Diurnal to Seasonal Dynamics of Groundwater, Evaporation, and Hydrology
Fluctuations at the Bonneville Salt Flats Saline Pan
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.