Climate change, population growth, urbanization, and interactions thereof may alter the water supply-demand balance and lead to shifts in water shortage characteristics at different timescales. This study assesses the vulnerability of water supply systems to the interannual to the decadal water shortage events across the contiguous United States (CONUS) by characterizing shifts in intensity, duration, and frequency (IDF) from current (1986-2015) to future (2070-2099) periods. The water yield was estimated using the Variable Infiltration Capacity (VIC) model driven with the Multivariate Adaptive Constructed Analogs (MACA) climate model with RCP 4.5 and 8.5. The water demand was projected under the A1B population growth scenario. The Water Evaluation and Planning (WEAP) model was applied to determine water shortage conditions in which water demand exceeds water supply. Changes in characteristics of shortage events were assessed using the Mixture Gamma-GPD model. The results indicate that the frequency and intensity of over-year (D>12 months) events at the monthly scale and decadal (D>10 years) events at the annual scale tend to increase in the Southwest, Southern, middle Great Plain, and Great Lakes. Conversely, the frequency of interannual (D<12 months) events at the monthly scale and annual (D>1 year) and multi-year (D>3 years) events at the annual scale may increase in the West Coast. Basins with a higher rate of aridification may experience more frequent over-year events while basins with a decrease in aridification may undergo more frequent interannual events due to an increase in the variability of extreme weather anomalies within a year under climate change.