ICG Agenda - November 28, 2018
Meeting Summary
Drought Status
Drought conditions at the end of 2017 water year were minimal due to the relatively wet winter of 2016-17 and a reasonably wet, though short, monsoon season. Only the southwest remained in moderate drought, central and eastern Arizona were abnormally dry, and the northwest and southeast experienced no drought. As the water year began in October 2017 however, the state had dried out and remained dry until mid-December. A few winter storms dropped scant precipitation through March, bringing severe and extreme drought back to the state. By April 2018, the entire state was in moderate drought or worse. The northwest and southern third of the state were in Severe Drought, while central and northeastern Arizona were in Extreme Drought. Spring continued to be quite dry with forest fires around the state, and water hauling for livestock and wildlife. The fire threat became so extreme that state lands were closed to recreational use. Groundwater wells ran dry in a number of places around the state. By the time the 2018 monsoon activity began, the moisture deficits were significant, and the monsoon rainfall was not sufficient to make up the deficits on the Colorado Plateau and in southwestern Arizona. However, the Mogollon Rim, southern Coconino and northern Yavapai counties, and the southeast corner of the state showed one-category drought improvement.
Weather Outlook
Water temperatures in the tropical Pacific have warmed fairly rapidly during the late summer and fall of 2018 leading to the likelihood of an El Niño phase during the winter of 2018-19. There is better than a 90% chance of an El Niño persisting through the winter months and perhaps persisting through spring 2019. While many other factors can influence the winter weather patterns in Arizona, the El Niño phase has historically provided some influence in long-term winter predictions for the Southwest United States. The El Niño phase this winter will likely peak only in a weak category but could briefly touch a moderate stage. A more prolonged moderate El Niño is unlikely, but a period of more heightened warmer Pacific waters could tilt the odds towards a wetter than normal winter. NOAA’s Climate Prediction Center official outlook for January-March 2019 indicates a better chance that the average temperature will be above normal. This is supported by both forecast models and the longer-term trend of distinctly warmer winters in the Southwest over the past 10-20 years (i.e. climate change).
Salt River & Verde River Watersheds – Water Supply Status
In 2018, the Salt River and Verde River watersheds experienced the lowest winter runoff season (January-May) on record dating back to 1913 with only 100,000 acre-feet of inflow. As a result, Roosevelt Lake saw little to no increase in storage remaining at approximately 58% throughout the winter. In addition, Bartlett and Horseshoe reservoirs on the Verde system declined from 59% to 31% following the dry winter. During the monsoon season, slightly above normal precipitation was received; however due to extremely dry conditions throughout the watershed, only minimal additional runoff occurred with little to no impact on overall storage. As of October 3, 2018, total storage of the Salt and Verde system was at 46% capacity compared to 65% at this time last year.
Colorado River – Water Supply Status
Cumulative precipitation received within the Upper Colorado River Basin during water year 2018 was 65% of average. The Colorado River total system storage experienced a net decrease of 4.9 MAF (~8%) and reservoir storage in Lake Powell and Lake Mead decreased by 3.629 MAF and 0.312 MAF respectively in water year 2018 compared to water year 2017. As of November 26, 2018, total system storage was 46% of capacity (27.39 MAF). Snowpack conditions throughout the 2018 snow accumulation season (October - April) also trended below average across most of the Colorado River Basin. On April 1, 2018, basin-wide snow-water equivalent measured 73% of average. April through July unregulated inflow volume to Lake Powell was 2.6 MAF, which is 36% of average. Lower Colorado River Basin tributary inflows upstream and downstream from Lake Mead were also below average for water year 2018. Though no shortage will be declared in 2019, the official operational forecast made by United States Bureau of Reclamation in August 2018 shows a 57% chance of a shortage declaration in 2020.
Impacts of Drought on Wildlife
Over one million gallons of water were hauled to various catchments around Arizona from January through August 2018. Over 400,000 gallons were hauled to the Yuma region alone. Populations of Arizona Toads, Chiricahua Leopard Frogs, and Sonoran Tiger Salamanders have been negatively impacted by the loss of breeding habitats such as streams, ponds, and stock tanks that have gone dry due to drought conditions. Additionally, the drought had likely played a role in an outbreak of epizootic hemorrhagic disease amongst deer populations in the Prescott area. Toxic algal blooms caused by low water levels and warmer temperatures have been observed in numerous lakes throughout the state, posing a threat to fish, wildlife, and people.
