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Umatilla Basin Ground-Water Study

Project Summary

Problem and Background

The 5,800 square mile Umatilla Basin is an arid area that supports a growing population and agricultural industry. Water demands continue to grow resulting in critical water management problems. Current issues facing water managers include long-term water level declines in basalt aquifers and potential streamflow depletion from ground-water withdrawals.


The tasks outlined in this proposal will provide information and understanding necessary to make informed management decisions regarding ground-water use in the Umatilla Basin. To achieve this goal, we propose to:

  • Develop, test, and refine a conceptual model of the hydrologic system of the Umatilla Basin
  • Describe the hydrologic system through reports and presentations that promote a common understanding of the resource within the Umatilla Basin
  • Construct numerical models that accurately represent the hydrologic system and can be used as tools to evaluate the effects of proposed management alternatives
  • Use the hydrologic models to identify optimal management alternatives based on specific management objectives and constraints on water resources

Funding to successfully meet these objectives of a large regional study is not available at this time. Data compilation of well data and ground-water levels, and collection of continuous ground-water levels and borehole geophysical data are funded with support from the Oregon Water Resources Department (OWRD) and the Confederated Tribes of the Umatilla Indian Reservation (CTUIR). The U.S. Geological Survey (USGS), OWRD, and CTUIR are actively seeking partners to continue and expand this study.


When fully funded, the study will be undertaken in phases so that each subsequent phase builds upon the knowledge gained from previous phases.

Phase 1 will involve project planning, compilation of existing data, evaluation of existing models, and design of a data collection plan. Current funding will allow completion of compilation of existing data and collection of some of the data proposed in phase 2.

Phase 2 (not yet funded) will collect water use, water-level, streamflow, water quality, and geologic information. In addition, watershed modeling will estimate recharge. This data will be used to develop a conceptual understanding of the ground-water flow system.

Phase 3 (not yet funded) will use data collected in phase 2 and the conceptual model developed in phase 2 as input for a model to simulate ground-water flow, water levels, and the interaction of surface and ground waters. Ground-water management scenarios will be simulated and evaluate using optimization methods.

Phase 4 (not yet funded) will include developing a data collection plan to evaluate the management actions implemented in the basin.

Umatilla Basin Ground-Water Study
Oregon Water Science Center Studies
Oregon Water Science Center Home Page
Contact: Terrence Conlon