California-Nevada Drought & Climate Outlook Webinar: September 26, 2022

Welcome to the California-Nevada Drought & Climate Outlook Webinar

Speaker: Amanda Sheffield, NOAA/National Integrated Drought Information System (NIDIS), Cooperative Institute for Research in Environmental Sciences (CIRES)

• Welcome to the September California-Nevada Drought & Climate Outlook webinar. 
• State and regional level drought information can be found on Drought.gov: California, Nevada, California-Nevada Drought Early Warning System.

Drought and Climate Update and Outlook

Speaker: John Abatzoglou, CNAP, UC Merced

• Record heat is (once again) the story for summer in the California-Nevada region.
• Warm season drought degradation was not as bad as in 2021. There was an unusual combination of hot and wet conditions (due to tropical storms, typhoons, and an active monsoon).
• Sierra reservoir storage is similar to last year. 
• Fire activity has slowed down recently.
• A continuing La Niña (3rd La Niña) suggests dry winter in the southern portion of the region, with dynamic models favoring dry conditions in Northern California
• This was the driest 36-month period for California in the instrumental record. Another dry year will rival the 2012–2016 drought. Warmer climate with higher evaporative demand further increases odds of drought persistence. 

Status of the Colorado River Basin

Speaker: Noe Santos | U.S. Bureau of Reclamation

• Overview of the Colorado River Basin: 
  • Operation is governed by the “Law of the River.”
  • 16.5 million acre-feet of water use allocated annually.
  • 60 million acre-feet of storage capacity.
  • 4,200 megawatts of installed hydropower capacity.
  • 70% of all use is for agriculture.
  • 40% the water is exported outside of the Basin.
  • Aside from the pulse flow event, the river hasn’t made it to the delta in decades.
• Drought response efforts: 
  • Lake Powell's current elevation is about 3,530 feet at 25% of capacity.
  • Lake Mead's current elevation is about 1,044 feet at 28% of capacity.
  • Lake Powell Drought Response Operations:
    • In light of the recent drought, the Department of Interior implemented an action to reduce the Glen Canyon Dam release from 7.48 million acre-feet to 7.00 million acre-feet.
    • This action was done in conjunction with the 2022 Drought Response Operations plan actions, which are anticipated to add about one million acre-feet of storage in Lake Powell by April 2023.
    • The decision to hold back 480 thousand acre-feet of water in Lake Powell will not impact future operating tier determinations and will be accounted for “as if” the volume of water had been delivered to Lake Mead. 
• Current and projected system conditions: Water Year 2023 Lake Powell forecast: 
  • Sept. Min Probable: 4.70 million acre-feet (49%)
  • Sept. Most Probable: 8.30 million acre-feet (86%)
  • Sept. Max Probable: 15.50 million acre-feet (161%)

Improving Drought Outlooks with Subseasonal Forecasts

Speakers: Shrad Shukla | CNAP, UC Santa Barbara

• Our research examined the value of subseasonal hydrologic forecasts for supporting drought outlooks.
• Subseasonal hydrologic forecasts derive skill from the knowledge of initial conditions and climate forecasts.
• Subseasonal drought forecasts during the 2012/13 to 2015/16 drought compare well with observations, and the U.S. Drought Monitor's “short-term” drought indicator.
• There is a high correlation between forecasts and observed area in drought (D0 to D4).
• At grid scale, there is higher skill in drought termination vs. drought onset forecasts, with limited skill beyond two weeks.
• Given the skill and routine weekly availability of subseasonal forecasts, potential exists for operational production and application of subseasonal hydrologic forecasts to support monthly drought outlook.

Question & Answer

Closing

Speaker: Amanda Sheffield, NOAA/NIDIS, CIRES

• Register now for the next webinar in this series on Monday, November 28, 2022.