Virginia Tech presents preliminary groundwater assessment showing recharge variability, recommends monitoring and gauges

Virginia Tech researchers gave the Floyd County Board of Supervisors a preliminary groundwater assessment on March 25 that summarizes thousands of well reports, maps groundwater flow within subwatersheds and models how precipitation becomes recharge across the county.

The presentation, led by Dr. Mark Wittison, a Virginia Tech engineer, and co‑presenter Ed Mendez, showed the project compiled roughly 3,660 well records from the Virginia Department of Health and county sources and used the USGS soil‑water balance (SWB) model on a 30‑meter grid to estimate recharge across 15 subwatersheds. "The average recharge rate through the period of record was about 11 inches per year," Wittison said, but drought years produced far lower numbers: the extended drought regionally analyzed dropped average recharge to about 5.4 inches per year and the single worst year studied (1988) produced roughly 3.4 inches per year.

The researchers summarized well construction data and reported averages from the compiled well logs: mean total well depth about 325 feet, mean depth to bedrock about 62 feet, mean depth to the…