Box 3 Use of Well Record Data to Identify Areas of the United States Vulnerable to Seawater Intrusion

A study (Jasechko et al., 2020) to identify coastal areas of the contiguous United States where most well water elevations lie below sea level, and therefore identify areas potentially vulnerable to seawater intrusion, made extensive use of well record databases from states with coastal exposures (Figure Box 3-1). The study used static water levels (i.e., measurements made following well completion but before a pump was installed in the well) from over 50,000 wells measured since the year 2000 as recorded on well construction reports. The measurements agreed with nearby monitoring well readings, suggesting that the well records provide reliable data on groundwater elevations. The use of the well record database afforded the study authors with a high density of observations and a wide range of aquifer depths.

Figure Box 3–1 – Well water elevations across the contiguous United States. The center map shows unique well locations within 50 km of the coastline, with the dot color corresponding to the well water elevation measured after January 1, 2000. Interpolated water level elevations are shown in the six inset maps.

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