Table 1 Temporal variations in the proportion newly drilled wells that are deeper than a nearby (within 20 km) well that pumps fossil water (Supplementary Fig. 2 for schematic of analysis).
From: Widespread and increased drilling of wells into fossil aquifers in the USA
Time interval | Total number of areas* analyzed | Number of areas* where the rank correlation coefficient is greater than zero (i.e., the proportion of wells being drilled deeper than a nearby well that is known to contain fossil water is, if anything, increasing over time) | Number of areas* where the rank correlation coefficient is less than or equal to zero (i.e., the proportion of wells being drilled deeper than a nearby well that is known to contain fossil water is not increasing over time) | Number of areas where the rank correlation coefficient is undefined | (the number of areas with rank correlation coefficient of greater than zero) divided by (the number of areas with rank correlation coefficient of less than zero) |
|---|---|---|---|---|---|
1950-1975 | 436 | 230 | 144 | 62 | 1.6 |
1975-2000 | 703 | 400 | 190 | 113 | 2.1 |
2000-2015 | 855 | 433 | 314 | 108 | 1.4 |
1950-2015 | 427 | 303 | 100 | 24 | 3.0 |
1975-2015 | 643 | 451 | 131 | 61 | 3.4 |
