The Confederated Tribes of the Umatilla Indian Reservation (CTUIR) seeks to ensure that ground and surface waters are available to satisfy CTUIR treaty rights, the needs of First Foods, CTUIR members and the citizens of the Umatilla Indian Reservation (UIR), and economic development.

To support this goal, the CTUIR-DNR Water Resources Program (WRP), in partnership with the US Geological Survey (USGS), has completed a three-year groundwater study of the upper Umatilla River basin. The purpose of this study is to improve the scientific understanding of groundwater and surface-water resources of the UIR and surrounding area.  Together, the CTUIR and USGS have collected and assembled available data to construct a 3-dimensional conceptual groundwater model and define a water budget of the upper basin.  This webpage highlights some of the findings.

The conceptual model will be the foundation for a numerical model with predictive capabilities. Once built, the numerical model will be used to predict impacts of water and land management activities on water resources and guide policy makers in management decisions.


Confederated Tribes of the Umatilla Indian Reservation

Department of Natural Resources (DNR) Mission:

To protect, restore, and enhance the First Foods - water, salmon, deer, cous, and huckleberry - for the perpetual cultural, economic, and sovereign benefit of the CTUIR. We will accomplish this utilizing traditional ecological and cultural knowledge and science to inform: 1) population and habitat management goals and actions; and 2) natural resource policies and regulatory mechanisms.



Upper Umatilla River Basin Groundwater Study









Study overview


·      Improve the understanding of the groundwater and surface-water system.

·      Develop a 3D-conceptual model of the Umatilla Indian Reservation and surrounding area that will help guide future groundwater development without causing harm to First Foods and other water uses.

·      Build Tribal capacity to conduct research with trainings.

·      Foster and strengthen partnerships with local, state and federal agencies.

·      Increase community awareness of CTUIR’s water resources and environmental stewardship


Terms & Definitions:

Water Budget: An accounting of all the inflow and outflow to a hydrologic system. 
Water inflow occurs from precipitation (rain and snow) to infiltration and runoff to surface waters and groundwater. Water outflow occurs from plant evapotranspiration, stream runoff out of study area, groundwater discharge to streams and springs, and groundwater outflow to adjoining basins.


Groundwater: Water that seeps into the ground and occupies the pore spaces in the sediment and rock beneath the water table.  The water table is the top of the “table” of saturated ground in the subsurface.  Not all water that seeps into the ground is groundwater; for example, soil moisture occurs in the pore space above the water table in the unsaturated ground along with air.


Aquifer: A sedimentary or rock formation that contains groundwater and stores and transmits water sufficiently to a pumping well. There are two primary types of aquifers in the Upper Umatilla River Basin.

·         Alluvial Aquifer – This aquifer occurs in stream deposited sand and gravel sediment called alluvium.

·         Basalt Aquifers – These aquifers occur in the porous and fractured spaces in the interflow zones between volcanic basalt flows. However, not all interflow zones are aquifers, because the interflow zone may lack sufficient pore space through which groundwater can flow.  The flow between basalt aquifers is limited due to the dense nature of the interior part of the basalt flow.



Confined aquifer:

Groundwater under sufficient hydrostatic pressure head to rise above the bottom of the overlying confining layer. Fine-grained sediments like clay and silt ofter act as confining layers as does the dense interior of a basalt flow.


Unconfined aquifer:

Groundwater under a hydrostatic pressure head that is the same as atmospheric pressure; no confining layer occurs above the unconfined aquifer. Alluvial aquifers are commonly unconfined and open to the atmosphere.


Piezometric Surface:

The level to which water in a confined aquifer would rise if it were tapped by a well.



Portion of streamflow that is sustained by groundwater discharge or input to the stream.



Sum of evaporation and plant transpiration from earth to the atmosphere.



Water that falls from the atmosphere to the ground in the form of rain, snow, sleet or hail.



Water flow that occurs over the land (overland flow) and in the subsurface.


Computer Models: Computer models represent natural flow in the hydrologic system, which is described by physical conditions and mathematical equations. Models are used to simulate and predict the distribution and rate of groundwater flow and its the interaction with surface waters. To build a computer model, an accurate accounting of water and description of the flow conditions must be defined first. A conceptual model is the foundation to a computer model.

