GEOLOGY GRAGUATE THESIS PROPOSAL

Using Trace Element Concentrations and 87Sr/86Sr Isotopes to Track Groundwater Migration in the

Upper Kittitas County

James Patterson and Dr. Carey Gazis

CENTRAL WASHINGTON UNIVERSITY GEOLOGY

400 EAST UNIVERSITY WAY ELLENSBURG, WA 98926

CELL: 253 225 5153 E-MAIL: PATTERSON@GEOLOGY.CWU.EDU

Problem, hypothesis, or question

I propose to use trace element concentrations and isotope geochemistry (87Sr/86Sr) to

track groundwater migration in the Upper Kittitas County (Central Cascades, WA). The Upper

County is a mountainous area that is dominated by faulted metamorphic, sedimentary, and

volcanic rocks (Figure 1). Due to the lack of significant alluvial material in this area, the water

is dominantly transported through bedrock fractures. As a result of this, standard hydrogeologic

models calibrated to basin fill will not accurately identify groundwater migration. Through the

use of geochemistry I plan to identify the paths of water migration based on the changes in water

chemistry. The chemistry of the water will be altered as it comes into contact with local

lithology, each having a different geochemical signature. The hydro-geochemistry is altered as a

consequence of the dissolution of the minerals for which the water interacts. This dissolution

during the water/rock interaction causes the water to incorporate the Strontium ratio (87Sr/86Sr) of

the partially dissolved mineral.

To accomplish this project I will collect and analyze ground-water, surface-water, and

rock samples from the Upper County. With this data I will identify the rock signatures and

identify how the water chemistry changes as it interacts with each rock. This will allow me to

constrain groundwater flow paths and identify water mixing through the use of detailed geologic

maps/cross sections and comparison with known 87Sr/86Sr values of aquifer rocks and minerals.

Importance of research  

Increasing water demands and poor understanding of groundwater migration/recharge

in the Upper Kittitas County (Yakima River Basin, WA) lead the Washington State Department

of Ecology (WADOE) to enact a moratorium on drilling of groundwater wells. A complete halt

does protect aquatic dependent ecosystems and legal water right holder, but it also to halts

development and economic growth. Many drilling, construction, and supply companies have

been adversely affected due to the reduction in business by this hiatus, but if growth and

installation of new wells were to continue senior water right holders would be adversely affected.

Before the WADOE can determine who, where, and how much water can be pumped from the

ground, they must determine aquifer capacities. Standard hydrologic models based on sediment

filled basins cannot identify water migration, but the geochemistry can show the history of the

water based on which rocks it interacted. The bedrock in this area is a combination of pre-

Tertiary to mid Miocene, metamorphic, volcanic, and sedimentary rocks covered only in small

part with Quaternary sediments (see Figure 1). In contrast to sediment filled basins where the

water flows through the pore spaces in an aquifer, in bedrock aquifers the water resides and

migrates through the bedrock fractures. Since standard hydrologic techniques do not apply to

this area, using Strontium isotopes as a geochemical tracer is an ideal method to identify

migration. To be able to use this technique the chemical signature of lithology must vary

between lithologic units. Due to the geologic complexity in the Upper County, the geochemical

signature of the lithologic units is very diverse. This geologic diversity provides ideal conditions

to develop this technique and it is in a location that requires significant research to accommodate

the rising demand on the limited water resource.

Significant prior research  

Upper  Kittitas  County  

There have been very few published geologic studies and even fewer hydrogeologic

and geochemical studies that focused in the upper county. Recently the USGS completed a 12-

year study modeling the groundwater throughout the entire Yakima River Basin (Ely, 2011).

However, as stated previously, their model is based upon the hydrologic properties of basins

dominated by unconsolidated sediments with underlying basalt. This model will not work to the

required resolution in a fractured bedrock dominated aquifer system as is seen in the upper

county. A more detailed study must be performed in this area to define the aquifer systems.

