Winter 2019-2020 precipitation was 150% above average, reducing or eliminating drought conditions in all but northeastern Arizona on the short and long-term scales. Northeastern Arizona, western Coconino, Navajo, and most of Apache County have remained drier than average. A combination of minimal precipitation and warmer than average temperatures in June led to an increase of wildfires throughout the state and to the introduction of Abnormally Dry (D0) conditions around central and southeastern Arizona. As of June 16th, about 7% of Arizona was in Severe Drought (D2), 7% was in Moderate Drought (D1), 19% experienced Abnormally Dry (D0) conditions, and 67% was out of drought. On June 26th, the National Oceanic and Atmospheric Administration (NOAA) calculated the new 30-year temperature and precipitation averages. The new “normals” range from 1991-2020 and are warmer and drier than the previous period (1981-1990).
According to climate models and past (10—15 year) trends in Arizona, warmer than average temperatures are expected for July, August, and September of 2020. There are currently no strong climate model trends to indicate how wet the monsoon may be this summer. Last year, moisture transport into the Southwest was hindered, likely due to cool sea surface temperatures (SSTs) in the Pacific. This year, there is a mix of warmer and cooler than average SSTs. Neutral tropical Pacific conditions will persist through the summer with La Niña conditions possibly developing by early fall. Should La Niña become the predominant Pacific oscillation, drier and warmer weather would become favored in Arizona during fall and Winter 2020-2021.
Colorado River – Water Supply Status
As of June 19, 2020, the total Colorado River Basin (CRB) System was at 51% of capacity (31.46 million acre-feet (MAF)). These levels were slightly better compared to the same time in 2019 (50% or 30.33 MAF). However, conditions throughout the CRB have been dry and the unregulated inflow into Lake Powell for Water-Year 2020 was forecasted at 62% of average (6,762 thousand acre-feet (KAF)). On April 1st, about two weeks earlier than normal, snow water equivalent in the CRB reached its highest point at 107% of peak seasonal median, and runoff was soaked up by the dry soils. According to a Bureau of Reclamation Stress Test Hydrology Model for the next five years at the Lower Basin and Lake Mead, Arizona is trending towards a drier future. Drought Contingency Plan (DCP) agreements and the resulting conservation measures have prevented any shortage conditions on Lake Mead with about 700,000 AF conserved by the Lower Basin states and Mexico in 2020. While there is no risk for shortage this or next year, there is some (9%) risk of shortage in 2022.
Salt River & Verde River Watersheds – Water Supply Status
Cumulative watershed precipitation this past fall, winter, and spring was at 130% of normal (9.30 inches) with two wet periods and a dry period in between. Winter stream inflow into the Salt, Verde, and Tonto rivers, which normally occurs during January-May, was at 150% of median (782,000 AF). Flows on the Salt River remained high into late April and early May with late season snowmelt. On May 7th, the total system peaked at 98% of storage capacity (2,255,824 AF). As of June 22nd, the total system was at 94% capacity (2,154,640 AF); the Salt River storage capacity was at 96% (1,914,464 AF) and the Verde River was at 84% (240,176 AF). These improved conditions lead to a reduction in SRP projected groundwater use in 2020 from 100,000 AF to 80,000 AF. SRP worked with the Bureau of Reclamation on the Salt and Verde River Reservoir System SECURE Reservoir Operations Pilot Study, which evaluated the reliability of the Salt and Verde River reservoir system for various future conditions and impacts.
Forest Health Update
Winter 2018-2019 precipitation improved drought conditions throughout the state, but the moisture also caused a native foliar blight that defoliated over 33,000 acres of aspen forest across northern Arizona. Bark beetle populations from Water Year 2018 caused tree mortality on approximately 459,239 acres in 2019, an increase of 66% (from 275,934 acres in 2018). Drought conditions have improved in 2020 and so has forest and woodland health. As a result, bark beetle related tree mortality is expected to decrease. The Aleppo Pine Blight and the Mediterranean Pine Engraver beetle populations are being monitored through ongoing urban forest health programs in the Phoenix Metropolitan area. While the Aleppo pine blight population was reduced in 2020, the Mediterranean pine engraver has the potential to spread to other tree species and thus requires control measures that will be tested in 2021.
Arizona Department of Water Resources Interactive Drought Dashboard
The ADWR Interactive Drought Dashboard shows short-term drought conditions in Arizona from 2000 to present and can be used to explore drought conditions for the entire period or for specific time frames; for the whole state or for a selected county. The ADWR Interactive Drought Dashboard can be found on the ADWR Drought website.
Drought in Arizona and reservoir conditions throughout the Colorado River, Salt River, and Verde River watersheds have improved compared to 2019. However, the beginning of the summer has been warm and dry, and these trends are expected to continue into fall and Winter 2020-2021. The Drought Interagency Coordinating Group unanimously recommended that both drought declarations be kept in place.
- Drought Status Update and Monitoring Technical Committee Activities, Nancy Selover, State Climatologist, Drought Monitoring Technical Committee Co-Chair
- Weather Outlook for Summer 2020 & Winter 2020-2021, Mark O'Malley, National Weather Service, Drought Monitoring Technical Committee Co-chair
- Colorado River Water Supply Update, Bret Esslin, Arizona Department of Water Resources
- Salt River & Verde River Watersheds Water Supply Update, Stephen Flora, Salt River Project
- Forest Health Update, Aly McAlexander, Arizona Department of Forestry and Fire Management
- Arizona Department of Water Resources Interactive Drought Dashboard, Némesis Ortiz-Declet, Arizona Department of Water Resources