Table 1.
Effect of Dropping Covariates and Their Associated Terms From the Comprehensive, National‐Scale GRM According to Adjusted Log Likelihood Ratio (LR) Test Proceduresa
| Covariates/Factors | DF | LR Test P Value (Adjusted) |
|---|---|---|
| Geology and Hydrogeological Variables | ||
| Surface geology and all statistical interactions | 56 | 0 |
| TSSC and its interaction with surface geology | 1 | 5.2 × 10−4 |
| Hydraulic conductivity | 1 | 0.0334 |
| Specific yield | 1 | 0.6129 |
| Darcy flux | 1 | 0.6633 |
| Well depth and interaction | 15 | 8.3 × 10−5 |
| Hydrodynamic and Groundwater Recharge Variables | ||
| Wet‐season groundwater table (GWT‐wet) | 1 | 0.9914 |
| Groundwater‐level trends | 1 | 0.0754 |
| Mean groundwater fluctuation | 1 | 0.3436 |
| Mean PGI recharge and statistical interaction | 15 | 0.0073 |
| Net changes in recharge | 15 | 0.0016 |
| Geographical, Altitudinal, and Seasonal Factors | ||
| Geographic coordinates (longitudes and latitudes) and statistical interactions | 7 | 0.0008 |
| Surface elevation | 1 | 0.9147 |
| Seasonality (sine + cosine of sampling dates) | 2 | 0.5839 |
| Geographic coordinates and interaction, surface elevation, and seasonality terms | 10 | 0.0008 |
| Groundwater‐Fed Irrigation | ||
| Irrigation trends (1985−1999) | 1 | 0.1470 |
| Irrigation trends and net recharge changes | 2 | 0.0011 |
| Irrigation trends, mean PGI recharge and its interaction, and net recharge changes | 17 | 3.8 × 10−7 |
| Statistical Interaction Terms | ||
| Only geological interaction terms | 42 | 0 |
a
P values derived from LR test and any value less than 10−10 is reported as zero. DF denotes degrees of freedom.