First of the First Foods: 

Water is first of the First Foods‐‐water, salmon, deer, cous, and huckleberry‐‐a serving order in the Longhouse that is based on the Creation belief. It is the responsibility of the people to take care of First Foods and, in turn, First Foods will take care of the people. Thus, wise management of water resources is mandatory and critical to the survival of both the people and First Foods.


Importance of Groundwater

·         Water is central to Tribal religion and culture.

·         Nearly 100% of household water use on the UIR and rural communities is supplied from groundwater

·         Rivers, streams, springs and groundwater are inter-connected; development of one resource affects the others.

·         Groundwater supports the baseflow (sustained instream flow) in the Umatilla River, streams, and springs throughout the year.

·         Groundwater influences both stream temperature and instream flow, which are critical for salmon, steelhead, and trout survival.

·         More than 95% of irrigated agriculture on the UIR and surrounding areas depend on groundwater.

·         Groundwater is a renewable resource unless pumping exceeds aquifer recharge (overdraft). Aquifer overdraft will reduce the flow to streams and springs and may harm plants, animals, people, farms, agriculture, and Tribal culture.


Benefits of Monitoring:

By maintaining a watchful eye on groundwater conditions, well owners and cultural, fishery and water resource managers can prepare for and respond to changing conditions caused by periodic drought, long-term climate change, and groundwater development. Benefits of monitoring groundwater include the ability to:

·         Evaluate longer-term changes in groundwater storage

·         Estimate the amount of water returning to groundwater annually (recharge rates)

·         Prevent water-level declines (overdraft of aquifer)

·         Define movement of groundwater (direction and gradient)

·         Improve understanding of aquifers and how they interact with surface water and springs

·        Improve knowledge for well construction and placement of pumps for efficient use of groundwater.




Kate Ely,
Umatilla Basin Hydrologist

Water Resources Program
Department of Natural Resources

Nixyáawii Governance Center
46411 Timíne Way
Pendleton, Oregon 97801





Barry, T.L, S.P. Kelley, S.P. Reidel, V.E. Camp, S. Self, N.A. Jarboe, R.A Duncan, and P.R. Renne, 2013, Eruption chronology of the Columbia River Basalt Group: in ed. Reidel, S.P., V.E. Camp, M.E. Ross, Wolff, J.A., Martin, B.S., Tolan, T.L., and Wells, R.E., 2013, The Columbian River Basalt Province, Geological Society of America, Special Paper 497, p. 45-66.


Ferns, M.L., V.S. McConnell, and I.P. Madin, 2006, Geology of the Umatilla River basin, Morrow, Umatilla, and Union Counties, Oregon: Oregon Department of Geology and Mineral Industries, Open File Report, 67 p.


Kahle, S.C., D.S. Morgan, W.B. Welch, D.M. Ely, S.R. Hinkle, J.J. Vaccaro, and L.L. Orzol, 2011: US Geological Survey Scientific Investigations Report 2011-5124, 66 p.






The Umatilla River watershed drains approximately 2,290 square miles from the western flanks of the Blue Mountains to the Columbia River in Northeastern Oregon. The Upper Umatilla River basin (the study area) is the eastern extent of the watershed and covers 913 square miles. In the study area, the elevation ranges from 950 feet in the west to 5,816 feet above mean sea level.


The Umatilla Indian Reservation (UIR) is 273 square miles and has a population of approximately 3,200 people (2010 census). Currently, the CTUIR is comprised of 2,836 Tribal members (Jan 2012), of which nearly half live on or near the UIR. The UIR is also home to another 300 Indians who are members of other tribes and approximately 1,500 non-Indians.


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Study Overview
Terms & Definitions

Conceptual Model

Data Collection
Geologic Framework
        Faults & Folds
        Surface Geology
        Subsurface Units
Piezometric Surfaces
Water Data
        River Baseflow
        Water Use
Hydrologic Budget
     Water Budget

Future Work


Contact Us




Conceptual Model

A conceptual model is a quantitative and qualitative description of how the hydrologic system is believed to behave.  A conceptual model is essential pre-requisite for a numerical model with predictive capabilities.



A conceptual model characterizes the hydrogeologic framework and hydrologic-flow system:

·                     Distribution and rates of inflow to the groundwater system. Inflow comes primarily from precipitation (rain and snow).

·                     Distribution and rates of outflow to the groundwater system. Outflow goes to streams and springs, pumping, evapotranspiration and subsurface discharge out of the basin through the groundwater system.

·                     Distribution of hydraulic head (water levels) over time and space.


