Fig. 3: Contribution of groundwater withdrawal to land subsidence in the United States.
From: Land subsidence risk to infrastructure in US metropolises
a, Linear regression analysis of groundwater-level trends and VLM across 13 US cities. The blue, yellow and red lines are the regression lines for confined, unconfined and unknown aquifers, respectively. b, Correlation between time series of VLM and changes in groundwater levels for confined, unconfined and unknown aquifers. Each square represents a single well in the respective city. ND, wells with no data, where the wells are more than 50 m away from an InSAR pixel. c, Probability curves showing the likelihood of vertical displacement exceeding −1 mm (that is, displacement < −1 mm) in response to groundwater-level changes in confined aquifers across 5 US cities: New York; Washington, DC; Houston; Memphis and San Diego. Groundwater levels have been normalized across cities to account for variations in well depths. The dashed black vertical line represents the probability of exceeding −1 mm displacement at half the maximum groundwater decline observed in each city (P[VLM < −1|nGWL = −0.5], where nGWL refers to the normalized groundwater level). d, Comparison of groundwater level and InSAR displacement for wells in Houston, New York and San Diego. The location of the wells for each city is summarized in Supplementary Table 7.
