest in these three higher elevation areas is in understanding the hydrologic processes, impacts on watershed systems, and causal agents in the atmosphere for the decline in snow cover. The examination of these factors is important because as conditions change, the competition for water for various uses (i.e., environmental needs, municipal and industrial, irrigation) during droughts will trigger a crisis-level water shortage.
An example of such a crisis is the 2001 water event in the Klamath basin. In response to issues that were effecting Reclamation's responsibilities, the Department of the Interior (DOI) requested that the National Research Council (NRC), which is part of the National Academy of Sciences, to provide an independent review of the scientific and technical basis of the U.S. Fish and Wildlife Service (FWS) and National Oceanic and Atmospheric Administration (NOAA) Fisheries Biological Opinions for protection of listed "threatened" and "endangered" fish species in the basin. Reclamation's role in this review was not limited to the water supply for agricultural and hydropower projects alone, but to meeting the environmental streamflow needs of critically endangered and threatened fish species.
More specifically, there has been sparse investigation to define the site-specific changes in hydrologic conditions within these basins due to changing climatic conditions. Without better data for developing and applying sound scientific measures, improved water operations in the basin can not be achieved and understanding the impacts to proposed environmental flow requirements will have little scientific basis. This research will contribute to the overall effort to define improved operational principles/practices for Reclamation facilities in the selected watershed areas.
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This information was last updated on April 1, 2015
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