In addition to analyzing lake level variability, we also examine trends in the variability of precipitation, evaporation, and basin runoff, the three dominant components of net basin supply (Figure 1). Interannual variability of overlake precipitation is increasing for all four basins for both the Mann-Kendall trend test and the Kendall-Tau test (p < 0.001), except for one increasing, though non-significant result for Lake Superior using the Kendall-Tau test (p > 0.05). Similarly, the interannual variability of runoff is increasing for all four basins for both tests (p < 0.001) with the exception of runoff into Michigan-Huron, which is significantly increasing when using the Kendall-Tau test (p < 0.01) and increasing, though non-significantly, using the Mann-Kendall trend test (p > 0.05). The interannual variability of evaporation is rising universally across all basins for both statistical tests (p < 0.001). Placing these trends within the greater context of the GLM-HMD time series, precipitation variability peaked over the past decade for Lakes Superior, Erie, and Ontario, and reached values not seen since around 1960 for Lake Michigan-Huron. The variability of evaporation has risen steadily for all lakes throughout the entire time series from 1950 onward. Variability for Lake Michigan-Huron peaked in the 2000s, again the only lake not to see a variability maximum in the 2010s. All lake basins endured variability maxima in runoff in the past decade at levels not seen since the 1940s or earlier. Thus, we note statistically significant trends that coincide with component maxima largely not observed over the past six decades.