**1. Introduction**

Southwestern United States drought persistence increases competition among various sectors of water use, affecting economic security. Continued dryness in the area is resulting in water level decline in various basins since 2000. Sustained dryness will result in water shortages not only for the immediate affected area, but other areas reliant on the basins for water. Local and state governments are implementing water conservation plans to allocate water usage [1]. For instance, the Colorado River basin will experience Tier 1 shortage in late 2021 and must implement drought contingency plans with lower basin states. As climate change continues, precipitation and temperature levels will be affected [2], thus there is a need to completely understand how water availability will be impacted.

Drought scenarios under climate change conditions at specific locations (Shasta Dam) have found changes in the drought frequency curves [3]. Expanded studies have looked at streamflow conditions at seven (7) locations in California under conditions forced from the coupled model intercomparison project (CMIP) in 2005 and highlighted changes in the seasonality of flows [4]. The distribution of streamflow under changing climate conditions was further evaluated in 2018 and identified a potential new normal of wetter winters and drier summers [5]. Pierce et al. predicted potential effects such as average annual temperature, precipitation, top level soil moisture, annual runoff, and snow water equivalent [6]. Piechota et al. studied water supply and drought duration, deficit (or magnitude) and severity in the Colorado River Basin to assess the deficit in relation to past paleo records [7]. However, there is a lack of information on the broad changes in California for water supply drought scenarios (e.g., duration, deficit and severity) under change climates.

**Citation:** Lynam, L.; Piechota, T. California Drought Outlooks Based on Climate Change Models' Effects on Water Availability. *Water* **2021**, *13*, 3211. https://doi.org/10.3390/ w13223211

Academic Editors: Alban Kuriqi and Luis Garrote

Received: 8 October 2021 Accepted: 10 November 2021 Published: 12 November 2021

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The specific objectives of the current study are to first evaluate water supply drought scenarios (duration, deficit, severity) for various river basins in California. Secondly, we evaluate the changes in water supply drought scenarios under climate change scenarios commonly used in assessment studies. The study provides novel contributions to the understanding of how climate change will impact water supply drought scenarios under changing climate conditions. Previous studies have not focused on understanding the impacts that climate change will have on drought (in the form of water supply) for multiple California streamflow stations. Analysis of streamflow and water supply under changing climates, regarding these three drought related categories will be a significant contribution.
