Document Type
Thesis
Abstract
Jamestown was the first permanent English settlement in America, and suffered high mortality rates from disease (up to 63%) during its early years. Historical documents detail symptoms consistent with widespread outbreaks of dysentery, typhoid fever, and salt poisoning during the early period. Jamestown was also settled at the start of the worst drought in the past 700 years. In this study, I present data on groundwater flow, specific conductivity, and the colony’s environment in order to evaluate salt poisoning as a cause of disease in the early colony. 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. Data from 18 groundwater-monitoring wells was used to measure groundwater head and specific conductivity using in situ pressure transducers, conductivity probes, and an acoustic look-down level sensor. Flow pathways suggest groundwater flows southward from the brackish swamp toward the Jamestown site. Groundwater specific conductivity decreases from 9000 uS/cm below the swamp to 200 uS/cm near the fort site. Modern observed salinities (0.8 g NaCl/L) within the fort are not high enough to cause acute health problems today. Hydraulic conductivity values obtained from well slug tests are ~10° m/s, and do not vary with depth despite a fining upward sequence found in the sediment. Based on hydraulic conductivity and continuous swamp, river, and head measurements over a four-month period, swamp waters take on average 6.5 years to reach colonist’s 1611 well. Dupuit simulations of water table elevation suggest that ~0.8m drops in water table elevation would occur during drought, a predicted lower 17" century sea level, and an extended colonial coastline. Swamp and river elevation averages were used to create a MODFLOW simulation and model the generalized water flow. A particle tracking simulation run using time averaged elevations found a swampto- 1611 well travel time of 8.7 years on average. This value takes into account the three-dimensional flow path of water in the shallow aquifer. Tidal oscillations in the groundwater table were recorded with pressure transducers. Tidal oscillations were used to calculate an aquifer storage of 4E-03 using both tidal lag and tidal efficiency metrics. Tidal amplitudes were found to attenuate in an east-west direction rather than with distance from the coastline as expected. This is interpreted as resulting from land disturbance related to the construction of a sea wall in 1905. This interpretation agrees with an analysis of 5 maps created over 333 years and writings from the engineer in charge of the project. This study proposes that during the colonial period, the brackish swamp was better connected to the James River, and that salinity introduction during drought would be enhanced. Drilling boreholes or using ground-penetrating radar in this area of the site may show evidence of the colonial-era extent of the swamp.
Date Awarded
2014
Department
Geology
Recommended Citation
Goodling, Phillip J., "Tidal river-aquifer salinity communication and its implications for drinking water quality in Jamestown, Virginia" (2014). Geology Senior Theses. William & Mary. Paper 313.
https://scholarworks.wm.edu/geologyseniors/313
