In January of 2015, I started a new run of "fish of the month," a tradition I started years ago with long-time friend Tom Grimes, who is a guide at Henry's Fork Anglers. The idea is to catch a wild trout or whitefish every month of the year in our local waters, the streams and lakes of Montana, Wyoming, and Idaho in the Yellowstone region. My previous record was 55 months, from July 2004 to January 2009. Five academic years spent in California broke that streak, but I'm four years into the current one. How did 2018 turn out?

Diversion from the Henry's Fork has decreased 30% over the past 40 years, yet consumptive use of water by crops has increased, there is less water in the river during the middle of irrigation season, and use of storage water has increased, all other things being equal. How could this be?

• Water-year 2018 ended up close to average, at 102% of average precipitation and 105% of average streamflow.
• Upper Henry's Fork subwatershed was below average in precipitation and streamflow, vs. above-average values in Fall and Teton rivers.
• However, Upper Henry's Fork water supply improved from 70% of average in 2016 to 91% in 2017 and 94% in 2018, indicating recovery of deep aquifers from 2013-2016 drought.
• May and June rain compensated for early snowmelt and resulted in below-average irrigation diversion.
• Despite very dry conditions and below-average streamflow during July, August and September, Island Park Reservoir ended the water year at 73% full, compared with 43% full on average, thanks to careful and precise water management.

• The month of July was a little warmer than average but very dry.
• Natural flow and diversion were both around 90% of average for most of the month.
• Moisture from May and June rain has kept total diversion for the season about 100,000 ac-ft below average.
• As of August 3, Island Park Reservoir is still 82% full, compared with an average of 70% full at this time of year.

• May 2018 saw warm temperatures, heavy rain, and above-average snowmelt.
• Only 30% of this year’s peak snow-water-equivalent (SWE) remains, compared with an average of 43% remaining on June 1.
• Water-year precipitation stands at 108% of average, but SWE has dropped from 117% of average at its peak in April to 82% of average on June 1.
• Lack of snow means that streamflow will drop rapidly once the current wet weather ends.