ICG Agenda - November 16. 2017
The 2016-17 winter through April was quite wet across the western U. S. and the northern two-thirds of the State received sufficient rain and snow to alleviate short-term drought. Southern Arizona did not receive as many winter storms and remained warm through the winter. Spring was also quite dry in southern Arizona, which prevented any short-term drought improvement. By the time the monsoon activity began, the moisture deficits were significant, and the monsoon rainfall was not sufficient to make up the deficits in south central and southwestern Arizona, even though Tucson had the wettest July ever with 6.80” of rain. Much of Graham and Cochise counties had frequent rain showers and short-term drought was eliminated there by the end of the summer. Northern Navajo and Apache counties were in good shape through the winter, but the relatively dry spring and summer brought abnormally dry conditions back by September. Much of the state is still experiencing abnormally dry or moderate drought conditions.
The official outlooks from NOAA’s Climate Prediction Center for January-March 2018 show a much better chance that the average temperature will be above normal. This is supported not only by forecast models and the influence of La Niña that is likely to persist through the winter, but more so the fact that Arizona winters are distinctly trending warmer over the past 10-20 years. The precipitation outlook depicts a slight tilt in odds towards drier than average winter, which is primarily a result of the La Niña forecast. Should La Niña conditions become stronger through the fall and winter, these odds may lean even more towards the drier than average side. The Climate Prediction Center’s outlook for July-September 2018 shows much better chances that the average temperature during these three months will be above normal.
Colorado River – Water Supply Status
The entire Colorado River Basin experienced a relatively wet winter, but these gains have weakened due to a warmer and drier than average spring. Total system capacity on the Colorado River Basin has improved from 51% at the end of 2016 water year to 55% at the end of 2017 water year. Reservoirs in the Upper Basin are relatively full, with some receiving over 200% of average inflow, and Lake Powell reached approximately 60% capacity. However, Lake Mead is only about 39% full, with less than 1,081 feet in elevation. Even though this winter helped generating higher-than-normal streamflow, Lake Mead could have declined to as low as 1,065 feet in elevation at the end of this calendar year, if rigorous conservation efforts were not pursued. Cumulatively, these efforts helped conserve about 1.5 million acre-feet in Lake Mead, which is around 18 feet of elevation. Both the conservation efforts and the wet winter helped keep Lake Mead out of a shortage in 2018; however, the probability of shortage in the very near future is still significant at 15% for 2019 and over 40% for the next three years. Furthermore, based on the last 28 years of historical hydrology, there is about 50% chance that Lake Mead will decline to a critically low elevation of 1,025 feet in as early as 2026.
Salt River & Verde River Watersheds – Water Supply Status
This is the first above-median runoff season (January-May) in the last seven years that the Salt and Verde River watersheds have experienced. As a result, Roosevelt Lake increased from 35% to 71% in capacity during the runoff season, and Bartlett and Horseshoe reservoirs on the Verde system increased from 45% to 100% full, and even had to spill some water. For the first time since 2010, water was also spilled over Granite Reef Dam. During the monsoon season, normal precipitation was received for the entire summer; however, its distribution was heavily weighted to July, resulting in well above normal monthly precipitation. The monsoon storms diminished rapidly in August and since then, dry conditions persisted across the entire system. Total storage in the Salt and Verde system has improved to 65% capacity, as of October 1, 2017, compared to 47% at this time last year. However, despite water supply improvements this water year, the wetter conditions were not sufficient to fully rehydrate the watersheds and reservoirs from the many previous years of consecutive drought.
Forest Health and Wildfire Season Update
The relatively wet winter enhanced vegetation growth, however dry conditions during the Spring lead to vegetation die-off which created substantial amounts of fine fuels. Due in part to these conditions, this fire season was extensive across the state; over 418,000 acres burned, compared to the yearly average of 300,000 acres. This year’s fires were also very costly; the Sawmill fire exhausted the yearly State wildfire budget of four million dollars before the season officially started, and so far, 15 million dollars were spent on wildfire abatement this year. Post-fire conditions lead to devastating floods, causing further social and environmental harms. Overall, the trend of acres consumed by fires is going up, and next year’s wildfire season is expected to be destructive as well. Though a lot of beneficial efforts were made to restore health to Arizona forests, much work is still needed. Brush and invasive species continue to reduce Arizona’s grasslands and the high cost of restoration is a big obstacle in improving forest health.
Impacts of Drought on Wildlife
Across the state, there are approximately 1,800 wildlife water structures that help ease some of the drought impacts by increasing water availability for wildlife, especially during the hotter and drier months. Construction of such systems started over six decades ago with smaller catchments, but as drought conditions persist, bigger catchments are being constructed to hold more water. Rainwater is also harvested in some locations to reduce water hauling. Nonetheless, drier than average fall conditions required more water hauling than usual: about 283,000 gallons this year, so far. Drought impacts on fisheries were also reported and significant declines in Rainbow Trout productions were observed in some hatcheries over the past 30 years. This is likely the result of declining spring flows, which rely on precipitation to recharge aquifers feeding these springs. Reduced spring flows have resulted in an increased cost of $230,000 needed to buy replacement trout to be stocked, in addition to increased hatchery operation costs.
The updates confirmed that Arizona remains in a long-term drought, even after this relatively wet winter, and the drought is expected to continue. The Drought Interagency Coordinating Group unanimously recommends that both drought declarations be kept in place.
Fall 2017 Drought ICG Recommendation Letter to the Governor
- Drought Status Update & Monitoring Technical Committee Activities, Nancy Selover, State Climatologist, Drought Monitoring Technical Committee Co-chair
- Winter 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, Bill Boyd, Arizona Department of Forestry and Fire Management
- Impacts of Drought on Wildlife, Ed Jahrke & Dave Weedman, Arizona Department of Game & Fish
- Governor's Water Solutions Conversation, Tom Buschatzke, Arizona Department of Water Resources Director, Interagency Coordinating Group Co-chair