Box 6 Use of Well Record Data to Identify Dry Wells in the Western USA
A study by Perrone and Jasechko (2017) used over two million water-well records from 1950 to 2015 in the western United States to estimate the percentage of wells that were dry during the years 2013 to 2015. The analysis of the water level from 2013 to 2015 compared to well depths was used to highlight potential groundwater management issues in the western United States. The study showed that approximately 3.3 percent of wells constructed between 1950 to 2015 had water well bottom elevations below interpolated water levels, 6.3 percent of the wells had a water level that was 0 to 5 m above the bottom of the well, and 17.5 percent of wells had a water level that was 0 to 10 m above the bottom of the water well. The analysis indicates that many domestic wells are vulnerable to declining water levels, including California’s central valley, which can lead to costly or challenging adaptation scenarios (Figure Box 6-1). Domestic wells tended to be shallower, and therefore more sensitive to water level declines, compared to agricultural wells.
Figure Box 6–1 – The map shows the percentages of wells with estimated water tables that are deeper than the bottom of the wells, which are interpreted to be dry wells for the western United States in 2013-2015. Black shaded regions have high topographic slopes (> 3 percent) and were not analyzed. Dark gray areas mark regions with slopes of less than 3 percent, but with insufficient groundwater well data for analysis (i.e., less than 20 groundwater wells were analyzed in the study). Modern water tables (2013-2015) were determined using wells shallower than 100 m.