Forest Health and Wildfire Season Update
As of November 26, 2018, 1,968 fires damaged 161,356 acres in Arizona in 2018, a decrease from the 419,418 acres burned by numerous large-scale wildfires in 2017. This decrease is mainly attributed to the closure of public lands for recreational activities and not to improved drought conditions, which in fact were much more severe in 2018 than in 2017. Heavy rainfall in October triggered an increased growth of warm weather vegetation, acting as fine fuels that will become susceptible to fire as they go dormant. The current drought stresses forests and urban vegetation and renders trees vulnerable and less capable of deterring pests. Based on historic data, Arizona is experiencing bark beetle conditions similar to the onset of the 2002-2003 infestation that impacted 2.2 million acres of trees during these very dry years. Currently, the 2018 aerial and ground survey detected 275,934 acres of trees impacted by bark beetles compared to 45,003 acres in 2017, which is an increase of 513%. Roughly 90% of the current bark beetle damage is occurring in ponderosa pine, one of the more valuable trees in Arizona.
Impacts of Drought on the Navajo Nation
The Navajo Nation experienced significant drought impacts during the past year, which triggered the renewal of the Nation’s Drought Emergency Declaration in February 2018. Each of the Nation’s five agencies have observed a downward trend in annual average precipitation since 1984. August and September were much drier than average, with areas receiving as little as 32% of average precipitation. Tropical storm activity in October however, brought all five agencies’ annual precipitation to above average. The Navajo Nation is currently updating its 2003 Drought Contingency Plan and is considering other drought indices, such as evapotranspiration.
Fall 2018 Drought ICG Recommendation Letter to the Governor
Presentations
- Drought Status Update and Monitoring Technical Committee Activities, Nancy Selover, State Climatologist, Drought Monitoring Technical Committee Co-Chair
- Winter 2018-2019 Weather Outlook, Mark O'Malley, National Weather Service, Drought Monitoring Technical Committee Co-chair
- Salt River & Verde River Watershed Water Supplies, Stephen Flora, Salt River Project
- Colorado River Water Supply Status, Rabi Gyawali, Arizona Department of Water Resources
- Impacts of Drought on Wildlife, David Weedman, Arizona Game & Fish Department
- Forest Health and Wildfire Season Update, John Richardson, Arizona Department of Forestry and Fire Management
- Impacts of Drought on the Navajo Nation, Carlee McClellan, Navajo Nation Department of Water Resources
Meeting Summary
Drought Status
This water year (WY) has been very dry across the western U. S. and Arizona received very little rain and snow, which exacerbated short-term drought conditions. Monsoon storms were almost entirely limited to the month of July, and from October through December, less than 25% of average precipitation was received. Snow cover is typically highest across the Southwest on March 1st; however, snow cover observed this March was minimal to non-existent, putting the entire basin in a snow drought. As of late May, 3% of the State was in Moderate Drought, 24% in Severe Drought, 57% in Extreme Drought and 16% in Exceptional Drought. This is a stark contrast to May of last year in which the northern half of Arizona was completely free of drought and the southern part was partly in abnormally dry and in moderate drought conditions. This exceptionally dry winter has extended the wildfire season, decimated forage, and led to many wells going dry. Even native desert vegetation, such as creosotes, appear to be dying in some locations. Over the past month, there has been an increase in water hauling, supplementing feed for livestock, and culling of herds. These drought conditions have also led to drought emergency declarations in Yuma County and the Navajo Nation. Long-term statewide average precipitation in WY 2017 seemed to be nearing the mean (12.59 inches) of recorded data, however that trend is now sloping downwards with less than 10 inches of rain in WY 2018 thus far.
Weather Outlook
NOAA’s Climate Prediction Center’s outlook for Summer 2018 suggests slightly enhanced odds for wetter than normal monsoon season due to warmer than average East Pacific waters and likelihood that the typical summer subtropical high-pressure system will be favorably located to frequently bring moisture into the State. However, summer thunderstorms are usually quite erratic and may only provide partial and local relief to long-term drought conditions. Temperatures this summer are likely to be warmer than average based on consistent trends in recent years. The weak to moderate La Niña conditions, which existed last Fall and Winter and were partially responsible for the poor rain and snow in the Southwest, are now transitioning into a neutral state. Based on past winters’ trend, there are better odds for above normal temperatures this winter. There is no large tilt in odds for above, below or near normal precipitation for the upcoming winter.