There is currently an extensive hydro-geochemical and geologic Upper Kittitas project

underway by the USGS. This project is to identify the base flow in tributary streams and how

interconnected the surface water is with groundwater. The goal of this project is to provide

current and complete scientific information for resource management (Ely, 2012)

Geochemical  Techniques  

The method of using radiogenic isotopes to track ground water migration has rarely

been used in this way due to its need of significant geochemically different lithologies in the

geographical area. This technique was used in Australia to differentiate sub-catchments and

track communication between aquifers (Cartwright et al., 2006; Raiber et al., 2008). After

quantifying dissolution rates of different minerals through unconsolidated sediment, Singleton et

al. (2006) used this method in the Northwestern United States to identify water mixing in the

Pasco Basin, WA. I will be using this technique, in a way similar to both. I will use the

geochemistry to determine path of water migration based upon what rocks/minerals the water

interacts as well as to identify mixing trends between aquifers. I will use this information to

create a conceptual model of the upper Kittitas County.

Research approach  

As a starting point I will incorporate the dissolution rate determined by Singleton and

others (2006) for the Pasco basin, which is located within close proximity to my research area. I

will also try to identify a procedure to prepare and analyze rock sample to best represent the

water/rock geochemical interaction.

Rock  chemistry  

To identify the soil-groundwater interaction I must first characterize the geochemistry

of each lithologic unit. To constrain the geochemical variations of each unit throughout the

upper county I plan to collect and analyze soil/rock samples. These samples will be collected in

locations where I can collect associated water samples that will directly correlate geochemically.

The rock samples will be shattered into chips and leached resulting in partial dissolution

representative of partial mineral dissolution during the water/rock interaction (Bohrson 1993).

The partial dissolution split will then be processed by column chromatography using cation

exchange resin to separate out the target analyte, Strontium (Ramos et al. 2004). This sample

preparation will be accomplished in the clean lab at Central Washington University (CWU). The

purified Sr samples will then be analyzed on the thermal ionization mass spectrometer (TIMS) at

New Mexico State University (NMSU) to obtain the 87Sr/86Sr signature of each unit.

A split of each rock will be crushed (in a shatter box) and glassified (in graphite

crucibles using a high temperature oven) repeatedly. This process will ensure complete

homogeneity before acid dissolution and analysis on the ICP-MS to obtain the major and trace

concentrations of each rock sample.

Water  chemistry      

Due to the limited coverage of wells (Figure 1), the ground water will be identified by

both wells and springs. Spring samples will be collected at the spring source in identifiable

lithologic units and well samples will be collected from specific domestic wells that extract water

from aquifers located in each geochemically distinct unit, where possible. The water samples

will be filtered through a 0.45 micron filter into acid washed 50mL narrow-mouth polypropylene

sample bottles.

Surface waters will be collected in reaches that have only one dominant rock unit.

This will allow for direct correlation of water signature to rock signature. A control meteoric

sample of both local rain and snow will be collected to identify the initial Surface water

signature. All surface and meteoric samples will be processed and analyzed using the same

techniques as ground water samples.

All water samples will also be analyzed on the Inductively Coupled Plasma Mass

Spectrometer (ICP-MS) at Central Washington University to obtain major and trace element

concentrations.

Interpretation  

The data will be analyzed to identify correlations and to characterize the extent of

geochemical variation resulting from the water/rock interaction (Figure 3). The isotopes will

also indicate which aquifers are in communication and the extent of water mixing (Figure 3).

Through mass balance of the original surface water signature, the formation signature, and the

groundwater signature relationships should become apparent. Ideally, once these connections

are identified the pathway from an aquifer will be tracked back to the surface through the

knowledge of which formations the water interacted during its migration to the aquifer.

Potential outcomes of research  

Through the use of geochemistry the paths of water migration should be accurately

identified. This information would allow me to develop a conceptual model of the aquifer

systems and possibly determine their capacities in the upper county. The geochemistry should

identify which aquifers are in communication and which bodies of water are different. The

geochemistry should also identify the main surface source locations for each aquifer allowing me

to construct a conceptual model mapping the flow path of water from surface to aquifer depth.

