ICG Agenda - November, 10, 2020
The benefits obtained by the Winter 2019-2020 precipitation were eliminated by the 2020 monsoon season (July to September), which was the hottest and driest on record for most of Arizona. By October 1, 2020, 3% of the state was in Exceptional Drought (D4), 67% was in Extreme Drought (D3), 24% was in Severe Drought (D2) and 6% was in Moderate Drought (D1). A similar trend was observed for long-term drought conditions, and by October 2020 Extreme and Exceptional Drought spread throughout northeastern, central, and east central Arizona, and Moderate Drought covered most of the state. These drought conditions have increased the need for groundwater use and irrigation throughout Arizona. As of October 31, 2020, Water Year 2021 precipitation was less than 25% of average throughout most of the state (except for a small portion of east central Arizona). At the same time last year, Water Year 2020 precipitation was less than 25% of average precipitation for the entire state.
Winter 2020-2021 Weather Outlook
2020 had the hottest and driest summer on record for Arizona, this follows a long-term trend of warming in the state. The minimal monsoon led to a significant decrease in soil moisture, which may negatively impact runoff in the upcoming water year even if near average snowfall occurs. The outlook for Winter 2020-2021 indicates La Niña conditions persisting through the spring and potentially reaching moderate to strong levels. La Niña events, with a few historical exceptions, result in drier and warmer than normal conditions across Arizona, which might be expected this winter.
Colorado River – Water Supply Status
Observed inflow into the Colorado River Basin (CRB) System for April through July 2020 was 3.76 million acre-feet (MAF), or 52% of average, just under the 5.85 MAF (54%) observed for the entire 2020 Water Year. While the observed inflow for October was at 18% of average, this is projected to increase into the winter and January 2021 inflow may reach 66% of average. As of November 5, 2020, the total CRB System storage was at 28.19 MAF or 46% of capacity. According to the U.S. Bureau of Reclamation October 24-Month study, Lake Powell is projected to be at elevation 3,584.57 feet, with 10.34 MAF (43% capacity) in storage at the end of Calendar Year 2020; Lake Powell operations in Water Year 2021 will be governed by the Upper Elevation Balancing Tier, with an initial water year release volume of 8.23 MAF and the potential for an April adjustment in 2021. As of the October 24-Month Study, Lake Mead is projected to be above 1,075 feet and below 1,090 feet for both the end of Calendar Years 2020 and 2021; this means that Arizona will be in a Tier Zero Drought Contingency Plan (DCP) contribution condition (192,000 AF) during Water Year 2021 and possibly Water Year 2022.
Salt River & Verde River Watersheds – Water Supply Status
The past two winters brought enough inflow into the Salt and Verde River reservoir system to nearly fill it to capacity this year. During March 2020 the reservoir system received 438,705 AF of inflow and by May 4, the total system peaked at 2,255,907 AF (98% of storage capacity). However, the monsoon season (June 15 to September 30) precipitation was 30% of normal (1.93 inches) and the driest over the 121-year record. Dry conditions throughout the summer led to the lowest monsoon season reservoir inflow (32,388 AF). While there was minimal runoff, Salt River Project (SRP) monitored a few storm events where local runoff and water quality into the lower elevation portions of the watershed were impacted by wildfires (ie. Bush Fire). As of November 3, the total Salt River Project surface water supply was at 1,803,570 AF (79% of total storage capacity). Total watershed precipitation for Water Year 2020 was at 91% of normal (16.61 inches) and the total Salt and Verde River reservoirs inflow was 124% of median (1,058,665 AF). Groundwater pumping has been minimal in the SRP service area this year and it is projected to be similar in 2021.
2020 Wildfire Season Update
As of November, about 2,324 fires were reported for 2020, burning approximately 959,000 acres of land (state, federal and tribal). This is more than 2017, 2018, and 2019 combined (about 948,449 total acres). About 81% of fires in 2020 have been human caused. Winter moisture contributed to abundant fine fuels (grasses and brush vegetation) and above normal spring temperatures dried these out quickly and early in the year. There were three large-scale fires that started in June: Bush Fire at Tonto National Forest (human caused), Bighorn Fire at Coronado National Forest (lightning caused) and the Magnum Fire at the Kaibab National Forest (cause unknown). Significant moisture throughout the Central Region of the state would be necessary to improve conditions. While the fire season typically peaks at the end of April and beginning of May in Arizona, fire activity has been observed throughout the year and is expected to continue through December due to La Niña conditions. Fire restrictions were in place up to November 11, 2020.
Impacts of Drought on Wildlife
As drought increased throughout Arizona this summer, the Arizona Game and Fish Department faced challenges hauling water to different water catchments and invested in re-designing these infrastructures to hold water for longer periods of time. Streams, springs, and wetlands have dried up due to drought, impacting wildlife such as Springsnails, which experienced a reduction in their populations, and waterfowl. While there was an increase in fishing license sales in 2020, the lack of precipitation throughout the state reduced water levels and quality in small reservoirs and lakes, affecting fish populations and the ability to stock trout for recreational fishing. Furthermore, the extreme heat and dryness has led to increased human and wildlife accidental interactions.
Impacts of Drought on Navajo Nation
Navajo Nation Department of Water Resources monitoring efforts and data management processes were challenged by the COVID-19 pandemic, affecting drought condition data collection. According to the National Aeronautics and Space Administration’s (NASA) Climate Engine Drought Severity Evaluation Tool (DSET), all Navajo Nation agencies (Chinle, Crownpoint, Fort Defiance, Shiprock, and Tuba City) 6-month average SPI levels were at or below -1.5 by September 2020, which ranges from Extreme Drought to Exceptional Drought conditions. Precipitation data from January to October 2020 showed minimal rain events, with peak precipitation averages in Fort Defiance Agency, which was under 0.55 inches around February 2020. Streamflow data showed little or no flow throughout the Chuska mountain range, Chinle, and the Defiance Plateau. Drought has impacted domestic water haulers, public drinking water systems, irrigators, dryland farmers and ranchers, wildlife, forestry, and recreation. This summer, the Navajo Nation Commissioners on Emergency Management reaffirmed the existing Drought Declaration, and the 2003 Navajo Nation Drought Contingency Plan is being implemented.
Drought in Arizona and reservoir conditions throughout the Colorado River, Salt River, and Verde River watersheds improved at the beginning of 2020. However, the monsoon season was the hottest and driest on record for most of the state and Winter 2020-2021 will likely be warmer and dryer than average due to La Niña conditions in the Pacific Ocean. The Drought Interagency Coordinating Group unanimously recommended that both drought declarations be kept in place.
Fall 2020 Drought ICG Recommendation Letter to the Governor
- Drought Status Update and Monitoring Technical Committee Activities, Nancy Selover, State Climatologist, Drought Monitoring Technical Committee Co-Chair
- Winter 2020-2021 Weather Outlook, Mark O'Malley, National Weather Service, Drought Monitoring Technical Committee Co-chair
- Colorado River Water Supply Update, Craig McGinnis, Arizona Department of Water Resources
- Salt River & Verde River Watersheds Water Supply Update, Stephen Flora, Salt River Project
- 2020 Wildfire Season Update, Tiffany Davila, Arizona Department of Forestry and Fire Management
- Impacts of Drought on Wildlife, David Weedman, Arizona Game & Fish Department
- Impacts of Drought on Navajo Nation, Carlee McClellan, Navajo Nation Department of Water Resources