Development of Improved Evapotranspiration Estimates for Predominant Marsh Plant Communities in the Upper Klamath River Basin

Project ID: 1504
Principal Investigator: Mark Spears
Research Topic: Water Marketing
Funded Fiscal Years: 2006
Keywords: None

Research Question

How can Reclamation improve upon existing methods to quantify environmental water demands? Specifically, are current estimates of consumptive water use associated with the marsh lands within the Upper Klamath River Basin accurate? The Reclamation study entitled Natural Flow of the Upper Klamath River includes the development of a water budget model which simulates the effects of agricultural development on natural river flows. The Klamath Basin Hydrologic and Economic Model (KBHEM) currently under review by Reclamation and others will likely provide the basis for future studies related to project operations. A primary component of these models is marsh consumptive use. Based on internal peer review and input through stakeholder collaboration, the accuracy of this component of the models should be verified. This formulation proposal describes the work plan to be developed initially and the research and development which would ultimately answer the above question.

Need and Benefit

In many cases, future decisions on Reclamation Project operations will be based on certain factors as they relate to Project basin hydrologic systems. An improved understanding of these systems and how potential changes such as wetlands restoration affect operations is critical to Reclamation, as the agency participates in studies, negotiations and planning processes associated with future operations.
For example, the success of the Klamath Basin studies is critical to the likely Endangered Species Act re-consultation and Environmental Impact Statement development regarding the Projects' long term operations. An improved understanding of the Upper Klamath River Basin hydrologic system is needed in order to address the issues associated with operation of the Klamath Project. A large component of the hydrologic system is the consumptive water use associated with the extensive marsh lands within the basin. More accurate estimates of marsh consumptive use would benefit Reclamation and other stakeholders as discussed below.
The competition for water in the Klamath Basin has escalated during the past 5 years. The situation worsened in 2001 when very dry conditions occurred in the basin causing a crisis-level water shortage. Due to the 2001 water crisis in the basin, DOI requested that the National Research Council (NRC), which is part of the National Academy of Sciences, provide an independent review of the scientific and technical basis of USFWS and NOAA Fisheries Biological Opinions for protection of listed "threatened" and "endangered" fish species in the basin.
Of the many conclusions in the 2002 NRC report, the committee concluded that "While information of a sporadic and anecdotal nature is available over as much as 100 years, routinely-collected data on environmental characteristics and fish are available only since 1990 or later.....the information at hand is actually limited to a period of ten years or less." More specifically, little/no natural vegetation consumptive water use data exists to better define the hydrologic conditions of the basin. Without better data for developing and applying sound scientific measures, improved water operations in the basin can not be achieved and the establishment of Klamath River flow requirements will have little scientific basis. This research will contribute to the overall effort to define improved operational principles/practices for Upper Klamath Lake levels and Klamath River flows.

The accuracy of the hydrologic models used in the various Klamath Basin studies is largely dependant on the accuracy of the crop and non-crop consumptive water use estimation methods incorporated into the models. Since these methods are based on empirical relationships and given the extensive crop water use data available, the accuracy confidence for the crop methods is generally much greater than for the non-crop methods. The predominant non-crop areas in the basin consist of various types of marshes and permanently inundated wetlands. Relative to other riparian and wetland plants of concern to Reclamation (cottonwoods, tamarisk, willows, etc.), only limited water use data are available on the plant communities in these marsh areas. Hence, the validity of the empirical relationships presently used to estimate marsh consumptive water use is in question.
The accuracy of the marsh consumptive water use estimations, at Klamath and other Reclamation Projects, could be improved significantly through direct measurements which would be used to develop empirical relationships for the predominant plant communities in the marshes. Although the proposed measurements would be made in the Klamath marsh areas, the results would be transferable to other areas (San Joquin, Platte, Rio Grande, etc.) and would provide benefits beyond Reclamation's Klamath Project. This would be facilitated by incorporating the findings into Reclamation's existing ET Toolbox internet site.

Contributing Partners

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Last Updated: 6/22/20