DYNAMIC CONTROLS ON GROUNDWATER DEPTH BENEATH PLAYAS, SABKHAS AND SALARS

Ground water depth plays a crucial role in the salt distribution, geomorphology and surface geology of playas lakes. However, ground water depth can be an incredibly dynamic feature of many playas, either rapidly changing in response to small weather (short term) inputs or changing only very slowly in response to major climate variations. When water tables are very close to the playa surface, climate forcing can lead to the sudden appearance of standing water, sometimes within hours. When water tables are deeper, fluctuations in the water table appear much more muted and have much slower response to climate changes.

The water table dynamics are controlled by both the climatic forcing regionally and in the recharge zones as well as by the vadose zone hydraulics of nearly saturated porous media. In this presentation, the vadose zone hydraulics responsible for water table responses beneath playas are examined and shown to be responsible for the damping of responses when the water table becomes deep. Examples are presented from the Bonneville Salt Flats in Utah and Owens Dry Lake in eastern California documenting the role of the vadose zone in water level response.