T32 Advances in Understanding Processes at or Near the Groundwater–Surface Water Interface (Posters)

Sunday, 22 September 2019
9:00 AM - 5:30 PM
Hall AB, North Building

PLANT TRANSPIRATION INFLUENCES ON GROUNDWATER IN A SHALLOW DOLOSTONE AQUIFER

Paper number: T32-7
Program: Technical Sessions
Time: 9:00 AM – 5:30 PM

Authors

Abstract

The water levels logged in observation wells is an important facet of many groundwater studies. As new technics are applied in water levels monitoring equipment, the more precise the data is, the more noise we would observer in the water level fluctuations. It is well known that a wide variety of hydrologic phenomena can result in water level fluctuations, such as precipitation, barometric pressure effects, earth tides, etc. In some cases, plant transpiration can also affect the water table as long as the roots of plant uptake the groundwater, and it is important that we understand the mechanism operating simultaneously.

Through a monitoring project in the woods in Guelph, Canada, we got continuously high temporal resolution data sets including groundwater levels, barometric pressure, precipitation and tree sap flow. The site is featured shallow dolostone aquifer with groundwater depth at 2 meters below ground surface. Multilevel monitoring method is implemented for assessing water head (level) in various fracture from distinct depth within the aquifer. We set the stage for determining the relationship between tree sap flow and water levels using the diurnal component (1 cpd) of the signal. Water levels are filtered of the precipitation recharge with a high pass filter and then barometric response are removed using deconvolution method. In order to check how well our barometric removal process is working, Fourier transformation is set to graph the spectrum of water levels, barometric pressure and tree sap flow. Further wavelet analysis displays show that tree sap flow and water levels are in-phase in all the sectors in the 16–32 hour band from June to September with significant common power, which means that changes in groundwater levels correspond with tree sap flow in a inversed relation. This finding is against other literatures, which report that trees pump water and drawdown the water level in sync. At last, a discussion is made to explain the mechanism how the water is taken from the vadose zone and creating a drawup cone.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-336758

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