IGC Meeting Spring 2021
Drought Status Update & Monitoring Technical Committee Activities
The benefits obtained by the 2019-2020 Winter precipitation were eliminated by the 2020 monsoon season (July to September), which was the hottest and driest on record for most of Arizona. Arizona 2020 average precipitation (6.58 inches) ranked as 2nd driest on record for the 1895-2021 period. Dry conditions have persisted and spread throughout the Southwest, the April 2020 to March 2021 period 12-month precipitation ranking (of 126 years) was driest on record for Arizona (4.87 inches), Nevada, Utah, and New Mexico.
As of April 30, 2021, Water Year 2021 precipitation was less than 25% of average throughout most of the state, except for some small areas in Coconino, Yuma, Gila, and Pima counties. Long-term drought conditions have worsened and by April 2021, most of the state was in Extreme (D3) and Exceptional Drought (D4). As for short-term drought conditions, by May 4, 2021, 58% of the state was in Exceptional Drought, 29% was in Extreme Drought, 8% was in Severe Drought (D2), 4% was in Moderate Drought (D1), and just 1% was in Abnormally Dry (D0) conditions. These conditions have increased the need for groundwater use and irrigation throughout Arizona.
2021 Weather Outlook
According to the new set of 30-year “normals” released by the National Center for Environmental Information, Arizona is now over 1.5 degrees warmer than the average last century. The state has experienced some of the driest years on record in the past 20 years combined with temperatures much warmer than the 1950s, conditions that have contributed to the current drought.
Winter 2020-2021 was a typical La Niña winter resulting in above-normal temperatures and below-normal precipitation. While climate models favor a warmer than average summer, there is a possibility of a wetter than normal 2021 monsoon season. This may resolve soil moisture deficits and contribute to inflow into regional reservoirs. However, the random nature of thunderstorms may result in some communities receiving below-average precipitation. There is an approximately 40% chance of La Niña redeveloping during fall/winter 2021-2022 with a 40% chance of El Niño-Southern Oscillation (ENSO). If La Niña does reemerge, drier conditions would be likely again next year.
Colorado River Water Supply Update
According to the Colorado Basin River Forecast Center, as of May 5, 2021, the Lake Powell Snow Water Equivalent (SWE) was at 59% of the median (6.9 inches) for 2021. The peak seasonal SWE typically occurs during the second week of April, however, this year it happened two weeks earlier and it was 89% of the median. If dry conditions persist in the Colorado River Basin (CRB), the April to July 2021 Lake Powell SWE is projected to rank 3rd worst on record.
As of May 5, 2021, the total CRB system supply was 22.46 million acre-feet (MAF) or 37% of capacity. During this time last year, the total system supply was at 30.65 MAF or 50% of capacity. By May 5, 2021, Lake Powell supply was at 8.46 MAF or 35% of capacity (3,561.79 feet (ft)), and Lake Mead was at 9.88 MAF or 38% of capacity (1,078.46 ft).
According to the U.S. Bureau of Reclamation April 2021 24-month Study, water levels are projected to decrease in both Lake Powell and Lake Mead by the end of Water Year and Calendar Year 2021. Lake Mead was projected to end the Calendar Year 2021 at 1,067.24 ft, under 1,075 ft, this means that Arizona will be in a Tier One shortage Drought Contingency Plan (DCP) contribution condition of 512,000 AF during 2022. Furthermore, based on the 24-month Study Inflow Scenarios, there is a projection of Lake Mead reaching a Tier Two shortage going into 2023. Full Hydrology and Stress Test Hydrology 5-year projections indicate that the chance of Lake Mead shortage from 2023 to 2025 exceeds 75% each year, with a 92% to 93% chance of shortage in 2023.
Salt River & Verde River Watersheds Water Supply Update
In May 2020, the Salt and Verde River reservoir system was at 98% of the total storage capacity (2,255,907 AF). This allowed the system to stay above median levels going into the 2020-2021 Winter, despite record warm and dry conditions during the summer of 2020. Dry conditions have persisted, reducing soil moisture throughout the watersheds, and leading to record (or near-record) low inflows into the Salt River Project (SRP) reservoir system.
A storm in January 2021 brought significant precipitation (2.51 inches, 124% of normal) into the Salt and Verde River watersheds, and from late January to early February, the Verde River received significant snowpack (124% of normal). However, any available runoff was soaked into the dry soils, leading to the second lowest ranking SRP streamflow projection on record for January to May 2021 (102,000 AF, 19% of median), after 2018 (100,000 AF).
As of May 1, 2021, the Water Year 2021 cumulative watershed precipitation was 47% of normal (5.19 inches). As of May 4, 2021, the total SRP reservoir system was in good condition at 74% of the total capacity (1,689,760 AF). However, drought conditions have persisted throughout the watersheds, and SRP increased groundwater pumping during February, which is expected to continue in 2022.
