Groundwater of the Umatilla River Basin

Science Center Objects

Water management in the arid Umatilla Basin has become increasingly complex in recent years. Competing demands from society for generating hydro-electric power, maintaining and restoring fisheries, restoring watershed health, providing water for growing communities, and increasing agricultural production through irrigation, have put water resources in the Umatilla Basin and throughout the northwest, under increasing pressure. Management of water resources requires a sound scientific basis so that “optimal” solutions can be identified that satisfy as many of the societal demands as possible.

Improved understanding of groundwater resources in the upper Umatilla River Basin is needed as demands for water in the region increase. Recharge to the groundwater system is directly correlated to precipitation, and is concentrated in the forested uplands of the Umatilla River Basin. A groundwater budget for the upper basin indicates the majority of the recharge in the study area reemerges as streamflow, and does not recharge the deeper basalt aquifers that serve as the principle source of water for municipal and irrigation use in the upper basin.

The goal of this project is to characterize the distribution of the age and geochemistry of springs and groundwater in the upper Umatilla River Basin to understand recharge area, recharge timing, residence time, and flowpath connectivity to improve management of groundwater resources in the study area. To understand this flow system, 28 wells and springs were sampled in September 2017. Additional sampling will occur in the summer of 2018. Geochemical tracers being evaluated include major ions, trace elements, nutrients, stable isotopes of water, tritium, carbon-14, sulfur hexafluoride, and noble gases.

Additional objectives include:

  • 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