Arrows represent directions of flow into and out of the hydrologic system.


Triangle represents the top of the water table and saturated ground.


Numerical Model

A numeric model is a tool (computer program) to mathematically represent and describe a large number of processes in the hydrologic system. It simulates various hydrologic scenarios (such as conditions before groundwater development, future groundwater development, impacts to streams, and changes in climate) that can be predicted, tested for uncertainty, and compared to a conceptual model (field conditions). A numerical model can better inform decision makers of the outcome from current and future water-management and development practices.








A simplified illustration of hydrologic processes in the upper Umatilla River basin. The movement of water is shown by the arrows for precipitation to evapotranspiration, discharge to springs, streamflow (runoff), as well as infiltration of water to recharge shallow and deep aquifers. Additionally, water is diverted from springs and streams, and pumped from groundwater for many uses. Both groundwater and surface waters are used by First Foods, to grow crops, maintain livestock, provide drinking water for households and city uses and businesses for economic development.




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Administration for
Native Americans


US Geological Survey


Bureau of Indian Affairs

State of Oregon, Water Resources Department


US Forest Service,

Umatilla National Forest


Confederated Tribes of the Umatilla Indian Reservation


Oregon Depart. of Geology and Mineral Industries



City of Pendleton






·        US Department of Agriculture - Agricultural Research Service

·        Oregon State University - Columbia Basin Agricultural Resesarch Center (CBARC)

·        Oregon Department of Envirnomental Quality

·        City of Pilot Rock

·        City of Weston

·        City of Athena

·        City of Adams

·        UIR Community


 Data Collection

A well-developed conceptual model requires the collection, analysis, and storage of data from the field. Examples of data types include well depth and location; stream and spring discharges, geology, precipitation, evapotranspiration, groundwater levels, water use, and land use.


Water levels in wells are measured using a steel or electronic tape. The tape is lowered in the well to measure the distance from a point above the ground to the water level below ground. The depth to water is computed from the length of wetted tape. In some places the hydraulic head is above ground. In this case the well is called a flowing artesian well. These wells are tested using a pressure gage that indicates how far the pressure head is above ground. Water-level measurements are used to determine groundwater-flow directions, gradients and to monitor changes in condition over time.


This project collected data from shallow and deep wells and evaluated the data for direction and gradient of the pressure heads and the general water-level trends. Spring sites were compared to predicted pressure heads


In addition, precipitation and evapotranspiration were analyzed to estimate recharge to the groundwater system (image below). Streamflow records were evaluated to estimate baseflow, which is the amount of groundwater that discharges to streams. The percent baseflow in streamflow is shown in an image below.


Water use was evaluated from census data, municipal records, water rights of record, meter readings and aerial imagery of irrigated lands. The City of Pendleton is the only city to use surface water in their water system. All other cities, communities and households in the study area use groundwater to meet their water-supply needs.




3-dimensional shaded relief map showing the location of wells in the upper Umatilla River basin

(view is looking northeast)



Location and depth of wells within the Upper Umatilla River Basin
Average Depth of wells: 200-300 feet
Maximum Depth of wells: 1,910 feet



Wells located in the study area, 1,108 total


Stratigraphic columns created from field survey of exposed rock from the mountain top to the river or creek bottom (Ferns and others, 2006), 9 total


Key wells with geophysical logs and geochemical data; these were used to identify the subsurface geologic units, 14 total

Light Blue:

Additional 59 deep wells were selected to correlate the geologic units identified by the key wells and the stratigraphic columns


Geologic Framework

Between 10 and 7 million years ago (Ma), the modern Umatilla River drainage system was formed during a period of uplift of the Blue Mountains (Ferns and others 2006). Tectonic forces acting on resilient rocks resulted in numerous structural features such as faults and folds. In the image below, the face of the Blue Mountains is defined by a series of large faults, which are defined by the red line, and a series of smaller faults as defined by the black lines. The blue line describes the axis of the Agency Syncline, a shallow-dipping down warp of the rocks. The compressional forces from the east and the west lead to the faulting and uplift of the Blue Mountains as indicated by the arrows.


Faults and Folds


Surface Geology


Modified from: Ferns, McConnell & Madin, 2006, Oregon Department of Geology and Mineral Industries.


