This metadata record describes a series of tabular datasets containing metrics used to characterize periods of anomalously low storage for select large reservoirs across the Conterminous United States for the climate years (April 1 – March 31) from 1981 to 2020. These data support the associated Simeone and others (2024) publication. The reservoirs in this dataset are those included in the ResOpsUS dataset, with sufficient data during the period of interest. These metrics include reservoir storage percentiles, identified low-storage anomaly events, annual low storages, low-storage anomaly statistics for each event, and trends in reservoir metrics. This data release contains the following files. ========== One version of the following three files for variable threshold method low-storage anomaly (weibull_jd), fixed threshold method low-storage anomaly (weibull_site), and operating curve-based low-storage anomalies (operating curve). Substitute each of these strings in parentheses for the strings here between *. 1) percentiles_1981_2020.zip: Percentile zip files for the period of 1981-2020. This zip file contains the reservoir storage, inflow, and outflow percentiles as individual csv files for each reservoir (for example, res_ops_XXX.csv, where XXX is the ResOpsUS reservoir identification number) including percentiles from each different method. The metadata contains column details for an example version of these files. 2) reservoir_1981_2020_*weibull_jd*_drought_properties.csv: This is a csv file that contains summaries of each low-storage anomaly event for each reservoir for each threshold. One of these files exists for each of our three low-storage anomaly methods. The three files included have different labels for each of the three different methods of identifying low-storage anomalies. 3) reservoir_1981_2020_*weibull_jd*_complete_annual_stats.csv: This csv is a csv file that contains the annual low-storage anomaly statistics for each climate year, threshold, and reservoir. The three files included have different labels for each of the three different methods of identifying low-storage anomalies. 4) reservoir_1981_2020_*weibull_jd*_trends.csv: This csv contains data on trends in low-storage anomaly characteristics for selected reservoirs during our primary period of interest from 1981 to 2020. 5) reservoir_metadata.csv: This csv file contains metadata for each reservoir.