Prince, Benjamin Hays (2017-12). Tracing Water Sources Along the Brazos River Alluvial Aquifer with 234U/238U Activity Ratios and Uranium Concentrations. Master's Thesis. Thesis uri icon

abstract

  • The combined use of 234U/238U activity ratios and uranium concentrations can be used to trace water sources within a hydrological system. Additionally, the specific uranium concentration and isotopic signature of each source can be applied to mixing calculations to estimate the relative contribution of each source in a river. 234U/238U activity ratios and uranium concentrations were measured over a 6-month period in the Brazos River watershed along the Brazos River Alluvial Aquifer to determine where water in the Brazos River is sourced from and to estimate groundwater discharge to the Brazos River. Results from this study indicate that lithology within the Brazos River watershed affects 234U/238U activity ratios and uranium concentrations along the studied stretch of river as there is a change from carbonate rocks to siliciclastic rocks downstream and an associated change in 234U/238U activity ratios. Rain was found to have a negligible effect on 234U/238U activity ratios of sources within the area, and only dilutes the concentration of uranium in these sources. 234U/238U activity ratios and uranium concentrations suggest water in the Brazos River near Bryan/College Station, Texas is sourced from Lake Whitney, groundwater, and tributaries. Groundwater appears to discharge from the alluvial aquifer to the river at a steady rate with slight increases in groundwater contributions as discharge increases in the Brazos River. This study demonstrates the utility of uranium as a natural tracer of water sources.
  • The combined use of 234U/238U activity ratios and uranium concentrations can be
    used to trace water sources within a hydrological system. Additionally, the specific
    uranium concentration and isotopic signature of each source can be applied to mixing
    calculations to estimate the relative contribution of each source in a river. 234U/238U
    activity ratios and uranium concentrations were measured over a 6-month period in the
    Brazos River watershed along the Brazos River Alluvial Aquifer to determine where
    water in the Brazos River is sourced from and to estimate groundwater discharge to the
    Brazos River.
    Results from this study indicate that lithology within the Brazos River watershed
    affects 234U/238U activity ratios and uranium concentrations along the studied stretch of
    river as there is a change from carbonate rocks to siliciclastic rocks downstream and an
    associated change in 234U/238U activity ratios. Rain was found to have a negligible effect
    on 234U/238U activity ratios of sources within the area, and only dilutes the concentration
    of uranium in these sources. 234U/238U activity ratios and uranium concentrations
    suggest water in the Brazos River near Bryan/College Station, Texas is sourced from
    Lake Whitney, groundwater, and tributaries. Groundwater appears to discharge from the
    alluvial aquifer to the river at a steady rate with slight increases in groundwater
    contributions as discharge increases in the Brazos River. This study demonstrates the
    utility of uranium as a natural tracer of water sources.

publication date

  • December 2017