Location: Soil Drainage ResearchTitle: Ground penetrating radar water content mapping of golf course green sand layers Author
|Freeland, Robert - University Of Tennessee|
|Grote, Katherine - Missouri University Of Science And Technology|
|Mccoy, Edward - The Ohio State University|
|Martinez, Luis - Rene|
Submitted to: Journal of Environmental & Engineering Geophysics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2016
Publication Date: 12/15/2016
Citation: Allred, B.J., Freeland, R., Grote, K., McCoy, E., Martinez, L.R., Gamble, D.L. 2016. Ground penetrating radar water content mapping of golf course green sand layers. Journal of Environmental & Engineering Geophysics. 21(4):215-229.
Interpretive Summary: Reducing water use on golf course greens requires accurate information about water content of the sand layer for improved irrigation scheduling. An approach using ground-penetrating radar (GPR) to measure sand layer volumetric water content on golf course greens was evaluated. GPR was compared to sand layer water content measured with a time-domain reflectometry (TDR) probe. GPR had an advantage over TDR, because the TDR probe only measured water content near the top of the sand layer, while GPR was able to provide a water content value averaged over the entire thickness of the sand layer. The overall results from this investigation will be valuable to golf course managers and superintendents for greens maintenance operations and overall golf course water management.
Technical Abstract: Information on the spatial distribution of water content across the sand layer component of a golf course green can be important to golf course superintendents for evaluating drainage effectiveness and scheduling irrigation. To estimate the bulk water content of the sand layer at point locations across the green, a technique was developed that combined (1) depth (thickness) of the sand layer measured with a steel shaft tile probe, (2) radar signal two-way travel time for the base of the sand layer obtained using a ground-penetrating radar (GPR) system with 900 MHz antennas, and (3) an empirical equation relating porous media dielectric constant to water content. To test this technique, two GPR surveys were first conducted on the Nursery Green (USGA design) at the Double Eagle Golf Club near Galena, Ohio and two GPR surveys were next carried out on the 9th Hole Green (California design) at the Delaware Golf Club near Delaware, Ohio. For comparison, time-domain reflectometry (TDR) water content values for the sand layer near the ground surface were obtained concurrent with each of the four GPR surveys. Results of the four golf course green GPR/TDR surveys carried out on September 8, 2014 (Double Eagle Golf Club - before irrigation), September 9, 2014 (Double Eagle Golf Club - after irrigation), April 21, 2015 (Delaware Golf Club), and April 29, 2015 (Delaware Golf Club) show that sand layer water content determined with GPR respectively averaged, 18.8%, 25.2%, 12.2%, and 11.3%, which were quite similar to the respective TDR sand layer water content averages of 20.3%, 25.7%, 11.0%, and 14.1%. The spatial correlation coefficient (r) between the GPR based sand layer water content values versus the TDR sand layer water content values for these four GPR/TDR surveys were 0.76 (September 8, 2014), 0.73 (September 9, 2014), 0.55 (April 21, 2015), and 0.70 (April 29, 2015). Sand layer water content was found to have moderate inverse spatial correlation (r) with ground surface elevation and elevation at the base of the sand layer. Consequently, the findings of this study clearly indicate that if sand layer depth values are available, then GPR can be utilized to accurately map sand layer water content across a golf course green, and conversely, in cases where sand layer water content (hence, radar velocity) spatial patterns are already known, then this information can be employed to provide more accurate GPR based sand layer depth values.