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Diurnal to Seasonal Dynamics of Groundwater, Evaporation, and Hydrology Fluctuations at the Bonneville Salt Flats Saline Pan
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  • Jeremiah Amen Bernau,
  • Brenda Bowen,
  • Eric R Pardyjak,
  • Evan L Kipnis
Jeremiah Amen Bernau
University of Utah

Corresponding Author:[email protected]

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Brenda Bowen
University of Utah
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Eric R Pardyjak
University of Utah
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Evan L Kipnis
University of Utah Geology and Geophysics
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Abstract

Saline pans are environments with evaporite crusts, high-salinity surface and groundwater brines, and low topographic gradients. These characteristics make them sensitive to diverse hydrological processes. The Bonneville Salt Flats, a valued and changing saline pan, was investigated to identify saline pan hydrology responses to diurnal to seasonal cycles. Seasonal changes in evaporation and relationships between groundwater levels and environmental processes in saline pans are not well understood. The results presented here, which improve characterizations of saline pan water balances and movement, enable predictions of salt growth or dissolution associated with geoengineering to mitigate the impacts of mining saline pans. Three months of eddy-covariance evaporation measurements were collected, spanning a flooded to desiccated surface transition. Two techniques, an artificial neural network and an albedo-based calibration of the Penman equation, were evaluated and used to estimate evaporation with over four years of inexpensive micrometeorological measurements. Albedo, a water availability proxy, inversely correlated with evaporation. Shallow groundwater levels varied seasonally by >50 cm and daily by >6 cm in response to temperature fluctuations. Groundwater level fluctuations should be carefully interpreted as they may not reflect recharge or discharge. Evaporation had a minor, <10 cm y-1, effect on groundwater levels. Surface moisture, primarily from rain, controlled evaporation. Summer desiccated surface evaporation was ~0.1 mm d-1. The net annual water balance was < +/-1.5 cm y-1, indicating the saline pan stabilizes the water table. Surface dynamics of these environmentally-sensitive and variable landscapes are increasingly important to understand as water scarcity in arid environments rises.