Atmospheric rivers (ARs) are extended, narrow bands of anomalously high water vapor transport that significantly affect the global water cycle and local weather patterns. They play a significant part in the hydrology of the West Coast of the United States, especially in California, where they affect the frequency of both floods and droughts. The three years of drought that California experienced from 2020 to 2022 were followed by devastating floods and debris flows, which were caused by strong landfalling ARs across the state. Climate change and aging flood-mitigation infrastructure increase the dangers presented by AR-induced floods. Using a reanalysis dataset, we characterize the series of AR events that occurred between December 2022 and January 2023 in terms of the intensity, AR category, etc. We quantify the impact of ARs using a variety of metrics from total precipitation to reservoir inflow rates/volumes. Not only do we identify the impact of a series of ARs on reservoirs throughout the state, but we also investigate each AR event and the antecedent conditions (e.g., soil moisture) to better understand how the combination of AR characteristics and land surface conditions present significant infrastructure challenges for water managers in their reservoir operations.