Subsurface Unit Structures


Interpretation of the surface and subsurface geology comes from several sources: (1) previous work by the US Geological Survey (Kahle and others, 2011), (2) interpretation of geochemical and geophysical well logs (this study), and (3) field mapping by the Oregon Department of Geology and Mineral Industries (Ferns and others, 2006). This study brought together previous work and new data into a refined definition of thickness and extent of the geologic units.


The image below shows the placement of the geologic units in the study area from oldest to youngest beginning with rocks older than the Columbia River Basalt Group (CRBG) called here as “basement rocks” with an undefined depth. Next are three formations within the CRBG—Grande Ronde Basalt, Wanapum Basalt, and the Saddle Mountains Basalt. Lastly, the image shows both the older and younger deposits of older sedimentary rocks, landslides and younger alluvium.



Basement Rock

Grand Ronde Basalt

Wanapum Basalt

Saddle Mountains Basalt



>17 Ma1

16 - 15.6 Ma2

15.6 – 15 Ma2

14.6 Ma2

15 – Present2

Max Depth


6,100 feet

800 feet

240 feet

325 feet

Mean Depth


3,000 feet

380 feet

75 feet

66 feet



531 cubic miles

28 cubic miles

1.8 cubic miles

3.3 cubic miles

Statistics are for just the areas within the study area

1. Kahle and others, 2012, US Geological Survey
2. Barry and others, 2013, Geological Society of America, SP497



Piezometric Surfaces


Research and data indicate that there are at least 3 distinct aquifers in the Upper Umatilla River Basin.
One is shallow, unconfined and directly tied to streams; the second is deeper, confined and leaky; and the third is confined and not directly connected to streams or upper aquifer systems. Analysis of well data indicates variability between well depth and aquifer confinement. However, in general, wells drilled deeper than 400 feet and sealed to depths greater that than 400 feet are highly confined. There are many wells at shallower depths with flowing artesian conditions.


Piezometric Surface (Wells <400’ deep)


Water elevation depths were determined in 2012 for a selection of wells with depths less than 400 feet.

Contours were generated from these elevation points and then calculated to create a piezometric surface.
Notice how the water level contours bend upriver reflecting the strong interaction between the river and the shallow aquifer.


Light Blue: sub-ground piezometric surface
Dark Blue: Area where piezometric surface is above ground level


After the surface was created we overlaid the location of springs (in Green) which were a result of a previous project completed in 2010. There is a visual association between the piezometric surface for the shallow aquifer and springs located near the river channels.


Piezometric Surface (wells >400’ deep)

Piezometric surface for wells greater than 400 feet deep. Notice how the contours are not as strongly influenced by the Umatilla River.


Light Blue: sub-ground piezometric surface

Dark Blue: Area where piezometric surface is above ground level.


The locations of the springs show a clear interaction between the deep surface and their location. especially in the upper along the upper benches of the Umatilla River Channel.


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Water Data



Estimated Groundwater Recharge


Percent discharge of groundwater to streams (baseflow)

The figure below shows the drainage area location of stream gaging stations.

The streamflow measured at each of the stations was analyzed for



Water Use

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Hydrologic Budget


The primary objectives of this project is to improve the understanding of the groundwater-flow system and to develop a 3D conceptual model of the UIR and surrounding area that will help guide future groundwater development without causing harm to streamflow and existing water uses.

This was accomplished by through the development of the 3D subsurface unit model [HERE] and tying our Water Data [HERE] together and developing a preliminary water budget:


Preliminary Water Budget

Study Area

913 square miles




1,400,000 AF

Estimated Recharge

500,000 AF



Stream Discharge

440,000 AF


320,000 AF

Potential Evapotranspiration

990,000 AF

Surface Water Use

5,100 AF

Groundwater Use

11,000 AF

Groundwater outflow to lower basin

25,000  AF




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Future work

The conceptual model is the foundation for the next step in developing a computer model (numerical model). The numerical model, once built, will be used to predict impacts from current and proposed water use and development on streamflow, water quality and groundwater availability. Future work includes:

·         Building a numerical model that combines everything known about the processes of the hydrologic system.

·         Test that the conceptual understanding is consistent with field observations and basic physics.

·         Continue collecting data that will refine the hydrogeologic framework and understanding of aquifer properties of recharge, discharge and storage.

·         Test how the hydrologic system will respond to new sets of conditions such as changes in pumping or climate

·         Expand the study area to include all areas that may affect the Reservation and First Foods

·         Develop policy that will balance the protection and use of all water resources of the upper Umatilla River Basin for long-term sustainability and resilience. 

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