UPPER KLAMATH BASIN GROUND-WATER STUDY

During phase I of the study, the USGS-Oregon District will coordinate with the USGS-California District and attempt to bring the California Department of Water Resources (CDWR) into the study as cooperators. In addition, the USGS and OWRD will coordinate with the U.S. Bureau of Reclamation (USBR) to insure their involvement in the successive phases of the study.

 The magnitude and scope of this study make it essential that there be good coordination not only between the agencies involved in the work, but also other state and Federal agencies with land- or water-management or scientific roles in the basin, Tribal governments, local governments, and other stakeholders in the basin. As previously described, a series of public meetings will be held approximately quarterly during phase I and throughout the remainder of the study. The purpose of these meetings is to keep interested parties apprised of project progress, plans, and preliminary results, and to facilitate communication between various agencies working in the basin.

Existing information related to wells, springs, stream and canal flow, climate, soils, water-use, and other geohydrologic data will be gathered with special attention given to assessing the accuracy and reliability of the information. Available information can be obtained from published reports, government agencies, public utilities, and other sources. Published reports (Leonard and Harris, 1974; Illian, 1970; Newcomb and Hart, 1958) contain information on wells used to assess geology, water levels, hydraulic properties, water use, and streamflow characteristics and include maps of geology, soils, land use, water tables, and other geohydrologic features. The OWRD maintains well information that can be used to help describe geology, water levels, hydraulic properties, and water use. All geohydrologic data will be stored in computer files whenever possible. Map data will be acquired and stored in GIS format whenever possible. Some of the types of data to be compiled and potential sources are listed below. Finally, existing digital geographic themes for the basin (transportation, hydrography, land ownership, etc.) will be compiled; these themes will be used to create digital base maps for the study area for use in reports and presentation materials.

An accurate and reliable understanding of the hydrologic system in the Upper Klamath Basin can only be developed from the analysis of accurate and reliable geohydrologic data. Results from data evaluations will indicate the value of existing data and guide how project resources will be allocated to collect new data to improve the understanding of the geohydrologic system. These evaluations will be critical to development of the detailed work plans for major elements of phase II. Some of the criteria to be used in this evaluation are: 1) the spatial distribution of the data, 2) the temporal distribution of the data, 3) the reliability and accuracy of measurement techniques, and 4) the collection frequency of the data.

Some data collection needs can be anticipated without the benefit of the results from the compilation and evaluation previously described. These needs are primarily for hydrologic data (e.g. water levels) that must be collected over a sufficient time period to characterize short-term variability and relations to other factors such as climate or water-use. The following type of data will be collected during phase I of the study:

Much of the data that will be used in phase II to define the geologic framework, estimate hydraulic properties, define SW/GW relationships, estimate ground-water pumpage, and quantify seasonal and long-term ground-water level changes, will be collected from existing water wells. In the later part of phase I we will begin the process of selecting and field-inventorying wells where data can be collected for use in phase II tasks. Relatively few wells have been inventoried in the basin since the studies by Newcomb (1958), Illian (1970), Leonard and Harris (1974), and Sammel (1976). As many as 1,000 additional wells may be field-inventoried in order to provide the spatial coverage required for this study; approximately half of these will be inventoried and entered in the well database in phase I.

 Some emphasis will be placed on choosing wells that will enhance our knowledge of vertical head gradients, the effects of structure on horizontal head gradients, and simply obtaining head data in areas where there is none available. Assistance will be sought from other government agencies in securing information on wells that they have drilled, particularly those near streams or canals that can be used to evaluate SW/GW relationships. It is essential to obtain accurate locations and elevations for these wells.

 Locations will be determined using global positioning system receivers and will be accurate to within 50 feet. For most wells, land surface elevations will be determined from USGS 7.5 minute scale topographic maps and will be accurate to within half of the contour interval of the map (typically 10 feet). Where horizontal hydraulic head gradients are low or where wells are near surface-water bodies and small head differences must be resolved, land surface elevations will be determined using more precise methods.

The principal objective of phase II is development of a sound conceptual model of the hydrogeologic system in the Klamath Basin that will serve as the basis for the numerical ground-water flow model to be constructed in phase III. The conceptual model is comprised of several components that must be understood both individually and collectively prior to constructing a numerical model of the system. In general terms, these components are: the geohydrologic framework, water budgets for ground- and surface-water systems, water-bearing characteristics of hydrogeologic units, and the pathways by which ground water enters, moves through, and discharges from, the subsurface. Within each component, individual tasks will be identified. For example, the water-budget component will include tasks such as constructing and calibrating watershed models, estimating ground-water withdrawals, estimating gains and losses on streams and canals, and estimating evapotranspiration from the saturated zone. The various tasks typically involved in developing each component of the conceptual model are described in the discussion of phase II later in this proposal.

 Phase II work plans will be developed for each of the major components of the conceptual model. The work plans will specify the methods of analysis for each task, adequacy of existing data, requirements for new data collection, and methods of data collection. Existing information compiled and evaluated during phase I will be used to determine the most appropriate methods of analysis and to design data-collection activities at spatial and temporal scales that will support those analyses. Associated personnel needs, costs, and time frames for each component will be estimated.

An initial conceptual model of the hydrologic system will be developed during phase I as existing data are gathered and evaluated and previous studies are assessed. On the basis of this conceptual model and knowledge of the quantity and quality of existing data, a modeling approach will be outlined that is consistent with the data quality and availability. As data collection proceeds and the conceptual model is refined in phase II, this approach may be modified.

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