Effect of Rapidly Changing River Stage on Uranium Flux through the Hyporheic Zone
At the Hanford Site, the flux of uranium contaminated groundwater into the Columbia River varies according to the dynamic changes in hydraulic gradient caused by fluctuating river stage. The river stage changes in response to operations of dams on the Columbia River. Piezometers were installed in the hyporheic zone to facilitate long term, high frequency measurement of water and uranium fluxes into the Columbia River in response to fluctuating river stage. In addition, measurement of the water level in the near shore unconfined aquifer enhanced the understanding of the relationship between fluctuating river stage and uranium flux. The changing river stage caused head fluctuations in the unconfined aquifer, and resulted in fluctuating hydraulic gradient in the hyporheic zone. Further, influx of river water into the unconfined aquifer caused reduced uranium concentration in near shore groundwater as a result of dilution. Calculated water flux through the hyporheic zone ranged between 0.3 and -0.5 L/min/m2. The flux of uranium through the hyporheic zone exceeded 30 ug/min/m2 during some time periods, but was generally on the order of 3 to 5 ug/min/m2 over the course of this study. It was also found that at this location, the top 20 cm of the hyporheic zone constituted the most restrictive portion of the aquifer, and controlled the flux of water through the hyporheic zone.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 985046
- Report Number(s):
- PNNL-SA-52010; ISSN 1745-6584; 830403000; TRN: US1006069
- Journal Information:
- Ground Water, Volume 45(6):753-760, Vol. 45, Issue 6; ISSN 0017-467X
- Country of Publication:
- United States
- Language:
- English
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