FULL OF SLIME AND FILTH: ASSESSING DRINKING WATER QUALITY DURING THE EARLY JAMESTOWN COLONY, VIRGINIA
The colony sat on an island in the James River estuary, and drinking water was drawn from shallow wells within the Jamestown fort site. The shallow unconfined aquifer here is fed by precipitation, a brackish swamp ~30 m from the fort site, and the James River directly adjacent to the fort site. We installed 18 groundwater-monitoring wells to measure groundwater head and water quality parameters. Flow pathways suggest groundwater flows southward from the brackish swamp toward the Jamestown site. Groundwater specific conductivity (SC) decreases from 9000 uS/cm below the swamp to 200 uS/cm within the fort site . Hydraulic conductivity values obtained from well slug tests are ~10-5 m/s, consistent with silty sands observed during well installation. Based on hydraulic conductivity and head gradients, swamp waters take several months to several years to travel to the fort site.
An end-member mixing model using dissolved organic carbon (DOC) and SC shows that precipitation makes up >50% in much of the modern aquifer, with its contribution increasing away from the swamp. Within the fort site where colonists extracted water, the mixing model suggests that ~15% of the water originated from the swamp. Using the ~70 yr precipitation record from the region, reconstruction of rainfall during severe drought suggests salinity would exceed 2 g/L NaCl in the groundwater. This is above the taste threshold, consistent with historical documents that describe “verie salt” water. Other water quality issues include 1) dissolved arsenic concentrations greater than 10 ppb in the aquifer and 2) rapid movement of fecal contaminants from surface to groundwater in precipitation events, suggesting water contamination by human wastes in the colony.