Salt River & Verde River Watersheds – Water Supply Status
Salt-Verde watershed cumulative precipitation for August through April amounted to 5.17 inches, which is 33% of normal and the driest on record (since 1896). Salt River, Tonto Creek, and Verde River spring runoff from 2011 to 2018 indicate the driest consecutive 8-year period on record. Inflow from January to May amounts to 99,000 acre feet compared to last year’s 970,440 acre feet. Since 2010, reservoir storage has declined 57% from 2.311 million acre feet (MAF) to 1.337 MAF. Utilizing both the gaged record and the University of Arizona’s Tree Ring Laboratory record from 1361 to 2005, SRP has determined that the last 23-years (1996—2018) have been the driest in the entire record (1361—2018), officially making the last few decades the worst megadrought in recorded history for the Salt and Verde basins. Despite the dry conditions, total system storage of Salt River Project (SRP) reservoirs amounts to 1.309 MAF (57% of maximum capacity) as of mid-May due to calculated water management.
Colorado River – Water Supply Status
This winter was exceptionally dry on most of the Colorado River basin, and the entire system reservoirs are at 51% of maximum capacity or 30.434 million acre feet (MAF). This is only a decrease of roughly 1% from last May. Lake Powell and Lake Mead are at 52% (12.679 MAF) and 39% (10.247 MAF) of capacity, respectively. Lake Mead’s elevation is just below 1,083 feet, eight feet above Tier-1 shortage. In the Upper Basin, this year’s snow water equivalent reached 12 inches at its peak, which is 4 inches below the 1981-2010 median, and only 51% (5.5 MAF) of unregulated inflow is projected for Lake Powell. Projected elevations for Lake Powell and Mead by year-end are approximately 3590.43 feet or 45% of capacity (a 13% decrease from December 2017) and 1079.1 feet or 38% of capacity, respectively. Though no shortage on the Lower Basin is currently predicated for 2019, the Bureau of Reclamation predicts a 52% probability of a Tier-1 shortage in 2020. Furthermore, this is the first time that the probability of a double-digit Tier-3 shortage has been projected within a 5-year outlook period.
Impacts of Drought on Wildlife
In the Pinetop Region, 110,150 gallons of water were already hauled so far this spring to 41 catchments. Increased salinity in SRP reservoirs and urban lakes due to low inflows cause growth of golden algae bloom, which is toxic to fish. Low spring inflow into one of the endangered Gila topminnow habitat cause the disappearance of one of its population as the habitat could no longer support the fish.
Forest Health and Wildfire Season Update
Many of last year’s burned acres regrew before the State launched into 120 days of dry weather providing ample fine fuels that invite greater opportunity for fire activity. As of May 20, there have been 611 fires: 604 of these were caused by human activity while 7 by natural conditions. Many state lands are currently closed to recreation, which have helped reduce wildfire occurrence. Drought stress in forest and urban vegetation render trees vulnerable and less capable of deterring pests. Increased juniper mortality due to drought stress has been observed this year. In addition, 80,469 acres of forest trees were killed or damaged due to bark beetles and defoliators/sap feeders in 2017. Yet these figures pale in comparison to the extremely dry years of 2002 and 2003 when bark beetles decimated 570,000 to 763,000 acres of ponderosa pine forest.
Northern Arizona Forest Fund Efforts
The Northern Arizona Forest Fund (NAFF), a regional initiative of the National Forest Foundation, supports watershed restoration projects across five forests in Northern Arizona. Over $2.5 million have already been invested over 4 years, engaging 24 donors and 200 volunteers who donated over 1500 hours. So far, 21 restoration projects have been completed in non-market-value, high-priority locations where restoration work would not have otherwise been funded. The NAFF is working on improving hydrologic functions through restoration of springs, wetlands, streams, and meadows. NAFF projects also focus on minimizing severe fire risk through prescribed burning, small-diameter tree thinning and sediment and erosion control improving the flow and quality of waterways and reservoirs. In program year 2017, NAFF efforts have reduced 31 tons of sediment on 37 miles of roads and trails, replenished 2.3 million gallons of water, and reduced fire risk by 27% on 3,500 acres.
Spring 2018 Drought ICG Recommendation Letter to the Governor
Presentations
- Drought Status Update & Monitoring Technical Committee Activities, Nancy Selover, State Climatologist, Drought Monitoring Technical Committee Co-Chair
- Summer 2017-2018 Weather Outlook, Mark O'Malley, National Weather Service, Drought Monitoring Technical Committee Co-chair
- Colorado River - Water Supply Update, Jeff Inwood, Arizona Department of Water Resources
- Salt River & Verde River Watershed - Water Supply Update, Charlie Ester, Salt River Project
- Forest Health & Wildfire Season Update Jeff Whitney, John Richardson, Steve Mckelvey, Arizona Department of Forestry and Fire Management
- Northern Arizona Forest Fund Efforts Rebecca Davidson, National Forest Foundation