2020-2021 Wildfire Season Update
A total of 2,520 fires were reported in 2020, burning approximately 978,519 acres of land (state, federal, and tribal). As of May 3, 2021, about 341 fires have been reported for the year, burning approximately 17,853 acres. Early fire activity was expected due to La Niña dry conditions, drought, and the carryover of fine fuels across the Sonoran Desert. By May 11, 2021, two Type 1 fire incidents were reported in Arizona. On a scale of 1 to 5, Type 1 fires are the most complex and require significant resources.
Widespread activity is predicted by late May and early June and the Arizona Department of Forestry and Fire Management is currently at a Preparedness Level 3 (moderate category). This means that two or more geographic areas (Arizona and New Mexico) require significant amounts of wildfire suppression resources from other states.
During 2020 about 82% of the fires in the state were human-caused, this is more than in 2019 (78%) and 2018 (68%). Human-caused fires are more prevalent in spring and early summer and coincide with windy and dry conditions, therefore fire restrictions are already in place.
2020-2021 Forest Health Update
Aerial surveys were conducted from July to September 2020 and showed an 82% decrease in total acres of bark beetle caused tree mortality (from 459,239 acres in 2019 to 81,031 acres in 2020). Any bark beetle damage that did occur mostly impacted ponderosa pine forests. There was, however, an increase in tree damage caused by forest insect defoliators and sap-feeding insects. Bark beetle caused tree mortality was observed to increase after the survey season due to the lack of monsoonal moisture and the La Niña winter. Therefore, an increase in tree damage is expected for the 2021 season. A wetter than normal 2021 monsoon season may result in improved forest and woodland health.
According to urban forest health surveys throughout the Phoenix Metropolitan area, there was an increase in Aleppo Pine Blight and Mediterranean pine mortality. The latter was caused by the Mediterranean Pine Engraver bark beetle.
Impacts of Drought on Wildlife
High temperatures and dry conditions have prompted the Arizona Game and Fish Commission and the Arizona Game and Fish Department (AZGFD) to monitor drought effects on wildlife with the objectives of responding to severe impacts and achieving sustainable management. As drought conditions increase, so do wildlife incidents. AZGFD staff conduct eagle rescues by providing food, health evaluations, rehabilitation, and rehydration. Additionally, staff and volunteers provide supplemental feeding to black-tailed prairie dog colonies during the dry months (March to June), to increase food availability during nutrient-dependent gestation and pup-rearing seasons, this also helps increase birth rate, by increasing nutrients during reproduction, and decreases predation and mortality.
AZGFD has been monitoring streamflow and water quality under drought conditions for fish stocking purposes as well as salvaging and relocating native fish species from drying habitats to wetter areas. Water hauling serves as an immediate relief for terrestrial wildlife during dry weather conditions, during 2020 a total of 2,393,190 gallons were hauled throughout the entire state. This was done with the help of over 15 partner organizations and more than 50 volunteers. Furthermore, the AZGFD had a “Send Water” campaign in 2019 and 2020, which increased financial support and awareness about the need for water in wildlife management.
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) data from December 2020 to May 2021, all Navajo Nation agencies (Chinle, Crownpoint, Fort Defiance, Shiprock, and Tuba City) average Standard Precipitation Index (SPI) levels have slightly improved from -2.0 or less (Exceptional Drought (D4)) to approximately -1.2 or -1.3 (Moderate (D1) to Severe Drought (D2)) due to winter precipitation. Precipitation data from November 2020 to May 2021 showed minimal rain events, with precipitation averages in Fort Defiance and Chinle agencies peaking at approximately 0.40 inches in January 2021. Drought has impacted domestic water haulers, public drinking water systems, irrigators, dryland farmers and ranchers, wildlife, forestry, and recreation. June is the driest month of the year for Navajo Nation and impacts are expected to continue.
Dry condition trends that started in 2020 have persisted into 2021, increasing short- and long-term drought conditions throughout the state. While the Salt and Verde rivers total reservoir supply is currently in good condition, Lake Powell and Lake Mead are projected to decline by the end of 2021, and there is a 97% chance that Arizona will be in a Tier One shortage in 2022. While there is a probability that the monsoon will be wetter than normal, some areas of the state may be drier than normal due to the random nature of thunderstorms. The Drought Interagency Coordinating Group unanimously recommended that both drought declarations (PCA 99006) and (Executive Order 2007-10) be kept in place.
- Drought Status Update and Monitoring Technical Committee Activities, Nancy Selover, State Climatologist, Drought Monitoring Technical Committee Co-Chair
- 2021 Weather Outlook, 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
- 2020-2021 Wildfire Season Update, Tiffany Davila, Arizona Department of Forestry and Fire Management
- 2020-2021 Forest Health Update, Alyssa McAlexander, 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