ICG Meeting 2017

ICG Meeting Fall 2017

ICG Agenda - November 16. 2017

Meeting Summary

Drought status

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.

Weather Outlook

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.

Recommendation

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

Presentations:

ICG Meeting spring 2017

Agenda - May 9, 2017

Meeting Summary

Drought status

This winter was considerably wetter across Arizona and throughout the Colorado River Basin than the previous five winters. Early winter storms in November and December combined with later storms in January and February brought significant rain and snow to northern and central Arizona. As a result, long-term drought and water supply conditions in northern Arizona are much better than they were over the past six to ten years. Southern Arizona had benefitted from a wet monsoon but missed out on the winter storm activity, leading to drought status degradation in the southeast part of the state. This winter, though relatively wet, was still not as wet as in late 1980s and early 1990s, before this drought began. While beneficial in the short-term, particularly for surface water supplies, the cumulative deficits to groundwater aquifers have not been alleviated. The drought status maps show much of the state is still abnormally dry and even the areas depicted as no drought have lost significant groundwater resources over the past two decades. Drought conditions are likely to worsen during the next few months, until the monsoon season starts.

Weather Outlook

Very weak La Niña conditions existed during fall 2016 and deteriorated through the winter, having little effect on winter’s temperatures and precipitation. Climate models suggest a 50% chance of El Niño conditions developing by late summer and fall, but these may not develop until September, which in this case will not influence Arizona’s Monsoon season. Sea surface temperatures are currently much warmer than average and could conceivably support more tropical systems and better moisture surges into southern Arizona this summer, especially if El-Niño conditions develop. The official Climate Prediction Center’s summer outlook predicts much better odds for above normal temperatures, continuing the trend of the past ten years of which eight were hotter than average (and the remaining two were near average). Arizona has not experienced a cooler than average summer since 1999. There are equal chances for above, below, or near average precipitation this upcoming summer.

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. The great snowpack accumulated in the Upper Basin during this winter, almost surpassed snowpack conditions in 2011 - the wettest year since this Basin-wide drought began in 2000. This snow, however, is rapidly melting due to the warmer and drier conditions that started in early March. Lower Basin intervening inflows between Lake Powell and Lake Mead are higher than normal, averaging at about 130%, which is 227,000 acre feet above average or 3 ft. of additional elevation in Lake Mead.

Total system capacity on the Colorado River Basin remines at around 51%, similar to last year, with elevations in Lake Mead improving from 1,076 ft. in November 2016 to about 1,085 ft. in early May 2017. Besides wetter conditions that increased flows to the River, rigorous water conservation efforts across the Basin helped keep additional 8 ft. of water elevation in the Lake. Bureau of Reclamation’s April 2017 24-Month Study projections for Mead’s elevations at the end of 2018 range from 1,075 to 1,132 ft., with the most probable elevations of 1,102 ft. Probabilities for Lower Colorado River Basin shortage have drastically decreased since last year from 48% to almost 0% chance of Tier1 shortage in 2018. However, over 30% chance of shortage still exists for 2019, and thus conservation efforts within Arizona and across the Basin should and will continue in order to keep more water in the Lake and reduce shortage probabilities even further.

Salt River & Verde River Watersheds – Water Supply Status

This is the first wet winter after six dry years on the Salt River and Verde River watersheds, improving reservoirs’ storage from 44% before winter to 76% after winter, which is roughly one million acre feet of additional storage. This year’s inflows are above median for the first time in seven years and have almost tripled compared to past few years. This winter storms seemed to have favored the Verde system, and its small reservoirs have filled beyond capacity resulting in over 100,000 acre feet of spill. On the Salt River system, however, conditions were not as favorable as on the Verde, and Roosevelt Lake - the largest reservoir on the Salt - did not fill to capacity, and as of May 8, 2017, held about 71% of storage.

Wildfire Outlook

Winter precipitation lead to substantial vegetation growth that have already dried out in lower elevations due to higher than average spring temperatures. Because of these conditions, higher than normal wildfire incidents are expected in lower elevations with larger acreage consumed by these fires. This year’s wildfire season has already started with significant wildfires – Sawmill and Mulberry fires – burning in southern Arizona, which spread very quickly due to windy conditions, but soil moisture helped preventing more severe damage to infrastructure and surrounding environments. Mid-elevation wildfire activity will depend on precipitation and wind conditions during the upcoming months. Higher elevations, containing most of Arizona’s forested landscape, are in much better shape due to the above normal precipitation received, which translates to a ‘normal’ wildfire danger in these areas; wildfire threat still exists, but those fires will be more manageable than some of the devastating fires experienced in high elevations in the past several years. Fire outlook suggests that Arizona will have an active wildfire season, but predicted early monsoon storms will help mitigate fire outcomes, though these often lead to higher incidents of lightnings, which in turn increase wildfire risk.

Recommendation

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.

Spring 2017 Drought ICG Recommendation Letter to the Governor

Presentations: