The Beaverhead County Drought Task Force held it’s monthly meeting on Monday, September 14th. Gina Loss of the National Weather Service in Great Falls presented a look back at the evolution of this summer’s hydrologic conditions, along with forecasts for what folks in Beaverhead County can expect for the coming weeks and months. This presentation can be viewed here.
August brought below average precipitation to northern Beaverhead County and above average precipitation to southern Beaverhead County. Lima Reservoir was under run-of-the-river operations in August, meaning that dam releases were roughly the same as reservoir inflows and no water was stored. The Joint Board for Clark Canyon Reservoir decided to begin ratcheting down releases from Clark Canyon Dam beginning on September 15th, and will gradually decrease over the subsequent seven to ten days to 30 cfs overwinter flows.
All agencies and stakeholders are keeping a watchful eye on the development of El Nino conditions and how they affect this winter’s climate in Beaverhead County. Much has been made in the media of the “Godzilla El Nino”, which could be the strongest El Nino on record. In general, El Nino conditions have tended to push the Polar Jet Stream further north into Canada, creating warmer and drier conditions for the northwestern U.S. and the Missouri River Basin. The October through December forecast reflects this by anticipating warmer and drier conditions for Beaverhead County. Extreme cold weather and snow events may be milder and less frequent. However, Ms. Loss astutely pointed out that each El Nino is different, and forecasts are based on trends and averages, rather than direct correlations. In essence, folks in Beaverhead County should prepare for a worst case scenario of warmer and drier winter conditions, but not discount the possibility of more favorable winter hydrologic conditions.
Last winter also had El Nino conditions, although they were far less pronounced. The below average snowpack may be attributable to those conditions, and likely contributed to the active fire season that we have seen this summer. Wildfire 100 hour and 1000 hour fuels (essentially how easily a fire is ignited) and energy release components (how hot fires are capable of burning) have shown to be only briefly mitigated by rain events. In other words, fire risks have rebounded quickly after rainfall.
To summarize the drought conditions of 2015, timely and healthy rains in May and July helped mitigate the drought impacts of below average winter snowpack, and good range production was a key sign of this. However, Beaverhead County continues to be in an overall water supply deficit going into what could be an even drier winter than last winter. Therefore drought conditions are predicted to get worse before they get better.