Ideally this research will not only provide the much needed conceptual model about

the hydrologic system in the Upper Kittitas County, but also provide high resolution tracking

would of groundwater to allow one to very precisely identify specific flow paths for all surface

and soil water. This information can be used in conjunction with other models to provide the

detailed understanding of water migration and aquifer capacities required for the regulating

agency (WADOE) to determine how much water can be distributed without impinging on legal

senior and junior water right holders or adversely affecting natural ecosystems.

Duration

2012 Summer Collect spring, rock, stream and river samples

2012 Fall Collect well samples; prepare samples in CWU’s Clean Lab; ICPMS at CWU

2012 Winter Isotope at New Mexico State University

2013 Winter Data interpretation

2013 Spring Thesis writing

2013 Summer Defend

Budget

Item/Expense Funding

-Isotope analysis (rock/water)- 40 samples at $60 $3,000 GSA Grant $2,500 -Polypropylene in-line filters Masters Fellowship 40 at $1/filter $40 CWU Grad $700 (not yet applied) -Sample Collection 600 miles at $0.55/mile $330 Covered by advisor $265 -Argon Gas for ICPMS Personal 1 tank fill at $100 $100 (Sample collection

and Per Diem) $555

-Travel to Analytical lab- Flight Seattle to New Mexico $325 -Per Diem- 5 Days at $45 / day $225 -Total $4,020 $4,020

Budget Justification

Samples will be collected at forty locations throughout the upper county with acid

washed polypropylene syringes and polypropylene in-line filters and stored in 50mL narrow-

mouth polypropylene sample bottles. The total driving mileage is estimated to be 600 miles with

a cost of $330 (at $0.55/mile). There is a supply of syringes and sample bottles, but the in-line

filters will need to be purchased ($1 each). The samples will be analyzed at NMSU with a cost

of $3000 ($75/sample). Estimated time to analyze 40 samples is 4 days plus 2 half days of travel

($45/day) costing $225 in per diem. Currently airlines quote $325 for round trip from Seattle,

WA to Las Cruces, NM. No lodging cost while in NM.

References

Bohrson, Wendy A. Alkaline and Peralkaline Magmatism in the Eastern Pacific Ocean: Socorro Island, Mexico. Los Angeles: University Of California, 1993. 263-269.

Cartwright, I., Weaver, T.R., and Petrides, B., 2006, Cation-exchange as a control on Sr isotopes in groundwater from the SE Murray Basin, Australia: Geochimica et Cosmochimica Acta, v. 70, no. 18, Supplement, p. A87, doi: 10.1016/j.gca.2006.06.087.

Ely, D.M., Bachmann, M.P., and Vaccaro, J.J., 2011, Numerical simulation of groundwater flow for the Yakima River basin aquifer system, Washington: U.S. Geological Survey Scientific Investigations Report 2011-5155, 90 p.

Ely, Matt., 2012, Upper Kittitas County. U.S.G.S., n.d. Web. <http://wa.water.usgs.gov/projects/kittitasgw/>

Raiber, M., Webb, J.A., and Bennetts, D.A., 2009, Strontium isotopes as tracers to delineate aquifer interactions and the influence of rainfall in the basalt plains of southeastern Australia: Journal of Hydrology, v. 367, no. 3–4, p. 188-199, doi: 10.1016/j.jhydrol.2008.12.020.

Ramos, F.C., Wolff, J.A., and Tollstrup, D.L., 2004, Measuring 87Sr/86Sr variations in minerals and groundmass from basalts using LA-MC-ICPMS: Chemical Geology, v. 211, p. 135–158, doi:10.1016/j.chemgeo.2004.06.025.

Singleton, M.J., Maher, K., DePaolo, D.J., Conrad, M.E., and Evan Dresel, P., 2006, Dissolution rates and vadose zone drainage from strontium isotope measurements of groundwater in the Pasco Basin, WA unconfined aquifer: Journal of Hydrology, v. 321, no. 1–4, p. 39-58, doi: 10.1016/j.jhydrol.2005.07.044.

Figures

Figure 2. Conceptual model of aquifer interaction between the Newer Volcanic basalts and the Streatham Deep Lead System (Raiber et al., 2009).

Figure 3. Expected rock and water signatures as well as potential water mixing.